- Email: [email protected]
Automated data-collection and analysis system for assay of whole-body radioactivity and lung burdens
NUCLEAR
INSTRUMENTS
AND
METHODS
I2!
(I974) 9!-95;
© NORTH-HOLLAND
PUBLISHING
CO.
A U T O M A T E D D A T A - C O L L E C T I O N A N D ANALYSIS S Y S T E M F O R A S S A Y OF W H O L E - B O D Y RADIOACTIVITY A N D L U N G B U R D E N S * J. R. W A T T S Savannah River Laboratory; E. I. du Pont de Nemours and Company, Aiken, South Carolina 29801, U.S.A. Received 22 M a y 1974 S i m u l t a n e o u s total-body b u r d e n s o f fission products a n d / o r induced activities and l u n g b u r d e n s o f t r a n s u r a n i c radionuclides are routinely m e a s u r e d using a c o m p u t e r - b a s e d pulse-height analyzer connected to two sets o f scintillation detectors. T h e pulse-height-analyzer code a n d the data-analysis code are in the c o m p u t e r m e m o r y . After a preset counting time, the analysis
p r o g r a m requests the operator to input i n f o r m a t i o n by Teletype t e q u i p m e n t for identification o f the person being counted. T h e p e r m a n e n t record o f each m e a s u r e m e n t is printed at the end o f the analysis and supplies a data s u m m a r y a n d status o f radioactivity in the subject.
1. Introduction [n-vivo measurements are a necessary adjunct to a personnel-monitoring program in a nuclear-energy facility and require two separate measurement geo-
metries: whole-body and chest. The whole-body geometry provides an equal detection efficiency for radioactive material at any location within the whole body. The chest geometry measures transuranic radionuclides whose characteristic radiations are low-energy (less than 120 keV) X and/or gamma rays. The measurements serve two independent purposes: routine samplings monitor the adequacy of the radioactivitycontainment program, and special measurements evaluate accidental assimilations. Routine sampling of employees both adds to the data base and complements other monitoring programs.
* This paper was prepared in connection with work u n d e r contract no. AT(07-2)-I with the U.S. A t o m i c Energy C o m mission. By acceptance o f this paper, the publisher a n d / o r recipient acknowledges the U.S. G o v e r n m e n t ' s right to retain a non-exclusive, royalty-free license in and to any copyright covering this paper, along with the right to reproduce and to authorize others to reproduce all or any part o f the copyrighted paper. t Teletype Corp., Skokie, 111. 60076, U.S.A.
Computer ADC Pulse Shape Analyzer
Preamplifier
Delay Amplifier
Linear Gate A
I
Del~y Line
Mixer-Router
Gate and Delay Generator
J-L
J'l.
Phoswich Detectors Linear Amplifier NaI(TI)
Linear Gate B
Preamplifier Amplifier Discriminator
A,
Preamplifier Amplifier Discriminator
)~
J'L
Detectors
I
Fig. 1. Block d i a g r a m o f detectors a n d electronics.
91
J"L
92
J.R. WATTS
Initial assessment of an accidental assimilation requires whole-body or chest measurements to obtain an immediate indication of the severity of the incident. The whole-body measurement will detect any gammaemitting radionuclide. At the Savannah River Plant (SRP), the whole-body measurement is used routinely to monitor for fission-product assimilation because the measurement is quantitative and sensitive.
