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


==A. INTRODUCTION==
==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.
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==
==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.
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.


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;
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.
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.
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.


When the sensitive area is occupied, the radiation level detected by the doorway monitor is compared with the mean background.
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.


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 quantit
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


====y. USAEC REGULATORY ====
====d. If the level is ====
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:
"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*
Director of Regulatory Standards.
*The square root of the mean of a Poisson-distributed quantity is the unbiased estimate of the standard deviation of that quantity.


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:  
USAEC REGULATORY GUIDES
Chief, Public Proceedings Staff.  applicants.
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.


Regulatory Guides are not substitutes for regulations and compliance with them is not required.
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.


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 the imuance or ontinuance of a permit or license by the Commission.


1. Power Reactors 6. Products 2. Reaseerd enid Test Reactors  
===6. Products ===
2. Reaseerd enid Test Reactors  


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


5. Materials and Plant Protection  
5. Materials and Plant Protection  
10. 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.
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


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.
====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.


Techniques to prevent this are des cribed in the Regulatory Position.
Areas, and Material Access Areas,") in such a manner that objects cannot be passed over, around, or under the detection area.


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.
. (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.


Measuring activ ity for longer periods will somewhat compensate for high background;
(3) Power, sensitivity, and other controls of the doorway monitor should be tamper-safed when unat tended.
however, longer measurement periods will make use of the doorway monitor less convenient.


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


(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.
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.


(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
The false alarm rate should be less than 0.1% (Appendix C). 
(1) Plutonium-239.
(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). 
(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 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. 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.


A doorway monitor used to detect uranium-233 should be capable of detecting within 4 hours of purification*
5.27-2
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.
background updating system, although such capability is preferred.


If circumstances dictate use of a doorway monitor in an area of high background, sufficient shielding should be provided to maintain necessary sensitivity.
(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.


a. Attended Doorway Monitor (1) If the doorway monitor is attended during use, it need not be equipped with an automatic
(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.
*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.
(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.


During use, the background should be checked and the alarm threshold reset at least each 15 minutes.
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.


(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.
(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.
(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.
(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


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,*
==E. BACKGROUND==
if attended, or at the monitoring point if the doorway monitor is unattended.
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


The instructions should clearly indicate the procedure for use of the doorway monitor and the procedure for setting thresholds, if appropriate.
TABLE II
(Cont'd)
MAXIMUM PERMISSIBL


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.
==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


*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
APPENDIX A
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
PROCEDURE FOR TESTING SNM DOORWAY MONITORS  
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
FOR  
TABLE II MAXIMUM PERMISSIBLE
FUNCTIONAL PERFORMANCE
BACKGROUND
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:  
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 PERMISSIBLE
1. With the detection area unoccupied, measure and record background.
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 PERMISSIBLE
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 PERMISSIBLE
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.
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.
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.


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.
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).
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  
5.27-10
APPENDIX B PROCEDURE  
 
FOR DETERMINING  
APPENDIX B
MAXIMUM PERMISSIBLE
PROCEDURE FOR DETERMINING MAXIMUM PERMISSIBL
BACKGROUND
 
Background should be measured over several work shifts to determine the setpoints for alarm threshold (with or without automatic background updating)  
==E. BACKGROUND==
to assure that normal operation will be minimally affected by alarms due to high 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.


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.
5.27-11


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


A minimum of 20 measurements should be taken. The variance of the background is given by N Var B 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.
==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. 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.
(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.


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
The condition for a false alarm* is written as b = B + j a-'"B> T
(2), and the instrument set accordingly.
(4)
where b is a single measurement without the source and
0 is a number corresponding to a false alarm probability P


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
====p. For P ====
CONFIDENCE
= 0.1%, 0 = 3.1. Hence the necessary condition for maintaining a false alarm rate below Pp is b = B +  
LIMITS, THRESHOLDS, AND MAXIMUM PERMISSIBLE
-"B  
BACKGROUND
< B + m ar.
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.
(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.


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 -& > 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 Pp. 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
5.27-12}}
\/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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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).

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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.

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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.

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