Regulatory Guide 5.27: Difference between revisions

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{{#Wiki_filter:June 1974 U.S. ATOMIC ENERGY COMMISSION
{{#Wiki_filter:June 1974 U.S. ATOMIC ENERGY COMMISSION  
                              REGULATORY                                                                                     GUIDE
REGULATORY GUIDE  
                              DIRECTORATE OF REGULATORY STANDARDS
DIRECTORATE OF REGULATORY STANDARDS  
                                                                REGULATORY GUIDE 5.27 SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS
REGULATORY GUIDE 5.27 SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS


==A. INTRODUCTION==
==A. INTRODUCTION==
2. General Characteristics Typically, the detectors of a doorway monitor are Paragraph (b), "Exit Requirement," of § 73.60, "Ad                               NaI(Tl) scintillators or solid or liquid organic scintilla ditional Requirements for the Physical Protection of                                 tors. Geiger-Mueller detectors have also been used in this Special Nuclear Material at Fixed Sites," of 10 CFR Part                             application, although the lower intrinsic efficiency of
Paragraph (b), "Exit Requirement," of § 73.60, "Ad ditional Requirements for the Physical Protection of Special Nuclear Material at Fixed Sites," of 10 CFR Part  
73, "Physical Protection of Plants and Materials,"
73, "Physical Protection of Plants and Materials,"  
                                                                                      these detectors renders them less suitable than scintilla requires that individuals exiting from material access tion detectors.
requires that individuals exiting from material access areas be searched for concealed special nuclear material (SNM). This guide describes means acceptable to the Regulatory staff for employing SNM doorway monitors to comply with that requirement.


areas be searched for concealed special nuclear material Detectors are arranged such that a detection area is (SNM). This guide describes means acceptable to the Regulatory staff for employing SNM doorway monitors defined by a plane perpendicular to the line of passage of individuals through the doorway monitor. Various to comply with that requirement.
==B. DISCUSSION==
Special nuclear material doorway monitors provide an efficient, sensitive, and reasonably unobtrusive means of searching individuals exiting from a material access area for concealed SNM. With proper installation and opera tion, gram quantities or less of SNM can be detected with a high level of reliability while maintaining a low false alarm rate.
 
I. Theory of Operation The doorway monitor is composed of a detector unit(s), associated electronics, and alarm logic. The detector unit(s) is sensitive to the radiations which emanate from the SNM and responds to these radiations (usually gamma rays) by generating current pulses. These pulses are amplified, filtered, and fed to alarm logic v'hich interprets the number (or rate) of pulses in some period of time, for example, one second. The alarm logic may be either a digital or analog system; in either case, if the number (or rate) of pulses exceeds a set level, an alarm condition ensues.
 
2. General Characteristics Typically, the detectors of a doorway monitor are NaI(Tl) scintillators or solid or liquid organic scintilla tors. Geiger-Mueller detectors have also been used in this application, although the lower intrinsic efficiency of these detectors renders them less suitable than scintilla tion detectors.
 
Detectors are arranged such that a detection area is defined by a plane perpendicular to the line of passage of individuals through the doorway monitor. Various arrangements of the detectors are possible; however, specific placement of detectors is usually dictated by the need to eliminate dead spots.


arrangements of the detectors are possible; however, specific placement of detectors is usually dictated by the  
Some commercially available doorway monitors are equipped with an automatic background updating system. The automatic background updating system periodically monitors and averages the background. A
doorway monitor equipped with an automatic back ground updating system is also provided with a treadle pad or beam-break system to indicate that the sensitive area is occupied. When the sensitive area is occupied, the radiation level detected by the doorway monitor is compared with the mean backgroun


==B. DISCUSSION==
====d. If the level is ====
need to eliminate dead spots.
"significantly" greater than the mean background, an alarm condition ensues. Significance is usually deter mined by comparing the radiation level when the sensitive area is occupied with the mean background plus some multiple of the square root of the mean back ground*
*The square root of the mean of a Poisson-distributed quantity is the unbiased estimate of the standard deviation of that quantity.


Special nuclear material doorway monitors provide an                                    Some commercially available doorway monitors are efficient, sensitive, and reasonably unobtrusive means of                              equipped with an automatic background updating searching individuals exiting from a material access area                              system. The automatic background updating system for concealed SNM. With proper installation and opera                                  periodically monitors and averages the background. A
USAEC REGULATORY GUIDES
tion, gram quantities or less of SNM can be detected                                  doorway monitor equipped with an automatic back with a high level of reliability while maintaining a low                              ground updating system is also provided with a treadle false alarm rate.                                                                      pad or beam-break system to indicate that the sensitive area is occupied. When the sensitive area is occupied, the I. Theory of Operation                                                                radiation level detected by the doorway monitor is The doorway monitor is composed of a detector                                      compared with the mean background. If the level is unit(s), associated electronics, and alarm logic. The                                  "significantly" greater than the mean background, an detector unit(s) is sensitive to the radiations which                                  alarm condition ensues. Significance is usually deter emanate from the SNM and responds to these radiations                                  mined by comparing the radiation level when the (usually gamma rays) by generating current pulses. These                              sensitive area is occupied with the mean background plus pulses are amplified, filtered, and fed to alarm logic                                some multiple of the square root of the mean back v'hich interprets the number (or rate) of pulses in some                              ground*
Copies of published guides may be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20545, Regulatory Guides are issued to describe and make available to the public Attention: Director of Regulatory Standards. Comments and suggestions for methods acceptable to the AEC Regulatory staff of implementing sPecific parts of improvements in these guides ae encouraged and should be sent to the Secretary the Commission's regulations, to delineate techniques .ned by the staff in of the Commission, US. Atomic Energy Commission, Washington, D.C. 20545, evaluating specific problems or postulated accidents, or to provide guidance to Attention: Chief, Public Proceedings Staff.
period of time, for example, one second. The alarm logic may be either a digital or analog system; in either case, if                          *The square root of the mean of a Poisson-distributed quantity the number (or rate) of pulses exceeds a set level, an                                  is the unbiased estimate of the standard deviation of that alarm condition ensues.                                                                  quantity.


USAEC REGULATORY GUIDES                                      Copies of published guides may be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20545, Regulatory Guides are issued to describe and make available to the public          Attention: Director of Regulatory Standards. Comments and suggestions for methods acceptable to the AEC Regulatory staff of implementing sPecific parts of    improvements in these guides ae encouraged and should be sent to the Secretary the Commission's regulations, to delineate techniques .ned by the staff in          of the Commission, US. Atomic Energy Commission, Washington, D.C. 20545, evaluating specific problems or postulated accidents, or to provide guidance to    Attention: Chief, Public Proceedings Staff.
applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods and solutions different from those set out in The guides ae issued in the following ten broad divisions:
the guides will be acceptable if they provide a basis for the findings requisite to the imuance or ontinuance of a permit or license by the Commission.


applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods and solutions different from those set out in    The guides ae issued in the following ten broad divisions:
===1. Power Reactors ===
the guides will be acceptable if they provide a basis for the findings requisite to                                              6. Products the imuance or ontinuance of a permit or license by the Commissio


====n.     ====
===6. Products ===
2. Reaseerd enid Test Reactors


===1. Power Reactors===
===7. Transportation ===
                                                                                      2. Reaseerd  enidTest Reactors           
3. Fuels and Materials Facilities
8. Occupational Health Published guidas will be revised periodically, as appropriate, to accommodate
4. Environmental and Siting
9. Antitrust Review comments amd to refloct new informeaion or experience.


===7. Transportation===
5. Materials and Plant Protection  
                                                                                      3.  Fuels and Materials Facilities        8. Occupational Health Published guidas will be revised periodically, asappropriate, to accommodate        4.  Environmental and Siting              9. Antitrust Review comments amd to refloct new informeaion or experience.                              5. Materials and Plant Protection       1
1


===0. General===
===0. General===


Thus the condition for an alarm can be written as                       Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the G > B + n,                                              detection area.
Thus the condition for an alarm can be written as G > B + n, where B is the mean background, G is the radiation level with the sensitive area occupied, and n is a multiplier, usually an integer between 4 and 10.* The value of n directly affects the false alarm rate, and the combination of B and n affect the sensitivity.
 
Although the automatic background updating system allows unattended use of the doorway monitor, for technical reasons, the system may be less effective in certain situations. Techniques to prevent this are des cribed in the Regulatory Position.
 
Doorway monitors not equipped with an automatic background updating system either must rely on the inherent sensitivity of the instrument and low back ground variation to ensure that concealed SNM will be detected or must be attended so that a measurement of background can be taken immediately prior to use and the alarm level set to maintain the desired sensitivity to concealed SNM. As with the doorway monitor equipped with an automatic background updating system, a doorway monitor not so equipped compares the activity with the detection area occupied with some set value, usually the measurement of background taken just prior to use. In any case, the expression above can be used as a condition of alarm by replacing B + nr'Wwith the set level.


. (2) The detector elements should be designed and where B is the mean background, G is the radiation level                    positioned so that detection sensitivity is as uniform as with the sensitive area occupied, and n is a multiplier,                    possible over the detection area; in no case should any usually an integer between 4 and 10.* The value of n                        areas where SNM is not detectible be permitted.
Whether or not a doorway monitor is equipped with an automatic background updating system, high back ground activity will decrease sensitivity. Measuring activ ity for longer periods will somewhat compensate for high background; however, longer measurement periods will make use of the doorway monitor less convenient.


directly affects the false alarm rate, and the combination                        (3) Power, sensitivity, and other controls of the of B and n affect the sensitivity.                                         doorway monitor should be tamper-safed when unat tended.
==C. REGULATORY POSITION==
1. Minimum Qualifications for SNM Doorway Monitors


Although the automatic background updating system                            (4) Signal lines connecting alarm relays to the allows unattended use of the doorway monitor, for                          alarm monitor should be supervised.
====a. General ====
(1) SNM Doorway monitors should be used in conjunction with a metal detector and should be installed in a passageway (see Regulatory Guide 5.7,
"Control of Personnel Access to Protected Areas, Vital
*Note that, in general, for a count rate system, the condition for afarm should be modified to account for the response time of the instrument as follows:
G > B + n1]0l - e-t/7)
where t is the counting time and r is the time constant of the instrument. If, as should be the case, t/,r > 5 the added factor is essentially unity.


technical reasons, the system may be less effective in                             (5) Some doorway monitors may require an indi certain situations. Techniques to prevent this are des                      vidual to occupy the detection area for a specified time, cribed in the Regulatory Position.                                          longer than a normal walking pace would provide. If this is the case, the doorway monitor should be provided Doorway monitors not equipped with an automatic                        with a treadle pad and a "clock" device to assure that background updating system either must rely on the                          the detection area is occupied for the requisite time. An inherent sensitivity of the instrument and low back                        aural and visual indication should be given if an ground variation to ensure that concealed SNM will be                      individual being searched does not occupy the area detected or must be attended so that a measurement of                      sufficiently long.
Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the detection area.


background can be taken immediately prior to use and                            b. System Specification the alarm level set to maintain the desired sensitivity to                        (1) Plutonium-239. A doorway monitor used to concealed SNM. As with the doorway monitor equipped                        detect plutonium should be capable of detecting a with an automatic background updating system, a                            minimum of 0.5 gram of plutonium-239 encased in a doorway monitor not so equipped compares the activity                      minimum of 3 mm of brass at a 90% confidence limit.
. (2) The detector elements should be designed and positioned so that detection sensitivity is as uniform as possible over the detection area; in no case should any areas where SNM is not detectible be permitted.


with the detection area occupied with some set value,                      The false alarm rate should be less than 0.1% (Appendix usually the measurement of background taken just prior                      C).
(3) Power, sensitivity, and other controls of the doorway monitor should be tamper-safed when unat tended.
to use. In any case, the expression above can be used as a                        (2) Uranium-233. A doorway monitor used to condition of alarm by replacing B + nr'Wwith the set                        detect uranium-233 should be capable of detecting level.                                                                      within 4 hours of purification* a minimum of 1 gram of uranium-233 containing between 7 and 10 ppm of Whether or not a doorway monitor is equipped with                      uranium-232 encased in a minimum of 3 mm of brass at an automatic background updating system, high back                          a 90% confidence limit. The false alarm rate should be ground activity will decrease sensitivity. Measuring activ                  less than 0.1% (Appendix C).
ity for longer periods will somewhat compensate for                                (3) Uranium-235. A doorway monitor used to high background; however, longer measurement periods                        detect uranium-235 should be capable of detecting a will make use of the doorway monitor less convenient.                       minimum of 3 grams of uranium-235 contained in uranium enriched to 20% or more in the uranium-235


==C. REGULATORY POSITION==
(4) Signal lines connecting alarm relays to the alarm monitor should be supervised.
isotope encased in a minimum of 3 mm of brass at a 50%
 
                                                                            confidence limit. The false alarm rate should be less than
(5) Some doorway monitors may require an indi vidual to occupy the detection area for a specified time, longer than a normal walking pace would provide. If this is the case, the doorway monitor should be provided with a treadle pad and a "clock" device to assure that the detection area is occupied for the requisite time. An aural and visual indication should be given if an individual being searched does not occupy the area sufficiently long.
1. Minimum Qualifications for SNM Doorway Monitors                        0.1% (Appendix C).
 
b. System Specification
(1) Plutonium-239. A doorway monitor used to detect plutonium should be capable of detecting a minimum of 0.5 gram of plutonium-239 encased in a minimum of 3 mm of brass at a 90% confidence limit.


