Regulatory Guide 3.12
| ML003740232 | |
| Person / Time | |
|---|---|
| Issue date: | 08/31/1973 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| References | |
| RG-3.12 | |
| Download: ML003740232 (6) | |
August 1973 U.S. ATOMIC ENERGY COMMISSION
REGULATORY
DIRECTORATE OF REOULATORY STANDARDS
GUIDE
REGULATORY GUIDE 3.12 GENERAL DESIGN GUIDE FOR VENTILATION SYSTEMS
OF PLUTONIUM PROCESSING AND FUEL FABRICATION PLANTS
A. INTRODUCTION
Ventilation systems are important to safety because they serve as principal confinement barriers in a multiple Each applicant for a license to possess and use confinement barrier system which guards against the special nuclear material in a plutonium processing and release of radioactive or other potentially dangerous fuel fabrication plant as defined in § 70.4 (r) of 10 CFR materials during normal or abnormal conditions.
Part 70, "Special Nuclear Material," must satisfy the Ventilation systems will be subject to variations in provisions of § 70.23, "Requirements for the Approval operating temperatures and pressures and to of Applications." Paragraphs (aX3) and (4) of § 70.23 environmental conditions associated with normal require that the applicant's proposed equipment and operation, maintenance, plant shutdown, and testing.
facilities and proposed procedures be adequate to They may also be subject to effects of natural protect health and minimize danger to'life or property. phenomena such as seismic motion and floods, missiles, fire and explosion, and other accidents.
At plutonium processing and fuel fabrication plants, a principal risk to health and safety is the release and The systems must continue to perform their safety dispersal of radioactive materials. The prevention of such functions effectively under all conditions by confining release and dispersal is an important function of the radioactive or other potentially dangerous materials. The ventilation systems. This regulatory guide presents systems must assure that the concentration of methods acceptable to the Regulatory staff for radioactive materials in the effluent gases is as low as complying with § § 70.23 (aX3) and (aX4) with respect practicable.
to the design of ventilation systems for plutonium processing and fuel fabrication plants. The continuity of necessary. ventilation can be assured by means such as standby equipment and
B. DISCUSSION
fail-safe control systems. The ability of the systems to perform their safety functions effectively can be assured Ventilation systems for a plutonium processing and by periodic testing of safety-related components during fuel fabrication plant may consist of air supply, normal operation of the systems to demonstrate their recirculating air, process ventilation, and exhaust air ability to perform at design efficiency andto verify their systems together with associated air filters, fans, availability for emergencies.
dampers, ducts, and control instrumentation. The air supply system draws in and conditions fresh air and
C. REGULATORY POSITION
distributes it throughout the plant. A portion of supply air enters the process ventilation system through glove The ventilation systems of a plutonium processing boxes, hoods, and other components and is removed and fuel fabrication plant should assure the confinement together with other plant air through the exhaust of hazardous materials during normal or abnormal ventilation system which discharges through a stack to conditions including natural phenomena, fire, and the environment. Part of the occupied-area ventilation explosion. The release of radioactive material to the air may be recycled to the air supply system through the environment, or to an area in which levels of recirculating air system. radioactivity are normally sufficiently low to permit USAEC REGULATORY GUIDES copie of published guides nay be WAined by request indiating ft division desired to the US. Atomic Energy Commission, Weshington, Dr.. 20645.
Regulatory Guide we Issued to describe and meks v41able to the public Attention: Director of Regulatory Standards. Comments end egestlon for methods acceptable to the AEC Regulatory staff of kIplementing egecific parts of Improvemnents In these guide amnd encouraged should be sent to die Secetay No Commission's reguletions, to delineate technklues used by the staff in of the Commission. U.S. Atomic Enerny Commisin Wedhlno, D.C. 20M45.
seifc problems or postulated eccidents, or to provide guidance to
,mlustinil Attention: Chief. Public Proceedings Staff.
aplicents. Regulatory Guides ae not substitutes for reguletlons nd Wcompliance wIth e is not equird. etods end solutions different from th let out in The guids we Issued in the followig ten b d ons:
the guides will be ecceptable If they provide a basis for the findings nequiste to goe Iuenc or continuerm of epermit or loiar by the Commission. 1. Power Reactors . Products
2. Resserch md Test Reactors
7. Transportation
3. Fuels And Materials Facilities L OccuptiOnal Health Published uides will be evised periodically. as appropriate, so accommodate 4. Enronmental end SIting 9. Antitrust Review eonmients end to reflect new informaton or experIence. "S. Materials and Plant Protection 1
0. General
personnel access, should be reduced to a level as low as fires, fire-resistant materials of construction, practicable in accordance with the provisions of 10 CFR fire-resistant filters, heat and smoke detectors, alarms, Part 20. heat removal devices, and fire-suppression equipment.
