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Analyses for some transuranic and natural radionuclides in the environmental samples
Environment International Vol. 1, pp. 75-83, 1978. Pergamon Press. Printed in Great Britain.
Analyses for some Transuranic and Natural Radionuclides in the Environmental Samples
John H. Harley u.s. Energy Researchand Development Administration, New York, U.S.A.
There is considerable present and expected future interest in the contamination of the environment 'with transuranic elements, particularly plutonium and americium. In addition, the alpha-emitting natural radionuclides are the usual standard of comparison for such transuranic element contamination. The present paper reviews the quality of data available for evaluating the distribution of ttansuranic elements and some natural radioactive elements in the environment. The overall quality cannot be documented for most programs and the data that are available indicate that the quality is poor. The fact that a few programs maintain high quality analyses indicates that the cause is poor analytical work rather than poor methods of analysis. (Plutonium-239; radium-226; lead-210; soil; air filters; sediment; tissue)
"There are few poor methods, but there are many poor analysts" - Anon. - , 1976. The interest in possible contamination of the environment has led to the requirement for analyses of various sample types for transuranic elements, particularly plutonium and americium. Large scale nuclear power production will also increase this requirement to include curium. The alpha-emitting natural radionuclides in the environment are the usual standard of comparison for the transuranic elements even through their behaviour is not necessarily the same either environmentally or metabolically. The preparation of this paper began as a review of the quality of the available methods for a number of radionuclides, but it became apparent that the problem in obtaining good data is not a matter of quality of the methods but of the quality of their application to the samples. The number of groups attempting to produce environmental data of scientific as opposed to monitoring quality is limited. Many of the groups do not report on their analytical quality, so much of the information reported here will come from our own laboratory. The bulk of the data available covers plutonium isotopes, radium226 and lead-210. Information on analytical quality comes from internal laboratory tests of precision or accuracy, from laboratory quality control programs and from interlaboratory comparisons. Data from the first source are frequently given with the publication of a particular analytical method and there has been no attempt to collect these values. Internal quality control programs are not well documented and most of them do not identify the laboratories concerned. I will identify our own laboratory and those who perform analyses for us under contract. Laboratory intercomparisons are the best method of establishing quality but
the preliminary arrangements, the sample distribution, and the collection and reporting of data sometimes stretch out for more than a year. Intercomparisons are thus not as useful as they should be. Analytical procedures
The analytical procedures for plutonium, americium, radium and lead-210 are generally adequate for the range of environmental samples that are of interest. The levels of americium in particular do tend to be towards the lower limit of detection and ability to handle larger samples could possibly be of some help. The radionuclides of concern must be separated from the bulk constituents of the sample and from interfering activities before measurement. Radiochemical analysis in general has relied on carrying out a number of separations in sequence to isolate the elements of interest. Tracers or carriers are usually available, so that the recovery of the process can be measured and thus the separations can be designed to emphasize removal of extraneous material as opposed to recovering 100% of the desired element. Table 1 indicates the analytical characteristics of the radionuclides covered in this paper including the final method of determination, tracer availability and the limit of detection. The analytical separation procedures now available can produce good results in the hands of a competent analyst. The limit on the amount of sample available frequently requires that sequential analyses be performed, and many of the quality control data reported here came from multinuclide analyses. This tends to inflate errors caused by lower recovery as well as causing other problems from the large number of manipulations required. The counting systems available are not a major source of error, provided sufficient equipment is on hand to provide 75
76
J o h n H. H a r l e y
T a b l e 1. A n a l y t i c a l c h a r a c t e r i s t i c s o f s e l e c t e d r a d i o n u c l i d e s Nuclide 238pu
Tracer
Method of Determination
Limit of Detection*
236pu, 242pu
~ Spectrometry
0.1
239pu-240pu
"
"
0. 1
241pu
"
"
0.1
241Am
243Am
"
0.1
226Ra
133Ba
222Rn Emanation
0.06
210pb
Stable Lead
~ Counting 210Bi ~r Counting 210po
0. 4 0. 4
hydrochloric acid solution and also purified by precipitation of lead iodide. After purification, the lead can be precipitated with sulfate and the growth of the bismuth210 daughter measured. Another procedure is to extract lead as bromide with an aliphatic amine. The bismuth-210 daughter can then be separated for beta-particle counting after a suitable time for growth. A longer growth time (several months) allows polonium-210 to be collected and assayed by alpha-particle counting. Availability of standards
* As defined in HASL P r o c e d u r e s Manual (ERDA Report HASL-300) in dpm por ~ample with a 400 minute count on a counter with normal background and efficiency.
the proper counting times. Alpha-particle spectrometers, in particular, are quite satisfactory and also allow a qualitative check on the composition of the product counted. The published procedures for the nuclides of interest are numerous since few analysts are willing to adopt a method developed by someone else. Thus we will only give some indications of the possibilities here. P l u t o n i u m - a m e r i c i u m analysis
Most procedures involve collecting the transuranics by coprecipitation with iron hydroxide or calcium oxalate. Plutonium may be absorbed on an ion-exchange column from nitric acid solution, then eluted with a mixed acid, collected again by coprecipitation and dissolved, electroplated and measured by alpha spectrometry. Either plutonium-236 or plutonium-242 are suitable tracers. The americium is collected by coprecipitation as the oxalate with either calcium or neodymium, absorbed on an ion exchange column from ammonium thiocyanate solution, eluted, electroplated and measured by alpha-particle spectrometry. Americium-243 is a suitable tracer. Plutonium-241 is a beta emitter and not readily measured. It is possible to allow its americium-241 daughter to grow in for a year or two and then separate and measure the americium. Otherwise, mass spectrometry is required. There are several other coprecipitation steps which are sometimes used and extraction with thenoyltrifluoroacetone (TTA) is possible. McDowell at Oak Ridge has published a procedure involving extraction of plutonium into a liquid scintillator and counting the mixture directly. This method requires, however, that the plutonium be present in only one to two milliliters of solution" for the extraction. Radium
Radium-226 is usually collected as the sulfate, purified, dissolved and stored in a bubbler for measurement by radon daughter de-emanation. The final counting can be done either in a scintillation bell or an ion chamber. The de-emanation step is a major purification process, since only gaseous radon is transferred to the counter. Lead-210