====a. General====
The false alarm rate should be less than 0.1% (Appendix C). 
        (1) SNM Doorway monitors should be used in                           2. Use of Doorway Monitors conjunction with a metal detector and should be                                In general, doorway monitors should be used in installed in a passageway (see Regulatory Guide 5.7,                        locations of minimum background and minimum back
(2) Uranium-233. A doorway monitor used to detect uranium-233 should be capable of detecting within 4 hours of purification* a minimum of 1 gram of uranium-233 containing between 7 and 10 ppm of uranium-232 encased in a minimum of 3 mm of brass at a 90% confidence limit. The false alarm rate should be less than 0.1% (Appendix C).
"Control of Personnel Access to Protected Areas, Vital                      ground fluctation. If circumstances dictate use of a doorway monitor in an area of high background,
(3) Uranium-235. A doorway monitor used to detect uranium-235 should be capable of detecting a minimum of 3 grams of uranium-235 contained in uranium enriched to 20% or more in the uranium-235 isotope encased in a minimum of 3 mm of brass at a 50%
*Note that, in general, for a count rate system, the condition for          sufficient shielding should be provided to maintain afarm should be modified to account for the response time of              necessary sensitivity.
confidence limit. The false alarm rate should be less than
0.1% (Appendix C). 
2. Use of Doorway Monitors In general, doorway monitors should be used in locations of minimum background and minimum back ground fluctation. If circumstances dictate use of a doorway monitor in an area of high background, sufficient shielding should be provided to maintain necessary sensitivity.


the instrument as follows:
a. Attended Doorway Monitor  
                                                                                a. Attended Doorway Monitor G > B + n1]0l - e-t/7)                                        (1) If the doorway monitor is attended during where t is the counting time and r is the time constant of the            use, it need not be equipped with an automatic instrument. If, as should be the case, t/,r > 5 the added factor is essentially unity.                                                        *Purification means removal of all decay products.
(1) If the doorway monitor is attended during use, it need not be equipped with an automatic  
*Purification means removal of all decay products.


5.27-2
5.27-2


(d) Activate the electronics and alarm logic background updating system, although such capability is               when an individual is within the detection area and preferred.                                                             initiate operation of the doorway monitor.
background updating system, although such capability is preferred.
 
(2) Prior to each use* of a doorway monitor not equipped with an automatic background updating system, a measurement of background should be taken, and the alarm threshold should be set to the proper value listed in Table I for the measured background and the proper n value as determined in Appendix B. Each individual to be checked should, in turn, enter the detection area and be required to remain sufficiently long for the device to operate properly. During use, the background should be checked and the alarm threshold reset at least each 15 minutes.
 
(3) With the individual being checked in the detection area, an alarm should sound if the activity in the detection area exceeds the alarm threshold T, as such a situation would indicate the presence of SNM.
 
(4) The doorway monitor should be equipped with a high-background alarm which will sound if the measurement of background exceeds the appropriate maximum permissible background level listed in Table II
as determined in Appendix C. The doorway monitor should not be used during such periods of high back ground.
 
b. Unattended Doorway Monitor
(1) If the doorway monitor is unattended, an automatic background update system should be incor porated into the doorway monitor electronics and alarm logic. The control circuitry, if possible, should be located at the central alarm station (or other monitoring point).
(2) Door interlocks and closed-circuit TV in combination with beam breaks, motion detectors, and/
or treadle pads, should be employed to:
(a) Indicate to the person manning the central alarm station that an individual has entered the secure access passageway and/or is approaching the doorway monitor, (b) Allow observation of the individual ap proaching the doorway monitor, (c) Preclude a slow approach to the sensitive area of the doorway monitor, and
*By use is meant an individual or several individuals, each, in turn, being checked for SNM by the doorway monitor. The maximum period between threshold sets while the doorway monitor is in use is determined by the stability of local background and may necessarily be more frequent than every
15 minutes.


(2) Prior to each use* of a doorway monitor not                        (3) An alarm should sound in the central alarm equipped with an automatic background updating                        station if, when occupied, the activity in the detection system, a measurement of background should be taken,                  area exceeds the internally set threshold level (the mean and the alarm threshold should be set to the proper                    background plus some multiple times the square root of value listed in Table I for the measured background and                the mean background), as such a situation would the proper n value as determined in Appendix B. Each                  indicate the presence of SNM upon the individual being individual to be checked should, in turn, enter the                    checked.
(d) Activate the electronics and alarm logic when an individual is within the detection area and initiate operation of the doorway monitor.


detection area and be required to remain sufficiently                        (4) The doorway monitor should be equipped long for the device to operate properly. During use, the              with a high-background alarm which will sound if the background should be checked and the alarm threshold                  average background at the location of the doorway reset at least each 15 minutes.                                      monitor exceeds the appropriate maximum permissible
(3) An alarm should sound in the central alarm station if, when occupied, the activity in the detection area exceeds the internally set threshold level (the mean background plus some multiple times the square root of the mean background), as such a situation would indicate the presence of SNM upon the individual being checked.
        (3) With the individual being checked in the                   background level listed in Table II as determined in detection area, an alarm should sound if the activity in               Appendix C. The doorway monitor should not be used the detection area exceeds the alarm threshold T, as such             during such periods of high background. Other moni a situation would indicate the presence of SNM.                        tored exits should be used.


(4) The doorway monitor should be equipped with a high-background alarm which will sound if the                   3. Testing and Calibration measurement of background exceeds the appropriate                         a. Testing maximum permissible background level listed in Table II                       Doorway monitors should be tested by passing an as determined in Appendix C. The doorway monitor appropriate source of the amount and isotope specified should not be used during such periods of high back                    in Regulatory Position C.l.b. through the doorway ground.                                                              monitor no less frequently than once per day.* In b. Unattended Doorway Monitor addition, a functional performance test should be carried
(4) The doorway monitor should be equipped with a high-background alarm which will sound if the average background at the location of the doorway monitor exceeds the appropriate maximum permissible background level listed in Table II as determined in Appendix C. The doorway monitor should not be used during such periods of high background. Other moni tored exits should be used.
          (1) If the doorway monitor is unattended, an                  out at least once per week. An acceptable functional automatic background update system should be incor                    performance test procedure is discussed in Appendix A
  porated into the doorway monitor electronics and alarm                of this guide logic. The control circuitry, if possible, should be located              b. Calibration at the central alarm station (or other monitoring point).                    Doorway monitors should be calibrated with a
          (2) Door interlocks and closed-circuit TV in                  source of the amount, configuration, and variety of SNM
  combination with beam breaks, motion detectors, and/                  to be detected (e.g., 0.5 gram Pu in 3 mm of brass).
  or treadle pads, should be employed to:                                Calibration should be carried out according to a proce (a) Indicate to the person manning the central              dure such as that in Appendix B.


alarm station that an individual has entered the secure                    c. Operating Instructions access passageway and/or is approaching the doorway                          Operating instructions should be posted near the monitor,                                                              doorway monitor,* if attended, or at the monitoring (b) Allow observation of the individual ap                  point if the doorway monitor is unattended. The proaching the doorway monitor,                                        instructions should clearly indicate the procedure for use (c) Preclude a slow approach to the sensitive              of the doorway monitor and the procedure for setting area of the doorway monitor, and                                      thresholds, if appropriate. In addition, the operating instructions should indicate what corrective action is to
3. Testing and Calibration a. Testing Doorway monitors should be tested by passing an appropriate source of the amount and isotope specified in Regulatory Position C.l.b. through the doorway monitor no less frequently than once per day.* In addition, a functional performance test should be carried out at least once per week. An acceptable functional performance test procedure is discussed in Appendix A
  *By use is meant an individual or several individuals, each, in be taken and who is to be notified in the event of a turn, being checked for SNM by the doorway monitor. The              malfunction.
of this guide b. Calibration Doorway monitors should be calibrated with a source of the amount, configuration, and variety of SNM
to be detected (e.g., 0.5 gram Pu in 3 mm of brass). 
Calibration should be carried out according to a proce dure such as that in Appendix B.


maximum period between threshold sets while the doorway monitor is in use is determined by the stability of local            *Doorway monitors used to search for concealed U-233 should background and may necessarily be more frequent than every            be tested according to §6 of Appendix A.
c. Operating Instructions Operating instructions should be posted near the doorway monitor,* if attended, or at the monitoring point if the doorway monitor is unattended. The instructions should clearly indicate the procedure for use of the doorway monitor and the procedure for setting thresholds, if appropriate. In addition, the operating instructions should indicate what corrective action is to be taken and who is to be notified in the event of a malfunction.


15 minutes.
*Doorway monitors used to search for concealed U-233 should be tested according to §6 of Appendix A.