The design of the fire protection system should include
1. General Safety provisions to protect against adverse effects in the event of operation or failure of this system. For example, a a. The ventilation systems should confine drain system should be provided to prevent a criticality radioactive materials within the process areas as close to incident in the event of water discharge on activation of the point of origin as practicable. They should also a water spray heat removal system or in the event of confine and prevent uncontrolled release of radioactive water leakage on failure of a heat removal system aerosols, noxious fumes, and vapors into rooms and component, such as a spray nozzle, while the system is areas normally occupied by personnel. not in operation.
b. Confinement of radioactive materials should be g. All ventilation systems should be capable of provided by multiple zones. Each zone is bounded by operating during a fire in the areas they ventilate and barriers such as vessel and glove box walls, building safely handle products of combustion through walls, and internal room walls. The primary confinement appropriate ventilation channels. A supply air system zone (Zone I) should be the process ventilation system should. remain operational; however, the option to for glove boxes, conveyors, transfer boxes, and other discontinue air supply to the involved space or spaces spaces that may contain plutonium or other radioactive should be maintained. Any system shut down should be materials during normal operations. A secondary protected from backflow.
confinement zone (Zone III) should be the operating and other potentially contaminated areas surrounding h. The materials of construction i for the the process ventilation system. Areas inside the building, ventilation systems should be fire resistant. to protect potentially free of 6ontamination and surrounding the against fires occurring within or without the systems. All primary confinement zone, but interposed between filters should be of a fire resistant type and, where Zones I and III, would constitute an additional applicable, approved by Underwriters' Laboratories, secondary confinement zone (Zone II).
Incorporated (UL). 1 Filters and exhaust fans, especially a final filter plenum and exhaust fan enclosure, should c. Pressure differentials should be maintained be located where they are not exposed to the direct between building confinement zones and also between effects of fire or explosion in the operating areas. Smoke the building confinement zones and the outside detectors and thermostats for fire detection, approved K
atmosphere to assure that aii flow is from zones of lesser by UL,2 should be provided in the ventilation systems.
potential for contamination to zones of greater potential for contamination, i.e., from the environs into the i. Fire- and smoke-suppression equipment should building, thence to secondary and primary confinement be so located as to assure that the integrity of final zones. Devices should be provided to control and high-efficiency filters or filter systems is not degraded.
indicate pressure differentials between confinement Spark and flame arresters and isolation valves may be zones. Alarms should be provided to indicate when used at filter installations in intermediate stages of pressure differentials are not maintained in a prescribed effluent cleaning. A heat removal system should precede range. the first stage of a high-efficiency filtration system d. All ventilation systems should be designed so serving as a final means of effluent cleaning (see that the failure of any one component (equipment or regulatory position C.8.e).
control device) will not affect the continuous operation j. If sources of combustible solvents, gases, and .1 of the ventilation systems. Ventilation systems and vapors are identified or postulated to be present in a components should have fail-safe features with provision ventilation system under normal or abnormal conditions, for alarm indication. they should be monitored by suitable continuous e. Onsite emergency power supply systems should monitoring systems as specified in Regulatory Guide be provided to operate the ventilation systems and 3.7.3 components as well as other systems and components k. The ventilation systems should be designed to important to safety. Ventilation systems should be withstand tornado conditions without loss of capable of operating, during normal power outage, at confimement capability due to mechanical damage to the capacities required to maintain confinement of system or components or due to the reduced ambient contaminants. The onsite emergency power sources and pressure at the intake and exhaust openings of the the electrical distribution circuits should have building. Protection against missiles should be provided independence and testability to assure performance of for the intake and exhaust openings.
their safety functions assuming a single failure.
f. The ventilation systems should be designed to 1. Components of the ventilation systems should withstand any credible fire and explosion and continue be designed to withstand the effects of earthquakes and to act as confinement barriers. Fire protection features remain functional to the extent that they will prevent K
of the ventilation systems should include fire doors and the uncontrolled release of radioactive materials to the dampers or other proven devices to restrict the spread of environment.