Lead can be absorbed on a cation column from
The preferable standards for calibration purposes are those prepared by the national standardizing bodies. Such standards are definitely always available for plutonium, americium and radium and can usually be obtained for lead-210. In addition, the International Atomic Energy Agency (IAEA) has had some of the nuclides available as standards in their program. Actually, the standardization of alpha-emitting radionuclides to the accuracy desired in environmental work is not difficult and a number of laboratories rely on single standards for calibration of alpha-particle counters. Greater availability of actual environmental standards would, of course, improve our estimates of analytical accuracy as opposed to precision. This topic and the subject of traceability will be covered in other sessions. Quality control programs The measurement of known samples during method development and testing furnishes m u c h useful information, but need not be covered here. This section will deal with evaluating the quality of analysis during continued operation of a program. Table 2 indicates a type of basic calibration exercise that must be carried out from time to time. The data represent overnight counts of radon transferred into pulse ion T a b l e 2. C a l i b r a t i o n , r a d i u m - 2 2 6 Lab: HASL Sample Type: Dilutionsof Two NBS Ra-226 Standards Units: Counts/hourper pg
Standard
Ion Chamber 4 5
1
2
3
6
7
8
1962 A
246
231
220
942
239
239
237
235
B
234
235
208
236
206
238
241
237
C
238
233
186
235
200
239
233
236
D
236
221
225
928
226
227
234
236
1975 A
239
238
229
237
234
231
229
239
B
230
234
225
230
233
237
228
234
C
235
233
228
241
148
166
234
224
D
236
223
225
251
236
163
232
239
Mean
237
231
218
236
215
218
234
235
Mean for 1962 Std. 1975
230 226
Overall Mean
228
Analyses for some radionuclides in environmental samples
77
chambers. The results confirm the adequacy of a single calibration factor for the 8 chambers. The Health and Safety Laboratory (HASL) maintains a quality control program for all analytical work involving a large number of samples. Many of the routine analyses are carried out under contract to commercial laboratories and the same quality control procedures and standards are applied to contractor analyses as to those performed at HASL. Ten to fifteen percent of the samples submitted are blanks, standards or blind duplicates (split samples not identified as such to the analyst) and the analyst is not aware in most cases of which samples are quality control samples. It is not always possible to have standards which cannot be visually distinguished from actual samples and in such cases there is more reliance on the precision of measurement as indicated by blind duplicates• Table 3. Analyst's quality control, radium-226 Lab: HASL Sample Type: Soil Duplicates and Blanks Units: pCi/g soil Reagent Blank
Year
Sample
1 9 7 3 (1 g)
1975 Added Found
2•6 0 2,0
2.3 0.06 2.1
6.4 7.6 0
6,9 8.0 0.09
9•4 8.8 0
9.2 9.0 O. 02
7•4 11.2 0
7.9 Ii•I 0•01
13.1 12.0 0
11.0 12.6 O. Ol
3.1 3.0 0
3•0 2.8 0.04
6.0 5.4 4.4
6.0 5.2 4.7
9.3 11.0 0
9•9 10.3 -0• 03
11.8 10.4 0
ii. 4 10.6 O. 04
10.7 I0,5 0
9.6 10.2 O. Ol
4.1 O 4.0
4.1 0.02 4.5
7.3 9.8 0
7.4 9.8 -0.01
9.7 12.7 o
9.2 12.2 o• 03
13.0 11.0
13.2 11.2
ii.0 14.7
0
0.07
0
10,8 13,8 0.03
4.3
4.9 7.4
6.8 7.5 0
6.9 7.4 O.s02
11.7 12,3 0
11.8 12.1 0.04
0 0 10.7
-0• 04 0.02 11.3
13.3 13.3
7.2
O
-0.06
4•4 7.2
10.8 11.0 0
10•0 11.0 0.00
11.5 12.5 0
11.4 12.5 0.04
9.9 0 8.9
9.2 0.03 7.2
9.7 9.8
0
4•4 7.8 0.03
0
0. I 9.2 -0 04
4.4 0 4.4
5.2 0.10 4,3
9.8 9.4 0
I1•0 9.1 0• 01
12.9 12.3 0
13.4 12.1 -0. O1
9.5
8.8
0 8.9
-0.04 8.6
10•1 8.6 0
9.3 8.3 0.07
6.0 7.1 6.5
6.3 6.8 6.3
11.6 12.5 O
11,5 12.0 O. 08
12.1 14.1 0
11.3 13.9 o. 20
9.1 0
9.0 0.00
7.4
7.0
13.9 9.2 0
13•9 9.2 0.01
7.4 0 6.3
7.5 0.03 7.0
10.7 11.4 O
10.3 11.2 0.06
U,O 0
10.4
U.2
10•5
I0.1 10.0 0
9.9 10.2 =0.02
6.0 -0•12 6.6
14.3
14.2
0
19•3
13.1
11•4 9.7
10.5 lb. 0
9•5 8.7
8,7 8.6
8.0 8.4
7.3
0.3
0
0,02
1.41 0.47
1.24 0.57
1• 1 2
0.07
5.2 0 6.5
O. 67 0.64 0.56
0.53 0.70 0.66
4.9 7•4 10.8
5.3 7•3 10.6
7•5 8•3 0
O. 05
9.5
0.74
0.77
1.36
1.71
6.0
7•7
7•5 7•2 0
7•6 7.2 0.01
7.4 0 7.8
0.065
0.67
0.63
0.057
0.99
0.97
0.072 0.079
1.47 1.70
1.41 1.51
O. 9 9
1.03
0.75
0.64
0.060
0.95
0.97
0.057
0.95
0.95
0.048 0.050
0.83
0.83
0
2
samples
3
4
5
6
.030
,033
.034
.029
• 034
.32
.32
.34
.34
.34
• 34
1968
.91
.94
. 95
. 91
.32
1.40
1.38
1.49
1.55
1.45
1.56
1.37
1.64
1968
1.21
1.10
1.16
1.12
1968
4.92
4.71
4.93
4.82
.014
.019
.016
.011
.016
.014
.016 .011
1969
1.10
1.10
1.04
1969
.38
.37
•42
1969
•29
.31
.34
1971
.33
.33
.32
.32
.32
1976
.77
.79
.75
.74
.71
.73
1976
1.38
1.39
1.36
I.31
1.44
1.38
. 070
.065
0.91
.37
. 065
0.04
0
9.9
.020
. 065
Found
0.64
1964
1976
1974
0.64
1963
1968
Added
0.83
Aliquot Number
1968
1973 Added FOund
0.76
Table 4. Analyst's quality control, radium-226
1
1972 Added Found
B
Lab: HASL Sample Type: Bone Ash, 10 g Units: pCi/g Ca
Year
1971 ~dded Found
A
1964 (5 g)
1971 (I g)
Table 5• Quality control, plutonium-239 Lab: tIASL Contractor (T,FEJ Sample Type: Spiked Air Filters Units: dpm per sample
-o• 03
10.3
o. 04
-0. 02
13.0 13.9
0
0.10
9.4
10.2 0 8.9
10.1 O. O0 8•9
7.7 0.01 7.4
9•1 0 10.4
9.2 0• 02 10.1
10.5 0 13.4
9.8 0. 04 11.8
9•6 O
10.0 -0.05
9.2 0
9.2 O. 09
0
-0. 14
It is unfortunate that a number of the more important analyses are not part of extensive programs and cannot be subject to quality control procedures. On the other hand, the analysts can inject their own test samples. The results of these plus the necessary integrity of the individual can be equivalent to an external program. Tables 3 and 4 show typical data of this type that can be accumulated. (In a number of cases, the counting was done on a blind basis.) Tables 5 - 1 0 show specific quality control programs for the nuclides of interest carried out by HASL over the past few years• Tables 5 and 6 indicate that quality can be maintained by a commercial contractor over a period of years. Since the spiked air filters are known to be quality-control samples and might receive special treatment, the results of the blind duplicates in Table 7 are reassuring. Tables 8 - 1 0 deal with blind duplicate soil analysis, the first with kilogram samples run at 3 laboratories during a single program and the third with mass spectrometry data for isotopic ratios• The use of analytical contractors requires a program to qualify laboratories for the required work. Tables 11 and 12 show a set of data reported by three laboratories doing commercial work but not qualified for our analyses• In the United States, the Environmental Protection Agency (EPA) operates a quality assurance program that is open on request to any laboratory. Simulated environmental samples, containing known amounts of one or more
78
John H. Harley Table 8. Quality control, plutonium-238, 239
Table 6. Quality control, lead-210
Lab: tIASI, C o n t r a c t o r (IPA) Sample Type: Soil, 1000 g leach, blind d u p l i c a t e s Units: f C i / g soil
Lab: HASL C o n t r a c t o r (LFE) S a m p l e Type: Spiked A i r F i l t e r s Units: dpm per sample 1975
1974 Added
Found
Added
Found
0 0 460
-8 9 460
520 470 0
480 440 -1
430 0 450
430 0 440
570 520 0
550 540 0
430 0 380
450 -I 360
580 540 0
580 600 0
440 0 490
450 -i 490
540 590 0
620 670 0
430 O
430 -1
560 520 0
610 590 0
480 470 0
550 590 0
Aliquot
Site Argonne,
Illinois
Pu-239
Pu-238
A B
4.6 4.4
0.15 0.14
A n g r a dos Reis, Brazil
A B
1.6 i .7
0.29 0.32
Roskilde,
A B
2,9 3 ,0
0. I0 0.09
Denmark
Ispra,
Italy
A B
ii .7 ii .4
0.39 0.38
Tokyo,
Japan
A B
9.4 9.2
0.33 0.33
~--t
I
= -+ a o
)
CONTROL LIMIT
460 540 0
530 600 0
610 470 0
640 550 0
JANUARY mm
440 530 0
500 600 0
47O 0
52O 2
0
5
I
~,
~" :
~o"~, ,~, z
,~ 11
MAY
Table 7. Quality control, plutonium-239 and lead-210
Freq.