5.27-3
5.27-3


TABLE I
TABLE I
                  ALARM THRESHOLD
ALARM THRESHOLD  
                      T
T
  B n=     4     5           6      7    8    9    10
B  
100     140  150      160      170  180  190  200
n=  
120       164  175      186      197  208  219  230
4
140     .187  199      211      223  235  246  258
5
160       211  223        236      249  261  274  286
100  
180       234  247        260      274  287  301  314
120  
200       257  271        285      299  313  327  341
140  
220       279  294        309      324  339  353  368
160  
240       302  317        333      348  364  379  395
180  
260       324  341        357      373  389  405  421
200  
280       347  364        380      397  414  431  447
220  
300       369  387        404      421  439  456  473
240  
320       392  409        427      445  463  481  499
260  
340     414  432        451      469  488  506  524
280  
360     436  455        474      493  512  531  550
300  
380     458  477        497      516  536  555  575
320  
400     480   500       520     540   560   580 600
340  
420      502   522        543      563  584  604  625
360  
440      524   545        566      587  608  629  650
380  
460      546   567        589     610  632  653  674
400  
480      568  590        611     633   655   677  699
420
500     589  612       634     657  679  701  724
440
520     611   634       657     680  702   725  748
460
540     633   656        679      703   726   749 772
480  
560     655   678        702     726   749   773 797
500  
580     676  700        724      749   773   797 821
520  
600      698  722        747      771  796  820  845
540  
620      720  744        769      794  819  844  869
560  
640      741  766        792      817  842  868  893
580  
660      763  788        814      840  866  891  917
600  
680      784  810        836      863  889  915  941
620
700      806  832        859      885  912  938  965
640
720      827  854        881      908  935  961  988
660
740      849  876        903      930  958  985 1012
680
760      870  898        925      953  981  1008 1036
700
780      892  920        948      975  1003  1031 1059
720
800      913  941        970      998  1026  1055 1083
740
820      935  963        992    1020  1049  1078 1106
760
840      956  985      1014    1043  1072  1101 1130
780
860      977  1007      1036    1065  1095  1124 1153
800
880      999  1028      1058    1088  1117  1147 1177
820
900    1020  1050      1080    1110  1140  1170 1200
840
920    1041  1072      1102    1132  1163  1193 1223
860
940    1063  1093      1124    1155  1185  1216 1247
880
960    1084  1115      1146    1177  1208  1239 1270
900
980    1105  1137      1168    1199  1230  1262 1293
920
                          5.27-4
940
960
980
6
140
164
.187
211
234
257
279
302
324
347
369
392
414
436
458
480
502  
524  
546  
568
589  
611  
633  
655  
676
698
720
741
763
784
806
827
849
870
892
913
935
956
977
999
1020
1041
1063
1084
1105
5.27-4
7
8
150
175
199
223
247
271
294
317
341
364
387
409
432
455
477
500  
522
545
567
590
612  
634  
656
678
700
722
744
766
788
810
832
854
876
898
920
941
963
985
1007
1028
1050
1072
1093
1115
1137
160
186
211
236
260
285
309
333
357
380
404
427
451
474
497
520  
543
566
589
611  
634  
657  
679
702  
724
747
769
792
814
836
859
881
903
925
948
970
992
1014
1036
1058
1080
1102
1124
1146
1168
170
197
223
249
274
299
324
348
373
397
421
445
469
493
516
540  
563
587
610
633  
657
680
703  
726  
749  
771
794
817
840
863
885
908
930
953
975
998
1020
1043
1065
1088
1110
1132
1155
1177
1199
180
208
235
261
287
313
339
364
389
414
439
463
488
512
536
560  
584
608
632
655  
679
702  
726  
749  
773  
796
819
842
866
889
912
935
958
981
1003
1026
1049
1072
1095
1117
1140
1163
1185
1208
1230
9
190
219
246
274
301
327
353
379
405
431
456
481
506
531
555
580  
604
629
653
677
701
725
749  
773  
797  
820
844
868
891
915
938
961
985
1008
1031
1055
1078
1101
1124
1147
1170
1193
1216
1239
1262
10
200
230
258
286
314
341
368
395
421
447
473
499
524
550
575
600
625
650
674
699
724
748
772
797
821  
845  
869  
893  
917  
941  
965  
988  
1012  
1036  
1059  
1083  
1106  
1130  
1153  
1177  
1200  
1223  
1247  
1270  
1293


TABLE I (Cont'd)
TABLE I (Cont'd)  
                      ALARM THRESHOLD
ALARM THRESHOLD  
                      T
T
  B   n =   4     5        6          7    8      9
B  
1000       1126  1158    1190      1221  1253  1285  1316
n =  
1200       1339  1373    1408      1442  1477  1512  1546
4
1400       1550  1587    1624      1662  1699  1737  1774
1000  
1600       1760  1800     1840      1880  1920  1960  2000
1200  
1800       1970  2012     2055       2097 2139   2182 2224
1400  
2000       2179  2224     2268      2313  2358  2402  2447
1600  
2200      2388  2435    2481      2528  2575  2622  2669
1800  
2400      2596  2645    2694      2743  2792  2841  289C
2000  
2600      2804  2855    2906      2957  3008  3059  3110
2200
2800      3012  3065    3117      3170  3223  3276  3329
2400
3000      3219  3274    3329      3383  3438  3493  3548
2600
3200      3426  3483    3539      3596  3653  3709  3766
2800
3400      3633  3692    3750      3808  3866  3925  3983
3000
3600      3840  3900    3960      4020  4080  4140  4200
3200
3800      4047  4108    4170      4232  4293  4355  4416
3400
4000      4253  4316    4379      4443  4506  4569  4632
3600
4200      4459  4524    4589      4654  4718  4783  4848
3800
4400      4665  4732    4798      4864  4931  4997  5063
4000
4600      4871  4939    5007      5075  5143  5210  5278
4200
4800      5077  5146    5216      5285  5354  5424  5493
4400
5000      5283  5354    5424      5495  5566  5636  5707
4600
5200      5483  5561    5633      5705  5777  5849  5921
4800
5400      5694  5767    5841      5914  5988  6061  6135
5000
5600      5899  5974    6049      6124  6199  6273  6348
5200
5800      6105  6181    6257      6333  6409  6485  6562
5400
6000      6310  6387    6465      6542  6620  6697  6775
5600
6200      6515  6594    6672      6751  6830  6909  6987
5800
6400      6720  6800    6880      6960  7040  7120  7200
6000
6600      6925  7006    7087      7169  7250  7331  7412
6200
6800      7130  7212    7295      7377  7460  7542  7625
6400
7000      7335  7418    7502      7586  7669  7753  7837
6600
7200      7539  7624    7709      7794  7879  7964  8049
6800
7400      7744  7830    7916      8002  8088  8174  8260
7000
7600      7949  8036    8123      8210  8297  8385  8472
7200
7800      8153  8242    8330      8418  8507  8595  8683
7400
8000      8358  8447    8537      8626  8716  8805  8894
7600
8200      8562  8653    8743      8834  8924  9015  9106
7800
8400      8767  8858    8950      9042  9133  9225  9317
8000
8600      8971  9064    9156      9249  9342  9435  9527
8200
8800      9175  9269    9363      9457  9550  9644  9738
8400
9000      9379  9474    9569      9664  9759  9854  9949
8600
9200      9584  9680      9775      9871  9967 10063 10159
8800
9400      9788  9885      9932    10079 10176  10273 10370
9000
9600      9992 10090    10188      10286 10384  10482 10580
9200
9800    10196 10295    10394      10493 10592  10691 10790
9400
                            5.27-5
9600
9800
1126
1339
1550
1760
1970
2179
2388
2596
2804
3012
3219
3426
3633
3840
4047
4253
4459
4665
4871
5077
5283
5483
5694
5899
6105
6310
6515
6720
6925
7130
7335
7539
7744
7949
8153
8358
8562
8767
8971
9175
9379
9584
9788
9992
10196
5
1158
1373
1587
1800  
2012  
2224
2435
2645
2855
3065
3274
3483
3692
3900
4108
4316
4524
4732
4939
5146
5354
5561
5767
5974
6181
6387
6594
6800
7006
7212
7418
7624
7830
8036
8242
8447
8653
8858
9064
9269
9474
9680
9885
10090
10295
5.27-5
9
6
1190
1408
1624
1840
2055  
2268
2481
2694
2906
3117
3329
3539
3750
3960
4170
4379
4589
4798
5007
5216
5424
5633
5841
6049
6257
6465
6672
6880
7087
7295
7502
7709
7916
8123
8330
8537
8743
8950
9156
9363
9569
9775
9932
10188
10394
7
1221
1442
1662
1880
2097  
2313
2528
2743
2957
3170
3383
3596
3808
4020
4232
4443
4654
4864
5075
5285
5495
5705
5914
6124
6333
6542
6751
6960
7169
7377
7586
7794
8002
8210
8418
8626
8834
9042
9249
9457
9664
9871
10079
10286
10493
8
1253
1477
1699
1920
2139  
2358
2575
2792
3008
3223
3438
3653
3866
4080
4293
4506
4718
4931
5143
5354
5566
5777
5988
6199
6409
6620
6830
7040
7250
7460
7669
7879
8088
8297
8507
8716
8924
9133
9342
9550
9759
9967
10176
10384
10592
1285
1512
1737
1960
2182  
2402
2622
2841
3059
3276
3493
3709
3925
4140
4355
4569
4783
4997
5210
5424
5636
5849
6061
6273
6485
6697
6909
7120
7331
7542
7753
7964
8174
8385
8595
8805
9015
9225
9435
9644
9854
10063
10273
10482
10691
1316
1546
1774
2000  
2224  
2447  
2669  
289C  
3110  
3329  
3548  
3766  
3983  
4200  
4416  
4632  
4848  
5063  
5278  
5493  
5707  
5921  
6135  
6348  
6562  
6775  
6987  
7200  
7412  
7625  
7837  
8049  
8260  
8472  
8683  
8894  
9106  
9317  
9527  
9738  
9949  
10159  
10370  
10580  
10790


TABLE II
TABLE II
      MAXIMUM PERMISSIBL
MAXIMUM PERMISSIBL


==E. BACKGROUND==
==E. BACKGROUND==
a = 0,   Pa = 50%
a = 0,  
                              B
Pa = 50%
    G  n=       4       5           6        7        8            10
B
                                                                  9
n=  
100           67      61         55       50      46        42  38
4
120          83      76          70       64      59      54    50
100
140          100      92          85       78      72        67  62
120
160        117      108        100         93      86        80  74
140
180.          134      124        116       107      100        93    87
160
200          151      141        131       123      114      107  100
180.
220          168      157        147       138      129      121  113
 
240          186      174        163       153      144      135  127
200
260          203      191        180       169      159      150  141
220
280          221      208        196       185      174      165  155
240
300          238      225        213       201      190      179  170
260
320          256      242        229       217      205      194  184
280
340          274      259        246       233      221      210  199
300
360          292      277        263       249      237      225  214
320
380          310      294        280       266      253      240  229
340
400          328      312        297       282      269      256  244
360
420          346      329        314       299      285      272  259
380
440          364      347        331       316      301      287  274
400
460          382      365        348       332      317      303  290
420
480          400      382        365       349      334      319  305
440
500          418      400        383       366      350      335  321
460
520          436      418        400       383      367      351  337
480
540          455      436        417       400      383      367  352
500
560          473      454        435       417      400      384  368
520
580          491      471        452       434      417      400  384
540
600          510      489        470       451      433      416  400
560
620          528      507        488       468      450      433  416
580
640          546      525        505       486      467      449  432
600
660          565      543        523       503      484      466  448
620
680          583      562        541       520      501      482  464
640
700          602      580        558       538      518      499  481
660
720          620      598        576       555      535      516  497
680
740          639      616        594       573      552      532  513
700
760          657      634        612       590      569      549  530
720
780          676      652        629       607      586      566  546
740
800          695      671        647       625      603      583  563
760
820          713      689        665       643      621      600  579
780
840          732      707        683       660      638      617  596
800
860          750      725        701       678      655      633  613
820
880          769      744        719       695      673      650  629
840
900          788      762        737       713      690      667  646
860
920          806      780        755       731      707      685  663
880
940          825      799        773       748      725      702  679
900
960          844      817        791       766      742      719  696
920
980          863      835        809       784      760      736  713
940
                                    5.27-6
960
980
5
67
83
100  
117
134
151
168
186
203
221
238
256
274
292
310
328
346
364
382
400
418
436
455
473
491
510
528
546
565
583
602
620
639
657
676
695
713
732
750
769
788
806
825
844
863 G
61  
76
92
108
124
141
157
174
191
208
225
242
259
277
294
312
329
347
365
382
400
418
436
454
471
489
507
525
543
562
580
598
616
634
652
671
689
707
725
744
762
780
799
817
835
6
55  
70  
85  
100  
116  
131  
147  
163  
180  
196  
213  
229  
246  
263  
280  
297  
314  
331  
348  
365  
383  
400  
417  
435  
452  
470  
488  
505  
523  
541  
558  
576  
594  
612  
629  
647  
665  
683  
701  
719  
737  
755  
773  
791  
809
5.27-6
7
50
64
78
93
107
123
138
153
169
185
201
217
233
249
266
282
299
316
332
349
366
383
400
417
434
451
468
486
503
520
538
555
573
590
607
625
643
660
678
695
713
731
748
766
784
9
10
8
46
59
72
86
100
114
129
144
159
174
190
205
221
237
253
269
285
301
317
334
350
367
383
400
417
433
450
467
484
501
518
535
552
569
586
603
621
638
655
673
690
707
725
742
760
42
54
67
80
93
107
121
135
150
165
179
194
210
225
240
256
272
287
303
319
335
351
367
384
400
416
433
449
466
482
499
516
532
549
566
583
600
617
633
650
667
685
702
719
736
38
50
62
74
87
100
113
127
141
155
170
184
199
214
229
244
259
274
290
305
321
337
352
368
384
400
416
432
448
464
481
497
513
530
546
563
579
596
613
629
646
663
679
696
713


