ML20094J980

Submits Listed Info in Response to Questions Received from NRC Dtd 910109.Advises That Statistical Repts Will Be Prepared & Maintained for NRC Review

ML20094J980
Person / Time
Site:	05000262
Issue date:	03/09/1992
From:	Donna Anderson Brigham Young University, PROVO, UT
To:	Alexander Adams Office of Nuclear Reactor Regulation
References
NUDOCS 9203170230
Download: ML20094J980 (35)

Text

- _. _. - -._._._.. _ -.. - _. _., _... _ _

l IIRIGilAM YOUNG UNIVI:RSITY m, wwi s m w + 3 i n w.,

M t%flNi% 1k 41n t % h l Wl MDi h l 1% I%1t l( F J V 1 t

Refer to Docket No. 50-262 March 9,1992 Alexander Adams,'Jr.

Project Manager Non Power Reactors, Decommissioning and Environmental Project Directorate Division of Advanced Reactors and Special Projects t

Office of Nuclear Reactor Regulation

Dear Sir:

i In response to the questions received from your office dated January 9,1991, we have prepared the following information:

h

1. A table of contents is enclosed.

2. A copy of Figure 1 is enclosed.

3. Statistical analysis reports will be prepared and maintained for NRC review.

1

4. Core samples will be obtained by drilling a one quarter inch hole in the respective material and placing a one gram sample of the material removed by the drill into LSC counting fluid for alpha and beta analysis using LSC counting techniques (it is assumed that gamma contamination will be picked up with standard surface survey instruments).

5.' A " Training Program Outline', is enclosed.

J

6. We will be using RAMP Industries incorporated with offices in Denver, Colorado as our radioactive waste broker. The Brigham Young University Radiation Safety Officer is charged with assuring compliance with all shipping and waste disposai regulations as well as monitoring the activities of_our brcker.

1 j,, f, ;,,,,,,

,f aem 920317o2$o 920309 AD0cKOSoog2

[

m

-PDR-P.

, ~:-.., _,

.. -.a.

l 1

7. One milliliter of shielding water and one milliliter of tap water (the shielding tank was l

fiPed with culinary water in 1967) were placed in liquid scintillation counting cocktail and cach sample was counted ten times.

The resulting means for_ the counts were respectively,-169.9 for the tap water and 169.6 for the shielding water.

Calculated ctandard errors for the means were 2,57 and 4.09. Assuming that the true mean for the tap water in this area is 169.9 there is a 95 % probability that the trus mean for the shielding water is less than 8 cpm above the background. Since efficiency for " C is-approximately 90% using this methodology and the more radiotoxic materials in general have an efficiency approaching 100% there is a 95% probability that the true contamination of the shielding water is less than 9 dpm per milliliter of water. This translates to a possible contamination level of 4.09 x 104 microcuries per milliliter, in addition NRC-Region IV pulled a sample of shielding water for analysis and we have requested the results frem thc? analysis. Prior to discharging the water we will repeat the analysis usino 2 milliliters of win pnd a 20 minute count.

8. The Pu/Be source was leak tested at the time of removal and the tests results were less than 0.0001 microcuries of removable surface contamlnamn.

In addition the exposure rate (gamma) survey taken at the time of removal was o.2 mrem / hour at one meter from the surface of the source and the neutron flux was 5 neutrons per second per -

square centimeter at one meter from the surface of the material with the thermal neutron shield in place.

Application has been made to transfer this source to License UT 2500091 which currently has a license limit of 83.5 grams of plutonium-239.

4

9. No material wi!! be released for unrestricted use unless it can be demonstrated to be within the following limits at a 95% confidence level.

2

a. 5000 dpm/100 cm for fixed beta / gamma contamination.

2 b.1000 dpm/100 cm for removable beta / gamma contamination.

2

c. 100 dpm/100 cm for fixed alpha contamination.

2 d.

20 dpm/1CO cm for removable alpha contam'ination.

V While we will accumulate the data on the above material we will not release any material as non-rad:.mactive from the reactor facility until the data including statistical analysis has been reviewed by the NRC, i

10. We shall not release facilities to unrestricted use unless we can, demonstrate with at 1

least a 95% probability, that exposure rates associated with those facilities are not more than 5 uR/ hour above background at one meter from the surface of those facilities.

11. Survey instruments shall be ca!ibrated within four weeks of the start of decommissioning activities. Since the time schedu'e submitted involves five weeks for completion of the project the instrument calibration will be performed within three months 2

l

of the completion of the project. - This is in keeping with new guidelines proposed by the Division of Radiation Control which allow survey instrument calibration at 3 month intervals. in addition the instruments will be checked with an appropriate calibrated sourca at least daily while they are in use.

Sincerely, 7f=( htJw D e F. Andersen 9

TIY cc: Bill Beach, NRC Region IV STATE OF UTAH

)

ss.

COUNTY OF UTAH

)

Subscribed and sworn to (or affirmed) before me this 9th day of March,1992 by Dee F. Andersen, the Administrative Vice President of Brigham Young University.

~Sr('

LtegnE RMY l Ci: 61M iTTf CIA y

g[. (l$([/*fg

[&gz

}y gfj(EM WML A R Ee' f'.jlV J-

/

f vacc mem

_j #

99119E U'bM Notary Public

1. ~

J d

3

~._ _. _ _._ -

t 1.

SUMMARY

OF PLAN.

1-1 1.1. Decommissioning Mtthod 1-1 1.2 Estimated Cost 1-1 1.3. Major Tasks.

1-1 1.4.

Items Subject to Quality Control 1-1 1.5. Items to Be Performed By Contractor.

1-1 1.6. Final Survey 1-1 2.

CHOICE OF DECOMMISSIONING ALTERNATIVE AND DESCRIPTION OF ACTIVITIES INVOLVED 2-1 2.1. Decommissioning Alternative 2-1 2.2. Decommissioning Activities, Tasks, and Schedules 2-1 2.2.1. Preliminary Survey:

2-1 2.2.2. Preliminary Survey Reviews 2-1 2.2.3. Dismantle Shield Tank:

2-1 2.2.4.

Determine Radiological Status of Remaining Structure:

2-2

' 2.5. Dismantle Remaining Shielding 2 2-2

' 2.6. Package Radioactive Waste:

2-3 e

.7.

Final Exit Survey.

2-3 4

.8.

Preparation of final Reports:

2-3

!.9.

Total Time to Completion of Decommissioning:

2-3 Decommissioning Organization and

.asponsibilities.

2-3 2.3.1.

Ultimate Responsible Party:

2-3 2.3.2.

High Level Administrative Contrcli 2-3 2.3.3.

Project Supervisor:

2-3 2.3.4.

Radiation Safety Officer (RSO):

'4 - 4 2.3.5. Project F:fety Officer:

2-4 l

2.3.6. Decommissioning Committee:

2-4 2.4. Training Progran 2-5 2.5. Contractor Assistance.

2-5

3. PROTECTION OF OCCUPATIONAL AND PUBLIC HEALTH AND SAFETY 3-1 3.1. Facility Radiological Status 3-1 3.1.1. Facility Operating History:

3-1 3.1.2. Current Radiological Status of' Facility:

3-1 1

3.2. Radiction Protection 3-2 3.2.1. Decommissioning ALARA Program:

3-2 i

3.2.2. Health Physics Program:

3-3 l

3.3. Radioactive Waste Management 3-4 l

3.3.1. Fuel Disposal:

3-4 l

3.3.2. Radioactive Waste Processing 3-4 3.3.3. Radioactive Waste Discosal:

3-5 3.3.4. Accident Analysis:

3-5 3.3.5. Minimization of Airbr>rie Hazards:

3-5 L

3.3.6. Accident Analysis:

3-5

4. PROPOSED FINAL RADI ATION S'JRVEY PLAN.

4-1 1

4.1. Acceptance criteria 4-3 1

l

. ~. _..

5. COST ESTIMATE FOR THE DECOMMISSIONING PROJECT AND PLAN FOR ASSURING AVAILABILITY OF FUNDS FOR THE COMPLETION OF THE PROJECT.

5-I 5.1. Cost Estimates 5-1 5.2. Funding Assurance.

5-1 6.

TECHNICAL AND ENVIRONMENTAL SPECIFICATIONS IN PLACE DURING DECOMMISSIONING 6-1

• I.

QUALITY ASSURANCE PROVISIONS IN PLACE DURING DECOMMISSIONING 7-1 7.1. Radiation Survey Equipment 7-1 7.1.1. Beta Survey Instrument Channel Check:

7-1 7.1.2. Alpha Survey Instruments 7-1 7.1.3 Ganuna Survey Instrument 7-1 7.1.4. Victorcen Ionization Chamber:

7 -- I 7.1.5.

Packard model 1500 Liquid Scintillation Counter (LSC):

7-1 8.

PHYSICAL SECURITY PLAN PROVISIONS IN PLACE DURING DECOMMISSIONING 0-1

9. ESTIMATED COLLECTIVE DOSE EQUIVALENT 9-1

10. REGULATIONS REGULATORY GUIDES AND STANDARDS 10-1 b

o a

t

-+.,-w s

4

-. ~-s

=

6

.I Figure 1 3

Reactor Cross Section

• g

- q -

• .4-

. s PMESSURL cal-ct RE ACTOR $*4tf LD T ANic p 1

,s y

r:::,

7 8iLLOvv%5[AL n-.____"*'**'

m n

j gp

• a--

3

-FUEL AND yg st valvts

=

4-CA$ LINE

______.' ~-~

• =w=w=.

6 ATtR SHlf LD O'

. v w

Jh_~y~^td ? g

~j

/

/ i s

• g

,~

, ;>,<M.

,:+.: A.........

(;9 Y

,,v...,..

"a,.6.......

..... y ;;

..l m,.,y..

. w..:._,,,

.:..:. + -, li e

4,;:', ',,

(

.. y' e

'8 y

eam.ai==

.y U.*t q

awa.*

T* ')f,ff - FIRST $Ht[LD f

• * * ' ' ' " ' ', ", * ',,,,,,,,,>-l,)f l[.'

',Q (Li AD AND DIPHENYL)

p. i*

. ;A s,,

V., *,, 9),

a :,. s

• L

'l FILL AND OFLAIN -

'V

\\

ly'.Ed;'n

~~_____.

• • =awa=d*a

~

f

.J LINL

>U. ".p

)

t x

,i m

g s

j

, ", [

)

REAC701 F

7 s 'OMATID PAR AFFIN) lN t CDND SHitL O

<.D 't

.',. *.'p' CORE op:

', g IS I.[4

.- w,

., i

'4 W

\\

l*la C ',l' h

r,

...i.o

? l.,

'7L ' 'g;j

/

- ~

/

["Y' \\

\\

r,*

'C l' j'$.

\\

, ",, t,,,[

,. $,h-THIRD $ Hit LD l?

' gy (Lt AD AND CORATED 1, '.

R:.. '

\\

. u &n' '

. < vs.- ---.

V -~FAM A F F IN) ia!h.

oa 38.;.j $....R g+

-- ----- ~

. $.:....$.p. ;:

0:::

......... +,

n

.._...?..,

~

-- m --

~

~

__1___.

se,m sa.p 4.p=ed

'^ ^:__ _ _^_

e 8ht.'ammmin te a

_--__c_e ei,sm ssw=.wi

' ' ^ ^ -

m4sms Shielding and Piping f

i l

l e

T

~

~

e

.--_.m 1

RADIATION SAFETY TRAINING OUTLINE 1.

Tissue Damage 1

1.1.

DNA 1.2.

Protein 1.3.

Free Radicals 2.

Ionizing Radiation and its interactions with matter.

2.1.

Compton Effect 2.2.

Bremestraahlung H

2.3.

Specific Ionization 2.4.

Pair Production 2.5.

Photoelectric effect 2.6.

Shielding 2.7.

Neutrons 4

3.

Types of Ionizing _ Radiation.

3.1.-

B origin and characteristics 3.2.

a origin and characteristics 3.3.

y origin and characteristics 3.4.

7.-ray 3.5, Neutrons 4.

Waste Disposal

(

4.1.

NRC regulations.

-5.

Personal Protection.

5.1.

Dosimetry 5.2.

--Surveys S.3.

Leak checking new material 5.4.

Shielding, distance, time 5.5.

Accident response.

5.5.1.

1.

protect life and health

2. Safely limit the spread

3. Notify RSO 6.

Regulations.

6.1, Waste Disposal.

6.2.

Pregnancy.

j 6. 3.-

NRC 6.4.

10 CFR part 20 6.5.

Security. Locked or attended l

6.6.

Reporting. 8-2222 or 911

~_-

7.

Radiotoxicity.