25
Lab: ltASL C o n t r a c t o r ( L F E ) Sample Type: Blind Duplicate A i r F i l t e r s Units: d p m p e r s a m p l e
=p=
Pb-210 1974
490 490 570 760 800
Pu-239 400 510 500 800 880
0.5 1.8 1.0 0.7 0,5
5
JULY J
~5
0.8 1.6 0.7 0.7 0.6
l
i"
=l J=
5
N O V E M BER
5. 1975
650 480 500 320 770 450 430 750 1200 36 260
660 480 480 320 820 520 510 780 1170 54 220
0.2 0, 2 0.3 0, 4 0, 6 0, 2 0.4 1, 5 1.8 2.0 0.7
0.2 0.1 0.3 0.4 0.3 0.1 0, 4 1.4 2, 0 1, 8 0.6
radionuclides, are prepared by the Quality Assurance Branch at the Environmental Monitoring and Support Laboratory in Las Vegas, Nevada. After submission of data, a report and control chart are returned to each participant. For the nuclides of interest here, water samples with
0 0
5
10 15 pCi/liter
20
25
Fig. 1. Data from EPA quality assurance program, radium in water for 1974 (~ is the mean value of all reporting laboratories and ~ is the amount added). radium (see Fig. 1) and water, air filters and soii with plutonium-239 are available. The Quality Assurance Branch exchanges samples with the National Bureau of Standards as a control on their own work. Another program of this type is being instituted by the Division of Safety, Standards and Compliance of the Energy Research and Development Administration
Analyses for some radionuclides in environmental samples
79
Table 9. Quality control, plutonium-239
Table 11. Qualification analyses, plutonium-239 Labs: Anonymous Sample Types: Blanks, Spikes, Standards on Air Filters Units: dpm per sample
Labs: HASL, IPA, TLW Sample TyPe: Soil, 100 g blind duplicates Unlts~ dpm per sample
Expected
Lab HASL IPA
TLW
Aliquot A
AnquotB
~8 700
16 300
171 000 33 19 17
151 000 27
II 600 220 230 91 90 48 35
13 000 200 240 96 92 41 49
Lab A
0 9.1 13.1 0.4 1.0
2.0 9.3 17.2 12.4 2.4
Lab B
0 8.1 12.1 1.3 1.0
<0.2 3.7 7.1 15.5 9.6
Lab C
0 8.7 12.2 0.4 0.6
<0.1 7.6 12.7 0.3 1.4
25
17
Table 10. Quality control, isotopic plutonium ratios Lab: KAPL Sample Type: Separated Pu Fractions, Blind Duplicates and R e p l i c a t e s Units: D i m e n s i o n l e s s
}40/239
241/239
.183 .191
.0085 .0087
.165 .142
.0066 .0055
.174 .171
.0078 .0080
.173 .179 .177 .178 .179 .166
.0079 .0080 .0081 .0080 .0082 .0074
.161 .176
.0059 .0083
.180 .163
.0083 .O095
.174 .171
.0075 .0076
.085 .085
.0033 .0033
Reported
Lab C (Second Try)
18,3 0 4.4
(ERDA), to be administered by HASL. Intercomparison samples including air filters, soil vegetation, water and tissue are to be distributed quarterly m all ERDA contractor laboratories presently doing environmental monitoring. Data will be collected by HASL and summaries distributed to the participating groups. The laboratories will not be identified in the published reports, at least at the beginning of the program. A great deal has been written about quality control, but a few reminders may not be amiss. A major factor in a good program is careful review of the data by a competent scientist. This saves many headaches. A second point is that the program results should be a basis for action, either complimentary or corrective. And finally, quality-control results should be published to establish the proper degree of confidence in the data being presented.
I00 <0.4 19.2 2.1 4.5
Table 12. Qualification analyses, lead-210 Labs: A n o n y m o u s Sample Types: Blanks, Spikes, Standards on Air F i l t e r s Units~ dpm per sample
Expected
Reported
Lab A
0 475 444
12 206 131
Lab B
0 424 503
4 823 541
Lab C
0 424 408
<4 207 246
0 639 0 1340 165
1000 2400 690 670 310
....
Measurement by m a s s s p e c t r o m e t r y
105 0
Lab C (Second Try)
Intercomparisons Even a tight internal quality-control program may go astray without cross-checking with other competent laboratories from time to time. Many of these intercomparisons are very informal and are never reported. Others may attain a. more formal status, but generally this means a considerable lag in reporting data. The simplest intercomparisons are those of prepared sources or pure solutions as shown in Table 13. These generally test only the counting equipment and the laboratory's standards but not its radiochemical and source preparation techniques. Tables 14 and 15 each show the results of 3 laboratories on actual samples of soil and human tissue, respectively. In the first case (Table 14), the true values were unknown, in the second (Table 15) the samples were spiked by the laboratory generating the samples. Table 16 gives the results of an intercomparison set up
80
John H. Harley
Table 13. Interlaboratory calibration, plutonium Labs~ Anonymous Sample Type: E l e c t r o p l a t e d Source Units: d p m Lab
242
239-240
238
1
8.83
4.09
.76
2
8.80
4.57
.78
3
8.83
4.63
.83
4
8.42
4.57
.72
5
8.63
3.93
.68
8.24
5.00
8.62 ± .25
4.46 ± . 3 9
6
Table 15. Intercomparison, plutonium-239 l,at~s: IIA81,, I,ASI~, PNL Sample Type: Spiked T i s s u e s Units: d p m / s a m p l e
Added Bone (20 g)
tlASL l,'ound
L a b s : L L L , MCL, L F E , LRE, EIC Sample Type: Solution, alpha s p e c t r o m e t r y Units: d p m / m l
Lung
Lab
Result
LLL
1320 L 20
MCL
1255 ± 15
LFE
1330 ± 27
LRE
1273 ± 64
EIC
1207 ~ 54 Liver (40 g)
Pu-239
0 0 0 0.12
Blank
0. 85
0.75 0.89 0.91
0.77
0.~;1 1.08 0.52
0.55
0.54 0.54 0.56
1.96
2.07 I. ~9 1.85
1.~;1
1.52 I. 50 1.82
1.06
1.95 1.03 1.11
t/Imlk
< . 92 < . 02 <" . 0 2 < . 92
Blank
0 0
Blank
0
O. 88
0.73 (). 97 9.94
0.7"3
0.64 O. 86 0.68
0.99
O. 82 o. 95 0.92
1.79
1.64 1.~8 1.75
I. (i~
1.66 1.78 1.59
1. ~1
1.78 1.82 1.83
Blank
< . 02 < . 02 < . 02 < . 02
Blank
0 0 0 0
Blank
0.96
0.92 0.95 1.01
0.69
0.74 0.56 0.78
9.89
0.8(; 0.96 0.84
1.82
1.73 1.92 1.80
1.14
1.14 1.14 l . 14
1.75
1.89 1.65 1.72
BROO~IAVEN
Spiking Solution (10 ml)
Pu-238
PNL Found
Blank
Table 14. Intercomparison, plutonium-238, 239
Lab
Added
< . 02 < . 02 < . 02 < .02
The e l c c t r o p l a l e d s o u r c e dala appeared in ERDA Report NVO-159 and the solution data in NVO-140.
I,abs: }IASI,, IPA, T L W Sample Type: Soil Units: f ( ' i / g
LASL Found
Blank
.77 0.76 ± °05
Added
1.73
.031 .002 .048 0
. I)25
0
.016
0
.027
1.55
.083 .040 .033 .025
1.81
(1970)
Table 16. EPA Intercomparison,thorium-230 HASL
19.5 19.0 18.7 18.6 19.8 19.0 19.2 18.3 18.7 18.4 18.7
" IPA "
TLW " Avg.
± 0.5% ± 0.5% -+ 0 . 5 % ± 1% ± 2% ± 2% ± 3% ± 2% ± 3% ± 3% ± 2%
18.9 ±
3%
" B L A C K SOIL" HASL IPA TLW Avg.
Avg.
0.77 ±18% (1958)
2.4
0.043 ± 3 7 %
±
3%
1.6 ± 1.9 ± l.S ±
10% 2% 6%
1.8 ±
9%
0.63
15% 88%
(1958)
LAKE
0 . 5 8 ± 4% 0.68 ± 16% Avg.