TABLE II   (Cont'd)
TABLE II  
    MAXIMUM PERMISSIBL
(Cont'd)
MAXIMUM PERMISSIBL


==E. BACKGROUND==
==E. BACKGROUND==
a -'0,   Pa = 50Z
B
                              B
G
  G    n =    4        5        6        7       8         9  10
n =
1000          881      854      827      802      777       753  730
4
1200        1069      1039      1009      981      953       926  900
1000
1400        1258      1225      1193    1161    1131     1101  1073
1200
1600        1448      1412      1377    1343    1310     1278  1247
1400
1000        1638      1600      1563    1527    1491     1457  1423
1600
2000        1829      1789      1749    1710    1673     1636  1600
1000
2200        2020      1978      1936    1895    1855     1816  1778
2000
2400        2212      2167      2124    2081    2039     199D  1958
2200
2600        2404      2357      2312    2267    2223     2180  2138
2400
2800        2596      2548      2500    2453    2407     2363  2318
2600
3000        2789      2738      2689    2640    2593     2546  2500
2800
3200        29S2      2929      2878    2828    2778     2730  2682
3000
3400        3175      3121      3068    3016    2964     2914  2865
3200
3600        3368    3312      3258    3204    3151     3099  3048
3400
3800        3561    3504      3448    3392    3338     3284  3232
3600
4000        3755      3696      3638    3581    3525     3470  3416
3800
4200        3949      3888      3829    3770    3713     3656  3600
4000
4400        4143      4081      4020    3960    3900     3842  3785
4200
4600        4337      4273      4211    4149    4088     4029  3970
4400
4800        4531      4466      4402    4339    4277     4216  4155
4600
5000        4725      4659      4593    4529    4465     4403  4341
4800
5200        4919      4852      4785    4719    4654     4590  4527
5000
5400        5114      5045      4977    4910    4843     4778  4713
5200
5600        5309      5238      5169    5100    5032     4966  4900
5400
5800        5503      5432      5361    5291    5222     5154  5087
5600
6000        5698      5625'    5553    5482    5411     5342  5274
5800
6200        5893      5819      5745    5673    5601     5531  5461
6000
6400        6088      6012      5938    5864    5791     5719  5648
6200
6600        6283      6206      6130    6055    5981     5908  5836
6400
6800        6478      6400      6323    6247    6172     60'97 6024
6600
7000        6673      6594      6516    6438    6362     6286  6212
6800
7200        6868      6788      6709    6630    6552     6476  6400
7000
7400        7064      6982      6902    6822    6743     6665  6588
7200
7600        7259      7176      7095    7014    6934     6855  6777
7400
7800        7455      7371      7288    7206    7125     7045  6965
7600
8000        7650      7565      7481    7398    7316     7234  7154
7800
8200        7846      7760      7674    7590    7507     7425  7343
8000
8400        8041      7954      7868    7782    7698     7615  7532
8200
8600        8237      8149      8061    7975    7889     7805  7721
8400
8800        8433      8343      8255    8167    8081     7995  7911
8600
9000        8628      8538      8449    8360    8272     8186  8100
8800
9200        8824      8733      8642    8553    8464     8376  8290
9000
9400        9020      8928      8836    8745    8656     8567  8479
9200
9600        9216      9122      9030    8938    8348     8758  8669
9400
9800        9412      9317      9224    9131    9039     8949  8859
9600
                                  5.27-7
9800
881
1069
1258
1448
1638
1829
2020
2212
2404
2596
2789
29S2
3175
3368
3561
3755
3949
4143
4337
4531
4725
4919
5114
5309
5503
5698
5893
6088
6283
6478
6673
6868
7064
7259
7455
7650
7846
8041
8237
8433
8628
8824
9020
9216
9412
5
854
1039
1225
1412
1600
1789
1978
2167
2357
2548
2738
2929
3121
3312
3504
3696
3888
4081
4273
4466
4659
4852
5045
5238
5432
5625'
5819
6012
6206
6400
6594
6788
6982
7176
7371
7565
7760
7954
8149
8343
8538
8733
8928
9122
9317 a -'0,  
Pa = 50Z
6
827
1009
1193
1377
1563
1749
1936
2124
2312
2500
2689
2878
3068
3258
3448
3638
3829
4020
4211
4402
4593
4785
4977
5169
5361
5553
5745
5938
6130
6323
6516
6709
6902
7095
7288
7481
7674
7868
8061
8255
8449
8642
8836
9030
9224
7  
802
981
1161
1343
1527
1710
1895
2081
2267
2453
2640
2828
3016
3204
3392
3581
3770
3960
4149
4339
4529
4719
4910
5100
5291
5482
5673
5864
6055
6247
6438
6630
6822
7014
7206
7398
7590
7782
7975
8167
8360
8553
8745
8938
9131
8  
777  
953  
1131  
1310  
1491  
1673  
1855  
2039  
2223  
2407  
2593  
2778  
2964  
3151  
3338  
3525  
3713  
3900  
4088  
4277  
4465  
4654  
4843  
5032  
5222  
5411  
5601  
5791  
5981  
6172  
6362  
6552  
6743  
6934  
7125  
7316  
7507  
7698  
7889  
8081  
8272  
8464  
8656  
8348  
9039
5.27-7
9
753
926
1101
1278
1457
1636
1816
199D
2180
2363
2546
2730
2914
3099
3284
3470
3656
3842
4029
4216
4403
4590
4778
4966
5154
5342
5531
5719
5908
60'97
6286
6476
6665
6855
7045
7234
7425
7615
7805
7995
8186
8376
8567
8758
8949
10
730
900
1073
1247
1423
1600
1778
1958
2138
2318
2500
2682
2865
3048
3232
3416
3600
3785
3970
4155
4341
4527
4713
4900
5087
5274
5461
5648
5836
6024
6212
6400
6588
6777
6965
7154
7343
7532
7721
7911
8100
8290
8479
8669
8859


TABLE II (Cont'd)
TABLE II  
    MAXIMUM PERMISSIBL
(Cont'd)
MAXIMUM PERMISSIBL


==E. BACKGROUND==
==E. BACKGROUND==
S= 1.3, Pa = 90%
B
                            B
G
  G    n      4        5        6        7        8       9  10
n
100          57        51        46        42      38       34  31
4
120          72        65        59        54      49       45  41
100
140          87        80        73        67      62       57  52
120
160          103        95        87        81      75       69  64
140
180        119      110      102        95      88       81  76
160
200        135      126      117      109      101       94  FS
180
220          151      141      132      123      115     107  100
200
240          168      157      147      138      129     121  113
220
260          185      173      163      153      143     135 127
240
280          201      189      178      168      158     149  1L0
260
300        218      206      194      183      172     163 154
280
320          235      222      210      198      187     177 167
300
340        252      239      226      214      202     191 181
320
360          270      255      242      229      217     206 196
340
380        287      272      258      245      233     221 210
360
400          304      289      275      261      248     236 224
380
420          322      306      291      277      263     251 22S
400
440          339      323      308      293      279     266 254
420
460          357      340      324      309      295     281 268
440
480          374      357      341      325      311     297  283
460
500          392      374      357      342      326     312 298
480
520          409      391      374      358      342     327 313
500
540          427      409      391      374      358     343 329
520
560          445      426      408      391      374     359 344
540
580          463      443      425      407      391     375 359
560
600          480      461      442      424      407     390 375
580
620          498      478      459      441      423     406 390
600
640          516      496      476      457      439     422 406
620
660          534      513      493      474      456     438 421
640
680          552      531      511      491      472     454 437
660
700          570      549      528      508      489     470 453
680
720          588      566      545      525      505     487 469
700
740          606      584      562      542      522     503 485
720
760          624      602      580      559      539     519 500
740
780          642      619      597      576      555     535 516
760
800          660      637      614      593      572     552 532
780
820          679      655      632      610      589     568 549
800
840          697      673      649      627      605     585 565
820
860          715      690      667      644      622     601 581
840
880          733      708      684      661      639     618 597
860
900          751      726        702      679      656     634 613
880
920          770      744      720      696      673     651 630
900
940          788      762      737      713      690     668 646
920
960          806      780      755      731      707     684 662
940
980          824      798      773      748      724     701 679
960
                                  5.27-8
980
57
72
87
103
119
135
151
168
185
201
218
235
252
270
287
304
322
339
357
374
392
409
427
445
463
480
498
516
534
552
570
588
606
624
642
660
679
697
715
733
751
770
788
806
824
5
51
65
80
95
110
126
141
157
173
189
206
222
239
255
272
289
306
323
340
357
374
391
409
426
443
461
478
496
513
531
549
566
584
602
619
637
655
673
690
708
726
744
762
780
798
6
46
59
73
87
102
117
132
147
163
178
194
210
226
242
258
275
291
308
324
341
357
374
391
408
425
442
459
476
493
511
528
545
562
580
597
614
632
649
667
684
702
720
737
755
773 S= 1.3, Pa = 90%
7
42
54
67
81
95
109
123
138
153
168
183
198
214
229
245
261
277
293
309
325
342
358
374
391
407
424
441
457
474
491
508
525
542
559
576
593
610
627
644
661
679
696
713
731
748
9
8  
38  
49  
62  
75  
88  
101  
115  
129  
143  
158  
172  
187  
202  
217  
233  
248  
263  
279  
295  
311  
326  
342  
358  
374  
391  
407  
423  
439  
456  
472  
489  
505  
522  
539  
555  
572  
589  
605  
622  
639  
656  
673  
690  
707  
724
5.27-8
34
45
57
69
81
94
107
121
135
149
163
177
191
206
221
236
251
266
281
297
312
327
343
359
375
390
406
422
438
454
470
487
503
519
535
552
568
585
601
618
634
651
668
684
701
10
31
41
52
64
76 FS
100
113
127
1L0
154
167
181
196
210
224
22S
254
268
283
298
313
329
344
359
375
390
406
421
437
453
469
485
500
516
532
549
565
581
597
613
630
646
662
679