2. Equipment description The block diagram of the detectors and electronics for both the whole-body and chest measurement system is shown in fig. 1. The whole-body geometry used four 5"-diam. by 4"-thick NaI(T1) detectors (Teledyne + model S-2016 U/5) arranged beneath the bed that supports the individual during the measurement. The two center detectors are 13½" below the bed, and the end detectors are 93" below the bed to give equal detection efficiency along the length of the bed. The signals from the NaI(TI) detectors are connected in parallel to a preamplifier-amplifier-discriminator unit (Nuclear Data ++ PAD-520). This unit supplies a logic signal coincident with a linear signal to a mixer-router (Nuclear Data ND-521 M/R). For the chest geometry, two 5"-diam. "phoswich" (Harshaw** type 20MBSH3M/5B-X) detectors mounted on dental X-ray arms are placed in contact with the upper chest area. Each "phoswich" detector consists of - Teledyne Isotopes, Inc., Westwood, NJ 07675, U.S.A. +- Nuclear Data, Inc., Palatine, 111.60067, U.S.A. ** Harshaw Chemical Co., Cleveland, Ohio 44106, U.S.A.
DATA •~
COLLECTION
a 3-mm NaI(TI) scintillator detector optically coupled to a 2"-thick CsT(TI) scintillator detector, and is viewed by a single photomultiplier tube. The 3-ram NaI(T1) detector detects the low-energy X and g a m m a rays, and the CsI(T1) detector located behind the NaI(TI) detector is an anticoincidence shield to reject those events that deposit energy in the NaT(TI) scintillator before scattering into the CsI(T1) scintillator. This discrimination is possible because the different decay times of the two scintillators give different rise times of the photo-multiplier-tube output pulses. The decay times are 0.25 lls for the NaT(T1) and 1.1 /~s fnr the CsI(TI) detectors. Outputs from the phoswich detectors are connected in parallel to a preamplifier (Harshaw NB-25A) and then are routed in parallel to a pulse-shape analyzer (Harshaw NC-25) and a linear amplifier (Ortec 451 A) +. The pulse-shape analyzer contains two doubly differentiated amplifiers for pulse-shape discrimination. As opposed to the normal method of measuring pulse rise times between the leading edge and the cross-over of the pulse, this module measures the difference between the cross-overs of the pulses of the two amplifiers. Within the pulse-shape-analyzer module, a time-toamplitude converter generates pulses whose amplitude is proportional to the rise times of the input. This distribution may be displayed on the pulse-height analyzer. The pulse-shape analyzer permits discrimination on the basis of pulse amplitude (energy of incident gamma) and pulse rise time (scintillator origin). Ortec Inc., Oak Ridge, Tenn. 37830, U.S.A.
ANALYSIS
Ready I Collection Data 1~__ - - I t Conversational Input/Output PHA Display / of Parameters
Data Summation from Energy Spectra Data Calculation
and Results
Fig. 2. Block diagram of data-collection and analysis program.
ASSAY OF W H O L E - B O D Y R A D I O A C T I V I T Y AND L U N G B U R D E N S
/k logic pulse is generated for each pulse satisfying both amplitude and rise-time requirements. This logic pulse either triggers linear gate A (Canberrat 1451) in the coincidence mode or blocks linear gate B (Canberra 1451) in the anticoincidence mode. The delay amplifier, delay line, and gate and delay generator and the preamplifier-amplifier-discriminator (Nuclear Data PAD-520) adjust timing and amplitude of each logic pulse relative to the linear pulse. The system uses a mixer-router (Nuclear Data ND-521 M/R) to place the acceptable low-energy data from the NaI(T1) scintillator into quadrant 1, the higher-energy data from the CsI(T1) scintillator into quadrant 2, and fissionproduct and/or induced-activity data into quadrant 3 of ~Lhe 1024 data channels of a computer. The computer (Nuclear Data ND-812) is a 12 bit computer with 8192 memory locations. The program occupies 6144 locations with 2048 locations allocated for the 1024 channels of pulse-height analyzer data. 3. Data collection and analysis
The block diagram of the computer code is shown in fig. 2. The code has two major parts: data collection and analysis. The printed output from the analysis is shown in fig. 3. The code for collecting and storing gamma spectral data is that supplied by the vendor § except for an on-site modification limiting total number of data channels to 1024. Control is transferred from the datacollection code to the analysis code when the preset counting time, usually 30 min, has elapsed. In the analysis code, the computer operates in a conversational mode using a Teletype unit to input information to identify the person being counted (date, time, name, payroll number, work location, department, age, sex, and reason for count) and also the necessary values (height, weight, and chest thickness) needed in the calculation of the radionuclide content of the person's body. Each request is labeled, anti input is limited to completing the remainder of the request line. A carriage return terminates an input sequence. Input is printed but not stored in the computer except for the body parameters. At the completion of the conversational mode of the input parameters, headings are printed, and gross counts are summed for preselected energy segments of the data regions. A previously entered average background is printed, and net counts are calculated. 5" Canberra Industries, Inc., Meridan, CT 06450, U.S.A. § Nuclear Data Program 41-1060-01; Nuclear Data, P.O.B. 451, Palatine, I11., U.S.A.