7.1. Biological half life.

7.2. Target Organ.

7.3. Specific Ion 17ation.

8. Units Of Measurement.

I 8.1. roentgen 8.2. RAD 8.3. REM 84 4. Gray 8.5. Sievert 8.6. Becquerel l

8.7. Coulombs /kg (C/kg) 9.

Instrumentation 9.1.

L.f. quid Scintillation 9.2.

Solid Scintillation 9.3.

Geiger--Muller Countor 9.4.

Ionization Chamber 9.5.

Gas Proportional Counter h

R ASICS OF RADIDACTIVITY 4.4 a

In order to assist in the training of users and potential users of radioactive materials, the Radioisotope Comittee is preparing a series of information sheets which will explain in simple terms various aspects of radioactivity and radiation safety.

These will be distributed to all interested persons in areas where radioactive materials are present. Suggestions are requested for new ideas and new topics which can be used in the series.

WHAT 15 RADI0 ACTIVITY?

Radioactivity occurs when the nuclei of certain unstable atoms emit particles allowing the atoms to become more stable. Each atom is characterized by an atomic This is characterized for the atom X as fX.

mass A and an atomic mmber 2.

If the A/Z ratio is too large or too smil, the atom becomes unstable and emits

(

either an alpha particle (a ) or a beta particle ( A ) to stabliize the atom. This disintegration ma more ganna rays (y leave the nucleus in an excited state, in which case one or v ) will be emitted. This process is known as nuclear decay or radioactivity.

WHAT IS NUCLEAR FISSION?

When atoms reach the mass of uranium or plutonium, the nucleus may become unstable and split'into two fragments of roughly the same size.

Extra neutrons are emitted in course of the fission.

These neutrons may stimulate the fission of additional uranium or plutonium-atoms, causing a chain reaction.

If sufficient fissionable -

uranium and plutonium are present to sustain the chain reaction, the critical mass is reached and the chain reaction will continue until the mass drops below criti-cality by any of a number of mechanisms. Nuclear reactors operate on the principle of-controlling the rate of chain reaction. Nuclear weapons achieve the state of an uncontrolled chain reaction.

WHAT IS AN ALPHA PARTICLE 7 An alpha particle is the nucleus of an helium atom consisting of two protons and two neutrons.

They are emitted only from atoms more mascive than lead with an atomic number of 82, with the exception of samarium which has an atomic number of 62.

Alpha particles are emitted with high energies, usually between 4 and 9 million electron volts (Mev) and are monoenergetic.

Because of their great mass and electric charge, alphas have short ranges of a few millimeters in air. Because

,1asics of Radioactivity Page 2 of the short range, alphas present little hazard from external radiation. The high energy release, however, could cause problems if the materials containing alpha radiation are ingested in the body, i

WHAT IS A BETA?

A beta particle is an electron or positron which is emitted from the nucleus cf an atom.

Its properities resemble those of any electron or positron of comparable energy.

Betas range in energy from a few thousand electron volts (key) to several Mev.

Betas are not moneenergetic as are alphas but have a range of possible energies with any particular disintegration. The most probable energy of emission is approximately one-third that of the maximum energy possible from that disintegra-tion.

Since betas are inuch less massive than alphas, the range is considerably greater for comparable energies. The maximum range of betas emitted by tritium in air is about 4 millimeters, the maximum range of betas from carbon-14 is about 25 centimeters, and betas resulting from the decay of strontium-90 could penetrate as much as 10 meters of air. Betas may produce X rays as they interact.with matter in the process of losing energy.

WHAT ARE GAMMA RAYS?

Garna rays are the electromagnetic radiation emitted by the nuclei of atoms during ('

decay.

Gamas are identical to X rays with energies ranging from several key to a few Nev._ Since gammas have no electrical charge, their penetration is greater than that of alphas and betas of comparable energy. The term

• range" has no-meaning with gar.as as it has with alphas and betas since there is no stopping distance associated with gamas. The intensity of the bea> decreases exponentially with respect to.the mass of the materials through which the beam passes. Since gamas are extremely penetrating with small amounts of localized energy loss, the

- greatest hazard is usually from external exposure. Some elements,- however, such as iodine will localize in a small organ of the body such as the thyroid and cause possible radiation damage if the materials is ingestd in large quantities.

WHAT IS A NEUTRON?

A neutron is a neutrally charge particle emitted from the nucleus of some atoms.

It reacts only by nuclear reactions with matter and is extremely penetrating with a large release of energy when absorbed. Special precautions'need to be taken when working with neutron emitting materials.

1 9

m n

n

,~?

~

B ACKGROUND RADIATION 4.4 COSMIC RADIATION Cosmic radiation originates when charged particles bombard the earth from outer space.

These particles interact with the earth's magnetic field which turns many of the particles away.

Those which reach the atmosphere react with it

-producing secondary particles whit.h continue to interact with the atmosphere causing a cascading of charged particles descending through the atmosphere.

In these reactions, cesmic rays are absorbed by the atmosphere, losing energy, such that the concentration of charged particles is greater at higher altitudes than at sea level.

In !!tah, the annual dose from cosmic radiation is about 115 mrem; however, the annual dose is only about 30 mrem in Hawaii and in the United States the average dose is 45 mrem.

TERRESTRIAL RADIATIO!!

The earth is composed of rocks containing uranium and thorium in varying concen-trations over the different portions of the earth.

Those arcas containing these elements in higher concentrations have greater background radiction levels than those areas with smaller concentrations of these elements.

Some areas of India, Brazil,. and France have background radiation levels exceeding those allowed for radiatica workers.

In Utah, the average terrestrial component of background radiation is 40 mrem per year, while in Colorado it is as high as 150 mrem per year.

Since uranium and thorium are natural components of both sand l

l and rock, cement, brick, and stone buildings will nornally have higher radiation L

levels inside them than will frame or steel buildings.

i AIRBOPSE RADIDACTIVITf One of the natural decay products of uranium and thorium is radon gas which diffuses cut of the rocks and soil into the air we breathe.

This decays into daughter products which collect on dust and can accumulate in the lungs of people breathing the air.

This ' type of exoosure is comon around soils with high uranium content such as the Vitro tailings in Salt Lake City.

Radon gas usually accumu-l-

lates in higher concentrations inside buildings built on thcse tailings or l

constructed from sand from the tailings. Heavy rainfall slows down the diffusion of radon gas out of the ground resulting in lower concentrations of radon in the air than found during dry spells.

Other radioactive elements found in the air

I

' Background Radiation Page-2 are carbon-14, tritium, and berillium-7, but they are in such low concentrations that they are insignificant.

The average annual exposure to airborne radio-activity is about 4.5 mrem.

RADICACTIVITY IN WATER As water passes through the soil it picks up minerals which may be radioactive.

The most prevelent contaminants are potassium-40, which comorises the body's greatest natural dose of radioactivity, and radon gas.

Other radioactive elements are also present in water depending on the natural composition of the rocks through which the water passes and the effects of radioactive fallout.

RADICACTIVITY IN FOOD All food that we eat has certain amounts of radioactivity.

Health officials are very concerned about increases in the natural intake of radioactivity resulting from nuclear fallout, waste disposal, cr other contamination of the food chain.

A good way to test fallout after a nuclear explosion is to measure the radioactive iodine in milk produced by cows in the suspected area.

Concentrations of radio-activity in the body due to foods eaten vary widely from one crea to another.

Allowable levels of waste disposal in one area may be governed by the radioactivity naturally occuring in tne food of another area. Potassium-40 is the most abundant isotope and is distributed uniformly throughout the tissues of the body.

Radium seeks bone structure and remains in the body for many years.

Carbon-14 is a natural contaminant in small con:entrations which distributes itself throughout the body.

The annual exposure to the gonads frca ingested radinactivity may be as high as 20 mrem per year.

RADICACTIVE FALLOUT A thermonuclear explosion vaporizes the materials near the blast and carries great amounts of sand and vapors into the upper atmosphere. The larger of these highly contaminated particles drop to the earth within a few miles of the blast site.

Smaller particles remain in the atmosphere until participated out by rain or snowfall.

Some contaminants remain in the upper atmosphere for years, covering the globe with a layer of radioactivity.

When this radioactivity reaches the earth it. becomes part of the food chain as explained above and may reate problems if the levels in a local area become too high. Estimates of the average dose to a person in tne United States during the next 70 years are placed between 400 and 900 mrem to the bone.

Exposures to other parts of the body are even less.,

I

R ADIATION ME ASURING INSTRUMENTS o

4.4 10N-CHAfSER 0051 METERS The original radiation-measuring device was the electroscope. The chamber walls forin the cathode while the anode consists of a flexible fiber attached to the central electrode. When a static charge is placed on the anode, the fiber is repelled from the electrode and remains in that state until the system is discharged.

Radiation passing through the chamber ionizes the air, which then discharges the system.

The rate of discharge indicates the amont of radiation present. Pocket dosimeters use this principle by adding a microscope eyepiece and a scale to follcw the movement of the fiber and measure the amount of discharge.

ION-CHAMBER SURVEY HETER 5 An ion chamber can be constructed of a thin wire anode inside a chamber with the walls forming a cathode. A constant charge can be applied between the anode and c

cathode with the discharge current being reasured by an electrometer. Each ion l

pair produced by the radiation in the chamber contributes one electron toward the discharge current, so the reading is proportional to the radiation present or the exposure. The unit of exposure due to X rays and garna rays is the Roenteen (R),

~

and exposure is neasured as Roentgens per hour (R/hr). Ion chambers are difficult to cnnstruct with great accuracy because of the small currents which must be measured and spurious noise which comes from the electronics of the system.

s

~

s PROP 0RTIONAL COUNTERS If the electric field between the anode and cathode of an ion chamber is increased, electrons released during ionization caused by radiation will be'able to ionize edditional atoms before they reach the anode. This cascading effect creates larger pulses which are dependent upon the field strength and also upon the energy released by the ionizing radiation. This makes it possible to distinguish between alpha radiation and beta radiation. A unit characterizing the amount of energy absorbed by a unit mass of material is known as the rad or Radiation Absorbed Dose.

The rad is used for measuring all types of ionizing radiation, whereas the Roentgen applies only to X rays and gamas.

GEIGER COUNTERS If the applied voltage between the anode and cathode is sufficiently great, each' ionizing event resulting from radiation will cause an avalanche effect which will fill the entire chamber. Thus, each ionizing praticle will create a large pulse

Radiation-measuring Instruments Page 2 which is easily detected and independent of the energy of the ionizing radiation.

(

A quenching gas must be included within the chamber to recharge the chamber af ter each event.

If the radiation levels are sufficiently high that quenching isn't co pleted before the next event, counts are lost. The readings frcm Geiger counters are registered in counts per minutes (cpn). Some Geiger counters have scales marked in R/hr or mR/hr bat these scales are calibrated for gamas of one energy only and must bs adjusted for ga. mas of differing energies.

SC!NTILL ATION CRYSTAL COLNTERS The crystals of certain materials such as sodium iodide (Nal) will scintillate, or emit light, when exposed to ionizing radiation, especially gammas. This light can be detected by a photomultiplier tube, which in turn gives a measure of the energy being released by the radiation. Gamas of different energies can be distinguished through proper electronic circuitry enabling the identification of radioisotopes by their gama spectr ums.

LIQUID SCINTILLATION COUNTERS To enable the detection and tensurement of low-energy betas such as tritium, carbon-14, and sulphur-35, the radioactive material is suspended in a naterial which scintillates due to the raaiation passing through it. A geometry efficiency of nearly 100 percent can be achieved by suspending the radioactive material within the detecting medium. The light is detected by photomultiplier tubes and pulses of differing energies can be dit tinguished through proper electronic circuitry.

FILM DCSitiETERS Ionizing radiation exposes film in the same manner as light exposes it. The amount of radiation causing the exposure is determined by measuring the light density of the film. The results obtained by measuring film density are influenced by such factors as age, fabrication processes, and the developing of the film, as well as other factors which make quality control difficult.

For many years, film dosineters were the best available means of recording personnel exposures over a period of tice. Today, TLD dosimeters are replacing filn in many areas.

THERMDLU.'tINESCENT D'JSIMETERS Certain ceramic materials will trap energy released by radiation passing through it.

This energy can be released by heating the ceramic material, which luminestes or gives off light in proportion to the radiation absorbed. These devices are callec thernoluminescent devices cr TLDs and are used as personnel dosimeters.

i MEASURING RADIDACTIVITY t

a

l RAD 10 ACTIVE DECAY The chemical properties of elements are characterized by the electrons surrounding the nuclees, which in turn are detemined by the nurcer of protons in the nucleus.