TABLE II   (Cont'd)
TABLE II  
        MAXIMUM PERMISSIBL
(Cont'd)
MAXIMUM PERMISSIBL


==E. BACKGROUND==
==E. BACKGROUND==
a = 1.3, P= = 90%
G
    G n=      4        5          6          7       8       9     10
n=
1000        843      816        790        765      741    718  695
4
1200      1027      997        968        940      913    887  861
1000
1400      1212    1180        1148      1117    1088    1059  1030
1200
1600      1398    1363        1329      1296    1264    1232  1201
1400
1800      1536    it48        1512      1476      1441    1407  1374
1600
2000      1773    1734        1695      1657      1620    1584  1548
1800
2200      1962    1920        1879      1839      1800    1761  1724
2000
2400      2151    2107        2064      2022      1980    1940  1900
2200
2600      2340    2294        2249      2205      2162    2119  2078
2400
2800      2530    2482        2435      2389      2344    2300  2256
2600
3000      2720    2670        2622      2574      2527    2481  2435
2800
3200      2911    2859        2808      2759      2710    2662  2615
3000
3400      3101    3048        2996      2944      2894    2844  2795
3200
3600      3292    3238        3183      3130      3078    3027  2976
3400
3800      3484    3427        3371      3317      3263    3210  3158
3600
4000      3675    3617        3560      3503      3448    3393  3340
3800
4200      3867    3807        3748      3691      3634    3577  3522
4000
4400      4059    3998        3937      3878      3319    3762  3705
4200
4600      4251    4188        4126      4066      4006    3946  3888
4400
4800      4443    4379        4316      4253      4192    4131  4072
4600
5000      4636    4570        4505      4442      4379    4317  4256
4800
5200      4828    4761        4695      4630      4566    4502  4440
5000
5400      5021    4953        4885      4819      4753    4688  4624
5200
5600      5214    5144        5075      5007      4940    4874  4809:
5400
5S00      5407    5336        5266      5196      5128    5061  4994
5600
6000      5600    5528        5456      5386      5316    5247  5180
5S00
6200      5793    5720        5647      5575      5504    5434  5365
6000
6400      5987    5912        5S38      5765      5692    5621  5551
6200
6600      6180    6104        6029      5954      5831    580G  5737
6400
6800      6373    6296        6220      6144      6070    5996  5923
6600
7000      6567    6488        6411      6334      6258    6184  6110
6800
7200      6761    6681        6602      6524      6447    6371  6296
7000
7400      r9955    6874        6794      6715      6636    6559  6483
7200
7600      7148    7066      6985      6905      6826    6747  6670
7400
7800      7342    7259        7177      7096      7015    6936  6857
7600
8000      7536    7452        7369      7286      7205    7124  7044
7800
8200      7731    7645        7561      7477      7394    7313  7232
8000
8400      7925    7838        7753      7668      7584    7501  7419
8200
8600      8119    8031        7945      7859      7774    7690  7607
8400
8800      3313    8225        8137      8050      7964    7879  7795
8600
9000      8508    8418        8329      8241      8154    8063  7983
8800
9200      8702    8611        8521      8433      8345    8257  8171
9000
9400      8897    8805        8714      8624      8535    8447  8360
9200
9600      9091    8998        8906      8815      8725    8636  8548
9400
98-00    9286    9192        9099      9007      8916    8826  8737
9600
                                5.27-9
98-00
843
1027
1212
1398
1536
1773
1962
2151
2340
2530
2720
2911
3101
3292
3484
3675
3867
4059
4251
4443
4636
4828
5021
5214
5407
5600
5793
5987
6180
6373
6567
6761 r9955
7148
7342
7536
7731
7925
8119
3313
8508
8702
8897
9091
9286
5
816
997
1180
1363 it48
1734
1920
2107
2294
2482
2670
2859
3048
3238
3427
3617
3807
3998
4188
4379
4570
4761
4953
5144
5336
5528
5720
5912
6104
6296
6488
6681
6874
7066
7259
7452
7645
7838
8031
8225
8418
8611
8805
8998
9192
6
790
968
1148
1329
1512
1695
1879
2064
2249
2435
2622
2808
2996
3183
3371
3560
3748
3937
4126
4316
4505
4695
4885
5075
5266
5456
5647
5S38
6029
6220
6411
6602
6794
6985
7177
7369
7561
7753
7945
8137
8329
8521
8714
8906
9099
5.27-9 a = 1.3, P= = 90%
7  
765
940
1117
1296
1476
1657
1839
2022
2205
2389
2574
2759
2944
3130
3317
3503
3691
3878
4066
4253
4442
4630
4819
5007
5196
5386
5575
5765
5954
6144
6334
6524
6715
6905
7096
7286
7477
7668
7859
8050
8241
8433
8624
8815
9007
8  
741
913
1088
1264
1441
1620
1800
1980
2162
2344
2527
2710
2894
3078
3263
3448
3634
3319
4006
4192
4379
4566
4753
4940
5128
5316
5504
5692
5831
6070
6258
6447
6636
6826
7015
7205
7394
7584
7774
7964
8154
8345
8535
8725
8916
9
718
887
1059
1232
1407
1584
1761
1940
2119
2300
2481
2662
2844
3027
3210
3393
3577
3762
3946
4131
4317
4502
4688
4874
5061
5247
5434
5621
580G
5996
6184
6371
6559
6747
6936
7124
7313
7501
7690
7879
8063
8257
8447
8636
8826
10
695  
861  
1030  
1201  
1374  
1548  
1724  
1900  
2078  
2256  
2435  
2615  
2795  
2976  
3158  
3340  
3522  
3705  
3888  
4072  
4256  
4440  
4624  
4809:  
4994  
5180  
5365  
5551  
5737  
5923  
6110  
6296  
6483  
6670  
6857  
7044  
7232  
7419  
7607  
7795  
7983  
8171  
8360  
8548  
8737


APPENDIX A
APPENDIX A
                        PROCEDURE FOR TESTING SNM DOORWAY MONITORS
PROCEDURE FOR TESTING SNM DOORWAY MONITORS  
                                                              FOR
FOR  
                                          FUNCTIONAL PERFORMANCE
FUNCTIONAL PERFORMANCE
    Doorway monitors should be tested by employing a               background taken immediately after the test varies by test source of the same isotope of SNM the doorway                 more than 2vN from the background taken before the monitor is used to detect as follows:                              test, the test should be repeated, for such a difference indicates nonrandom fluctuations of the background or
Doorway monitors should be tested by employing a test source of the same isotope of SNM the doorway monitor is used to detect as follows:
1. With the detection area unoccupied, measure and                  equipment malfunction. The probability of such an record background.                                                  occurrence due to the randomness of the background is less than 8%.
1. With the detection area unoccupied, measure and record background.
2. Determine alarm threshold T from Table I (see Appendix B).                                                        5. A calibration source (Appendix B) should be carried repeatedly to various places within the detection area of
 
3. Place a test source in the detection area of the                  the doorway monitor in simulation of actual use to doorway monitor. The test source should be such that                verify that the SNM can be detected everywhere within the activity in the detection area slightly exceeds the T            the detection area and to assure proper operation of level.* The doorway monitor should go into an alarm                  treadle pads, beam-break, or similar devices if the condition if operating properly.                                    doorway monitor is so equipped.
2. Determine alarm threshold T from Table I (see Appendix B). 
3. Place a test source in the detection area of the doorway monitor. The test source should be such that the activity in the detection area slightly exceeds the T
level.* The doorway monitor should go into an alarm condition if operating properly.
 
4. Remove test source to its original location and measure background once again. If the measurement of
*The test source may be improvised by partially shielding the calibration source.
 
background taken immediately after the test varies by more than 2vN  
from the background taken before the test, the test should be repeated, for such a difference indicates nonrandom fluctuations of the background or equipment malfunction. The probability of such an occurrence due to the randomness of the background is less than 8%.
5. A calibration source (Appendix B) should be carried repeatedly to various places within the detection area of the doorway monitor in simulation of actual use to verify that the SNM can be detected everywhere within the detection area and to assure proper operation of treadle pads, beam-break, or similar devices if the doorway monitor is so equipped.


4. Remove test source to its original location and                  6. Doorway monitors used to search for concealed measure background once again. If the measurement of                uranium-233 should be tested with each uranium purification run, but no more frequently than daily. The
6. Doorway monitors used to search for concealed uranium-233 should be tested with each uranium purification run, but no more frequently than daily. The test source should be freshly purified uranium-233 (within four hours of removal of decay products).
*The test source may be improvised by partially shielding the        test source should be freshly purified uranium-233 calibration source.                                              (within four hours of removal of decay products).
5.27-10
                                                            5.27-10


APPENDIX B
APPENDIX B
            PROCEDURE FOR DETERMINING MAXIMUM PERMISSIBL
PROCEDURE FOR DETERMINING MAXIMUM PERMISSIBL


==E. BACKGROUND==
==E. BACKGROUND==
Background should be measured over several work               found from Table II, the sensitivity of the doorway shifts to determine the setpoints for alarm threshold               monitor will generally be below that specified as (with or without automatic background updating) to                 minimum in Regulatory Position C.l.b of this guide.
Background should be measured over several work shifts to determine the setpoints for alarm threshold (with or without automatic background updating) to assure that normal operation will be minimally affected by alarms due to high background.
 
The doorway monitor should be calibrated with the amount of the appropriate isotope specified in Regula tory Positions C.l.b(1), (2), or (3) of this guide (e.g., 0.5 gram plutonium-239 in 3 mm of brass). 
The calibration procedure described below is essen tially a means of determining maximum permissible background for effective operation of the doorway monitor.


assure that normal operation will be minimally affected by alarms due to high background.                                        The parameter n is a function of the background variation and the permissible false alarm rate and is The doorway monitor should be calibrated with the              calculated from amount of the appropriate isotope specified in Regula tory Positions C.l.b(1), (2), or (3) of this guide (e.g., 0.5                                                1 /2 gram plutonium-239 in 3 mm of brass).                                                    n >3.1 (var B)                          (2)
1. Place a calibration source variously about the detec tion area and take readings to determine the least sensitive point. This location of minimum sensitivity should be maintained as the calibration point.
    The calibration procedure described below is essen tially a means of determining maximum permissible                      Generally, n is taken as an integer. If n satisfies the background for effective operation of the doorway                    above expression, the expected false alarm rate (Appen monitor.                                                            dix C) due to background fluctuations should be less than 0.1%. Larger values of n will decrease the expected
1. Place a calibration source variously about the detec             false alarm rate; however, the maximum allowable tion area and take readings to determine the least                 background for a given G will also decrease.


sensitive point. This location of minimum sensitivity should be maintained as the calibration point.                      4. For doorway monitors equipped with automatic background updating systems, the alarm threshold is
2. Measure background over several workshifts to deter mine the periods of high background and the range of background. A minimum of 20 measurements should be taken. The variance of the background is given by N
2. Measure background over several workshifts to deter mine the periods of high background and the range of                                     Counts > B + nVii,                      (3)
Var B N*-
background. A minimum of 20 measurements should be taken. The variance of the background is given by                   where n should be derived from expression (2), and the instrument set accordingly.
1 (Bi-B)2
(1)  
where N is the number of measurements, B is the mean of the background measurements, and Bi is the ith background measurement.


N
3. With the calibration source at the calibration point, the mean gross counts G should be determined during a period of high background to establish the upper operating range of the doorway monitor. Table II lists various maximum permissible background levels for a given value of G for values of the parameters n and a.
              Var B      1 N*-        (Bi-B)2                (1)        5. The high-background alarm should be set at the B
                                                                    value given in Table II for the measured G and calculated n values.


where N is the number of measurements, B is the mean ith of the background measurements, and Bi is the                       6. For doorway monitors not equipped with an auto background measurement.                                            matic background update, the value of n determined above should be employed in the use of the doorway
During periods when the background exceeds the value found from Table II, the sensitivity of the doorway monitor will generally be below that specified as minimum in Regulatory Position C.l.b of this guide.
3. With the calibration source at the calibration point,            monitor according to Regulatory Position C.2.a.


the mean gross counts G should be determined during a               *The false alarm rate is estimated by the probability that an period of high background to establish the upper                      observation of a quantity distributed normally about some operating range of the doorway monitor. Table II lists                value X will exceed X by n(Std. deviation of X). The factor 3.1 various maximum permissible background levels for a                  limits the false alarm rate to 0.1%, while the factor given value of G for values of the parameters n and a.              (Var B/B) 1 /2 compensates for observed deviations in the During periods when the background exceeds the value                  background distribution from Poisson.
The parameter n is a function of the background variation and the permissible false alarm rate and is calculated from n >3.1 (var B) 1/2
(2)
Generally, n is taken as an integer. If n satisfies the above expression, the expected false alarm rate (Appen dix C) due to background fluctuations should be less than 0.1%. Larger values of n will decrease the expected false alarm rate; however, the maximum allowable background for a given G will also decrease.
 