5% 6% 6% 7% 4% 4% 5% 6% 5% 7% 5%
0.054 ± 0.032 ±
WOODCLIFF IPA TLW
± ± ± ± ± ± ± ± ± ± ±
2.5 ± 1 0 % 2.4 ± 2% 2.4 ± 5%
"RED SOIL" HASL IPA TLW
0.86 0.76 0.81 0.47 0.86 0.72 0.76 0.72 0.75 0.72 1.0
± 11%
0.058 ± 15% 0.076 ± 36% 0.067 ±
19%
(1970) 0.014 ± 50% 0.081 ± 99%
Labs: Anonymous Sample Type: Spiked A i r F i l t e r s , EPA, 1974 Units: pCi/filter
Known Value
16
ttASL
10, 8, 11
Lab D
6, 10, 8
LabJ
13, 14, 14, 14, 15, 14
Lab W m,
9, 8, 8
Net v a l u e s are r e p o r t e d , a blank f i l t e r showed about 6 pCi of Th-230
by the EPA in the United States. This differed from many of the others reported here in that the analysis was not being performed routinely at any of the laboratories. The National Bureau of Standards (NBS) has issued a river sediment standard and some of the data collected in the establishment of standard values are shown in Table 17. This approach is most likely to yield useful standard samples of environmental materials. The first two Tables (18 and 19) of IAEA Intercomparisons deal with radium-226. Obviously the data are good for pure solutions, but the agreement is poor when chemistry is required. No data are available for lead-21(L
Analyses for some radionuclides in environmental samples Table 17. Intercomparison, NBS standard sediment L a b s : Anonymous Sample Type: D r i e d R i v e r S e d i m e n t Units: dps p e r g r a m
81 Table 20. IAEA intercomparisons, plutonium-239 Labs: Anonymous Sample Type: Spiked Air F i l t e r s Units: p C i / f i l t e r
I>u-239, 240 (NBS C e r t i f i e d as 1.4 x 10 -8) HASL
1.4 x 10 -3
HSL
1 . 3 x 10 . 3
WHOI
1.45 x 10 -3
Known Value
200
Lab
180 80 191 187 73 150 64 353 141 193 219 188 199 152 280 84
T h - 2 3 2 (Uneertified) HASL
3.1 x 10 - 2
HSL
3 . 8 x 10 - 2
P u - 2 3 8 (Uncertified) NBS
7 . 3 x 10 -5
HSL
7 . 6 x 10 -5
WHOI
5.8x 10-5
Am-241 (Uneertified) ItSL
3.1 x 10 -4
WtIOI
3 . 2 x 10 -4
Table 21. IAEA intercomparison, plutonium-238, 239
Table 18. IAEA intercomparison, radium-226 Labs: Anonymous Sample Type: A n i m a l Bone A s h (A-1O, R e p o r t e d 1975) Units: p C i / g ash
Labs: Anonymous Sample Type: S e a w a t e r Units: f C i / k g , pCi/kg Results Lab SW - 1 - 1 (fCi/kg)
L a b Code
Result
2 5 (ftASL) 6
1.87 1.84 1.47
7 8 11
1.18 1.43 1.36
12 16 17
1.48 1.65 2.30 (Rejected) Mean
Water
1 2 3 4 5 6 (tfASL) 7 8 9 10 11 12 13
116 115 112 141 137 126" 106 112 126 120 124 126 122
* I n d i v i d u a l v a l u e s 124, 127, 127, 126, 125, 124
-
80
SW - 1 - 2 ( f c i / k g )
1 2 3 4 5 (HASL) 6 (WItOD 7 8 9 10 11 17
22 40 22 40 26 33 48 51
90 227 280 169 200 222 275 239 340 254 130 200
SW - A - 1 (fCi/kg)
7 8 9 12 (WItOI) 15 16 18 (ItASL) 20
SW - I - 3 (pCi/kg)
6 8 9 10 (WtIOl) 11 16 18 24
Mean R e s u l t 1.68 1.10 .57 .42 .26 .45 .54 .23 .48 .43
10 11
54 84 80 100 100 85 92 69 770 116 I00
Table 19. IAEA intercomparison, radium-226
1 2 3 4 5 6 7 8 9 10 (IIASI,)
7.5 7 11 20 7 8.9 1O. 5 120
Pu-239
6
L a b s : Anonymous Sample Types: Soil, W a t e r Units: p C i / g , p C i / g
Soil
1 2 3 4 5 (IIASL) 6 (WllOl} 7 8 9
Pu-238
17
1.52 _+ .23
Lab #
2 (HASL) 3 4 5 7 11 13 14 17 19 23 25 28 29 30 31
30
1.24 0.9 1.5 1.2 <18 70 1.0 o. ~) 22 40 17 15
100 70 110 118 240 113 60 320
The IAEA plutonium results are similar, in that spiked air filters can be analyzed by a number of laboratories to + 10% (Table 20), but the more difficult marine samples are subject to an excessive spread in values. This spread is no less marked as the level of activity increases, as shown in the sea water samples.
82
John H. Harley Table 22. IAEA intercomparison, plutonium-238, 239
Labs: Anonymous Sample Types: Seaweed, Units: p C i / g
Sediment
Results
-I
AG -I
SD
-
B
-
1
Lab
Pu-238
Pu-239
1 2 3 4 5 (IIASL) 6 (WHOI) 7 8 9 I0 11 12 13 14 15 16 17
2.7 3.9 4.1 4.1 3.9 4.8 3.8 4,2 3.7 7.0 3.1
19.7 28.2 28 23.0 28.6 30.0 26,7 30.0 25.1 27.9 20.8 28 24.3 22.3 27.3 26.1 24
1 (WtlOI) 2 3 4 5 6 7 8 9 10 11 (HAS/,) 12 13 14 15 16 17 18
3.6 3.3 3.9 3.0 .060 .040 .048 .027 .040
. 89 1.01 .64 1.09 .93 . 94 2.05 .06 . 88 t.04 .95 1.06 .82 .93 .98 1.06 1.02 1.15
.032 .034 .027 .053 ,055 .041 ,045 .035 .054
nuclides considered here and of course it is not possible to use such anonymous reporting to evaluate published papers interpreting the environmental significance of the results of analytical measurements. It would seem that it might also be useful for the IAEA to request certain competent laboratories to participate in intercomparisons where they would be identified. If the agency were to start with a very large initial sample, other laboratories could then receive material which had a certain status as a standard. This would be similar to the programs used by the National Bureau of Standards and other bodies for issuing standard ferrous and non-ferrous metals.
Summary This rather pedestrian report has summarized a considerable body of data on the quality of analyses for plutonium isotopes, radium-226 and lead-210. While there is a group of laboratories turning out results of adequate quality, the overall quality of the data is variable to poor. It shoul d be remembered that the results of these analyses are used as a basis for interpretive reports on physical phenomena and it would appear that proper interpretation can only be arrived at by chance. In the opinion of the author, the present chemical methods, instrumentation and standards are adequate "for our requirements for environmental analyses. Improvement in quality can only come from increased attention to analytical detail and confidence in the results can only be improved by maintaining and reporting adequate quality control and intercomparison programs. List of Laboratories Appearing in Tables
Table 23. IAEA intercomparison, plutonium-239 Labs: Anonymous S a m p l e Type: Dried Marine Animal Tissue Units: f C i / g Result La b MA - B - 1
MA-B-2
Pu-23£
Pu-239
10
< 4 < 44
11 13 (IIASL) 14 17 (WlIOI) 20 31
1,41 + .25 2.6 + .8 1.5 + .2
0+_ 10 50 + 20 < 25 60 +_ 10 34 + 15 < 60 3 8 . 3 _+ 1 . 4 43 + 3 36 + 4
7 8
7 8
10 11 13 (HASL) 14 17 (WHOI) 31
< 18 < 26
0.76 + .12 0.95 i .06
0+50 < 12 < 11 20 +_ 5 2.4 i 1.0 < 70 1.05 i .17 1 . 0 + .1
The broadest intercomparison coverage has been obtained by the IAEA with a large number of laboratories participating. Tables 2 0 - 2 3 show tile results of these intercomparisons. In these tables, the Woods Hole Oceanographic Institution (WHOI) has agreed to be identified and we have also indicated the HASL data where we participated. The overall quality of the data is poor for the
EIC HASL HSL IPA LFE LLL LRE MCL TLW KAPL LASL NBS PNL WHOI
Eberline Instrument Corporation Health and Safety Laboratory Health Services Lab., Idaho Falls Isotopes, Pale Alto LFE, Environmental Analysis Laboratory Lawrence Livermore Laboratory Laboratory of Radiation Ecology McClellan Central Laboratory Traceflab West, now LFE Knolls Atomic Power Laboratory Los Alamos Scientific Laboratory National Bureau of Standards Pacific Northwest Laboratory Woods Hole Oceanographic Institution
Discussion Bowen: Dr. Harley will remember, as I do, another variable in the data produced by NBS "preferred" or "starred" laboratories. We b o t h worked in one of these in the early 1940s, and were divided, always, between a m u s e m e n t and dismay when we heard (very frequently) the Chief Chemist emerge from his sanctum, data sheet in hand, to call "Who analyzed that last NBS sample?", and to continue, once the analyst was identified, "Well, that was n o t what the Bureau got, so run it again!" Clearly, it was by agreeing with "The Bureau" that a laboratory kept its preferred position, and so long as there was c o m m u n i c a t i o n o f unofficial results outward from the Bureau, a strong, b u t n o t - I believe - quite desirable feed-back loop was set up. For such a system as Dr. Harley proposes to work at its ideal best, all data m u s t be rigidly confidential until the final analysis is produced.
Analyses for some radionuclides in environmental samples Although one feels intuitively that the best analytical performance should be elicited by good treatment and encouragement, I recently encountered another variable: of about eight young people in my laboratory, all doing radiochemistry on sediments containing falloutqevel radionuclides, one clearly stands out in respect to obtaining good data on quality control samples, high chemical yields, and a large rate of data production; she also is the least trained academically. In a recent discussion of this performance, I was dismayed to have her explanation turn out to be "Well, the others all know what they are doing, but I really don't, so I'm just plain afraid all the time, and much more careful!" Only with great reluctance would I try to keep my young assistants "afraid all the time" - and yet one must admit that her point is clear and pertinent. Suschny: If calibration standards are supplied with the (unknown) sample, some improvement is achieved, in particular in instrumental measurements (e.g. of ~37 Cs). For determinations involving chemical separations (e.g. 90 Sr), this improvement is not considerable. Another point I would like to raise is this: to avoid the possibility of claims being made that a sample, which gave bad results in intercomparison, was perhaps inhomogenous, it is advisable to send out several randomly selected sub-samples to each
83 participating laboratory. Good intraqaboratory precision will then prove homogeneity of a sample while the difference of an individual laboratory mean from the (known) true value or, where the true value is not known, from the overall inteflaboratory mean may serve to show up systematic errors. Gans: We have had the experience that furnishing standard solutions in an intercomparison program does not really improve the quality of results if the quality of the participating laboratories is not too good. In one of the round robin tests we carried out before the one I reported on yesterday, we furnished a standard of 5~,-emitters as well as a list of nuclear data of all nuclides possibly present in the sample. The results of the measurements of some laboratories showed good agreement in the concentrations of those nuclides that were contained in the standard solutions, but nevertheless the agreement for the other nuclides was very poor. The last intercomparison program, when no standard solutions were shipped, showed much better results, this meaning - in our opinion - that the general standard of the laboratories has improved. Aten: Did the spiked samples (e.g. in Table 2) also contain other activities that might be present? Harley: Yes, they contained fission products at levels comparable to air samples taken at that time.