Inc.,
93
The second part of the analysis code utilizes a baseline obtained by measuring a group of employees who have no possibility of occupational assimilation. From these data, the counts in each energy segment are calculated as functions of natural-radioactivity contents and body parameters. An algebraic relation is obtained by means of a linear least-squares regression analysis of data1). A standard deviation of the fit of the data to the equation is calculated. The equation and the standard deviation for each energy segment are contained in the analysis code. A calculated count (labeled " C A L C ' ) is obtained as described above. The difference (labeled " D i F F " ) between the net count and calculated count is compared to a previously entered value. If the positive difference exceeds this, a statistically significant amount of radioactivity is assumed to be present for that energy region. At the conclusion of the print-out, a note is printed for each energy region with significant counts of fission products and/or induced activities (as shown in fig. 3 for the channel groupings of 81 through 91 and 118 through 129). The total potassium and 137Cs content are calculated for all subjects counted. if the energy region of the transuranic radionuclides spectrum has significant counts, the amount of radioactivity represented by those counts is calculated. The counts in the l l through 23 keV region are calculated as 238pu, 239pu, o r 2 4 4 C m ; the choice is made from work-location information. The calculation of a statistically significant count in the 11 through 23 keV energy region is shown in fig. 3. The 48 through 68 keV energy region is calculated as 241Am. An appropriate correction for its scatter into the 11 through 23 keV region is made before the latter region is calculated. In all cases, a minimum detectable amount (MDA) is calculated for all potential internal contaminants. The MDA is that amount of radioactivity in the lungs which would give a net count of two standard deviations (2 a) of counts through the chest wall. When the output is complete, control is transferred back to the pulseheight-analysis code for data collection from the next subject. Additional features exist in the code to facilitate routine operation: 1) For measurement of background, the conversational mode is terminated when the count is named backglound. The gross counts are labeled as background and summed and printed. Control is returned from the analysis code to the pulse-height-analyze~ code. 2) The background used for analysis is an average background from several counts to minimize back-
94
J. R
DATE
112174
TIME
1140
NAME
,I. E . D O E
PR#
05412
LOCN
700A
DEPT
ADM I N
AGE
45
SEX
MALE
REQU
ROUT
HT 6 9 . 5 WT 1 7 4 C THKS
1• 9
CH#
CS
WATTS
INE
23-29
30-40
+
5046
+11896
+16521
+14095
+13253
+13366
+
8594
+
6365
t-'3KGD +
3504
+10892
+13903
+13300
+10672
+12578
+
8360
+
5899
BET
1452
+
1004
+
2617
+
794
+
2580
+
787
+
234
+
467
+
+
671
+
2213
+
1526
+
1547
+
773
+
+
+
332
+
404
-
731
+
1033
+
442 208
~05
+
CALC DIFF ~H#
CTS
7-14
81-91
15-22
14
45-55
-
60-70
92-102
103-117
118-129
130-154
155-175
176-199
~OS
+
4501
+
5259
+
3569
+
3897
+
2368
+
6093
+
2310
+
1621
)-]4GD NET CALC
+ + +
4401 10 259
+ + +
4063 1106
3418 150 268
+ + +
3787 109
2256 112 192
4859
+ -
2317
+ -
1623
394
+ + +
+ +
252
+ + +
DIFF
-
249
+
o43
-
117
-
284
-
80
KEV a0S
70-80
6-10
11-23 1160
+
24-47 1230
+
48-68 1470
+
69-90 +
1407
+
+
~00
+
355
+
324
+
430
+
329
NET
+
360
+
884
+
1146
+
977
+
1172
+
g59
+
1235
@FF
+
173
+
186
+
24
+ +
GM K NCI CS-137 23-29 gl-Ol
+ + >3SD >3SD
EITHER PU-239 DU-238 CM-244
+ + +
61 27 34
NCI NCI NCI
+
21
NCI
1005 140
+ +
012 64
-
7
91-128 1502
BKGD CALC
1234
62
117 1.92
MDA PU-23Q
+
AM-241
+
.23
NCI
Fig. 3. T y p i c a l c o m p u t e r p r i n t o u t ; a p e r m a n e n t r e c o r d o f d a t a collected on a n i n d i v i d u a l .