.~

Nuclear properties of an atom are characterized by the ratio of neutrons to protons in the nucleus, or the A/Z ratio. Each elemert contains atoms with the same number of protons, but isotopes of the element contain varying numbers of neutrons.

When the number of neutrons in an atom is either too great or too small to balance the number of protons, the atom is unstable and decays emitting either an alpha or beta particle.

The atom resulting from this decay or disintegration may be excited and emit garnas before resting in a stable state. The nature of radioactive decay h a property of each unstable isotooe and is unique with each isotope. The probability of an atom in a radioactive material decaying within a specified time is measuroble and is known as the actlyig of the material. Activ-12 ity of a radioactive material is neasured in curies (2.? x 10 disintegrations 6

per minute (dpm)), millicuries (2.2 x 10 dpm), or microcuries (2.2 x 10 dpm).

Specific activity is the activity per unit mass or linTt volume of the material j

such as rallicuries per gram or microcuries per microliter.

HALF LIFE The activity of a radioactive material may be known at one point in time but it changes as some atoms decay, decreasing the total number of atoms whichare unstable.

The activity at any point of time can be characterized by the fonnula A = A e g

l where A is the activity of interest, A is the known activity at the time t = 0, A g

is the decay constant which is a property of the radioactivo isotope, and t is the time since the activity was known. The activity will decrease to half of its original activity in the time t = T which is known us the half life of the material.

y In other words, the activity will decrease by one-half in each half life. The half life of a radioactive material is a property of the radioisotope and is character-ized by Tg = 0.693/A.

The half life of tritium is 12.33 years, of carbon-14 is 5730 years, of phosphorus-32 is 14.31 days, and of iodine-125 is 59.7 days.

i 10N HING RADIATION Radiation, whether in the form of alphas, betas, gamas, or X rays, with sufficient energy to ionize atoms is known as ionizing radiation. An atom is ionized when it Carpus Safety Office, YiATH, B.Y.U., Provci, UT 84602, 374-1211 ext. 2597

_ ~

tieasuring Radioactivity Pace 2 loses one or more electrons fron its electron orbitals through inteiaction with the radiation. The conventional method of detecting ionit'm radiation is to construct a chamber with a thin wire anode and a conducting outer surface which serves as a cathode. A static electric field is then mair.'ained between the anode and cathode.

As ionizing radiation passes through the chanber it ionizes molecules of air or gas within the chamber. The electrons are attracted toward the anode, and the heavier positive ions are attracted toward the cathode. A discharge can then be measured in the electrical circuitry connecting the anode with the cathode of the instrument. An ion counter will record a small current, but a Geiger counter will record a series of pulses, each in proportion to the ionizing radiation entering the chamber. The majority of oortable radiation-t detection devices utilize the concept of an ionization chamber.

COUNTING EFFICIENCY The problem with measuring radioactivity is in relating the reading on the meter of an instrument with the acountof radioactivitypresent. Alphas and many betas may be absorbed by the walls of the detector without entering the countino chamber.

On the other hand,- high energy gammas may pass through the chamber in great numbers without interacting with the ionizing gas, and, therefore, never be detected.

The ratio bc tween the number of counts measured and the activity of m

the material being measured is known as the counting efficiency. The ef ficiency

.I or sensitivity of a radiation detector or counter depends on many factors. The basic factors which must always be considered are (1) the intrinsic efficiency of the counter, (2) the background count rate, (3) absorption factors, and (4) geom-e t ry.

These factors will be discussed below, concluding the topic of Measuring Radiation.

I 1.

The intrinsic efficiency is the probability that radiation entering the sensi-

l tive volume of the detector will actually be counted.

This depends on the construction of the detector as well as the nature of the radiation. Charged particles will be detected in a gas-filled chamber with about 100 percent efficiency until shturation or over-loading occurs, but only 1 percent of the gammas entering the chamber may be detected.

P.

A certain amount of ioni:ing radiation is around us et all times. This is known as the natural background. Sonetimes tne amount of activity we are trying to detect is hidden in the statistical variation of the background. The background, therefore, must be considered in any measurement taken and can vary widely between instruments, location, and even the day in which measurements are made.

3.

Charged particles such as alphas and betas lose energy while passing through matter.

When the kinetic energy is gone, they stop or are absorbed, and can no I

longer be detected.

Absorption may occur in the material itself, in the walls of the detector, or in the air between.

Care must be taken in measuring radiation which may be absorbed so that zero readings on the meter aren't interpreted as no radio-a c ti vi ty.

A good instrument design must be coupled with proper survey techniques in order to measure or even detect some materials such as tritium and carbon-14.

Ctcpus Safety Office, EATH, B.Y.U., Provo, trT 84602, 374-1211 ext. 2597

Measuri rn Radioactivity Page 3 4.

Radiation is emitted f rom a radioactive material in a random manner in all directions.

Unless the detector surrounds the radioactive source, the geometric factor must be considered.

A detector with 100 percent intrinsic efficiency and no absorption could only detect 50 percent of the radiation emitting from a flat surface.

A hand-held probe any distance from the source will detect a smaller fraction of the emitted radiation depending on the fraction of solid angle incor-

! l porated by the detector.

A geometric correction must also be made to account for the size of the source with respect to the size of the detector. An extended source will give a different reading than a point source of the same activity.

A 1

'i l

s If I,

i i

l.

Carou.; Safety Office, %ATil, b.Y.U, Provo, UT 84f202, 374-1211 ext. 2597

4 BIOLOGIC AL EFFECTS OF RADIATION 4.A a

REM, THE UNIT OF BIOLOGICAL EXPOSURE The biological effects of radiation are due to energy absorbed by tissues from the radiation passing through.

Some foms of radiation such as neutrons and alpha particles are more destructive to tissues than are gamas and betas of the same energy.

The uni-t of radiation exposure which relates the exposure in rads to the biological effect of each p6rticular type of radiation is called the rem. The nvMer of rems is detemined by multiplying the exposure in rads by a quality factor. Q", which is equal to 1 for gamma and beta radiation,10 for alphas, and 1-10 for neutrons depending on the neutron energy.

STRUCTURE AT NATURE OF CELLS

(.

All tissue is made of cells consisting of both a nucleus which contains genetic infomation and cytoplasm within which cell functions and growth take place. Some cells such as bone marrow or blood-forming cells are active and divide frequently.

Other cells such as bone or muscle cells are more mature and have less activity.

Cells of a small child or a fetus are much more active than those of an adult.

The radiosensitivity of cells is directly related to cell activity or how frequently cells divide producing new tissue.

EFFECT OF RADIATION ON Celt.S As radiation penetrates cells, it loses energy to the cell material. Since about 70 percent of the cell is composed of water, the majority of the radiatio *: interacts with the water to fom ions or free radicals, which, in turn, enter into chemical and biological reactions within the cell.

Radiation can also break molecular bonds causing confusion in enzymes or genetic information.

Certain radioisotopes can be incorporated into vital cell functions, which functions are modified when the isotope decays and foms another element. An example is that of carbon 14 decaying into nitrogen 14 which has different properties from those of carbon.

Cells have natural nechanisms to repair damage caused by radiation and other factors, but if the amount of damage exceeds the ability to repair, the cell either dies nr begins to malfunction. -It is the excessive death or malfunctioning of cells in tissues which cause the biological effect.

SOMATIC EFFECTS Somatic effects are short-tem biological effects which can be medically identified and related to radiation.

These may include damage to the blood and bone marrow, 25

t Biological Effects of Radiation P' age 2

()

i lymphatic system, digestive tract, reproductive organs (which might cause temporary or permanent sterility), central r.ervous system, thyroid gland, eyes (through the formation of cataracts), lungs, liver and gallbladder, kidneys, circulatory system, skin, hair, and bones.

The severity of these scmatic effects are related to the type and amount of radiation received, the age and physical health of the person exposed, the portion of the body exposed, and how vital the organ is to body processes.

It is often possible to medically assist a vital body process which has been damaged, 4

allowing the person to live until the organs can regenerate themselves, repair the damage, and being functioning.ormally. Severe ciamage to the digestive tract and the central-nervous system are usually fatal.

LATINT EFFECTS Sometimes radiaticn causes damage which doesn't manifest itself for many years.

These effects may be a shortening of life, cancer, tissue effects like cataracts or sterility, and effects on growth, especially to the fetus. Each of these effects results from combinations of diverse causes, radiation being one potential factor.

They are difficult to attribute to radiation rr any(other sinule factor exceDt through a statistical analysis of numerous persons or animals) receiving specified levels of exposures which are evaluated over long periods of time.

In this respect, radiation is one of many environmental pollutents to which we are continually exposed.

(

GENETIC OR HEREDITARY EFFECTS Genetic effectr are not manifest in the generation receiving the radiation exposure.

They are caused only by mutations transmitted sexually from one generation to the next.

Since mutations occur naturally, and since hign radiation doses will destroy cells rather than leave them viable in a mutated state, these effects are extremely difficult to detect.

No genetic effects due to radiation have ever been identified in man.

Genetic effects have been observed in animals exposed to high levels of radiation, but not for low exposures approximating natural background. The fear of creating a weird beast through radiation exposure is scientifically unfounded.

CONCLUSION Radiation affects the biological processes of cells in the tissues and organs of the body.

The severity of the effect is a result of the type and amount of radia-tion exposure as measured in rems, the radiosensitivity of the tissues which are exposed, how vital the exposed organs are to body functions, the age and health of the exposed individual, as well as other factors not enumerated herein. These effects may manifest themelves as somatic effects which are easil.y recognized, latent or long-ter effects, or genetic and hereditary effects. Latent and hered-itary effects are difficult to identify because of other factors which contribute to any effects which might be observable.

l I

q 82 awracoucrton to nrat.ru rnysico acosoact <try 33-The quantitative relationship between half-life, 7, and decay constant. A, where N, is the number of radioa :tive atoms in existence at time i = 0. Since may be found by setting A/A. in equation (4.18) equal to }, and solving the equation for t. In this case, of course, the time is the half. life.

1. "" #*'a,*

A we have

== { = c,,

a A.

f4.21)

T=== - 693

,,1

,3 g,,a, dt.

(4.23)

A Ne.

#^

%*s expre sion, when integ.nted by parts, shows the value for the me n life Given that the decay comtant for '"Rn is 4.38 x 10-' per year, calculate of a radioisotope to be the half.1;fe for radium.

,a O'#

1 I

), T = 0.693 r

-r, v.

(4.24

}

A T

^T I

0.693 ff the expression for the decay comtant in terms of the half-life of the radio-XI IT~'

4,3g

isotope,

= 1580 years.

3, 0.693, Averere ILife T

Although the half. life of an isotope is a unique, reproducible characteristic is substituted into equation (4.22), the relatiomhip between the half-life and of that isotope, it is nevertheless a statistical property, and is valid only the mean life is found to be because of the very large number of atoms involved. (One microgram radium contains 2.79 x 10" atoms.) Any particular atom of a radioisotope may T

v

, y,43 7, (4,73) disintegrate at any time, from rero to infinity, after it is obse-ved. For some 0.693 applications, such as in the case of dosimetry ofinttrnally deposited radioiso.

topes (to be discussed in Chapter 6), it is convenient to use the average life of the tsdioisotope. De average life is dermed simply as the rum of the life-e Corte times of the individual atoms divided by th total number of atoms origina!'y Uranium-238 and its daughter "Th each contain about the same number present.

of atoms per gram; appro-imatzly 2.5 x 10". Deir half-lives. however, are The instantaneous disintegration rate of a quantity of radioiatope con-greatly difierent; *U has a half-life of 4.5 x 10' years while *n has a tainieg N atoms is AN. During the time interval between t and t + dt, the half-life of 24.1 days (or 6.63 x 10-* years). Dorium-234, therefore, is total number of disintegrations is ANdt. Each of the atoms that decayed decaying 6.8 x 10" times faster than "U. Another example of greatly during this interval, however, had existed for a total lifetime i since the begin-different rates ordecsy that may be cited is "S and "P.Dese two radioisotopes, ning of observation on them. The sum of the lifetimes, therefore, of all the which have about the same number of atoms per gram, have half-1.ves of atoms that deented during the time interval between t and i + dt, after having 87 and 14.3 days respectively. De radiophosphorous, therefore, is decaying surv!ved since time t = 0,is tANdt.De average life of the radioactive species, about 6 times faster than the "S. When radioisotopas are used, the radiations v, is are the center erinterest. In this context, therefore,i of a gram of"P is about equivalent to I g of **S in radioactivity, while 15 micromscrograms of"Th I

,,,,,, ' t A N dr*

(4.22) is about equivalent in activity to I g of *U. Obviously, therefore, when in-N.,

terest is centered on radioactivity, the gram is not a very useful unit of quantity. To be meaningful, the unit for quantity of radioactivity must be

l 84 INTRODtJCTION TO HE ALTH PHY9IC3 f

R A DIOACTIVITY I

1 based on activity. Such a unit is called the curic (symbolized by Ci) and is Muftiples of the curie that are frequently used are the kilocurie and the mer:

~

defined as follows:

j cvrie. These quantities are generally not abbreviated.