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2. Occupied-Area Ventilation Systems 3 Process Ventilation Systems
3.
a. Supply air should be properly conditioned and a. Air or inert gas should enter each ventilated distributed at or near the ceiling to the potentially glove box or process enclosure through at least one contaminated areas of the facility. fire-resistant HEPA filter and be discharged through at b. Outdoor makeup air supply units should be least one fire-resistant HEPA filter to exhaust ductwork protected from the weather. For example, intakes leading to a final filter system (see regulatory position should be arranged so as to minimize the effects of high C.8.e). The inlet filter prevents any backflow of winds, rain, snow, ift, and debris on the operation of the contaminants into the work areas, and the outlet filter system. Heaters may be necessary in areas where icing minimizes contamination of the exhaust ductwork.
can cause significant supply filter damage. Screens should be provided over supply air inlets to protect b. All process ventilation systems should have moisture separators and filters from wind-blown debris. adequate capacity and appropriate controls to maintain at least 125 linear feet per minute inward air flow c. Air from each Zone II or Zone III area should through the maximum credible breach and thereby be removed near the floor through, individual area grills prevent the escape of particulates.
or registers, each equipped with a fire-resistant c. Air or inert gas from glove boxes or other medium-efficiency filter. The filter should have an process enclosures where wet chemical operations take atmospheric dust spot efficiency 4 rating of place should be treated to protect the ventilation approximately 90% or better. Filtered air can be ductwork, final filters, and filter plenums from exposure recirculated or can be discharged through an exhaust to wetting or deleterious chemical attack.
ventilation system. d. Consideration should be given to recirculation d. Part of the Zone II ot Zone Ill filtered air may of exhaust air or inert gas to glove boxes and other be recirculated to reduce thermal loads. The point of process enclosures to minimize release of radionuclides Zone II or Zone III air withdrawal should be selected so to the biosphere. If recirculation is used, the exhaust gas that Zone I air streams cannot be drawn into the Zone 11 from these enclosures should be filtered through two or Zone Ill air supply. Local exhaust effluent that may stage's of fire-resistant HEPA filters in series before being contain noxious, toxic, or corrosive gases and vapors recirculated.
should not be recirculated into a Zone 11or Zone IIl area. Recirculated air should be passed through two
+,, stages of fire-resistant high-efficiency particulate air 4. Fans (HEPA) filters in series'before it is returned to Zone I]
or Zone I11 areas. a. Installed spare fans and isolation dampers e. Provision should be made for continuous should be provided for the supply air and exhaust air monitoring of recirculated air prior to the second stage systems. When any one fan is inoperative in a system, a of' HEPA filtration. Upon an indication that the limits backflow damper should automatically isolate the idle for soluble isotopes of plutonium specified in Table 1, fan from the system. Standby fans should automatically Column I of Appendix B to 10 CFR Part 20 or in the start and have sufficient capacity to maintain minimum license conditions have been exceeded, the air in the system air flow.
recirculating system should be diverted to a b. Alarms should be provided to indicate once-through exhaust ventilation system for discharge malfunction of each ventilation fan (see regulatory through a final filter plenum. The point of diversion of position C5.f).
Zone I1 or Zone Ill filtered air into the once-through c. Supply air fans should be interlocked with an exhaust ventilation system should be prior to the heat exhaust air plenum pressure sensor to prevent supply fan removal system preceding the final filter plenum. operation unless the exhaust fans are running. This will Recirculation of Zone I1or Zone Ill air may be resumed prevent pressurization of any process room or area on correction of offending operations and/or equipment should exhaust ventilation fail.
deticicncies. d. Emergency power should be supplied to fans in f. A final filter plenum should have at least two the, event of failure of the normal power supply (see stages of fire-resistant HEPA filters in series. HEPA regulatory position C.le).
filters should be designed to military specifications MIL-F-51068Cs and MIL-F-51079A6 and should satisfy S. Ventilation System Construction and Layout the requirements of UL-586. 7 Final filtration systems incorporating high-efficiency filters other than HEPA a. The material of construction for the ventilation filters and having equivalent efficiency and resistance to systems should be carefully selected according to such fire are also acceptable (see regulatory, positions C.8.e. safety considerations as strength to withstand accident and C.8.g). conditions; corrosion resistance, particularly when g. The filtered ait should be discharged to the associated with chemical processes; fire resistance; long environs through a stack of sufficient height to reduce operating life 'to avoid frequent replacement of close-in ground-level concentrations of radioactive or contaminated equipment; and smooth surface finish to other potintially dangerous contaminants. aid in decontamination.