Analyses for some Transuranic and Natural Radionuclides in the Environmental Samples
John H. Harley u.s. Energy Researchand Development Administration, New York, U.S.A.
There is considerable present and expected future interest in the contamination of the environment 'with transuranic elements, particularly plutonium and americium. In addition, the alpha-emitting natural radionuclides are the usual standard of comparison for such transuranic element contamination. The present paper reviews the quality of data available for evaluating the distribution of ttansuranic elements and some natural radioactive elements in the environment. The overall quality cannot be documented for most programs and the data that are available indicate that the quality is poor. The fact that a few programs maintain high quality analyses indicates that the cause is poor analytical work rather than poor methods of analysis. (Plutonium-239; radium-226; lead-210; soil; air filters; sediment; tissue)
"There are few poor methods, but there are many poor analysts" - Anon. - , 1976. The interest in possible contamination of the environment has led to the requirement for analyses of various sample types for transuranic elements, particularly plutonium and americium. Large scale nuclear power production will also increase this requirement to include curium. The alpha-emitting natural radionuclides in the environment are the usual standard of comparison for the transuranic elements even through their behaviour is not necessarily the same either environmentally or metabolically. The preparation of this paper began as a review of the quality of the available methods for a number of radionuclides, but it became apparent that the problem in obtaining good data is not a matter of quality of the methods but of the quality of their application to the samples. The number of groups attempting to produce environmental data of scientific as opposed to monitoring quality is limited. Many of the groups do not report on their analytical quality, so much of the information reported here will come from our own laboratory. The bulk of the data available covers plutonium isotopes, radium226 and lead-210. Information on analytical quality comes from internal laboratory tests of precision or accuracy, from laboratory quality control programs and from interlaboratory comparisons. Data from the first source are frequently given with the publication of a particular analytical method and there has been no attempt to collect these values. Internal quality control programs are not well documented and most of them do not identify the laboratories concerned. I will identify our own laboratory and those who perform analyses for us under contract. Laboratory intercomparisons are the best method of establishing quality but
the preliminary arrangements, the sample distribution, and the collection and reporting of data sometimes stretch out for more than a year. Intercomparisons are thus not as useful as they should be. Analytical procedures
The analytical procedures for plutonium, americium, radium and lead-210 are generally adequate for the range of environmental samples that are of interest. The levels of americium in particular do tend to be towards the lower limit of detection and ability to handle larger samples could possibly be of some help. The radionuclides of concern must be separated from the bulk constituents of the sample and from interfering activities before measurement. Radiochemical analysis in general has relied on carrying out a number of separations in sequence to isolate the elements of interest. Tracers or carriers are usually available, so that the recovery of the process can be measured and thus the separations can be designed to emphasize removal of extraneous material as opposed to recovering 100% of the desired element. Table 1 indicates the analytical characteristics of the radionuclides covered in this paper including the final method of determination, tracer availability and the limit of detection. The analytical separation procedures now available can produce good results in the hands of a competent analyst. The limit on the amount of sample available frequently requires that sequential analyses be performed, and many of the quality control data reported here came from multinuclide analyses. This tends to inflate errors caused by lower recovery as well as causing other problems from the large number of manipulations required. The counting systems available are not a major source of error, provided sufficient equipment is on hand to provide 75
76
J o h n H. H a r l e y
T a b l e 1. A n a l y t i c a l c h a r a c t e r i s t i c s o f s e l e c t e d r a d i o n u c l i d e s Nuclide 238pu
Tracer
Method of Determination
Limit of Detection*
236pu, 242pu
~ Spectrometry
0.1
239pu-240pu
"
"
0. 1
241pu
"
"
0.1
241Am
243Am
"
0.1
226Ra
133Ba
222Rn Emanation
0.06
210pb
Stable Lead
~ Counting 210Bi ~r Counting 210po
0. 4 0. 4
hydrochloric acid solution and also purified by precipitation of lead iodide. After purification, the lead can be precipitated with sulfate and the growth of the bismuth210 daughter measured. Another procedure is to extract lead as bromide with an aliphatic amine. The bismuth-210 daughter can then be separated for beta-particle counting after a suitable time for growth. A longer growth time (several months) allows polonium-210 to be collected and assayed by alpha-particle counting. Availability of standards
* As defined in HASL P r o c e d u r e s Manual (ERDA Report HASL-300) in dpm por ~ample with a 400 minute count on a counter with normal background and efficiency.
the proper counting times. Alpha-particle spectrometers, in particular, are quite satisfactory and also allow a qualitative check on the composition of the product counted. The published procedures for the nuclides of interest are numerous since few analysts are willing to adopt a method developed by someone else. Thus we will only give some indications of the possibilities here. P l u t o n i u m - a m e r i c i u m analysis
Most procedures involve collecting the transuranics by coprecipitation with iron hydroxide or calcium oxalate. Plutonium may be absorbed on an ion-exchange column from nitric acid solution, then eluted with a mixed acid, collected again by coprecipitation and dissolved, electroplated and measured by alpha spectrometry. Either plutonium-236 or plutonium-242 are suitable tracers. The americium is collected by coprecipitation as the oxalate with either calcium or neodymium, absorbed on an ion exchange column from ammonium thiocyanate solution, eluted, electroplated and measured by alpha-particle spectrometry. Americium-243 is a suitable tracer. Plutonium-241 is a beta emitter and not readily measured. It is possible to allow its americium-241 daughter to grow in for a year or two and then separate and measure the americium. Otherwise, mass spectrometry is required. There are several other coprecipitation steps which are sometimes used and extraction with thenoyltrifluoroacetone (TTA) is possible. McDowell at Oak Ridge has published a procedure involving extraction of plutonium into a liquid scintillator and counting the mixture directly. This method requires, however, that the plutonium be present in only one to two milliliters of solution" for the extraction. Radium
Radium-226 is usually collected as the sulfate, purified, dissolved and stored in a bubbler for measurement by radon daughter de-emanation. The final counting can be done either in a scintillation bell or an ion chamber. The de-emanation step is a major purification process, since only gaseous radon is transferred to the counter. Lead-210
Lead can be absorbed on a cation column from