The curie is the activity of that quantity of radioactive materialin which j

Speellic A(tivity the number of disintegrations per second is 3.7 x 10" it should be emphasired that, although the curie is defined in terms of a Note that the curie, although used as a unit of quantity, does not mentim number of disintegrating atoms p r second, it is not a measure of rate of anything about the mass er volume of the radioactive materist in which ti" decay. The curie _/ta mccrure_caly orquentity of radioactive material. The specified number of disintegrations per recond occur. The concentration o a

phrase " disintegrations per second"as used in the definition of the curiels not radioactivity, or relationship between the mass of radioactive material ant the ectivity, is called the specific activ;ty. Specific activity is the number o' synonymous with number of particles ernitted by the radioactive isotope. In curies per unit mass or volume. The specific activity of a carrier free radmno the case of a simpie pure beta emitter, for example, I curie, or 3.7 x 10" tepe, that is, a radioisotope that is not mixed with any other iwtope of th-disintegrations per second, does in fact result in 3,7 x 10" beta particles per v.me element, may be calculated as follows:

• co If A is the d: cay constant in units of reciprocal seconds, then the number yo3u y,y of disintegrating atoms per second ameng an aggregation of Natoms is sirnrh F (?p disintegrations, 3 g L T.1173 v v second e

%g[

If the radioisotope under considention weighs 1 then, acco ding to equa-i) tion (4.20), the number of stoms is simp!y equal to T.1732 p.v 6.03 x 10" atoms / mote "M

\\

A g/ mote Fe. 4.12. CoMt.60 6 esy h wher* A is the atomic weight of the isotope. The ac ivity per unit time, there-a fore, is second. In the case of a more complex radioactive isotope, however, such as g

y y, A x 6.03 x 10" dis p

"Co, Fig. 4.12, each disintegrstion re' esses 1 beta particle and 2 g=mma A

secfg photons; the total number of rsdiations, therefore, it 3 x 3.7 x 10", or 11.1 x 10" per second per curie "Co. In the case of "K, Fig. 4.6, on the N"ation (4.26) gives the desired relationship between activity and weight of other hand,20% of the be*a decays are accompanied by a single quantum

"" /s tore; The unit for activity m the equation may be converted from of gamma radiation. The total number of emissions fredi 1 curie "K, there.

dmntegrations per second to curies by application of the fact that there am 7

3.7 x 10" dismtegrations per second per curie:

3.7 x 10* + 0.2 x 3.7 x 10" 4.44 x 10" p r see.

ggc,

, A x 6.03 x 10"/A dps/g For health physica, as well as for many other purposes, the curie is a very l

3.7 x 10* dps/cune,

large quantity of activity. Submu!tiples of the curie, as listed be!ow, therefore A curies are esed:

I SpeciSc activity - 1.63 x 10a (4.27)

I A gram I

1 millicurie (mC) = 10-8 G A

c

{

Note that the decay constant, A, in equation (4.27), muet be la reciprocal e

1 mic*ocurie (pCi) - 10d O M

seconds. Equation (4.27) may be rewritten in terms of half-life rather than I cacoeurie (nCi)

• O k I **"*'a nt.

/

4 A 1 picoeurie (pCi) = 10-25 GD

'J S.A.

1.63 x 10a 0.693 1.13 x 10" curies g4.28) x

1. V m.-

i e

e M

l

/

U.S. NUCLEAR REGULATORY COMMISSION Mv 1981 n

j gg

) OFFICE OF NUCLEAR REGU GUIDE

%,...c REGULATORY GUIDE 829 (Task OH 902 4)

INSTRUCTION CONCERNING RISKS FROM OCCUPATIONAL RADIATnN EXPOSURE A. INTRODUCTION Concerns about these biological effects have resulted in controls on doses to individual worlers and in efforts to Section 19.12 of 10 CFR Part 19," Notices, instructions control the collective dose (person-tems) to the workes and Reports to Workers; Inspections," requins that all population.

persons workingin or frequenting any portion of a restricted area be instructed in the health protection problems asso-NRC-licensed activities result in a significant traction of ciated with esposure to radioactive materials or radiation.

the total occupational radiation exposure in the United This guide describes the instruction that should be provided States. Regulatoly action has recently focused more atten-to the worker concerning biological risks frorn occupational tion on maintaining occupational radi tion caposure at radiation exposure. Additional guides are being or will be levels that are as low as is reasonably acLevable ( A1. ARA).

developed to address other aspects of radiation protection Radiation protection training for all workers who may be training.

expcaed to ionizing radiation is an essential comporient of any program designed to maintain exposure levels Al. ARA.

B. DISCUSSION A clear understanding of what is prevntly known about the biological risks aeociated with exposure to radiation mill It is generally accepted by the scientific cominunity that result in more effective radiation protection training and exposure to ionhing radiation can cause biological effects snould generate more interest on the part of the worker in that are harmful to the exposed organism. Triese effects are minin izing both individual and collective doset In addition, classified into three categor.es:

radiation workers hkve the right to whatever information on radiation risk is available to enable tlem to imke informed Somatic ff/ccis:

Effects occumng in the exposed decisions regarding thr acceptance ci these risks. lt is interded person that, in turn, may be dhided into two classes:

that workers who receive this instruction develop a healthy respect for the risks invoked rather than excessive fear or hompt efferts that are observable soon after a large indifference, or acute dose (e.g,100 rems' on more to the whole body in a few hours), and At the relatively low levels of occupational radiation exposure in the United States,it is difficult to demonstrate IWyed effect/ such as cancer that may occur years a relationship between exposure and effect. There is con-after exposure to radiation, siderable uncertainty and controversy regarding estirnates of radiation risk. In the appendix to this guide, a range of Centric Effects? Abnormalities that inay occur in the risk estimatts is provided (see Table I). Information on future children of exposed individuals and in subsequent radiation risk has been included from such sources as the generations.

1980 National Academy of Sciences' Report of the Committee on the Biological Effects of ionizing Radiation (liEIR 80).

Trratogenic Effects: Eifects that may be observed in the Internatmnal Commission on Radiological Protection children v ho were exposed dunng the fetal aid embryonic (ICRP) Publication 27 entitled *Troblems in Developic; an stages of development.

Index of flarm," the 1979 report of the science work group of the Interagency Task I'orce on the ficalth Effects of I tn the interriational System or 11 nits (SI lonizing Radiation, the 1977 report of the United Nations bs the s evsrt.100 rsms is equal to a snvert (Sd) the rem is repheed Scientific Committee on the Effects of Atomic Radiatiott 2

M se

, an nuemsp sed adch We Genetic effects escre&ng normat incidence base not been observed in any or th, studna of esposed humans.

the bibliography to the appendix).

l U$NnC ff cGULATOR v GtJtDES comments shoulft be ser*t to the secretary of the 1 ommission, U.S.

feuclear Regulator ) Comrussion. Wasnington, D.C 20S5s, Regulatory ouries are issued to descr6be and ande avaltable to the AtteWon: Ducheleng a% Service manck pu Diac rnethods,acceptaoh to the NHC sta t 09 em ple me n ting r

specifec parts of tte commission's regulateons, to de'ineaie tech-The Dukes are issued in the polic wing ten broad dmslons:

ruques used by the statt in evaluating spec 8fic problems or posto-

( _

them is not required. Methods ano sosutions d4f ferent from the be set lated accidents or to wide guidance to applicants. teagulatory 1 Power Reartbr$

6. Produc ts Guides ave nol substitutes fod rMala+ ions, and compliance with

2. Aesearch and Test neactors

? Transpo*tation

3. f uels and Materials F acitaties

a. Oc.cupational Hssith i

out an tne gueries wul t>e acceptable 6f they provide a bases for the 4, f'noronments' and %stmg

9. Antnrue' and F anuc641 ~4e,6ew

+:

• ^

findings reconsste to the 8siuance or continuance of a permit or S. Materials anG Plant Prof %ction so. General

{

bcense by the c.umtr ission.

I Ce pies of iswed guides rnay be purchased at the current Govesnment This guide was issued af+er coe Oceration of comments received from Printmg Of fer.e perce, A suusc'inteon service for futuee go,o es en pg e-l the pubuc. Comments and suggestions for smorovements in these ci4c civisions is available throug' the Government Ptiviterg Of tsce.

9 aides s'e encourebe's at all 1.mes, and g.nices wm be revnet as (Mormahun on e sactription se'vne anc current GPG pkes may 40crorredte, to accommocate comments and to reflect new informa.

be ortamed t v wrHing the U.S Nucle ar Hegulatory Commissmeg i

16pn or o r perienc e.

W a sh mq1 on, O C. 2 cts ( A t ten tion : dud!getions ".,Mes Managee.

C REGULATORY POSITION sessions. Each individual should be given an opportunity to ask questions and should be asked to acknowledgein wTiting Strong management support is considered essential to an that the instruction has been retened and understood.

k adequa'e radiation protection training prograrn. Instruction

/

to woners performed in compliance with j l9,12 0f l0 CF R D. IMPLEMENTATION Part 19 sh >uld be given prior to assignrnent to work in a restricted area and periodically thereafter, in providing The purpore of this section is to provide information to instruction concerning health protection problems associate d applicants regarding the NRC stafI's plans for usms this with esposure to radiation, all workers, including those in terulatory guide, supervisory roles, should be given specific instruction on the risk of biolog3 cal effects resulting from exposure to Except in those cases in which an applicant or licensee rid ta tion, proposes an acceptable alternative method for complying with specified portions of the Commission's terulations, the The instruction should be presented both orally and in methods described in this guide will be used in the evalua-printed form to all affected workers and supervisors. It should tion of the training program for al) individuals working in include the information provided in the appendix to this or frequenting any portion of a restricted area and for all guide ' The information should be discuswd during training supuvisory personnel after December 15,1981, 3

/"

Copies of the er nots to th unde are evausdie et the curren Governners FeintinsErnceyru,is Inch may be odianned by writtrg, vided in this guide on or before December 15,1981, the w

Ios s s*, ErEn Io'nNbhcluYdaieNaN."hNrNEz*is not pertinent portions of the application or the licensee's perfor-copyrist ted. and Comrntsalim approvei ta nos required to reproduce it.

trance will be evaluated on the basis of this guide,

)

l B.Y.U. DEPADOFAt l

l l

l l

l l

8 29-2

U S. NUCLEAR REGULATORY COMMISSION APPENDlx TO REGULATORY GUIDE 8.29 INSTRUCTION CONCERNING RISKS FROM OCCUSATIONAL RADI ATION EXPOSURE

(

1his instructional material is intended to proside the The biolopcal effects that are known to occur ef ter 2

user with the Nst available information concernint what is exposute to hyh doses (hundreds of rems ) of radiation are currently known about the health risks from expoture to Jiscuued early in the dacument; discus 6cns of the esti-nonitinE radiation ' A question and answer fortnat has been

. mated risks frorn the low occupational dose (<5 ten,s per uwd. The questions were developed by the NRC staff it, year) follow. It it intended that this information will help consultation with workers, union repre se ntatives, and develop an attitude of healthy respect for the ruks asso-heensee representatnes experienced in radiation protection ciated with radiaJon, rather than unnecessary fear or lack training Rnk estimatts base been compiled from numerous of concern, Additional ruidance is being or will be devel-sounes generauy recognized as rehable. A bibbography is ope d concerning other topics in radiation protection l

indudtd for the user interested in further study, training 1.

What is meant by rid ?

amme that some health effects do occur at the lower expo-sure levelt Risi can be defmed in reneral as tir probaMhty klance)

.L What (s meant by prompt effects, delayed effects, and of injury,. illness, or death resulting from some activity,

""## 'll##UI flowever, the perception of risk is affected by how the individual views its probability and its severity. The intent

a. Prompt effrets are observable mortly afterreceiving of this document is to provide estimates of and explain the a very large dose in a short period of time. For example, a basis for possible risk of irduty, iunen or death teruttinE whole body" dose of 450 rerns (90 times the annual dose from occupational radtation exposure,(See Questions 9 and limit for routine occupational exposure) in an hout to an 10 fot estimates of radiation risk and comparisons with averate adult will cane vomiting and dianhea within a few other types of risk.)

hours, Inn of hair, feser, and weight lou within a few weeks, and about a 50 percent chance of death within

~

What are the pouible heahh effects of exprnure to g,0 days vsthout medwal tscatment.

rudtarion ?

b. Delayed effects such as cancer rnaj occur years Snroe of the health effects that exposure to radiation after exposure to radiation may cause are cancer (includtny leukemia), turth defects in

c. Genetic effects c.an occur when there is radiation the future children of exposed parents, and cataracts.