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b. Ducts and housings should be designed, given to locating continuously operating exhaust fabricated, and erected with a minimum of ledges, samplers after each stage of HEPA filtration.
protrusions, and crevices that could collect dust -and e. In addition to a local station alarm, the CAMS
moisture or that could impede personnel or create a and stack monitoring systems should have readout and hazard in performance of their work. Duct runs and flow alarm panels in the central control area(s).
distributors should assure uniform, representative air flow past monitoring and sampling stations as well as 7. Glove Boxes and Other Process Enclosures through filter installations.
a. Glove boxes. should be constructed using the c. The design should permit convenient highest quality of materials and workmanship to assure inspection, maintenance, decontamination, and/or total containment and minimize leakage. Combustible replacement of critical components such as filters, fans, materials that are an integral part of the glove box and dampers. should be held to a minimum.
d. Housings, filter mounting frames, and ducts b. The design of enclosures should be based on should be designed to withstand system pressure changes downdraft ventilation flow to minimize the spread of without distortion, fatigue, or yielding of such fire. Heat detectors and combustible gas and vapor magnitude that inleakage or bypassing of the filters detection meters should be provided on glove boxes or results. enclosures where fire or explosion hazards exist.
e. Supply, recirculation, process ventilation, and Automatic fire suppression equipment should be exhaust ducting should incorporate manual and provided in these boxes or enclosures. Where automatic automatic dampers and controls to distribute and systems are not required, fire detectors should be regulate the movement of air in each room, area, and installed and provisions made for manual fire ventilation system and to prevent possible backflow in suppression.
case of pressure reversal. c. Small glove box or enclosure systems supplied f. The ventilation systems should be appropriately with gases under positive pressure should have instrumented to read out and alarm in one or more positive-acting pressure-relief devices (discharging into an central control areas. These areas should be designed to exhaust system) to prevent overpressurization. Further, permit occupancy and actions to be taken to operate the should these systems be recirculating, all necessary ventilation systems safely during normal or abnormal cleanup and detection equipment for noxious, corrosive, conditions. or explosive vapors or gases.should be considered.
d. The glove box or enclosure design should
6. Ventilation System Testing and Monitoring permit filter replacement with minimum exposure to
"personnel performing this task and with minimum a. Provisions should be made so that components release of contaminants to the environment outside of of ventilation systems can be tested periodically for the glove box or enclosure.
operability and required functional performance. They e. The minimum instrumentation for a glove box should include capability for periodic measurement of or enclosure ventilation system should include devices to air flows in exhaust ducts and in or at equipment, hoods, indicate the pressure differential between the box or and glove boxes. enclosure and the surrounding work area, the filter b. The capability should be provided to test, resistance, and the exhaust flow rate from the box or under conditions as close to design as practicable, the enclosure. When box operations are not in full-time operating sequence that wotild briig ventilation systems attendance for a continuous process, a sensor should be into action, including the transfer to alternate power provided to monitor abnormal pressure or temperature sources and the design air flow delivery capability. and alarm at a point where cognizant personnel are c. All exhausting ducts and stacks which may stationed.
contain plutonium contaminants should be provided with two monitoring systems: a continuous monitor
8. Filtration Systems
[Continuous Air Monitoring System (CAMS)) and a fixed sampler. The probes for sampling purposes should a. Each exhaust filter housing should have a rigid be designed for isokinetic sampling and located to obtain mounting frame for the filter. The complete housing representative samples. Each system should be structure should have minimum leakage from outside to connected to an emergency power supply (see regulatory inside, inside to outside, or across the filter sealing position C.l.e). The continuous stack sampler should barrier (exclusive of the filter).
alert cognizant personnel through an audible and visual b. The filter access opening in these housings annunciator if the airborne radioactive effluents reach should permit filter removal and replacement with prescribed limits. minimum exposure to personnel performing this task d. Air monitoring and warning systems (including and with minimum release of contaminants outside of CAMS) should be installed in areas where radioactive the housing.
material is handled. Air sampling heads should provide a c. The filter housings should be equipped with represrntative sample of the potential airborne necessary test ports to permit reliable in-place testing of radioactivity being breathed. Consideration should be all filter stages with dioctyl phthalate (DOP).