4. For doorway monitors equipped with automatic background updating systems, the alarm threshold is Counts > B + nVii,
(3)
where n should be derived from expression (2), and the instrument set accordingly.
 
5. The high-background alarm should be set at the B
value given in Table II for the measured G and calculated n values.
 
6. For doorway monitors not equipped with an auto matic background update, the value of n determined above should be employed in the use of the doorway monitor according to Regulatory Position C.2.a.
 
*The false alarm rate is estimated by the probability that an observation of a quantity distributed normally about some value X will exceed X by n(Std. deviation of X). The factor 3.1 limits the false alarm rate to 0.1%, while the factor (Var B/B) 1/2 compensates for observed deviations in the background distribution from Poisson.


5.27-11
5.27-11


APPENDIX C
APPENDIX C
                                DETECTION CONFIDENCE LIMITS, THRESHOLDS,
DETECTION CONFIDENCE LIMITS, THRESHOLDS,  
                                  AND MAXIMUM PERMISSIBL
AND MAXIMUM PERMISSIBL


==E. BACKGROUND==
==E. BACKGROUND==
With a calibration source at the calibration point, the             The condition for a false alarm* is written as condition for an alarm is, in general, b= B +j      a-'"B> T                  (4)
With a calibration source at the calibration point, the condition for an alarm is, in general, g> T = B + m/Va' B
                  g> T = B + m/Va' B                   (1)       where b is a single measurement without the source and
(1)
                                                                  0 is a number corresponding to a false alarm probability Pp. For P = 0.1%, 0 = 3.1. Hence the necessary where g is a single measurement of G (the mean                    condition for maintaining a false alarm rate below Pp is radiation level with the source), B is the mean back ground, and m is some multiplier. The detection                                  b= B+       -"B   < B+ m ar.                 (5)
where g is a single measurement of G (the mean radiation level with the source), B is the mean back ground, and m is some multiplier. The detection confidence limit is the probability that with the calibra iton source at the calibration point, any single determin ation of G will exceed a threshold T, i.e., the above inequality will be satisfied. For any given probability Pa.,
confidence limit is the probability that with the calibra However, the doorway monitor actually compares b iton source at the calibration point, any single determin with B + ni, hence the condition on n becomes ation of G will exceed a threshold T, i.e., the above inequality will be satisfied. For any given probability Pa.,                      orV         < rn'VaTr   = nvff             (6)
there exists a value a such that g > G-
there exists a value a such that                                  or g > G-                            (2)                            n>0 ( Va B ) 1/2                       (7)
(2)  
                                                                      In Table I threshold values of T were determined by with a probability of Pa, where g is any single measure          substituting equation (6) into equation (3):
with a probability of Pa, where g is any single measure ment of the quantity G. Hence the condition for a detection confidence limit of Pais G - &
ment of the quantity G. Hence the condition for a detection confidence limit of Pais                                                          T = B + nv'r The values of B in Table II were then calculated for G- &      _-r*-G > T = B + m,,/'r B.        (3)      a = 1.3 and a = 0 from equation (3) assuming that, for the determination of G, the background should be reasonably stable and therefore \/Var G -\
_-r*-G > T = B + m,,/'r B.
For a given value of G, solving (3) gives the maximum permissible B at which the doorway monitor will detect            *False alarm means an alarm condition generated by statistical the source with a confidence Pr-For Pa = 90%, a = 1.3,              fluctuations in the background radiation or by instabilities of the electronics which appear as background fluctuations when and for Pa = 50%, a = 0.                                            the detection area is occupied.
 
(3)
For a given value of G, solving (3) gives the maximum permissible B at which the doorway monitor will detect the source with a confidence Pr- For Pa = 90%, a = 1.3, and for Pa = 50%, a = 0.
 
The condition for a false alarm* is written as b = B + j a-'"B> T
(4)
where b is a single measurement without the source and  
0 is a number corresponding to a false alarm probability P
 
====p. For P ====
= 0.1%, 0 = 3.1. Hence the necessary condition for maintaining a false alarm rate below Pp is b = B +  
-"B  
< B + m ar.
 
(5)  
However, the doorway monitor actually compares b with B + ni, hence the condition on n becomes orV  
< rn'VaTr  
= nvff  
(6)  
or n>0 ( Va B ) 1/2
(7)
In Table I threshold values of T were determined by substituting equation (6) into equation (3):  
T = B + nv'r The values of B in Table II were then calculated for a = 1.3 and a = 0 from equation (3) assuming that, for the determination of G, the background should be reasonably stable and therefore \\/Var G -\\  
*False alarm means an alarm condition generated by statistical fluctuations in the background radiation or by instabilities of the electronics which appear as background fluctuations when the detection area is occupied.


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Latest revision as of 02:07, 17 January 2025

Special Nuclear Material Doorway Monitors
ML003740050
Person / Time
Issue date: 06/30/1974
From:
Office of Nuclear Regulatory Research
To:
References
RG-5.27
Download: ML003740050 (12)
v • d • e


June 1974 U.S. ATOMIC ENERGY COMMISSION

REGULATORY GUIDE

DIRECTORATE OF REGULATORY STANDARDS

REGULATORY GUIDE 5.27 SPECIAL NUCLEAR MATERIAL DOORWAY MONITORS

A. INTRODUCTION

Paragraph (b), "Exit Requirement," of § 73.60, "Ad ditional Requirements for the Physical Protection of Special Nuclear Material at Fixed Sites," of 10 CFR Part

73, "Physical Protection of Plants and Materials,"

requires that individuals exiting from material access areas be searched for concealed special nuclear material (SNM). This guide describes means acceptable to the Regulatory staff for employing SNM doorway monitors to comply with that requirement.

B. DISCUSSION

Special nuclear material doorway monitors provide an efficient, sensitive, and reasonably unobtrusive means of searching individuals exiting from a material access area for concealed SNM. With proper installation and opera tion, gram quantities or less of SNM can be detected with a high level of reliability while maintaining a low false alarm rate.

I. Theory of Operation The doorway monitor is composed of a detector unit(s), associated electronics, and alarm logic. The detector unit(s) is sensitive to the radiations which emanate from the SNM and responds to these radiations (usually gamma rays) by generating current pulses. These pulses are amplified, filtered, and fed to alarm logic v'hich interprets the number (or rate) of pulses in some period of time, for example, one second. The alarm logic may be either a digital or analog system; in either case, if the number (or rate) of pulses exceeds a set level, an alarm condition ensues.

2. General Characteristics Typically, the detectors of a doorway monitor are NaI(Tl) scintillators or solid or liquid organic scintilla tors. Geiger-Mueller detectors have also been used in this application, although the lower intrinsic efficiency of these detectors renders them less suitable than scintilla tion detectors.

Detectors are arranged such that a detection area is defined by a plane perpendicular to the line of passage of individuals through the doorway monitor. Various arrangements of the detectors are possible; however, specific placement of detectors is usually dictated by the need to eliminate dead spots.

Some commercially available doorway monitors are equipped with an automatic background updating system. The automatic background updating system periodically monitors and averages the background. A

doorway monitor equipped with an automatic back ground updating system is also provided with a treadle pad or beam-break system to indicate that the sensitive area is occupied. When the sensitive area is occupied, the radiation level detected by the doorway monitor is compared with the mean backgroun

d. If the level is

"significantly" greater than the mean background, an alarm condition ensues. Significance is usually deter mined by comparing the radiation level when the sensitive area is occupied with the mean background plus some multiple of the square root of the mean back ground*

  • The square root of the mean of a Poisson-distributed quantity is the unbiased estimate of the standard deviation of that quantity.

USAEC REGULATORY GUIDES

Copies of published guides may be obtained by request indicating the divisions desired to the US. Atomic Energy Commission, Washington, D.C. 20545, Regulatory Guides are issued to describe and make available to the public Attention: Director of Regulatory Standards. Comments and suggestions for methods acceptable to the AEC Regulatory staff of implementing sPecific parts of improvements in these guides ae encouraged and should be sent to the Secretary the Commission's regulations, to delineate techniques .ned by the staff in of the Commission, US. Atomic Energy Commission, Washington, D.C. 20545, evaluating specific problems or postulated accidents, or to provide guidance to Attention: Chief, Public Proceedings Staff.

applicants. Regulatory Guides are not substitutes for regulations and compliance with them is not required. Methods and solutions different from those set out in The guides ae issued in the following ten broad divisions:

the guides will be acceptable if they provide a basis for the findings requisite to the imuance or ontinuance of a permit or license by the Commission.

1. Power Reactors

6. Products

2. Reaseerd enid Test Reactors

7. Transportation

3. Fuels and Materials Facilities

8. Occupational Health Published guidas will be revised periodically, as appropriate, to accommodate

4. Environmental and Siting

9. Antitrust Review comments amd to refloct new informeaion or experience.

5. Materials and Plant Protection

1

0. General

Thus the condition for an alarm can be written as G > B + n, where B is the mean background, G is the radiation level with the sensitive area occupied, and n is a multiplier, usually an integer between 4 and 10.* The value of n directly affects the false alarm rate, and the combination of B and n affect the sensitivity.

Although the automatic background updating system allows unattended use of the doorway monitor, for technical reasons, the system may be less effective in certain situations. Techniques to prevent this are des cribed in the Regulatory Position.

Doorway monitors not equipped with an automatic background updating system either must rely on the inherent sensitivity of the instrument and low back ground variation to ensure that concealed SNM will be detected or must be attended so that a measurement of background can be taken immediately prior to use and the alarm level set to maintain the desired sensitivity to concealed SNM. As with the doorway monitor equipped with an automatic background updating system, a doorway monitor not so equipped compares the activity with the detection area occupied with some set value, usually the measurement of background taken just prior to use. In any case, the expression above can be used as a condition of alarm by replacing B + nr'Wwith the set level.

Whether or not a doorway monitor is equipped with an automatic background updating system, high back ground activity will decrease sensitivity. Measuring activ ity for longer periods will somewhat compensate for high background; however, longer measurement periods will make use of the doorway monitor less convenient.

C. REGULATORY POSITION

1. Minimum Qualifications for SNM Doorway Monitors

a. General

(1) SNM Doorway monitors should be used in conjunction with a metal detector and should be installed in a passageway (see Regulatory Guide 5.7,

"Control of Personnel Access to Protected Areas, Vital

  • Note that, in general, for a count rate system, the condition for afarm should be modified to account for the response time of the instrument as follows:

G > B + n1]0l - e-t/7)

where t is the counting time and r is the time constant of the instrument. If, as should be the case, t/,r > 5 the added factor is essentially unity.

Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the detection area.

. (2) The detector elements should be designed and positioned so that detection sensitivity is as uniform as possible over the detection area; in no case should any areas where SNM is not detectible be permitted.

(3) Power, sensitivity, and other controls of the doorway monitor should be tamper-safed when unat tended.

(4) Signal lines connecting alarm relays to the alarm monitor should be supervised.

(5) Some doorway monitors may require an indi vidual to occupy the detection area for a specified time, longer than a normal walking pace would provide. If this is the case, the doorway monitor should be provided with a treadle pad and a "clock" device to assure that the detection area is occupied for the requisite time. An aural and visual indication should be given if an individual being searched does not occupy the area sufficiently long.

b. System Specification

(1) Plutonium-239. A doorway monitor used to detect plutonium should be capable of detecting a minimum of 0.5 gram of plutonium-239 encased in a minimum of 3 mm of brass at a 90% confidence limit.

The false alarm rate should be less than 0.1% (Appendix C).