6 mW i

& TW die m 6 y These effects (with the exception of renetic effects) have as birth defects or other conditions in the future children of been observed in studies of medical radiologists, suanium the exposed individual and succeeding gener.itions, as miners, radium workers, and radiotherapy patients who gg g

have received large doses of radiation Studies of people renetic effects clearly caused by radotion hase not been exposed to radiation from atomic weapons have ah observed in human populations etposed to radiation,it has prosided data on radiation effects In addition, radiation been observed, howevu, that radiation can change the effects ciudies with laboratory animals have provided a s6 & of the hurnan body. Thus, the pouibility large body of data on radution-irsduced health effects, gg ggg g

gg g g, indudint Fenetu effecto doses even though no direct evidence exists as ytt.

The obsers ations and studies nrntioned abose, however, 4,

In worAcr protterion, which efferturre of most corrern involve levels of radiation cuposure that are much higher to the NRC?

(hundreds of rems) than those permitted occupationally today ( <5 rems per year) Although studies have not shown a The rnain concern to the NRCis the delayed incidente cause effect relationship tsetween heCth effects and current of cancer.The chance of dela>vd cancerisbebevedtodepend levch of occupational radicion exponre, it is prudent to 3 Cataracts differ frutn other tediation efferb in that a certain level of dme to the lens of the tre (=200 rems)is segered before I lonomt redation consem of energs or small rarticles such as the y are otwerved

('

w.amrua. beta, or alr4 i radiaton emstted from rednachve materuls g hch, when s N eted b IMng imue, can cause chemini and

$ hy sw al damarr a D h moetent to dutinruish between whole body and paeml-bud) earw*e.106 rems to the wbde t ody wul have swe effect

• Ibe tem it the untt of measure for to Ntion dme and relates to than 100 to a hand I w ensmple, capoone of a hand woutJ alitet a the bml,ynsi effect of the S ubed f adumm.

smatt frac tson of IIe t'one marrow and a bnuted parbon of the abn.

6293

on how much raduition exposure a person gets; therefore, One theory is that radiation can damne chromosomes in a every rea onable effort should be made to keep exposures cell, and the cell i, then directed along abnormal growth lo w.

pa tt e rn s. Another is that radiation reduces the body's normal resistance to existing viruses which can then multiply Immediate or prompt effects are very urdikely since and damage cells. A third is that radiation activates an larFe exposures would normally occur only if there were a existing vtms in the body which then attacks normal serious radiation accident. Accident rates in the radiation ceus causing them to grow rapidly.

industry have beer low, and ortly a few aaidents have resulte d in ex posures ex ceeding the legal timits. The probabil-What is known is that, in groups of highly caposed ity of serious genetic effects in the future children of people, a higher than normalincidence of cancer is obsened.

S workers is estimated in the BEIR repor*, based on animal liigher than normal rates of cancer can also be Produced in studies, at less than one-third that of delayed cancer (5-65 laboratory animals by high levels of radiation. An increased genetic effects per million rems compared to If etSO incidence of cancer has not been demonstrated at radiation cancer cues). A clearer understanding of the cause<ffect levels below the NRClimitt relationship between radiation and human genetic effects will not be possible until additional research studies are 7.

if I receive a radiatica dese, does that mean I am completed, certain to get cancer?

I khat is 14e difference between acute and chronic Not at all. Everyone gets a radiation dose every day (see exposure?

Question 25), but most people do not ret cancer. Even with doses of radiation far abose legal tiraits, most individuals Acute radiation exposure, which causes prompt effects wdl experience no delayed consequences. There is evidence and rnay also cause delayed effects,usually refers to a large that some radiation damage can be repaired. The danger dose of radiation received in a short period of time; for frorn radiation is much hke the danger from ciprette smoke.

example,450 terrs received within r few hours orless. The Only a fraction of the people who breathe cigarette smoke effects of acute exposures are well known from studies of get lung cancer, but there is good evidence that smoking radiotherapy patients, some of whom received whole-body increases a person's chances of getting lung carcer. Similarly, doses; atomic bomb victims; and the few accidents that there is evidence that the larger the radiation dose, the ftave occurred in the early days of atomic weapons and larger rhe increase in a person's chances of getting cancer, teactor development, industrial radiography, and nuclear fuel processing. There have been few occupationalincidents Radiation is hie most substances that cause cancer in that have resulted in large exposures. NRC data indicate that the effects can be seen clearly only at high doses.

that, on the average, I accidental overexposure in which Estimates of the risks of cancer at low levels of exposure any acute symptoms are observed occurs each year. Most are derived from data available for exposures at high dow of these occur in industrialradiography ard involve exposures levels and I igh dose rates Genetally, for radiation protection of the hands rather than the whole body.

purposes these estimates are made using the linear model (Cune 1 in Figure 1). We have data on health effects at high Chroruc e x posure, widch may esuse delayed effects but doses as shown by the sohd line in Figure 1. Below abour not prompt effects, refers to small doses received repeatedly 100 rems, studies have not been able to accurately measure over long time periods; for example,20-100 mrem (a the rid, primarily because of the smallnumhrs of exposed mrem is ons-thousandth of a rem) per week every week for people and t<cause the effect is small compared to d fferences several years. Concern with occupational radiation risk is in the normal incidence from year to year and place to place.

primanly focused on chronic exposure te low leveh of Most scientists beheve that there is some degree of risk no radiation over long time periods.

matter how small the dose (Cunes 1 and 2). Some seien:ists behese that the rid drops off to zern st som ivw duw 6.

How does radiation case cancer?

(Curve 3), the threshold effect A few believe that nsklevels off r.o that even very small doses imply a significant risk flow radiation causes cancer is not well understood.

(Curve 4). The majority of scientists today endorse either It is impossible to tell whether a given cancer was caused by the 1 meat model (Curve 1) or the Unear quadratic model radiation or by some othe, of the many apparent causes.

(Curve 2). The NRC endorses the linear model (Cune 1),

flowever, most daeases are caused by the interaction of which shou the number of effects decreasing as the dose several factors. General physical condition, inhented traits, decreases, for radiation pro'ection pt.r;;oses.

age, ser, and exposure to other cancer-causing agents sach as agarette sinole are a few possible contributing factors It is prudent to assume that smaller doses have soine chance of causing cancer. Uus is as true for ratural cancer-causers such as sunlight and natural radiation as it is for those that are man made such as ciprette snuke, smog, and s' The Ntma d Aca Jerrn ot &sences estabished a cr memttee on man-made rad:ation. As even vety small doses may enf ad the Lescal irretts of toming Ra&ahan (BIIH) whme IHo sW small mk, it follows that rio dose should bc taken regnt un the enects on rottantes or earmre to tow newts or without a reason. Thus, a principle of raalation protection (oruimg fadahon pr ovwf es m uch of thr hc k groun d for t hts gme.

ts to do rnore than metely meet the alloud regtdatory

8. 2 %1

h?.

E ig@S xm

[@

$u z4 9.

m

&O E

~ /s /

u.

ta

/

s 4

/.

/

2 4

/

I

/

/-

/3

/

J' l

l

(

100 DOSE (FIEMS)

Figure 1. Some proposed rnodels for how the effects of radiation vary with doses at low levels.'

r

._ limits; doses should te kept as low as is reasonably achievable 1000 draws. We can say that if you receive a radiation dose,

'(ALARAK you will have increased your ch'arices of eventually developing cancer it is assumed that the mere radiation exposure you We don't know exactly what the chances are of getting get, the more you increase your chances of cancer, cancer from a low 4evel radiation dose, but we can make

+

estimates based on extensive scientific knowledge. The estirnates ot radiation risks are at least as reliable as estimates Not all workersincur the same level of risk. The radia-for the effects from any chemical hazard. Being expased tion risk incurred by a worker depends on the amount of

- to typical occupational raciation doses is taking a chance, dose received. Under the linear model explained above, a but that chance is reasonably well understood.

worker who receives 5 rems in a year incurs 10 times as rnuch risk as anather wcsker (the same age) who receives It is important to understand the probabihty factors only 0.5 rem. The risk depends not only on the amount of here. A similar question would be: If you select cne card dose, but also on the age of the worker at the tirne the dose is from e full deck,' will you get the ace of spades? This received. This age difference is due,in part, to the fact that question cannot be answered with a simple yes or no. The a yoting worker has more time to live than an older worker, best answer is that your chances are 1 in 52. Ilowner,if and the risk is believed to depend on the number of years 1000 people caeh select one card from full decks, we can of hfe following the dow. The more years left, the larger predict that about '20 of them will get an ace of spades, the risk. It should be clear that, even within the regulatory

(

spades, but there is no way that we can predict which persons Each person wl!! have 1 chance in 52 of drawing the ace of dose limits, the risk may vary a great deal from one worker to another. Fertunately, t,nly a very few workers receive will get the right card. The issue is further compheated by the doses near 5 rems per year; as pointed out in the answer to fact that in I drawing by 1000 people, we might get on.ly Question 19, the average annual dose for all radiation 15 successes and in another perhaps 25 correct cards in workers is less than 0.5 rern.

8.29 5 e

.2 w~

-r, IABLEI A reasonable comparisen intoh es exposure to th. 2.Ws rays. Frequen short exposures prosiJe tinie for the v ^ %

s repair. An acute exposure to the sun can result in p:141 Istimates of Excess Cancer in-idence imm Esposure to Loolesel Radiation burning, und excesne es posure has been show n to a a skin cancer. Ilowever, whether exposure to the sun's ro s is wt Number of Adjitionale Cancers Estimated short term or spread over time, some of the injury.

S une to Occur in i Mdlion Peopic Af ter i

repaired and raay eventually result in skin cancer.

Luposure of f ach to 1 Rem of Radiation The effect upon a group of workers occupatv ' dY of exposed to radiation may be an increased inciden 4 b

cancer over and abose the number of cancers that mid BEIR,1980 1604 50 normally be expected in that poup. Each exposed indrdal ICRP,1977 200 has an increased probabihty of iricurring subsequent car wr.

We can wy that if 10,000 workers each receive an aju.r.nal UNSCE A R, ! 977 150-350 I rem in a year, that group is more likely la have a M8er incidence of canar than 10,000 people who do not receive the additional radiation. An estimate of the intimed prot abthty of caneer from low radiation doses d(hvered to u.ht.onal meane above the noemat incidente ut cnnc,,,

e large groupa is one measure of occupational risk ard a bAtt three grosmi estimated emature deaths tro.n radiatmn.

induced cancers. the Amerkan bncet Society has recenuy stated ducursed in Question 9.

that only about unehit et all cantef cases are fatal. Thus, to estituals incidence of can<ct, the pubhard nuin* ert were mhtty hed 8.

What swups of expert scienthts hcve studied the ruk br t Note that the three groups are sa <tose agreement on the ruk et radastion4nduced cancet, from exposunt to radiation?

. rem, we could estimate that thret would develor cancer I

In 1956., the National Academy of Sciences estah! ded advisory committees to consider radiation rhks. The first of because of that exposure, although the actual nurnber could be more or less than three.

these was the Advisory Committee on the Diclogical i ffects of Atomic Radiations (BEAR) and more recently it was tenamed the Advisory Committee on the Biological i f fects The Anierican Camer Societ; tus temrted that approti-of lonizing Radiation (BELR). These co m tnit te e, have mately 25 percent of all adults in the 20- to tis year age-bracket will develop cancer at some time from all ponible periodically renewed the estens2Ve rescatch being done on the health effects of ioniring radiation and have published causes such as smoking, food, alcohol, drugs, air pollutants, estimates of the risk of cancer (rorn exposure to rad:ation and natural background radiation. Thus in any group of 10,000 warkers not exposed to radiation on the job, we can l

(1972 and 1%0 BEIR reports). The lehrnational Cornmission on Radiological Protecti~n (ICRP)and the National council espect at out 2,500 to develop cancer. If this entire poup of 10,000 workers were to receive an occupational radation on Radiation Protection and Measurement (NCRP)are two dose of I rem each, we could estimate that three additional other groups of scientists who have studied radiation effects and pub!ished risk estimates (ICRP Publication 26,1977),

cases might occur which would give a total of about 2,503.