3
ASSAY OF W H O L E - B O D Y R A D I O A C T I V I T Y AND L U N G BURDENS
ground variations. The code permits background entry from the Teletype keyboard. Upon completion, control is transferred to the pulse-height analyzer ,:ode. 3) Because of possible analysis improvements, data from previous counts may be recalculated with new parameters. A short overlay to the code permits data entry of gross sums from the Teletype keyboard rather than from summation of energy spectra. Recalculation proceeds in the routine method with any new parameters desired.
95
4. Conclusions
The computer-based pulse-height analyzer and associated analysis code have performed very effectively in routine use at SRP. The system permits a high counting rate, offers rapid results, and eliminates manual data manipulation with its concomitant potential errors. Reference 1) F. D. Knight, Generalized linear regression analysis, USAEC Report DP-1128; E. I. du Pont de Nemours and Company. Savannah giver Laboratory, Aiken, South Carolina (1968),
INSTRUMENTS
AND
METHODS
I2!
(I974) 9!-95;
© NORTH-HOLLAND
PUBLISHING
CO.
A U T O M A T E D D A T A - C O L L E C T I O N A N D ANALYSIS S Y S T E M F O R A S S A Y OF W H O L E - B O D Y RADIOACTIVITY A N D L U N G B U R D E N S * J. R. W A T T S Savannah River Laboratory; E. I. du Pont de Nemours and Company, Aiken, South Carolina 29801, U.S.A. Received 22 M a y 1974 S i m u l t a n e o u s total-body b u r d e n s o f fission products a n d / o r induced activities and l u n g b u r d e n s o f t r a n s u r a n i c radionuclides are routinely m e a s u r e d using a c o m p u t e r - b a s e d pulse-height analyzer connected to two sets o f scintillation detectors. T h e pulse-height-analyzer code a n d the data-analysis code are in the c o m p u t e r m e m o r y . After a preset counting time, the analysis
p r o g r a m requests the operator to input i n f o r m a t i o n by Teletype t e q u i p m e n t for identification o f the person being counted. T h e p e r m a n e n t record o f each m e a s u r e m e n t is printed at the end o f the analysis and supplies a data s u m m a r y a n d status o f radioactivity in the subject.
1. Introduction [n-vivo measurements are a necessary adjunct to a personnel-monitoring program in a nuclear-energy facility and require two separate measurement geo-
metries: whole-body and chest. The whole-body geometry provides an equal detection efficiency for radioactive material at any location within the whole body. The chest geometry measures transuranic radionuclides whose characteristic radiations are low-energy (less than 120 keV) X and/or gamma rays. The measurements serve two independent purposes: routine samplings monitor the adequacy of the radioactivitycontainment program, and special measurements evaluate accidental assimilations. Routine sampling of employees both adds to the data base and complements other monitoring programs.