The preferable standards for calibration purposes are those prepared by the national standardizing bodies. Such standards are definitely always available for plutonium, americium and radium and can usually be obtained for lead-210. In addition, the International Atomic Energy Agency (IAEA) has had some of the nuclides available as standards in their program. Actually, the standardization of alpha-emitting radionuclides to the accuracy desired in environmental work is not difficult and a number of laboratories rely on single standards for calibration of alpha-particle counters. Greater availability of actual environmental standards would, of course, improve our estimates of analytical accuracy as opposed to precision. This topic and the subject of traceability will be covered in other sessions. Quality control programs The measurement of known samples during method development and testing furnishes m u c h useful information, but need not be covered here. This section will deal with evaluating the quality of analysis during continued operation of a program. Table 2 indicates a type of basic calibration exercise that must be carried out from time to time. The data represent overnight counts of radon transferred into pulse ion T a b l e 2. C a l i b r a t i o n , r a d i u m - 2 2 6 Lab: HASL Sample Type: Dilutionsof Two NBS Ra-226 Standards Units: Counts/hourper pg
Standard
Ion Chamber 4 5
1
2
3
6
7
8
1962 A
246
231
220
942
239
239
237
235
B
234
235
208
236
206
238
241
237
C
238
233
186
235
200
239
233
236
D
236
221
225
928
226
227
234
236
1975 A
239
238
229
237
234
231
229
239
B
230
234
225
230
233
237
228
234
C
235
233
228
241
148
166
234
224
D
236
223
225
251
236
163
232
239
Mean
237
231
218
236
215
218
234
235
Mean for 1962 Std. 1975
230 226
Overall Mean
228
Analyses for some radionuclides in environmental samples
77
chambers. The results confirm the adequacy of a single calibration factor for the 8 chambers. The Health and Safety Laboratory (HASL) maintains a quality control program for all analytical work involving a large number of samples. Many of the routine analyses are carried out under contract to commercial laboratories and the same quality control procedures and standards are applied to contractor analyses as to those performed at HASL. Ten to fifteen percent of the samples submitted are blanks, standards or blind duplicates (split samples not identified as such to the analyst) and the analyst is not aware in most cases of which samples are quality control samples. It is not always possible to have standards which cannot be visually distinguished from actual samples and in such cases there is more reliance on the precision of measurement as indicated by blind duplicates• Table 3. Analyst's quality control, radium-226 Lab: HASL Sample Type: Soil Duplicates and Blanks Units: pCi/g soil Reagent Blank
Year
Sample
1 9 7 3 (1 g)
1975 Added Found
2•6 0 2,0
2.3 0.06 2.1
6.4 7.6 0
6,9 8.0 0.09
9•4 8.8 0
9.2 9.0 O. 02
7•4 11.2 0
7.9 Ii•I 0•01
13.1 12.0 0
11.0 12.6 O. Ol
3.1 3.0 0
3•0 2.8 0.04
6.0 5.4 4.4
6.0 5.2 4.7
9.3 11.0 0
9•9 10.3 -0• 03
11.8 10.4 0
ii. 4 10.6 O. 04
10.7 I0,5 0
9.6 10.2 O. Ol
4.1 O 4.0
4.1 0.02 4.5
7.3 9.8 0
7.4 9.8 -0.01
9.7 12.7 o
9.2 12.2 o• 03
13.0 11.0
13.2 11.2
ii.0 14.7
0
0.07
0
10,8 13,8 0.03
4.3
4.9 7.4
6.8 7.5 0
6.9 7.4 O.s02
11.7 12,3 0
11.8 12.1 0.04
0 0 10.7
-0• 04 0.02 11.3
13.3 13.3
7.2
O
-0.06
4•4 7.2
10.8 11.0 0
10•0 11.0 0.00
11.5 12.5 0
11.4 12.5 0.04
9.9 0 8.9
9.2 0.03 7.2
9.7 9.8
0
4•4 7.8 0.03
0
0. I 9.2 -0 04
4.4 0 4.4
5.2 0.10 4,3
9.8 9.4 0
I1•0 9.1 0• 01
12.9 12.3 0
13.4 12.1 -0. O1
9.5
8.8
0 8.9
-0.04 8.6
10•1 8.6 0
9.3 8.3 0.07
6.0 7.1 6.5
6.3 6.8 6.3
11.6 12.5 O
11,5 12.0 O. 08
12.1 14.1 0
11.3 13.9 o. 20
9.1 0
9.0 0.00
7.4
7.0
13.9 9.2 0
13•9 9.2 0.01
7.4 0 6.3
7.5 0.03 7.0
10.7 11.4 O
10.3 11.2 0.06
U,O 0
10.4
U.2
10•5
I0.1 10.0 0
9.9 10.2 =0.02
6.0 -0•12 6.6
14.3
14.2
0
19•3
13.1
11•4 9.7
10.5 lb. 0
9•5 8.7
8,7 8.6
8.0 8.4
7.3
0.3
0
0,02
1.41 0.47
1.24 0.57
1• 1 2
0.07
5.2 0 6.5
O. 67 0.64 0.56
0.53 0.70 0.66
4.9 7•4 10.8
5.3 7•3 10.6
7•5 8•3 0
O. 05
9.5
0.74
0.77
1.36
1.71
6.0
7•7
7•5 7•2 0
7•6 7.2 0.01
7.4 0 7.8
0.065
0.67
0.63
0.057
0.99
0.97
0.072 0.079
1.47 1.70
1.41 1.51
O. 9 9
1.03
0.75
0.64
0.060
0.95
0.97
0.057
0.95
0.95
0.048 0.050
0.83
0.83
0
2
samples
3
4
5
6
.030
,033
.034
.029
• 034
.32
.32
.34
.34
.34
• 34
1968
.91
.94
. 95
. 91
.32
1.40
1.38
1.49
1.55
1.45
1.56
1.37
1.64
1968
1.21
1.10
1.16
1.12
1968
4.92
4.71
4.93
4.82
.014
.019
.016
.011
.016
.014
.016 .011
1969
1.10
1.10
1.04
1969
.38
.37
•42
1969
•29
.31
.34
1971
.33
.33
.32
.32
.32
1976
.77
.79
.75
.74
.71
.73
1976
1.38
1.39
1.36
I.31
1.44
1.38
. 070
.065
0.91
.37
. 065
0.04
0
9.9
.020
. 065
Found
0.64
1964
1976
1974
0.64
1963
1968
Added
0.83
Aliquot Number
1968
1973 Added FOund
0.76
Table 4. Analyst's quality control, radium-226
1
1972 Added Found
B
Lab: HASL Sample Type: Bone Ash, 10 g Units: pCi/g Ca
Year
1971 ~dded Found
A
1964 (5 g)
1971 (I g)
Table 5• Quality control, plutonium-239 Lab: tIASL Contractor (T,FEJ Sample Type: Spiked Air Filters Units: dpm per sample
-o• 03
10.3
o. 04
-0. 02
13.0 13.9
0
0.10
9.4
10.2 0 8.9
10.1 O. O0 8•9
7.7 0.01 7.4
9•1 0 10.4
9.2 0• 02 10.1
10.5 0 13.4
9.8 0. 04 11.8
9•6 O
10.0 -0.05
9.2 0
9.2 O. 09
0
-0. 14
It is unfortunate that a number of the more important analyses are not part of extensive programs and cannot be subject to quality control procedures. On the other hand, the analysts can inject their own test samples. The results of these plus the necessary integrity of the individual can be equivalent to an external program. Tables 3 and 4 show typical data of this type that can be accumulated. (In a number of cases, the counting was done on a blind basis.) Tables 5 - 1 0 show specific quality control programs for the nuclides of interest carried out by HASL over the past few years• Tables 5 and 6 indicate that quality can be maintained by a commercial contractor over a period of years. Since the spiked air filters are known to be quality-control samples and might receive special treatment, the results of the blind duplicates in Table 7 are reassuring. Tables 8 - 1 0 deal with blind duplicate soil analysis, the first with kilogram samples run at 3 laboratories during a single program and the third with mass spectrometry data for isotopic ratios• The use of analytical contractors requires a program to qualify laboratories for the required work. Tables 11 and 12 show a set of data reported by three laboratories doing commercial work but not qualified for our analyses• In the United States, the Environmental Protection Agency (EPA) operates a quality assurance program that is open on request to any laboratory. Simulated environmental samples, containing known amounts of one or more
78
John H. Harley Table 8. Quality control, plutonium-238, 239
Table 6. Quality control, lead-210
Lab: tIASI, C o n t r a c t o r (IPA) Sample Type: Soil, 1000 g leach, blind d u p l i c a t e s Units: f C i / g soil
Lab: HASL C o n t r a c t o r (LFE) S a m p l e Type: Spiked A i r F i l t e r s Units: dpm per sample 1975
1974 Added
Found
Added
Found
0 0 460
-8 9 460
520 470 0
480 440 -1
430 0 450
430 0 440
570 520 0
550 540 0
430 0 380
450 -I 360
580 540 0
580 600 0
440 0 490
450 -i 490
540 590 0
620 670 0
430 O
430 -1
560 520 0
610 590 0
480 470 0
550 590 0
Aliquot
Site Argonne,
Illinois
Pu-239
Pu-238
A B
4.6 4.4
0.15 0.14
A n g r a dos Reis, Brazil
A B
1.6 i .7
0.29 0.32
Roskilde,
A B
2,9 3 ,0
0. I0 0.09
Denmark
Ispra,
Italy
A B
ii .7 ii .4
0.39 0.38
Tokyo,
Japan
A B
9.4 9.2
0.33 0.33
~--t
I
= -+ a o
)
CONTROL LIMIT
460 540 0
530 600 0
610 470 0
640 550 0
JANUARY mm
440 530 0
500 600 0
47O 0
52O 2
0
5
I
~,
~" :
~o"~, ,~, z
,~ 11
MAY
Table 7. Quality control, plutonium-239 and lead-210
Freq.