These two groups have no government affihation. In lhis means that a brem dow to each of 10,000 workers might increase the cancer rate from 25 percent to 25.03 addition, the United Nations estab'shed an independent a

study group that published an extensive report in 1977, percent, an increase of about 3 hundredths of one percent.

including estirrates of cancer risk from ionizing radiation As en individual.if your cumulative occupational radia-(UNSCE AR, I977y tion dose is I rem, your chances of eventually developing cancer durmg your entire lifetime may have increased from Several individual resarch groups or scientists un as 25 percent to 25.03 percent. If your lifetime occupational Ahec Stewart, LS. Gilbert, T.F. Mancuso, T.W. Amfer50n-dose is 10 rems we could estimate a 25.3 percent chance of to name a few, have pubbshed studies concerning low level radistion effects. The bibhography to this appenda italudes developing cancer. thing a simple linear model, a lifetime dose of 100 rems may have increated your chances of several articles for the reader who wishes to do further cancer from 25 to 28 percent.

study. The REIR-80 report includes analysis of the work of many independent researchers.

The normal chance of developing cancer if you receise no occupational radiation dose is about equal to your chance 9.

What ore the estimates of the ruk of cancerfrom radur.

Of Fetting any spade on a single draw frorn a full deck of rio<t czposure?

playing cards, which is one chance out of four. The addi-tional chance of develoring cancer from an occupational The cancer risk est. mates (developed by the orpnim tions identified in Question 8) are presented in g Ale 1.

exp sure of I rem is less than your charees of drawirm an ace from a full deck of cards three timesin a row.

}

(

/

l In an ef fort to explain the signifmame of thne nt t"We5 Sinca cancer resulting from emnare to radiation usuall3 we wi!] use an approximate average of 300 eue,s oncer occurs 5 to 25 years af ter the expmure and smce not all cases per milhon people, each exposed to i rera of innatng cancers are fatal, another useful measure of r +k is years of radiation If in a group of 10.000 workers ca h rne,ves gW

1

$te expectancy lost on the averare from a radiation indaced TAllt E 2 cancer, it has been estimated in several studies that the

(

escrare loss of bfe expectancy from exposure to radiatmn is I.stimated t oss of 1.ife l'apectancy from lienhh Risks' i

about I day per tem of exporure. In other words, a person exposed to I rern of radiation may, on the averate, lose I day of life 1he words "on the average" are important, Estimates of Days of however, because the person who gets cancer from radiation Life Empectancy lost.

may lose sescral years oflife expectanc) while his comorkers Ilealth Risk Average suf fer no loss.1he ICRP estims',cd that the averne nun ber of years of jlife lost from fatal industrial accidents is 30 Smoking 20 citarettes/ds>

2370 (6.5 ) cars) while the averate number of pars c,f life lost from a fatal Omt seight (by 207) 935 (2.7 yents) radiation-induced cancer is 10, The shorter loss of hic All accidents comlined 435 (1.2 ) ears) expectancy is due to the dela)ed onset of cancer.

Auto accidents 200 Alcohol consumption (U.S averare) 130 It is important to realire that these risk numbers are llome accidents 95 only estimates Many difficulties are involved in designing ritowning 41 research studies that can accurately measure the small Natural background radiation, h

increases in cancer cases due to low exposures fo radiation calculated as compared to the normal rate of cancer. There is still Medical diagnoshe x-rays (U S.

6 uncertainty and a great deal of controversy with regard to averate), calculated estimates of radiation risk. The riumbers used here result All catastrophes (earthquake, e tc.)

3.5 from studies involving ldgh doses and high dose rates, arid I rem occupational radiation dose, I

they may not apply to doses at the lower occupational calculated (industry average for levels of exposure. The NRC and other agencies both in the the higher dose job categories is l!nited States and abroad are cantinuing eatensive hnerange 0 65 rem /yr) research pror.rarns on radiation risk.

I rem /yr for 30 years, calculated 30 Some memters of the National Academy of Sciences 13LIR Advisory Committee and others fccithat risk estimates Ada ed trem Cotan and tv "A Catalorve or luskarnes/th a

in Table 1 are higher than would actually occur and represent Payscs, Eut. 36 hne is'r9.

an upper limit on the risk. Other scientists believe that the estimates are ;ow and that the risk could be higher.

A second useful comparixm is to look at estimates of flowever, these estimates are considered by the NRC staff the averare number of days Lf life expectancy lost from to be the best available that the worker can uv to make an exposure to radiation and from commonindustrial accidents informed d' cision concerning acceptance of the risks asso-at rviiation related facilitws and to compare this number ciated with exposure to radiation. A worker who decides to with days lost from other occupational accidents. Table 3 accept this sin shouh' make every effort to keep exposure shows averare days of lift carectancy lost as a result of to radution ALARA to avoid unrucessary sisk. '!he worber.

fatal work related accidents. Note that the data for occupa-af ter all, has the first hne responsiMhty for protectmg himwlf tions other than radstion related do not include death risks from radation hazards.

from other pcx sible hatards such as eaposure to toxicchem-icals, du45, or unusud tamperatures. Note also that the 10.

flow can we compare radiariori rist to other Ainds of unlikely occupational exposure at 5 rems per year for 50 hralth risks?

years, the masirnum allowable risk level, m,y result in a risk comparable to the averare risks in mining and heavy Perhaps the most useful unit for comparison among construction.

health riska is ll.c nerage number c)f dayr of life expntar.cy lost per unit of exposure to each particular health risk.

Industrial accident rates m the nuclear industry and Estimates are calculated by hvaking at a larfe numbes of per-re!ated occupational areas have been relatively low duru g sons, recordmg the age when death occurs f rom apparert the entire history of the industry (see Table 4). This is causes, and estimating the number of days of life lost as a beheved to be due to the early and continuing emphasis on result of these casly deaths The total number of days of tight s fety controls lhe relative safety of various occupa-Lfe lost is theo averard over the total group observed.

tional areas can be seen by comparing the probabihty of death by accident per 10,000 workers over a 40 year Seseral studies have compared the projectedloss of hfe working lifetime. lhese figures do not include death expectancy resultmg from esposure to radiation with other from pouible causes such as enposure to toxic chemicals or health risks. Some representative nambers are presented in radiation.

Tabic 2.

]1, Orn a worker become sterile or.!mpotentfrom occupa-These ostinutes indicate that the health risks from occu-tional radiation exporutv7 l

p.tional radiation expomic are strealler than the risks asso-i cisted with many other eventsor activities we encounter and Ohretvation of radiation therapy patients who receive localised exposures unually spread over a few weeks. has accept m normal day to-day actmties_

8 29-7

TABLE 3 shown that a dme of 100 800 rems to the gonads can produce permaner.t stenuty in males or females (an acute htimsted Losa ml Life Expectancy from industriallf arards' whole-body dose of thi magnitude would probably result in death within 60 dayst An acute dose of 20 rems to the testes can result in a rneacuiable but temporary reduction in Estimates of Days of sperm count. Such high exrosures on the job could result Life Expectancy Lost, only from serious and unl'kely radiation accidents. Although Industty Type Ascrage high doses of radiation can affect fertility, they have no eflect on the ability to fugction sexuaUy. likewise, exposure All industry 74 to permitted occupationailevels of radiation has no oberved Trade 30 effect on fertility and a:So has no effect on the ability to Manufacturmg 43 function sexuaUy.

Service 47 Govern ment 55 12.

What are the NRC external radiation dose limirs?

Transportation and utihties 164 Agriculture 277 l'ederal regulation; c urrently line t crcupational e xternal Cc istruction 302 whole-body radiation d ne to 1% rems in any cilendar Mining and quarrying 328 quarter or specified 3 ;ti mth period, llowever, when there Radiation accidents, decth from s1 is documented evidence that a worker's previous occupa-exposure tional dose is low enough, a heensee may permit a dose of Radiation dose of 0.63 rem /yr 20 up to 3 rems per quarter s 12 rems per year, Tht. accumulated (industry average) for 30 yents, dose may not esceed 54 N. I 8) rems

• where Nis the person's calculated age in years, i.e., the Ufe'ime occupational dose may not Radiation dose of 5 rerns/yr for 250 exceed an average off 5 rems for each year above the age 50 ) cars of 18.

Industrial accidents at nuclear 58 facihtses (nonradia tion)

An additional whole-body dose of approximately 5 rems per year is permitted from internal exposure. (See Question 28.)

• Adapted imm Cohen and f.ee, **A Catalogue of Risk," #calth Phpes VrA 36, June 1979, and World Itealth Orpnlastion, Heg/tn 13.

h. hat (s meant b y J y.j gj.p Imphcations of NucJear Poner SWruction. December 1975.

In addition to i ding an upper limit on a person's permissible radiatior sure, the NRC also requires that its licensees maintr.

apational exposures as far below the Hmit as is reason v achievable ( ALARA). This means TABLE 4 that every activity a auclear facility involving exposure to radiation should be. planned so as to minimize unnecessary probabihty of Accidental Death by Type of Occupation

• cxposure to individad workers and also to the wcirker popula tion. A job that involves exposure to radiation should be scheduled mly when it is clear that the benefit Number of Accidental justifies the risks assumed. All design, construction, and Deaths fet 10,000 operating procedures :hould be reviewed with the objective Occupation Workers for 40 Years of reducing unnecessary esposures.

Mining 252 14.

lias the ALAR lI concept been styptied if, instead of Construction 228 traching dose lh:ths during the f&st week of a quarter, Agricultute 216 the worAer's det. is spreadout over the wbie quarter?

Transportation and pud 116 1

utihties No. For radiatPm protection purposes, the risk of All industries 56 cancer from low dosedis assumed to be proportional to the Government 44 amount of exposure, not.he rate at which it is received.

Nuclear industry (1975 data 40 Thus it is awumed tht spreading the dose out over time or excluding construction) over larger numbers j f people does not reduce the overall Manufacturing 36 risit The A LARA conept has been foUowed ora!y whci the Services 28 individual and couecive doses are reduced by reducing the Wholesale and trade 24 time of exposure qr decressing radiation levets in the "The NRC has pu had a proposed rule change for public comment that would ch 'ninste the s(N 18) formula Th;s s*roposal Le currently under consiJetation by a task force reviewing aH of in Cf R

' Adapted from Nationet Sarrty Council, A rcidmr Farre,1979; Part 20. RMent EPA giidance recommands etmunating the $(N 18)

/

,i and Atomic Energy Commisspen. Operwriang1 Accideur and Rahe-rovmeda. It adopad,stie maximum allowed annual dose wm be s rems i

dos f spomre Expenence, w ASil I l92,1975.

rather than 12.

8.29-8 L

--~.. -. ---

fndnidual and solktfite dows are seduted t) reducing ths tanur f or the worker population. At best, the total thk 14rne of cipmure or decresunt radation leieb b the remains the s,imt and it rna) een be increased. lhe only w orlint en@onrnent, way to reduce the risk is to reduce ihe collecine dose,that can be dota only by seducing the radiation lesch, the lh What u meerrt by collectivt dvsr and uh.s should it woding tsmes, or both.

be rnair,ta;ned ALA R A ?

I7 Why doesn't the b'RCimpost collectue de:c hmits?

Nuclear industry acthitie:es pine an increasint runi5et of peoph to occunational radiation in addition to the sa fia-Compliarne with indi'4 dual dose limits can be achiend hun doser, they recebe from natural t.ackground radiation simply by usmr estra workers However,somphance mth a and inedical radiation esposures lhe collectise occupational collecthe due hmit (5 urn as 100 person tems per year for a dow (person remd is the sum of all occupational radiation bc e n*:c ) would require trauction of r4.diation levels.

estwure sectned by all the workers in an entire worker wo:Linr tunes, or both. but there att many problems popultition. l or enstnple,1f 100 w orkers tach receive 2 rems, associated *sth setting appropriate collective dose limits.

the indnidual dose is 2 rems and the collecthe dow is 200 perr.on-rems lhe total additional tid of carner and renetic

! or caample, s e raight consider appl)ing a smrle effects in an esposed population is 6uumed to depend on collector dow hmit te alllicensecs,lhe selection of such a the collectne d ac, collecthe dose hmir would be altnost impossible because of the wide tariations in collecthe dosrs aruont bcthwes.