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d. Damper valves should be so located that a bank f. HEPA filter systems should be tested after filter of filters can be completely isolated from the ventilation installation using a !'cold DOP" test. Acceptance should systems during filter replacement operations. be based on an efficiency. of 99.95% or better for DOP
e. A HEPA filtration system serving as a final having a light-scattering mean 'diameter of approximately means of effluent cleaning should have at least two 0.7 microns. Regular in-place testing of both on-line and stages of fire-resistant filters in series in a filter plenum. standby filter installations should be performed because A heat removal system and a spark arrester should of system deterioration that can take place even when precede the first stage of filters. If a cooling spray such the installations are not being used. Test procedures used as a water spray system is used for heat removal, it should comply with the recommendations contained in should be followed by a combination spark ORNL-NSIC-65, "Design, Construction and Testing of arrester/demister screen to also remove entrained High-Efficiency Air Filtration Systems for Nuclear droplets, thereby protecting filters from plugging and Application"s and in Regulatory Guide 3.2.'
damage. A roughing filter should be mounted behind g. Final filtration systems Incorporating these components to -remove the bulk- of the high-efficiency filters other than HEPA filters and having draft-carried debris so as to avoid loading the HEPA equivalent efficiency and resistance to fire are also filters installed downstream. acceptable.
The cooling spray system should operate automatically (with a manual override) upon abnormal heat rise in the cooling chamber inlet indicated by 9. Quality Assurance Program detectors in exhaust ducts feeding the filter plenum. A
manually operated valve actuating the spray system A quality assurance program should be established should also be provided as a backup. If a drain system is for the design, construction, testing, operation, and installed to prevent accumulation of liquid in the maintenance of all structures, systems, and components plenum, the collection tanks should be of favorable addressed in this guide in accordance with the criteria in geometry. Appendix B of 10 CFR Part 50.
3.12-5
REFERENCES
1. Underwriters' Laboratories Building Materials List Naval Publications and Forms Center, 5801 Tabor Avenue, Philadelphia, Pa. 19120.
(latest edition). Copies may be obtained from Underwriters' Laboratories, Inc.,.207 -East Ohio
6. MIL-F-51079A, "Filter Medium, Fire-Resistant, Street, Chicago, IlI. 60611.
High-Efficiency," Military Specification. Copies may be obtained fropt Commanding Officer, Naval
2. Underwriters' Laboratories Fire Protection Publications and Forms Center;. .5801 Tabor Equipment List (latest edition). Copies may be Avenue, Philadelphia, Pa. 19120.
obtained from Underwriters' Laboratories, Inc., 207 East Ohio Street, Chicago, Ill. 60611.
7. Underwriters' Laboratories' Standard UL-586,
"High-Efficiency Air Filtration Units," (also
3. Regulatory Guide 3.7, "Monitoring of Combustible designated ANSI B 132.1-1971). Copies may be Gases and Vapors in Plutonium Processing and Fuel obtained from Underwriters' Laboratories, Inc., 207 Fabrication Plants," Directorate of Regulatory Standards, USAEC,. East Ohio Street, Chicago, Il. 60611.
4. ASHRAE (American Society of Heating, 8. C. A. Burchsted and A. B. Fuller, "Design, Refrigerating and Air Conditioning Engineers) Construction, and Testing of High-Efficiency Air Standard 52-68, "Method of Testing Air Cleaning Filtration Systems for Nuclear Application,"
Devices Used in General Ventilation for Removing ORNL-NSIC-65, Oak Ridge National Laboratory, Particulate Matter," Section 9. Copies may be January 1970. Copies may be obtained from obtained from American Society of Heating, National Technical Inf6rmation Service, U.S.
Refrigerating and Air Conditioning Engineers, Inc., Department of Commerce, Springfield, Va. 2215 1.
United Engineering Center, 345 East 47th Street, New York, N.Y. 10017. 9. Regulatory Guide 3.2, "Efficiency Testing of MIL-F-51068C, "Filter, Particulate, High. Air-Cleaning Systems Containing Devices for
5.
Removal of Particles," Directorate of Regulatory Efficiency, .Fire-Resistant,' Military Specification.
Standards, USAEC.
Copies may be obtained from Commanding Officer, K
3.12-6