* This paper was prepared in connection with work u n d e r contract no. AT(07-2)-I with the U.S. A t o m i c Energy C o m mission. By acceptance o f this paper, the publisher a n d / o r recipient acknowledges the U.S. G o v e r n m e n t ' s right to retain a non-exclusive, royalty-free license in and to any copyright covering this paper, along with the right to reproduce and to authorize others to reproduce all or any part o f the copyrighted paper. t Teletype Corp., Skokie, 111. 60076, U.S.A.
Computer ADC Pulse Shape Analyzer
Preamplifier
Delay Amplifier
Linear Gate A
I
Del~y Line
Mixer-Router
Gate and Delay Generator
J-L
J'l.
Phoswich Detectors Linear Amplifier NaI(TI)
Linear Gate B
Preamplifier Amplifier Discriminator
A,
Preamplifier Amplifier Discriminator
)~
J'L
Detectors
I
Fig. 1. Block d i a g r a m o f detectors a n d electronics.
91
J"L
92
J.R. WATTS
Initial assessment of an accidental assimilation requires whole-body or chest measurements to obtain an immediate indication of the severity of the incident. The whole-body measurement will detect any gammaemitting radionuclide. At the Savannah River Plant (SRP), the whole-body measurement is used routinely to monitor for fission-product assimilation because the measurement is quantitative and sensitive.
2. Equipment description The block diagram of the detectors and electronics for both the whole-body and chest measurement system is shown in fig. 1. The whole-body geometry used four 5"-diam. by 4"-thick NaI(T1) detectors (Teledyne + model S-2016 U/5) arranged beneath the bed that supports the individual during the measurement. The two center detectors are 13½" below the bed, and the end detectors are 93" below the bed to give equal detection efficiency along the length of the bed. The signals from the NaI(TI) detectors are connected in parallel to a preamplifier-amplifier-discriminator unit (Nuclear Data ++ PAD-520). This unit supplies a logic signal coincident with a linear signal to a mixer-router (Nuclear Data ND-521 M/R). For the chest geometry, two 5"-diam. "phoswich" (Harshaw** type 20MBSH3M/5B-X) detectors mounted on dental X-ray arms are placed in contact with the upper chest area. Each "phoswich" detector consists of - Teledyne Isotopes, Inc., Westwood, NJ 07675, U.S.A. +- Nuclear Data, Inc., Palatine, 111.60067, U.S.A. ** Harshaw Chemical Co., Cleveland, Ohio 44106, U.S.A.
DATA •~
COLLECTION
a 3-mm NaI(TI) scintillator detector optically coupled to a 2"-thick CsT(TI) scintillator detector, and is viewed by a single photomultiplier tube. The 3-ram NaI(T1) detector detects the low-energy X and g a m m a rays, and the CsI(T1) detector located behind the NaI(TI) detector is an anticoincidence shield to reject those events that deposit energy in the NaT(TI) scintillator before scattering into the CsI(T1) scintillator. This discrimination is possible because the different decay times of the two scintillators give different rise times of the photo-multiplier-tube output pulses. The decay times are 0.25 lls for the NaT(T1) and 1.1 /~s fnr the CsI(TI) detectors. Outputs from the phoswich detectors are connected in parallel to a preamplifier (Harshaw NB-25A) and then are routed in parallel to a pulse-shape analyzer (Harshaw NC-25) and a linear amplifier (Ortec 451 A) +. The pulse-shape analyzer contains two doubly differentiated amplifiers for pulse-shape discrimination. As opposed to the normal method of measuring pulse rise times between the leading edge and the cross-over of the pulse, this module measures the difference between the cross-overs of the pulses of the two amplifiers. Within the pulse-shape-analyzer module, a time-toamplitude converter generates pulses whose amplitude is proportional to the rise times of the input. This distribution may be displayed on the pulse-height analyzer. The pulse-shape analyzer permits discrimination on the basis of pulse amplitude (energy of incident gamma) and pulse rise time (scintillator origin). Ortec Inc., Oak Ridge, Tenn. 37830, U.S.A.