It shound be rmted that, frorn the viewpoint of rid to A pocer reactor could reasonably be espected to hate an a total population,it h the courctne dose that must be con-aserare annpal (ollective dose of several hundred person-trolled, l'or a rnen collectise dose, the number of health rems. Iloweser, a small industrial r:diography brensee effects is assamed to be the same even if a larger number of could scry well hase t collective dose of only a, few perwn-people shs e the dose.1hu. fore, spreading the done out rems in a ycar.

truy reduce the individual tid Aut not that of the populatiort IAen choosing a collecthe dose litnit for a rtoup of h

I fiorts shooto be made to inaintain the collectne dose similar licenwes would be almost as diffnult. Radiopat y A LARA so as not su unnecemrily increase the c verall popula-Inenwes as a poup had an averare collective dow in 1977 tien inci4 tcc of d neer and renetic ef fects.

of 9 person rtms Ilowever, the smallest co!!cttive' dose for a radiogr&phy licenwe was less than 1 penorerem, and the It is the sne of ca rm wotAres a good wws to erdure ruAs?

largest was 401 person-rern There is a "yes" answer to this question and a "no"

$cthnt a reasonable collective dow Smit for eachindi ans cr. l'or a ghen job invoMnr caposure to raiiation, sidual hcenwr would also be stry difheuh. It would the more prc;1e who share the w crk,:he lower the astrate require a record of all past coDecthe doses on wttich to base dow to an indhidual. The lower the dose, the lower the such hmits. Settitr an annual collecthe dose hmit would risk. So, los yo" as an indindual, the answ er Ls "> cs."

then amouta lo an attempt io ptedict a reasonable c ollecthe doa fcr each futute year lo order to do this,it would be Itut how aba j the risk to the entirepoupof workers?

necemry to be able to predict changes in e.ch licensed Under assumptions uwd by the NRClot purpows of protec-activity that would increase or decicaw the collectise dose, tmn, the tid of ca l er deper h on the total amount of k addition, annual sollectivt doses tary signifscantly from idiation energy absoibed b; huinan tissur, not on the year to ) ear accordmr to the kird and amount of rnainte-riumber of ri)ple to whom this tinue belongs. Thertfore,if nance required, which cannot generally be predicted in 30 workers are und to do a job instead of 10, and if both advarne, l'ollowing al' such changes and trvising limits up poups ret the same collectne dose (person-rems), the total and dow n w ould be very dif f acnit if not imponible. Ilowes er, canter rnk is 'he same, and nothing wu rained for the theu efforts would be necessary if a collective dose limit pour by usir.J 30 morters l' tom this sie apuint the answer wetc to be reawnable and nelp minimite dows and rids, is "n o. " 1he tid was not reduced but simpl) spre nd around amorr a larper number of persons.

18. Ilow are rodsation dose hmits estabhshed?

i j

Unfortunately,spreadmr the tid around often results l he NRC estal"ishes occupational radiation dose in a larrer collecthe dose for the job Workers are esposed limits based on ruidance to Irede:al agencies from the

(

as they approach a job, while they are retting oriented to I nitronmental Protection Agency (l.PA) and, in addition, do thz lcl, and as they withdraw from the job. The dow considen NCRP and ICRP recommendations. Scientific rectned dortnr these atoons is called nonproductne, if resiews of researsh data on biolorical effects such as the everal crew chantes are required, the nonpoductne dose ist lR report are also considered.

can become vt r> le.;e. Thus it can be seen that the use of estra worlea may actually mcreaw the total occuptional l'on example, recM il'A ruidance recommended i

dose and the resullmt collective tids that the annual whole bog dnse hrnit be established at 5 rems per > car and mdicated that exposun, year after ) ear, lhe uw of extra workers to cornply with NRC dose to $ rerns would imohe a tid to a worker comparable to hmitri is not the w a) to reduce tbc risk of radiation in

/

the aserage tids incurred tg workers in the hit.her tid jobs th29 9 l

. - - - - -, -,. = -, -... - - - _ - - -,. _.

suth as ruimnt in f an !c w worber4 ner feath such a hmit, th re n %ryer, I nu edmr a limit don not irnply that you much Icu year af ter ) ear, and the raks aaouated wqh have suffered an mjury. A rood comparnon as with the ac tual e sp nutes arr, considered s y the I PA to t e cony aratle hghwas spred lomt, whhh is selected to lumt wident ink to it.c ufer job cattrones. A Swm per-) cat hnot woulJ and stiu aUow you to ret somewhere. If you drne at 75 allow oassionW high dose jotu to tv done without esenne mpF, you mcrease your risk of an auto aniJent to lesels tuk.

that are not conudered aucplable by the people *ho set speed hmits, e cn though you may not actually h;ise an 19.

Inst ere the typitof ru.tkrtise'shsra rectintf l'y wrkers ?

acciictit. If a worktt's tahation c se terratedly cuerds 3 rrms in a quarter, the risk of healti ef fet ts u>ulJ eventually fht NitC requires that certain categories of hcenscrs mcrease to a level that is riot tonsi'ered acceptable to the rt port data on annual worker doses ari doses for all workers NRC. I n 6cedmg an N RC protec tio, limit does not rnean who leave employment with licenseess Ihte were received that any a herw health effects are rs ing to occur, it does on the occupational dosesin 1977 of approstmately 100,000 mean that a licenset's safety propam has failed in some workces in power reactors, industrial radiopaphy, fuel respect and thrat the NRC and the hcensee should 'nststicate prouir.g snd fabrication facdifics, and mandactarint, to male save the problems are corrected.

and diaribution facdities. Of this total c.roJp, B$ percent secched an annual dose et less than I tem; 95 percent If an meresposure occurs,the regulations prohibit any received less than 2 sems, fewer than 1 percent etcccJed additional occupational esposure to that person durarer the

$ rems in i yel The average annual dosc of those workers remainder of the calendar quarterin which the oserenposure who were monitored and had measurable exposurcs was occurred. The licensee is required to fde an overczposute A,ut 0 65 rem. A study completed by the I PA, using repon ta the Nkr and rnay posubly be subject to a fine, 19F cuposure data for 1,260,000 workets, indicateu that just as you are subject to a traffic fme for ent:erding the the Wrare annual dose for all wcrkers who recched a speed limit. In both cases, the imes and,in some serious or rne. urable dos,e was 0.34 re rn.

repetidve cases, ira pension of licent.c are intended to entourage effets to operate within the limitt The tafest lable $ hsts average occuptiotal en tusures for workers limits would be 0 rnph and O rem per quarter. But then we (persor,a who had measucalde exposure above backpound w ouldn't ret an> where.

Irvels) in sadous occupations, based on the 1975 data.

21.

Why do wmr faciltries establish administrutwe inmits i%DLE$

that are below the NRClimits?

U.S. Onupational Laposure Estimates

• 1hese are two reasons. first, the NRCreguistions state that b6erisees should kerp esposures to radiation ALAR A.

Aterate Whole-liy requiring specific approval for werkte doses in excess of Occupational Hody Dose Colleethe Dose set lesels, more caref ul risk bene 0t analysis can tw made as Subgroup (etullisems)

(person rems) each additional mcrement of dose is approved for a worker.

Secondly, a facihty admini>trative limit that is set lower Medicine 320 51,400 than the quarterly NRC limit provides a ufety ina. gin Industrial R adiopaphy 30 5,700 designe<t to help the bcensee avoid overesposures.

Source Manufacturing 630 2.D3 Power Reactors 760 21,400 Yuel f abtication and

$60 3,100 22.

Several scientists hace suggested that NRClimits air Reproccumy tw high smd shou!J be lowered. Wkst are the arguments Uranium Inrichmen t 70 400 for lowerms thc limits?

Nuclear Waste Disposal 920 100 Uraniem Mills 360 760 in general, those critical of present doselimits uy that Department of 1. netty 300 11,800 the individual risk is hir.her than is estimated by the HI1R racihties Committee, the ICRP, and UNSCF AR Based on studies of Department of Defense 180 10,l00 tow-level nposures to large poups, some researchers he e I acihties concluded that a pren dose of radiation may be more likely i

E ducational Institutions 206 1,500 to cause biological effects than presiously thought. Some of Transportation 200 2,300 these studies are listed in the bibbopaphy (Mancuso, Archer) and the Bf IR 80 seport irkludes a uctica analyrirm l

I

'Adarted trom Cook and Nelson, occuratio wl ricowes to differs on the validity of the research methods used and the l1

/prldiRasiamJarocUmredse,ner.Acomerrrnnve.wmma,y tairv a

l

, Drari, tanroemenm twecm.c AsentO

. metho$ of statntical arialysit The probiern is that the l,

espected additunal incidence of radiationsaused effects li 20.

What heppens if e wor Act tzrreds the quarterfy crpe such as cancer is difficult to defect in comparison with the sure limit?

ruh istpr normal incidence. It ca mot be shawn without question that these ef tects wtre snoN frequent in the Radiation protection Smits, such as 3 remsin 3 months, espmed study group than in the uneaposed group used ior are not t$soWie hmits below which it is ufe and abose w hich cornparison, or that the observed effects were caased l

l 82410 l

l

i s

by radiation 1he lillR committee concluded that claims lesel tadirtion anordmr to the knear model explained in i

of forher tal had "r o substance."

Question 7. llaw d on thh ar proach, the regulationsin 1001 R Patt 20, " Standards for Protection Arainst Radiation," also I

.(

1 he NRC 6taf f ceratinually review s t.ic itsubs id re hearch state that beenser, should rnait tain all rathalion esposures,

~

un radiatmn rists. With respect to large scale studies of and releases of radioictive materials 'n eIthients, as low as is l

radation induce d health c'!sen m human populatmns reasonably achievable. Mort recent scientific actiews of the t

esposed to low-level sonitinr radbtior., the NRC and ! PA large bcdy of esperimental data, such as the Ill.lR40 and I

haie treently concluded that there is no one population the recent i PA guidance, cor tinue to support the vies. that pour avadable for w hich sud, a study could te espected to use of a 3 rem per.) cat hmit is acceptable in practice.

Proside a more sneaninghal estnut? of the low lesel radw I sperience has shown that, under thia limit, the average bon risk. This is duc, in latre part, to the obscrted and dow to workers is near 0 5 rarn/yr with stry few workers i

estimated low iruidence of fadet-on he:lth effects from ce nsistently approaching the lirrot.

low doser. I!cerver, the renits of ongoint at 16, sch n that on outlear shipyard w ken, will be care #uPy revnewed c 1here is httle to rain.

and the development of a radiation wolker retittry is being considered u a posut.le data base for future f.tudies.

Redu cing the dow timit s, for e s ample, to 0.$ tem /yr I

has been analysed by Ihe NkC staf f. An estimated 24 railhon 2.F.

hhr are the reasons for emt lowering the NRC dase person rems could be snved from 1960 through the year j

d hmirs ?

2000 by nurlear porer plant licenwes if comphance

}

i with the riew hrnit west achicved by lowerint the radiation Assuming that the $ rernter year hmit is adopted, levels, woiking times, or both, rather than by using estia there are three renons:

w orkers lt is estimrted that something ble $ 23 tillion woulJ be spent toward this purpose. Spendir g $23 bi! hon totave r

a. Ilealth risl.s are already low.

24 milhon person-terns would amount to spendier $30 to 190 rnithon to prevent each potential radiation induced

[

1he estirnated he:lth ;isks associated with current prernature cancer death. Society considers chis co>t urucce pt.

i averare occupational radiation doses (e.g,0,5 remhr for ally hir.h for individual protection.

l

$0 years) are comparable to or less than risk levels in 9ther occupational arcar considered to be amont the safest. If a 24, Are rhece any arcos of cor: tern abour radiation rhis pctnn were esposed to the masimum v1 $ rems ptt year ther enight ersuit in changing the NRC dose funirs!

(,

for 50) ears, which virtually tiever occurs, he or she might sncur a risk cornparable to the averare risks in mining and Yes lbree areas of corcern to the NRCstaff are streih-heavy construction. An occasional $ rern annual dose might caly identified below; be necesury to allow s9me jobs to be done without a sigmhcant increev in the collecHvt dose. If the dose limits

a. An indepenjent study by Rossland Maysandother t

were lowered sir.nificantly, the riurnSer of people required biolor;, cal research have indicated that a rjven dow of to complete inany jobs would increaw.1he collectne donc ricutron radiation may be nare likely to caut.c biological would then increase since more indmJuals would be effects than was previously thought. Other recent studies recei mr nonproductive e s posure w hile entertnr and cut doubt on the assue. The NCRP is cunently studying the leavmr the work area and preparing for the job.1he total data related to the neutron redistion qutstion and is l

number o' health effects might to up as the collective dosc expected to male recommendations as to whether neutron increased, dow hmits should be chanred. - Although the scientific community has not yet come to agreement on this question,

b. The curent terWationa ve comidered sound workers should be adviwd of the possibihty of higher risk 3

when entering areas where exposure to neutrons will occur.