(2) Uranium-233. A doorway monitor used to detect uranium-233 should be capable of detecting within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of purification* a minimum of 1 gram of uranium-233 containing between 7 and 10 ppm of uranium-232 encased in a minimum of 3 mm of brass at a 90% confidence limit. The false alarm rate should be less than 0.1% (Appendix C).

(3) Uranium-235. A doorway monitor used to detect uranium-235 should be capable of detecting a minimum of 3 grams of uranium-235 contained in uranium enriched to 20% or more in the uranium-235 isotope encased in a minimum of 3 mm of brass at a 50%

confidence limit. The false alarm rate should be less than

0.1% (Appendix C).

2. Use of Doorway Monitors In general, doorway monitors should be used in locations of minimum background and minimum back ground fluctation. If circumstances dictate use of a doorway monitor in an area of high background, sufficient shielding should be provided to maintain necessary sensitivity.

a. Attended Doorway Monitor

(1) If the doorway monitor is attended during use, it need not be equipped with an automatic

  • Purification means removal of all decay products.

5.27-2

background updating system, although such capability is preferred.

(2) Prior to each use* of a doorway monitor not equipped with an automatic background updating system, a measurement of background should be taken, and the alarm threshold should be set to the proper value listed in Table I for the measured background and the proper n value as determined in Appendix B. Each individual to be checked should, in turn, enter the detection area and be required to remain sufficiently long for the device to operate properly. During use, the background should be checked and the alarm threshold reset at least each 15 minutes.

(3) With the individual being checked in the detection area, an alarm should sound if the activity in the detection area exceeds the alarm threshold T, as such a situation would indicate the presence of SNM.

(4) The doorway monitor should be equipped with a high-background alarm which will sound if the measurement of background exceeds the appropriate maximum permissible background level listed in Table II

as determined in Appendix C. The doorway monitor should not be used during such periods of high back ground.

b. Unattended Doorway Monitor

(1) If the doorway monitor is unattended, an automatic background update system should be incor porated into the doorway monitor electronics and alarm logic. The control circuitry, if possible, should be located at the central alarm station (or other monitoring point).

(2) Door interlocks and closed-circuit TV in combination with beam breaks, motion detectors, and/

or treadle pads, should be employed to:

(a) Indicate to the person manning the central alarm station that an individual has entered the secure access passageway and/or is approaching the doorway monitor, (b) Allow observation of the individual ap proaching the doorway monitor, (c) Preclude a slow approach to the sensitive area of the doorway monitor, and

  • By use is meant an individual or several individuals, each, in turn, being checked for SNM by the doorway monitor. The maximum period between threshold sets while the doorway monitor is in use is determined by the stability of local background and may necessarily be more frequent than every

15 minutes.

(d) Activate the electronics and alarm logic when an individual is within the detection area and initiate operation of the doorway monitor.

(3) An alarm should sound in the central alarm station if, when occupied, the activity in the detection area exceeds the internally set threshold level (the mean background plus some multiple times the square root of the mean background), as such a situation would indicate the presence of SNM upon the individual being checked.

(4) The doorway monitor should be equipped with a high-background alarm which will sound if the average background at the location of the doorway monitor exceeds the appropriate maximum permissible background level listed in Table II as determined in Appendix C. The doorway monitor should not be used during such periods of high background. Other moni tored exits should be used.

3. Testing and Calibration a. Testing Doorway monitors should be tested by passing an appropriate source of the amount and isotope specified in Regulatory Position C.l.b. through the doorway monitor no less frequently than once per day.* In addition, a functional performance test should be carried out at least once per week. An acceptable functional performance test procedure is discussed in Appendix A

of this guide b. Calibration Doorway monitors should be calibrated with a source of the amount, configuration, and variety of SNM

to be detected (e.g., 0.5 gram Pu in 3 mm of brass).

Calibration should be carried out according to a proce dure such as that in Appendix B.

c. Operating Instructions Operating instructions should be posted near the doorway monitor,* if attended, or at the monitoring point if the doorway monitor is unattended. The instructions should clearly indicate the procedure for use of the doorway monitor and the procedure for setting thresholds, if appropriate. In addition, the operating instructions should indicate what corrective action is to be taken and who is to be notified in the event of a malfunction.

  • Doorway monitors used to search for concealed U-233 should be tested according to §6 of Appendix A.

5.27-3

TABLE I

ALARM THRESHOLD

T

B

n=

4

5

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

680

700

720

740

760

780

800

820

840

860

880

900

920

940

960

980

6

140

164

.187

211

234

257

279

302

324

347

369

392

414

436

458

480

502

524

546

568

589

611

633

655

676

698

720

741

763

784

806

827

849

870

892

913

935

956

977

999

1020

1041

1063

1084

1105

5.27-4

7

8

150

175

199

223

247

271

294

317

341

364

387

409

432

455

477

500

522

545

567

590

612

634

656

678

700

722

744

766

788

810

832

854

876

898

920

941

963

985

1007

1028

1050

1072

1093

1115

1137

160

186

211

236

260

285

309

333

357

380

404

427

451

474

497

520

543

566

589

611

634

657

679

702

724

747

769

792

814

836

859

881

903

925

948

970

992

1014

1036

1058

1080

1102

1124

1146

1168

170

197

223

249

274

299

324

348

373

397

421

445

469

493

516

540

563

587

610

633

657

680

703

726

749

771

794

817

840

863

885

908

930

953

975

998

1020

1043

1065

1088

1110

1132

1155

1177

1199

180

208

235

261

287

313

339

364

389

414

439

463

488

512

536

560

584

608

632

655

679

702

726

749

773

796

819

842

866

889

912

935

958

981

1003

1026

1049

1072

1095

1117

1140

1163

1185

1208

1230

9

190

219

246

274

301

327

353

379

405

431

456

481

506

531

555

580

604

629

653

677

701

725

749

773

797

820

844

868

891

915

938

961

985

1008

1031

1055

1078

1101

1124

1147

1170

1193

1216

1239

1262

10

200

230

258

286

314

341

368

395

421

447

473

499

524

550

575

600

625

650

674

699

724

748

772

797

821

845

869

893

917

941

965

988

1012

1036

1059

1083

1106

1130

1153

1177

1200

1223

1247

1270

1293

TABLE I (Cont'd)

ALARM THRESHOLD

T

B

n =

4

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

5600

5800

6000

6200

6400

6600

6800

7000

7200

7400

7600

7800

8000

8200

8400

8600

8800

9000

9200

9400

9600

9800

1126

1339

1550

1760

1970

2179

2388

2596

2804

3012

3219

3426

3633

3840

4047

4253

4459

4665

4871

5077

5283

5483

5694

5899

6105

6310

6515

6720

6925

7130

7335

7539

7744

7949

8153

8358

8562

8767

8971

9175

9379

9584

9788

9992

10196

5

1158

1373

1587

1800

2012

2224

2435

2645

2855

3065

3274

3483

3692

3900

4108

4316

4524

4732

4939

5146

5354

5561

5767

5974

6181

6387

6594

6800

7006

7212

7418

7624

7830

8036

8242

8447

8653

8858

9064

9269

9474

9680

9885

10090

10295

5.27-5

9

6

1190

1408

1624

1840

2055

2268

2481

2694

2906

3117

3329

3539

3750

3960

4170

4379

4589

4798

5007

5216

5424

5633

5841

6049

6257

6465

6672

6880

7087

7295

7502

7709

7916

8123

8330

8537

8743

8950

9156

9363

9569

9775

9932

10188

10394

7

1221

1442

1662

1880

2097

2313

2528

2743

2957

3170

3383

3596

3808

4020

4232

4443

4654

4864

5075

5285

5495

5705

5914

6124

6333

6542

6751

6960

7169

7377

7586

7794

8002

8210

8418

8626

8834

9042

9249

9457

9664

9871

10079

10286

10493

8

1253

1477

1699

1920

2139

2358

2575

2792

3008

3223

3438

3653

3866

4080

4293

4506

4718

4931

5143

5354

5566

5777

5988

6199

6409

6620

6830

7040

7250

7460

7669

7879

8088

8297

8507

8716

8924

9133

9342

9550

9759

9967

10176

10384

10592

1285

1512

1737

1960

2182

2402

2622

2841

3059

3276

3493

3709

3925

4140

4355

4569

4783

4997

5210

5424

5636

5849

6061

6273

6485

6697

6909

7120

7331

7542

7753

7964

8174

8385

8595

8805

9015

9225

9435

9644

9854

10063

10273

10482

10691

1316

1546

1774

2000

2224

2447

2669

289C

3110

3329

3548

3766

3983

4200

4416

4632

4848

5063

5278

5493

5707

5921

6135

6348

6562

6775

6987

7200

7412

7625

7837

8049

8260

8472

8683

8894

9106

9317

9527

9738

9949

10159

10370

10580

10790

TABLE II

MAXIMUM PERMISSIBL

E. BACKGROUND

a = 0,

Pa = 50%

B

n=

4

100

120

140

160

180.

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

680

700

720

740

760

780

800

820

840

860

880

900

920

940

960

980

5

67

83

100

117

134

151

168

186

203

221

238

256

274

292

310

328

346

364

382

400

418

436

455

473

491

510

528

546

565

583

602

620

639

657

676

695

713

732

750

769

788

806

825

844

863 G

61

76

92

108

124

141

157

174

191

208

225

242

259

277

294

312

329

347

365

382

400

418

436

454

471

489

507

525

543

562

580

598

616

634

652

671

689

707

725

744

762

780

799

817

835

6

55

70

85

100

116

131

147

163

180

196

213

229

246

263

280

297

314

331

348

365

383

400

417

435

452

470

488

505

523

541

558

576

594

612

629

647

665

683

701

719

737

755

773

791

809

5.27-6

7

50

64

78

93

107

123

138

153

169

185

201

217

233

249

266

282

299

316

332

349

366

383

400

417

434

451

468

486

503

520

538

555

573

590

607

625

643

660

678

695

713

731

748

766

784

9

10

8

46

59

72

86

100

114

129

144

159

174

190

205

221

237

253

269

285

301

317

334

350

367

383

400

417

433

450

467

484

501

518

535

552

569

586

603

621

638

655

673

690

707

725

742

760

42

54

67

80

93

107

121

135

150

165

179

194

210

225

240

256

272

287

303

319

335

351

367

384

400

416

433

449

466

482

499

516

532

549

566

583

600

617

633

650

667

685

702

719

736

38

50

62

74

87

100

113

127

141

155

170

184

199

214

229

244

259

274

290

305

321

337

352

368

384

400

416

432

448

464

481

497

513

530

546

563

579

596

613

629

646

663

679

696

713

TABLE II

(Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

B

G

n =

4

1000

1200

1400

1600

1000

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

5600

5800

6000

6200

6400

6600

6800

7000

7200

7400

7600

7800

8000

8200

8400

8600

8800

9000

9200

9400

9600

9800

881

1069

1258

1448

1638

1829

2020

2212

2404

2596

2789

29S2

3175

3368

3561

3755

3949

4143

4337

4531

4725

4919

5114

5309

5503

5698

5893

6088

6283

6478

6673

6868

7064

7259

7455

7650

7846

8041

8237

8433

8628

8824

9020

9216

9412

5

854

1039

1225

1412

1600

1789

1978

2167

2357

2548

2738

2929

3121

3312

3504

3696

3888

4081

4273

4466

4659

4852

5045

5238

5432

5625'