25
Lab: ltASL C o n t r a c t o r ( L F E ) Sample Type: Blind Duplicate A i r F i l t e r s Units: d p m p e r s a m p l e
=p=
Pb-210 1974
490 490 570 760 800
Pu-239 400 510 500 800 880
0.5 1.8 1.0 0.7 0,5
5
JULY J
~5
0.8 1.6 0.7 0.7 0.6
l
i"
=l J=
5
N O V E M BER
5. 1975
650 480 500 320 770 450 430 750 1200 36 260
660 480 480 320 820 520 510 780 1170 54 220
0.2 0, 2 0.3 0, 4 0, 6 0, 2 0.4 1, 5 1.8 2.0 0.7
0.2 0.1 0.3 0.4 0.3 0.1 0, 4 1.4 2, 0 1, 8 0.6
radionuclides, are prepared by the Quality Assurance Branch at the Environmental Monitoring and Support Laboratory in Las Vegas, Nevada. After submission of data, a report and control chart are returned to each participant. For the nuclides of interest here, water samples with
0 0
5
10 15 pCi/liter
20
25
Fig. 1. Data from EPA quality assurance program, radium in water for 1974 (~ is the mean value of all reporting laboratories and ~ is the amount added). radium (see Fig. 1) and water, air filters and soii with plutonium-239 are available. The Quality Assurance Branch exchanges samples with the National Bureau of Standards as a control on their own work. Another program of this type is being instituted by the Division of Safety, Standards and Compliance of the Energy Research and Development Administration
Analyses for some radionuclides in environmental samples
79
Table 9. Quality control, plutonium-239
Table 11. Qualification analyses, plutonium-239 Labs: Anonymous Sample Types: Blanks, Spikes, Standards on Air Filters Units: dpm per sample
Labs: HASL, IPA, TLW Sample TyPe: Soil, 100 g blind duplicates Unlts~ dpm per sample
Expected
Lab HASL IPA
TLW
Aliquot A
AnquotB
~8 700
16 300
171 000 33 19 17
151 000 27
II 600 220 230 91 90 48 35
13 000 200 240 96 92 41 49
Lab A
0 9.1 13.1 0.4 1.0
2.0 9.3 17.2 12.4 2.4
Lab B
0 8.1 12.1 1.3 1.0
<0.2 3.7 7.1 15.5 9.6
Lab C
0 8.7 12.2 0.4 0.6
<0.1 7.6 12.7 0.3 1.4
25
17
Table 10. Quality control, isotopic plutonium ratios Lab: KAPL Sample Type: Separated Pu Fractions, Blind Duplicates and R e p l i c a t e s Units: D i m e n s i o n l e s s
}40/239
241/239
.183 .191
.0085 .0087
.165 .142
.0066 .0055
.174 .171
.0078 .0080
.173 .179 .177 .178 .179 .166
.0079 .0080 .0081 .0080 .0082 .0074
.161 .176
.0059 .0083
.180 .163
.0083 .O095
.174 .171
.0075 .0076
.085 .085
.0033 .0033
Reported
Lab C (Second Try)
18,3 0 4.4
(ERDA), to be administered by HASL. Intercomparison samples including air filters, soil vegetation, water and tissue are to be distributed quarterly m all ERDA contractor laboratories presently doing environmental monitoring. Data will be collected by HASL and summaries distributed to the participating groups. The laboratories will not be identified in the published reports, at least at the beginning of the program. A great deal has been written about quality control, but a few reminders may not be amiss. A major factor in a good program is careful review of the data by a competent scientist. This saves many headaches. A second point is that the program results should be a basis for action, either complimentary or corrective. And finally, quality-control results should be published to establish the proper degree of confidence in the data being presented.
I00 <0.4 19.2 2.1 4.5
Table 12. Qualification analyses, lead-210 Labs: A n o n y m o u s Sample Types: Blanks, Spikes, Standards on Air F i l t e r s Units~ dpm per sample
Expected
Reported
Lab A
0 475 444
12 206 131
Lab B
0 424 503
4 823 541
Lab C
0 424 408
<4 207 246
0 639 0 1340 165
1000 2400 690 670 310
....
Measurement by m a s s s p e c t r o m e t r y
105 0
Lab C (Second Try)
Intercomparisons Even a tight internal quality-control program may go astray without cross-checking with other competent laboratories from time to time. Many of these intercomparisons are very informal and are never reported. Others may attain a. more formal status, but generally this means a considerable lag in reporting data. The simplest intercomparisons are those of prepared sources or pure solutions as shown in Table 13. These generally test only the counting equipment and the laboratory's standards but not its radiochemical and source preparation techniques. Tables 14 and 15 each show the results of 3 laboratories on actual samples of soil and human tissue, respectively. In the first case (Table 14), the true values were unknown, in the second (Table 15) the samples were spiked by the laboratory generating the samples. Table 16 gives the results of an intercomparison set up
80
John H. Harley
Table 13. Interlaboratory calibration, plutonium Labs~ Anonymous Sample Type: E l e c t r o p l a t e d Source Units: d p m Lab
242
239-240
238
1
8.83
4.09
.76
2
8.80
4.57
.78
3
8.83
4.63
.83
4
8.42
4.57
.72
5
8.63
3.93
.68
8.24
5.00
8.62 ± .25
4.46 ± . 3 9
6
Table 15. Intercomparison, plutonium-239 l,at~s: IIA81,, I,ASI~, PNL Sample Type: Spiked T i s s u e s Units: d p m / s a m p l e
Added Bone (20 g)
tlASL l,'ound
L a b s : L L L , MCL, L F E , LRE, EIC Sample Type: Solution, alpha s p e c t r o m e t r y Units: d p m / m l
Lung
Lab
Result
LLL
1320 L 20
MCL
1255 ± 15
LFE
1330 ± 27
LRE
1273 ± 64
EIC
1207 ~ 54 Liver (40 g)
Pu-239
0 0 0 0.12
Blank
0. 85
0.75 0.89 0.91
0.77
0.~;1 1.08 0.52
0.55
0.54 0.54 0.56
1.96
2.07 I. ~9 1.85
1.~;1
1.52 I. 50 1.82
1.06
1.95 1.03 1.11
t/Imlk
< . 92 < . 02 <" . 0 2 < . 92
Blank
0 0
Blank
0
O. 88
0.73 (). 97 9.94
0.7"3
0.64 O. 86 0.68
0.99
O. 82 o. 95 0.92
1.79
1.64 1.~8 1.75
I. (i~
1.66 1.78 1.59
1. ~1
1.78 1.82 1.83
Blank
< . 02 < . 02 < . 02 < . 02
Blank
0 0 0 0
Blank
0.96
0.92 0.95 1.01
0.69
0.74 0.56 0.78
9.89
0.8(; 0.96 0.84
1.82
1.73 1.92 1.80
1.14
1.14 1.14 l . 14
1.75
1.89 1.65 1.72
BROO~IAVEN
Spiking Solution (10 ml)
Pu-238
PNL Found
Blank
Table 14. Intercomparison, plutonium-238, 239
Lab
Added
< . 02 < . 02 < . 02 < .02
The e l c c t r o p l a l e d s o u r c e dala appeared in ERDA Report NVO-159 and the solution data in NVO-140.
I,abs: }IASI,, IPA, T L W Sample Type: Soil Units: f ( ' i / g
LASL Found
Blank
.77 0.76 ± °05
Added
1.73
.031 .002 .048 0
. I)25
0
.016
0
.027
1.55
.083 .040 .033 .025
1.81
(1970)
Table 16. EPA Intercomparison,thorium-230 HASL
19.5 19.0 18.7 18.6 19.8 19.0 19.2 18.3 18.7 18.4 18.7
" IPA "
TLW " Avg.
± 0.5% ± 0.5% -+ 0 . 5 % ± 1% ± 2% ± 2% ± 3% ± 2% ± 3% ± 3% ± 2%
18.9 ±
3%
" B L A C K SOIL" HASL IPA TLW Avg.
Avg.
0.77 ±18% (1958)
2.4
0.043 ± 3 7 %
±
3%
1.6 ± 1.9 ± l.S ±
10% 2% 6%
1.8 ±
9%
0.63
15% 88%
(1958)
LAKE
0 . 5 8 ± 4% 0.68 ± 16% Avg.