ANALYSIS
Ready I Collection Data 1~__ - - I t Conversational Input/Output PHA Display / of Parameters
Data Summation from Energy Spectra Data Calculation
and Results
Fig. 2. Block diagram of data-collection and analysis program.
ASSAY OF W H O L E - B O D Y R A D I O A C T I V I T Y AND L U N G B U R D E N S
/k logic pulse is generated for each pulse satisfying both amplitude and rise-time requirements. This logic pulse either triggers linear gate A (Canberrat 1451) in the coincidence mode or blocks linear gate B (Canberra 1451) in the anticoincidence mode. The delay amplifier, delay line, and gate and delay generator and the preamplifier-amplifier-discriminator (Nuclear Data PAD-520) adjust timing and amplitude of each logic pulse relative to the linear pulse. The system uses a mixer-router (Nuclear Data ND-521 M/R) to place the acceptable low-energy data from the NaI(T1) scintillator into quadrant 1, the higher-energy data from the CsI(T1) scintillator into quadrant 2, and fissionproduct and/or induced-activity data into quadrant 3 of ~Lhe 1024 data channels of a computer. The computer (Nuclear Data ND-812) is a 12 bit computer with 8192 memory locations. The program occupies 6144 locations with 2048 locations allocated for the 1024 channels of pulse-height analyzer data. 3. Data collection and analysis
The block diagram of the computer code is shown in fig. 2. The code has two major parts: data collection and analysis. The printed output from the analysis is shown in fig. 3. The code for collecting and storing gamma spectral data is that supplied by the vendor § except for an on-site modification limiting total number of data channels to 1024. Control is transferred from the datacollection code to the analysis code when the preset counting time, usually 30 min, has elapsed. In the analysis code, the computer operates in a conversational mode using a Teletype unit to input information to identify the person being counted (date, time, name, payroll number, work location, department, age, sex, and reason for count) and also the necessary values (height, weight, and chest thickness) needed in the calculation of the radionuclide content of the person's body. Each request is labeled, anti input is limited to completing the remainder of the request line. A carriage return terminates an input sequence. Input is printed but not stored in the computer except for the body parameters. At the completion of the conversational mode of the input parameters, headings are printed, and gross counts are summed for preselected energy segments of the data regions. A previously entered average background is printed, and net counts are calculated. 5" Canberra Industries, Inc., Meridan, CT 06450, U.S.A. § Nuclear Data Program 41-1060-01; Nuclear Data, P.O.B. 451, Palatine, I11., U.S.A.
Inc.,
93
The second part of the analysis code utilizes a baseline obtained by measuring a group of employees who have no possibility of occupational assimilation. From these data, the counts in each energy segment are calculated as functions of natural-radioactivity contents and body parameters. An algebraic relation is obtained by means of a linear least-squares regression analysis of data1). A standard deviation of the fit of the data to the equation is calculated. The equation and the standard deviation for each energy segment are contained in the analysis code. A calculated count (labeled " C A L C ' ) is obtained as described above. The difference (labeled " D i F F " ) between the net count and calculated count is compared to a previously entered value. If the positive difference exceeds this, a statistically significant amount of radioactivity is assumed to be present for that energy region. At the conclusion of the print-out, a note is printed for each energy region with significant counts of fission products and/or induced activities (as shown in fig. 3 for the channel groupings of 81 through 91 and 118 through 129). The total potassium and 137Cs content are calculated for all subjects counted. if the energy region of the transuranic radionuclides spectrum has significant counts, the amount of radioactivity represented by those counts is calculated. The counts in the l l through 23 keV region are calculated as 238pu, 239pu, o r 2 4 4 C m ; the choice is made from work-location information. The calculation of a statistically significant count in the 11 through 23 keV energy region is shown in fig. 3. The 48 through 68 keV energy region is calculated as 241Am. An appropriate correction for its scatter into the 11 through 23 keV region is made before the latter region is calculated. In all cases, a minimum detectable amount (MDA) is calculated for all potential internal contaminants. The MDA is that amount of radioactivity in the lungs which would give a net count of two standard deviations (2 a) of counts through the chest wall. When the output is complete, control is transferred back to the pulseheight-analysis code for data collection from the next subject. Additional features exist in the code to facilitate routine operation: 1) For measurement of background, the conversational mode is terminated when the count is named backglound. The gross counts are labeled as background and summed and printed. Control is returned from the analysis code to the pulse-height-analyze~ code. 2) The background used for analysis is an average background from several counts to minimize back-
94
J. R
DATE
112174
TIME
1140
NAME
,I. E . D O E
PR#
05412
LOCN
700A
DEPT
ADM I N
AGE
45
SEX
MALE
REQU
ROUT
HT 6 9 . 5 WT 1 7 4 C THKS
1• 9
CH#
CS
WATTS
INE
23-29
30-40
+
5046
+11896
+16521
+14095
+13253
+13366
+
8594
+
6365
t-'3KGD +
3504
+10892
+13903
+13300
+10672
+12578
+
8360
+
5899
BET
1452
+
1004
+
2617
+
794
+
2580
+
787
+
234
+
467
+
+
671
+
2213
+
1526
+
1547
+
773
+
+
+
332
+
404
-
731
+
1033
+
442 208
~05
+
CALC DIFF ~H#
CTS
7-14
81-91
15-22
14
45-55
-
60-70
92-102
103-117
118-129
130-154
155-175
176-199
~OS
+
4501
+
5259
+
3569
+
3897
+
2368
+
6093
+
2310
+
1621
)-]4GD NET CALC
+ + +
4401 10 259
+ + +
4063 1106
3418 150 268
+ + +
3787 109
2256 112 192
4859
+ -
2317
+ -
1623
394
+ + +
+ +
252
+ + +
DIFF
-
249
+
o43
-
117
-
284
-
80
KEV a0S
70-80
6-10
11-23 1160
+
24-47 1230
+
48-68 1470
+
69-90 +
1407
+
+
~00
+
355
+
324
+
430
+
329
NET
+
360
+
884
+
1146
+
977
+
1172
+
g59
+
1235
@FF
+
173
+
186
+
24
+ +
GM K NCI CS-137 23-29 gl-Ol
+ + >3SD >3SD
EITHER PU-239 DU-238 CM-244
+ + +
61 27 34
NCI NCI NCI
+
21
NCI
1005 140
+ +
012 64
-
7
91-128 1502
BKGD CALC
1234
62
117 1.92
MDA PU-23Q
+
AM-241
+
.23
NCI
Fig. 3. T y p i c a l c o m p u t e r p r i n t o u t ; a p e r m a n e n t r e c o r d o f d a t a collected on a n i n d i v i d u a l .
3
ASSAY OF W H O L E - B O D Y R A D I O A C T I V I T Y AND L U N G BURDENS
ground variations. The code permits background entry from the Teletype keyboard. Upon completion, control is transferred to the pulse-height analyzer ,:ode. 3) Because of possible analysis improvements, data from previous counts may be recalculated with new parameters. A short overlay to the code permits data entry of gross sums from the Teletype keyboard rather than from summation of energy spectra. Recalculation proceeds in the routine method with any new parameters desired.
95
4. Conclusions
The computer-based pulse-height analyzer and associated analysis code have performed very effectively in routine use at SRP. The system permits a high counting rate, offers rapid results, and eliminates manual data manipulation with its concomitant potential errors. Reference 1) F. D. Knight, Generalized linear regression analysis, USAEC Report DP-1128; E. I. du Pont de Nemours and Company. Savannah giver Laboratory, Aiken, South Carolina (1968),