5819

6012

6206

6400

6594

6788

6982

7176

7371

7565

7760

7954

8149

8343

8538

8733

8928

9122

9317 a -'0,

Pa = 50Z

6

827

1009

1193

1377

1563

1749

1936

2124

2312

2500

2689

2878

3068

3258

3448

3638

3829

4020

4211

4402

4593

4785

4977

5169

5361

5553

5745

5938

6130

6323

6516

6709

6902

7095

7288

7481

7674

7868

8061

8255

8449

8642

8836

9030

9224

7

802

981

1161

1343

1527

1710

1895

2081

2267

2453

2640

2828

3016

3204

3392

3581

3770

3960

4149

4339

4529

4719

4910

5100

5291

5482

5673

5864

6055

6247

6438

6630

6822

7014

7206

7398

7590

7782

7975

8167

8360

8553

8745

8938

9131

8

777

953

1131

1310

1491

1673

1855

2039

2223

2407

2593

2778

2964

3151

3338

3525

3713

3900

4088

4277

4465

4654

4843

5032

5222

5411

5601

5791

5981

6172

6362

6552

6743

6934

7125

7316

7507

7698

7889

8081

8272

8464

8656

8348

9039

5.27-7

9

753

926

1101

1278

1457

1636

1816

199D

2180

2363

2546

2730

2914

3099

3284

3470

3656

3842

4029

4216

4403

4590

4778

4966

5154

5342

5531

5719

5908

60'97

6286

6476

6665

6855

7045

7234

7425

7615

7805

7995

8186

8376

8567

8758

8949

10

730

900

1073

1247

1423

1600

1778

1958

2138

2318

2500

2682

2865

3048

3232

3416

3600

3785

3970

4155

4341

4527

4713

4900

5087

5274

5461

5648

5836

6024

6212

6400

6588

6777

6965

7154

7343

7532

7721

7911

8100

8290

8479

8669

8859

TABLE II

(Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

B

G

n

4

100

120

140

160

180

200

220

240

260

280

300

320

340

360

380

400

420

440

460

480

500

520

540

560

580

600

620

640

660

680

700

720

740

760

780

800

820

840

860

880

900

920

940

960

980

57

72

87

103

119

135

151

168

185

201

218

235

252

270

287

304

322

339

357

374

392

409

427

445

463

480

498

516

534

552

570

588

606

624

642

660

679

697

715

733

751

770

788

806

824

5

51

65

80

95

110

126

141

157

173

189

206

222

239

255

272

289

306

323

340

357

374

391

409

426

443

461

478

496

513

531

549

566

584

602

619

637

655

673

690

708

726

744

762

780

798

6

46

59

73

87

102

117

132

147

163

178

194

210

226

242

258

275

291

308

324

341

357

374

391

408

425

442

459

476

493

511

528

545

562

580

597

614

632

649

667

684

702

720

737

755

773 S= 1.3, Pa = 90%

7

42

54

67

81

95

109

123

138

153

168

183

198

214

229

245

261

277

293

309

325

342

358

374

391

407

424

441

457

474

491

508

525

542

559

576

593

610

627

644

661

679

696

713

731

748

9

8

38

49

62

75

88

101

115

129

143

158

172

187

202

217

233

248

263

279

295

311

326

342

358

374

391

407

423

439

456

472

489

505

522

539

555

572

589

605

622

639

656

673

690

707

724

5.27-8

34

45

57

69

81

94

107

121

135

149

163

177

191

206

221

236

251

266

281

297

312

327

343

359

375

390

406

422

438

454

470

487

503

519

535

552

568

585

601

618

634

651

668

684

701

10

31

41

52

64

76 FS

100

113

127

1L0

154

167

181

196

210

224

22S

254

268

283

298

313

329

344

359

375

390

406

421

437

453

469

485

500

516

532

549

565

581

597

613

630

646

662

679

TABLE II

(Cont'd)

MAXIMUM PERMISSIBL

E. BACKGROUND

G

n=

4

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

3600

3800

4000

4200

4400

4600

4800

5000

5200

5400

5600

5S00

6000

6200

6400

6600

6800

7000

7200

7400

7600

7800

8000

8200

8400

8600

8800

9000

9200

9400

9600

98-00

843

1027

1212

1398

1536

1773

1962

2151

2340

2530

2720

2911

3101

3292

3484

3675

3867

4059

4251

4443

4636

4828

5021

5214

5407

5600

5793

5987

6180

6373

6567

6761 r9955

7148

7342

7536

7731

7925

8119

3313

8508

8702

8897

9091

9286

5

816

997

1180

1363 it48

1734

1920

2107

2294

2482

2670

2859

3048

3238

3427

3617

3807

3998

4188

4379

4570

4761

4953

5144

5336

5528

5720

5912

6104

6296

6488

6681

6874

7066

7259

7452

7645

7838

8031

8225

8418

8611

8805

8998

9192

6

790

968

1148

1329

1512

1695

1879

2064

2249

2435

2622

2808

2996

3183

3371

3560

3748

3937

4126

4316

4505

4695

4885

5075

5266

5456

5647

5S38

6029

6220

6411

6602

6794

6985

7177

7369

7561

7753

7945

8137

8329

8521

8714

8906

9099

5.27-9 a = 1.3, P= = 90%

7

765

940

1117

1296

1476

1657

1839

2022

2205

2389

2574

2759

2944

3130

3317

3503

3691

3878

4066

4253

4442

4630

4819

5007

5196

5386

5575

5765

5954

6144

6334

6524

6715

6905

7096

7286

7477

7668

7859

8050

8241

8433

8624

8815

9007

8

741

913

1088

1264

1441

1620

1800

1980

2162

2344

2527

2710

2894

3078

3263

3448

3634

3319

4006

4192

4379

4566

4753

4940

5128

5316

5504

5692

5831

6070

6258

6447

6636

6826

7015

7205

7394

7584

7774

7964

8154

8345

8535

8725

8916

9

718

887

1059

1232

1407

1584

1761

1940

2119

2300

2481

2662

2844

3027

3210

3393

3577

3762

3946

4131

4317

4502

4688

4874

5061

5247

5434

5621

580G

5996

6184

6371

6559

6747

6936

7124

7313

7501

7690

7879

8063

8257

8447

8636

8826

10

695

861

1030

1201

1374

1548

1724

1900

2078

2256

2435

2615

2795

2976

3158

3340

3522

3705

3888

4072

4256

4440

4624

4809:

4994

5180

5365

5551

5737

5923

6110

6296

6483

6670

6857

7044

7232

7419

7607

7795

7983

8171

8360

8548

8737

APPENDIX A

PROCEDURE FOR TESTING SNM DOORWAY MONITORS

FOR

FUNCTIONAL PERFORMANCE

Doorway monitors should be tested by employing a test source of the same isotope of SNM the doorway monitor is used to detect as follows:

1. With the detection area unoccupied, measure and record background.

2. Determine alarm threshold T from Table I (see Appendix B).

3. Place a test source in the detection area of the doorway monitor. The test source should be such that the activity in the detection area slightly exceeds the T

level.* The doorway monitor should go into an alarm condition if operating properly.

4. Remove test source to its original location and measure background once again. If the measurement of

  • The test source may be improvised by partially shielding the calibration source.

background taken immediately after the test varies by more than 2vN

from the background taken before the test, the test should be repeated, for such a difference indicates nonrandom fluctuations of the background or equipment malfunction. The probability of such an occurrence due to the randomness of the background is less than 8%.

5. A calibration source (Appendix B) should be carried repeatedly to various places within the detection area of the doorway monitor in simulation of actual use to verify that the SNM can be detected everywhere within the detection area and to assure proper operation of treadle pads, beam-break, or similar devices if the doorway monitor is so equipped.

6. Doorway monitors used to search for concealed uranium-233 should be tested with each uranium purification run, but no more frequently than daily. The test source should be freshly purified uranium-233 (within four hours of removal of decay products).

5.27-10

APPENDIX B

PROCEDURE FOR DETERMINING MAXIMUM PERMISSIBL

E. BACKGROUND

Background should be measured over several work shifts to determine the setpoints for alarm threshold (with or without automatic background updating) to assure that normal operation will be minimally affected by alarms due to high background.

The doorway monitor should be calibrated with the amount of the appropriate isotope specified in Regula tory Positions C.l.b(1), (2), or (3) of this guide (e.g., 0.5 gram plutonium-239 in 3 mm of brass).

The calibration procedure described below is essen tially a means of determining maximum permissible background for effective operation of the doorway monitor.

1. Place a calibration source variously about the detec tion area and take readings to determine the least sensitive point. This location of minimum sensitivity should be maintained as the calibration point.

2. Measure background over several workshifts to deter mine the periods of high background and the range of background. A minimum of 20 measurements should be taken. The variance of the background is given by N

Var B N*-

1 (Bi-B)2

(1)

where N is the number of measurements, B is the mean of the background measurements, and Bi is the ith background measurement.

3. With the calibration source at the calibration point, the mean gross counts G should be determined during a period of high background to establish the upper operating range of the doorway monitor. Table II lists various maximum permissible background levels for a given value of G for values of the parameters n and a.

During periods when the background exceeds the value found from Table II, the sensitivity of the doorway monitor will generally be below that specified as minimum in Regulatory Position C.l.b of this guide.

The parameter n is a function of the background variation and the permissible false alarm rate and is calculated from n >3.1 (var B) 1/2

(2)

Generally, n is taken as an integer. If n satisfies the above expression, the expected false alarm rate (Appen dix C) due to background fluctuations should be less than 0.1%. Larger values of n will decrease the expected false alarm rate; however, the maximum allowable background for a given G will also decrease.

4. For doorway monitors equipped with automatic background updating systems, the alarm threshold is Counts > B + nVii,

(3)

where n should be derived from expression (2), and the instrument set accordingly.

5. The high-background alarm should be set at the B

value given in Table II for the measured G and calculated n values.

6. For doorway monitors not equipped with an auto matic background update, the value of n determined above should be employed in the use of the doorway monitor according to Regulatory Position C.2.a.

  • The false alarm rate is estimated by the probability that an observation of a quantity distributed normally about some value X will exceed X by n(Std. deviation of X). The factor 3.1 limits the false alarm rate to 0.1%, while the factor (Var B/B) 1/2 compensates for observed deviations in the background distribution from Poisson.

5.27-11

APPENDIX C

DETECTION CONFIDENCE LIMITS, THRESHOLDS,

AND MAXIMUM PERMISSIBL

E. BACKGROUND

With a calibration source at the calibration point, the condition for an alarm is, in general, g> T = B + m/Va' B

(1)

where g is a single measurement of G (the mean radiation level with the source), B is the mean back ground, and m is some multiplier. The detection confidence limit is the probability that with the calibra iton source at the calibration point, any single determin ation of G will exceed a threshold T, i.e., the above inequality will be satisfied. For any given probability Pa.,

there exists a value a such that g > G-

(2)

with a probability of Pa, where g is any single measure ment of the quantity G. Hence the condition for a detection confidence limit of Pais G - &

_-r*-G > T = B + m,,/'r B.

(3)

For a given value of G, solving (3) gives the maximum permissible B at which the doorway monitor will detect the source with a confidence Pr- For Pa = 90%, a = 1.3, and for Pa = 50%, a = 0.

The condition for a false alarm* is written as b = B + j a-'"B> T

(4)

where b is a single measurement without the source and

0 is a number corresponding to a false alarm probability P

p. For P

= 0.1%, 0 = 3.1. Hence the necessary condition for maintaining a false alarm rate below Pp is b = B +

-"B

< B + m ar.

(5)

However, the doorway monitor actually compares b with B + ni, hence the condition on n becomes orV

< rn'VaTr

= nvff

(6)

or n>0 ( Va B ) 1/2

(7)

In Table I threshold values of T were determined by substituting equation (6) into equation (3):

T = B + nv'r The values of B in Table II were then calculated for a = 1.3 and a = 0 from equation (3) assuming that, for the determination of G, the background should be reasonably stable and therefore \\/Var G -\\

  • False alarm means an alarm condition generated by statistical fluctuations in the background radiation or by instabilities of the electronics which appear as background fluctuations when the detection area is occupied.

5.27-12


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