1ne tryulatory standards for dow limits are based on the recommendatioro of the i ederal Radiation Council,

b. It has hen known for some tirne that rapidly At the tirne these star.deds were devein.d. shout 1960,it growing hvirr tissue is more sensitive toirduty from radiation

/

wn wmidered urihtely that e aposure to these lesels dutmr than tissue in which the rells are not reproducing rapidly.

i o work nr hfetime would result in clinical evidence of 1hus the embryo or fetus is more sensitive to radicion I

injury or daeau ddlerent from that occurring in the injury than an adult. The NCRP recomrr, ended in Report unespowd population. The scientific data baw for the No. 30 that specist precautions be taken when an occupa-stambrds consisted pnmarily of human experience (x ray.

tionally exposed woman could be prernent in order to i

esposercs to rnedical practitioners and patients, intestion protect the embr)o or fetus. In 1975. the NRC issued of r.diurn by watch dial painters. early effects obtened in Rerulatory Guide 813, "Ir.,truction Concerning Prenstel Japanew atomic hornb survivors, ra, don esposures of Radiatiori Esposure," in which it is recornmended that uranium mmen, ocrupational radiation accidents)insolving beenwes i'istruct workers conceniing this special risk.

very large dows delisered at high dose ratcs. ~lhe data base lhe guide recommeras that all workert, bt advised that the aka includeJ the results c,f a large number of animal bCRP recormnended that the masimum perminible dose to esperimeuf s involving high doses ar.d dose ra~.es. The animal the embryo or fetus from occupational exposure of the esperiments were particularly useful in the evaluation of mother should not exceed 0.5 rem for the full 9-month renetic effects. The chwned effects were related to low.

pregnancy permi in addition, the ruide suggeste options 8.29 11

~,. _ _ _.. _, _.. _. _ _ _. _ _

+ e avad4Ne to the Ismale trnfinpe who shomes not to Ihus, the aserne inaniOalin the pnetal popubtw e spose he embry o or fetus to this aJJitioral ri,L secenes about 0 2 rem of radiation caposute cash )r u from wurtes that are a part of our natutal and materna 1 he United States ILpaitment of llealth aM Hurmn ensironment. By the are of 20 ) cars, an individual h n Fermo is umdarly conterricJ about prenatal caposure actun ulated about 4 remt the most hkely tarret for from sneJaal ersys. In 1979 they put hsheJ proposed reduction o' population e s posure is me dical uses.

ruidehnes for phpicians wntermng abJumm.d ersys f or pouably pregnsnt women, lhe raidel'nes nn elfett entourate h Why ordt me fical esposures conniered as jot of a the n-ray staff to inde efforts to determir e whether a wurAct; lim.ed do set feudie patient i.s prernant and to d(fer eta)s iI pomNe untd af ter the chdd is born.

I qual doses of medicalanj otcupational radiation hat e 7

e qual risks Medical esposure f o radialmn Onuld be justified

c. Aho of spectat mterest is the indication that fernale for reasons qmte diff rent, however, from thwe apphsable woikers are subject to more itsk of cancer incidence than to o(cupalsonal c A posure. A physician ptracribing an n ray snale w orkeis In terms o' ali t) pes cluncer encept lenkemia, shou!J tic consmced that the beneht to the patier t of the the tillR40 andyus indicates that female workers have resulting medical information justifies the rak aswdated a rkk of doelopmg radiation-induced camer that is approxi-with trie radicion. I ath worker r ust decide on the ntept-instely orie and one half times hat for males. This increned ante of occupational radiation rak just as t ach worker must 3

risk is pntnardy due to the incidence of breast and thyroid decije on the screptabdity of any other occupational cancer in women. These types of cancer, however, have a hwatd.

high cure rate.1hus the difference between men and women Li cancer rnottahty is not great. Incidence of l'or aruther point d vbw, cisisider a worker a horeteiven radtation indeed leukemia a about the sarne for both a dose of 2 rems from a series of Urays or a radioactive seirs. l'emale workers should be aware of this difference in medicine in connection with an irdury or dlnen 1his dose the risks of radiation induced cancer in decidmg w'acther and the irnphed risk should be jushfied en medical grstmdt ut not to seek work involerig esposure to radiation.

If the worker had also receased a dose u 2 rerns on the job, the comtined dow of 4 rems would not incapacitate the Ji How snuch rodhtbn does the arrrge person whrs worker. A dose of 4 rems is not espnia!!y dangerous and is does not work in the nutfrorindustry recetret not large compated to the cumulativelifetime dose itesttlet-ing the worker from additional job expmure during the We are all esposed from the moment of conception remainJet of the quarter would have no effect one way or to ioninns radiation from sescraisources. Our environment, the other on the risk from the 2 tems tdready neceived from f

and even the human body, contams naturally occurring enedical esposure. If the ir dividual worker accepts the risks radioactive materials that contribute some of the background associated with the n rays on the basis of the rnedical radhitton we recch e. Cosmic radiation onginating in space benefits and the itsks anociated with jot >related esposure and in the sun contributes aJJitional exposure.1he use of on the basis of employment benefits, it would be unfair to erns and raJioactive matenals in mediciae and dentistry restrict the iniividual from employment in tsjiation areas adds condderabf) to our population exposure.

for the rernainder of the quarter.

Table 6 shows eshmated aseran indiviJul exposme Some therapeutie medical doses such as thme received in mdhrems from natural t ackground and other sources.

irom cobalt 40 treatment can range as high as 6900 rems to a smal part of the body, spread over a perind of se$eral TADLli 6 weeb or months.

U.S. Ge neral l'opulation k s posure i stimates (1978)*

27.

khar is mrant by internal e r posure?

Asetage individual The total radirition dose to the worker is the external i

Source Dose dose (measured by the film badge and reported as "whole-(mremh r) boJy dme") plus the dose from internal emitters. T he I

monitoring of the additional internal dose is dif ficult.

Natural background taverage in U.S.)

100 Decause there is the possibthty of internal dows occurring, a Releasc of raJmacthe matenalin pood air momtming program should be estabbshed when natural gas, snining, mdhnf, etc.

u arrante d.

Medius Whole-body equivalent) 09 Nuclear weapons yrimardy f a.llout)

$4 T he uptake of radioactise materials by wurkers is gener-j Nuclear enerry 0 28 ally due to breathing contaminated att. RaJmactive materialt, I

consumer prouucts 0 03 may be rresent as firw dust or gases in the workplace atnosphere. The surfaces of equipment atxl workbenches I

Total M00 miem/yr

)'

)

• Ada Task bree on the n h tibety that a sarnincant portion or teported medical a ray Health !pteJ trom a report by the It teragene by the therartment eatiosure is to g arts r;f the boJy only. An esposure or too mrem to f ftcts of tanisint Radiatiori t'utche nt nenhh. t ducatu;n. anJ M chare.

'he wide body h more syntfacant than a 100 nuem chest s esy.

&2412

may k contaminattd Roboactne tnatenah rm enter the

,o 94 by tur breathed ir6 talen in oth ' pod os drink, or hmit. ICRP recornmends that the internaland es tetral6tes bemy aterbed thrmth tht sltn. Nrt4ularly if the slm h should be appropriatrly added. This #ccommenuation is curiently unda study by the valls of the NRC, the I PA,

(

b? <4 ~

and the Occus ational Safety and llcalth Administration (0511 A h Af ter catering the bods, the udioacthe rnaterial udl migratt to pa titular engans cr particular parts of ;he body J 0.

depenoms on the lumbernhtr> t f the material. I or a rample, Ilo w is s wor Aer i r.a frinalrodistion dvsr determinedt i

uranium will lend to depostt in fhe bones where it wdl ternein for a lorig time, it is shwly eliminated from the A worker may wear thr*e types of radiation measuring body, snostly ley wsy of the kidneys. Radrum will also tend devkes. A self readingpocket doumrterracosds tbrespos'ne to der out in the bones. Radioacthe io;tme will sect out the to incident radiation and can be trad out immediately upon thyrmd gjeda (located in the n3 cit and depout there.

(mkhing a job insohirit extrrnal exposure to radiation. A film badre or TLD badge records radiation dow, tither by Tbc dose fron these interrol emitters camot lx rnea-the amount of datkening of the film or by storing energy in sured eithen by the it!m hadre or b) other ord' nary doum-the TLD cry stal. Both these devices require procening to eters ratried by the wotAct,1his incans that the internal deterrmne the dose but are considered snore reliable than f adiation dose rnust be separctely rnonitored using other the pocket dodmeter. A worker's official report of dme detection rnsthods.

recched h normally based on istm or 1LD badge readmts, which psovide a curnulative total and att rnore accurate.

Interntnl enrosce can be est!rnated by incasurivt the 31, radiation tmitted from the body or by mean%ng the What are my options if I decide not to accept the ruts radsoacthe snatesials conIained in biologicalsamples such as suweiated with orrupationalrnrdiation tspcturet urine or feces Dose estimates can aho tm rnade it one knows how rnuch radioacthe insterialis in the air and the if the thks from esposure to radiation that rnay be lenrth of tirne durint w hich the air was br*sthed expected to occut durlag your work are unacceptable to you, you could request a transfer to a job that does not

^26 Ilo w are the limits for internn!espsu.e sett insohe exposure to radiation. Ilowever, the this associated with esposure to radsation that worLers, on the avetate, Standards have been estabinhed for the instimurn actually receive are considered acceptable, cornpared to permhuble arnount of each radionuchde that may be other occupational this, by sittually all the scientific accumulated in the critical organs" of the wotler s body.

poups that have studied them. Yotr ernployer is probat,1y not obbpted to Fuaranter you a transfer if you decide not Calculations att anade to deterrnine the quantity of to axept an asugnment requiring caposure to radiation.

radioac!he inat riai that has been taken into the body and the total dose that would result. Then, baird on hmits estabbshed for particular body organs simi!at to IM roms You aho haic the option of seeking other ernplo3 ment in a rionradiation occupation. llowever, the studies that in a calendar quarter for whole body esposuse, the sepula-have compared occupationaltisksin the nuclear industry to tions spccify maximum permimble concentrations ol tadh activr materialin the air to which a w orker can be exposed those in other job areas indicate that nuchar work is for 40 hours4.62963e-4 days <br />0.0111 hours <br />6.613757e-5 weeks <br />1.522e-5 months <br /> per week over 13 weeks or I calendar qumer.

relatively safe, lhus, )ou will not necessarily fmd signif-kantly low er risks in another job, The regulatior.s abo requitr that efforts de made to keep internal exposurc ALA R A.

A third optio i would be to prntice the ruost effecthe Internalexposure h controlled by tirniting the scleau of work procedures m as to keep your exposure ALAR A. lie aware that reducing time of esposure, rnaintaining distance radioactive materialinto the air and by carefully monitoring from radiation sources. and using shieldmg can all lower ll.c work area for airbortir nadioacthily and surface con-your esposure. Han radiation jehs carefully to increase ternination. hotecthe clommc and respiratory (breathiny) efficier.cy whb m the radiation area. Learn the rnost protection sho dd be used w hencier the pmsibihty of contact with loou radioactise rnaterialcannot le presented.

effective inethods of utint prottetive clothing to asoid contamination. Dhcuss your job with the radialmn protec-29, is the dose o perwn recekedfrom internal esposure tion personnel who csn surfest aiditional ways to reduce your esposure.

added to that receivedfrom raternal:xposure?

32.

lspmure to radiation that results frorn radioacthe Where cat igetackfirimaliqfornairron ors rudiarian obk1 materiah taken into the hdy is measured, recorded, end reported to the worter separately from enternal dose. The The following th1 suggests sources of usefulinforma-i tion on tsdiation ruk; intertial dow to the whole body or so specific organs does not at this time count against the 3-remttt-calendwquarter Four llmployrr o.

t'nhtat orgst. reters be thme t arrt et the t.udy vvinerabh to r certam rebume ciateru.h m. rurwo, and othe, nurmi ades' The radiation protection or health rhysics office tion aamn sut o done, h, tere tu contentrate er taien trito the tuto m the facihty wherr you are employed, l

,. e b Nuclear Regulatory Commission

e. Department of Elechh and lluman Services Regional Offices Office of the Uitectot King of Prussia, PA 19406 215 337 $000 Dureau of RadiologicalIIrelth (Ill X Il Atlanta, G A 30303 404 121 4503 Departrnent of llcalth and flutnan Services Gina l.llyn, 11. 60137 312 932 15i20 5600 l'asheri Lane Arlington.1X 76012 Rockville, Af D 20857 817 334 2841 Walnut Creek, CA 94596 41$ 943 3700 lelephone: 301-443-4690 litadquanns

d. Environmentalhotretion Agency Occupational Radiation Protection Branch Office of Nucless Regulatory Research Office of Radiation Progratns U.S. Nuclear Regulatory Comrniuion U S. L7nvironmental Protection Agency Wathington, D C. 20$$1 401 M Street, SW Washington, D C. 20460 lelephone: 301443-$970 Telephone: 703 557 9710 s

8.2 %I4 i

-