5% 6% 6% 7% 4% 4% 5% 6% 5% 7% 5%
0.054 ± 0.032 ±
WOODCLIFF IPA TLW
± ± ± ± ± ± ± ± ± ± ±
2.5 ± 1 0 % 2.4 ± 2% 2.4 ± 5%
"RED SOIL" HASL IPA TLW
0.86 0.76 0.81 0.47 0.86 0.72 0.76 0.72 0.75 0.72 1.0
± 11%
0.058 ± 15% 0.076 ± 36% 0.067 ±
19%
(1970) 0.014 ± 50% 0.081 ± 99%
Labs: Anonymous Sample Type: Spiked A i r F i l t e r s , EPA, 1974 Units: pCi/filter
Known Value
16
ttASL
10, 8, 11
Lab D
6, 10, 8
LabJ
13, 14, 14, 14, 15, 14
Lab W m,
9, 8, 8
Net v a l u e s are r e p o r t e d , a blank f i l t e r showed about 6 pCi of Th-230
by the EPA in the United States. This differed from many of the others reported here in that the analysis was not being performed routinely at any of the laboratories. The National Bureau of Standards (NBS) has issued a river sediment standard and some of the data collected in the establishment of standard values are shown in Table 17. This approach is most likely to yield useful standard samples of environmental materials. The first two Tables (18 and 19) of IAEA Intercomparisons deal with radium-226. Obviously the data are good for pure solutions, but the agreement is poor when chemistry is required. No data are available for lead-21(L
Analyses for some radionuclides in environmental samples Table 17. Intercomparison, NBS standard sediment L a b s : Anonymous Sample Type: D r i e d R i v e r S e d i m e n t Units: dps p e r g r a m
81 Table 20. IAEA intercomparisons, plutonium-239 Labs: Anonymous Sample Type: Spiked Air F i l t e r s Units: p C i / f i l t e r
I>u-239, 240 (NBS C e r t i f i e d as 1.4 x 10 -8) HASL
1.4 x 10 -3
HSL
1 . 3 x 10 . 3
WHOI
1.45 x 10 -3
Known Value
200
Lab
180 80 191 187 73 150 64 353 141 193 219 188 199 152 280 84
T h - 2 3 2 (Uneertified) HASL
3.1 x 10 - 2
HSL
3 . 8 x 10 - 2
P u - 2 3 8 (Uncertified) NBS
7 . 3 x 10 -5
HSL
7 . 6 x 10 -5
WHOI
5.8x 10-5
Am-241 (Uneertified) ItSL
3.1 x 10 -4
WtIOI
3 . 2 x 10 -4
Table 21. IAEA intercomparison, plutonium-238, 239
Table 18. IAEA intercomparison, radium-226 Labs: Anonymous Sample Type: A n i m a l Bone A s h (A-1O, R e p o r t e d 1975) Units: p C i / g ash
Labs: Anonymous Sample Type: S e a w a t e r Units: f C i / k g , pCi/kg Results Lab SW - 1 - 1 (fCi/kg)
L a b Code
Result
2 5 (ftASL) 6
1.87 1.84 1.47
7 8 11
1.18 1.43 1.36
12 16 17
1.48 1.65 2.30 (Rejected) Mean
Water
1 2 3 4 5 6 (tfASL) 7 8 9 10 11 12 13
116 115 112 141 137 126" 106 112 126 120 124 126 122
* I n d i v i d u a l v a l u e s 124, 127, 127, 126, 125, 124
-
80
SW - 1 - 2 ( f c i / k g )
1 2 3 4 5 (HASL) 6 (WItOD 7 8 9 10 11 17
22 40 22 40 26 33 48 51
90 227 280 169 200 222 275 239 340 254 130 200
SW - A - 1 (fCi/kg)
7 8 9 12 (WItOI) 15 16 18 (ItASL) 20
SW - I - 3 (pCi/kg)
6 8 9 10 (WtIOl) 11 16 18 24
Mean R e s u l t 1.68 1.10 .57 .42 .26 .45 .54 .23 .48 .43
10 11
54 84 80 100 100 85 92 69 770 116 I00
Table 19. IAEA intercomparison, radium-226
1 2 3 4 5 6 7 8 9 10 (IIASI,)
7.5 7 11 20 7 8.9 1O. 5 120
Pu-239
6
L a b s : Anonymous Sample Types: Soil, W a t e r Units: p C i / g , p C i / g
Soil
1 2 3 4 5 (IIASL) 6 (WllOl} 7 8 9
Pu-238
17
1.52 _+ .23
Lab #
2 (HASL) 3 4 5 7 11 13 14 17 19 23 25 28 29 30 31
30
1.24 0.9 1.5 1.2 <18 70 1.0 o. ~) 22 40 17 15
100 70 110 118 240 113 60 320
The IAEA plutonium results are similar, in that spiked air filters can be analyzed by a number of laboratories to + 10% (Table 20), but the more difficult marine samples are subject to an excessive spread in values. This spread is no less marked as the level of activity increases, as shown in the sea water samples.
82
John H. Harley Table 22. IAEA intercomparison, plutonium-238, 239
Labs: Anonymous Sample Types: Seaweed, Units: p C i / g
Sediment
Results
-I
AG -I
SD
-
B
-
1
Lab
Pu-238
Pu-239
1 2 3 4 5 (IIASL) 6 (WHOI) 7 8 9 I0 11 12 13 14 15 16 17
2.7 3.9 4.1 4.1 3.9 4.8 3.8 4,2 3.7 7.0 3.1
19.7 28.2 28 23.0 28.6 30.0 26,7 30.0 25.1 27.9 20.8 28 24.3 22.3 27.3 26.1 24
1 (WtlOI) 2 3 4 5 6 7 8 9 10 11 (HAS/,) 12 13 14 15 16 17 18
3.6 3.3 3.9 3.0 .060 .040 .048 .027 .040
. 89 1.01 .64 1.09 .93 . 94 2.05 .06 . 88 t.04 .95 1.06 .82 .93 .98 1.06 1.02 1.15
.032 .034 .027 .053 ,055 .041 ,045 .035 .054
nuclides considered here and of course it is not possible to use such anonymous reporting to evaluate published papers interpreting the environmental significance of the results of analytical measurements. It would seem that it might also be useful for the IAEA to request certain competent laboratories to participate in intercomparisons where they would be identified. If the agency were to start with a very large initial sample, other laboratories could then receive material which had a certain status as a standard. This would be similar to the programs used by the National Bureau of Standards and other bodies for issuing standard ferrous and non-ferrous metals.
Summary This rather pedestrian report has summarized a considerable body of data on the quality of analyses for plutonium isotopes, radium-226 and lead-210. While there is a group of laboratories turning out results of adequate quality, the overall quality of the data is variable to poor. It shoul d be remembered that the results of these analyses are used as a basis for interpretive reports on physical phenomena and it would appear that proper interpretation can only be arrived at by chance. In the opinion of the author, the present chemical methods, instrumentation and standards are adequate "for our requirements for environmental analyses. Improvement in quality can only come from increased attention to analytical detail and confidence in the results can only be improved by maintaining and reporting adequate quality control and intercomparison programs. List of Laboratories Appearing in Tables
Table 23. IAEA intercomparison, plutonium-239 Labs: Anonymous S a m p l e Type: Dried Marine Animal Tissue Units: f C i / g Result La b MA - B - 1
MA-B-2
Pu-23£
Pu-239
10
< 4 < 44
11 13 (IIASL) 14 17 (WlIOI) 20 31
1,41 + .25 2.6 + .8 1.5 + .2
0+_ 10 50 + 20 < 25 60 +_ 10 34 + 15 < 60 3 8 . 3 _+ 1 . 4 43 + 3 36 + 4
7 8
7 8
10 11 13 (HASL) 14 17 (WHOI) 31
< 18 < 26
0.76 + .12 0.95 i .06
0+50 < 12 < 11 20 +_ 5 2.4 i 1.0 < 70 1.05 i .17 1 . 0 + .1
The broadest intercomparison coverage has been obtained by the IAEA with a large number of laboratories participating. Tables 2 0 - 2 3 show tile results of these intercomparisons. In these tables, the Woods Hole Oceanographic Institution (WHOI) has agreed to be identified and we have also indicated the HASL data where we participated. The overall quality of the data is poor for the
EIC HASL HSL IPA LFE LLL LRE MCL TLW KAPL LASL NBS PNL WHOI
Eberline Instrument Corporation Health and Safety Laboratory Health Services Lab., Idaho Falls Isotopes, Pale Alto LFE, Environmental Analysis Laboratory Lawrence Livermore Laboratory Laboratory of Radiation Ecology McClellan Central Laboratory Traceflab West, now LFE Knolls Atomic Power Laboratory Los Alamos Scientific Laboratory National Bureau of Standards Pacific Northwest Laboratory Woods Hole Oceanographic Institution
Discussion Bowen: Dr. Harley will remember, as I do, another variable in the data produced by NBS "preferred" or "starred" laboratories. We b o t h worked in one of these in the early 1940s, and were divided, always, between a m u s e m e n t and dismay when we heard (very frequently) the Chief Chemist emerge from his sanctum, data sheet in hand, to call "Who analyzed that last NBS sample?", and to continue, once the analyst was identified, "Well, that was n o t what the Bureau got, so run it again!" Clearly, it was by agreeing with "The Bureau" that a laboratory kept its preferred position, and so long as there was c o m m u n i c a t i o n o f unofficial results outward from the Bureau, a strong, b u t n o t - I believe - quite desirable feed-back loop was set up. For such a system as Dr. Harley proposes to work at its ideal best, all data m u s t be rigidly confidential until the final analysis is produced.
Analyses for some radionuclides in environmental samples Although one feels intuitively that the best analytical performance should be elicited by good treatment and encouragement, I recently encountered another variable: of about eight young people in my laboratory, all doing radiochemistry on sediments containing falloutqevel radionuclides, one clearly stands out in respect to obtaining good data on quality control samples, high chemical yields, and a large rate of data production; she also is the least trained academically. In a recent discussion of this performance, I was dismayed to have her explanation turn out to be "Well, the others all know what they are doing, but I really don't, so I'm just plain afraid all the time, and much more careful!" Only with great reluctance would I try to keep my young assistants "afraid all the time" - and yet one must admit that her point is clear and pertinent. Suschny: If calibration standards are supplied with the (unknown) sample, some improvement is achieved, in particular in instrumental measurements (e.g. of ~37 Cs). For determinations involving chemical separations (e.g. 90 Sr), this improvement is not considerable. Another point I would like to raise is this: to avoid the possibility of claims being made that a sample, which gave bad results in intercomparison, was perhaps inhomogenous, it is advisable to send out several randomly selected sub-samples to each
83 participating laboratory. Good intraqaboratory precision will then prove homogeneity of a sample while the difference of an individual laboratory mean from the (known) true value or, where the true value is not known, from the overall inteflaboratory mean may serve to show up systematic errors. Gans: We have had the experience that furnishing standard solutions in an intercomparison program does not really improve the quality of results if the quality of the participating laboratories is not too good. In one of the round robin tests we carried out before the one I reported on yesterday, we furnished a standard of 5~,-emitters as well as a list of nuclear data of all nuclides possibly present in the sample. The results of the measurements of some laboratories showed good agreement in the concentrations of those nuclides that were contained in the standard solutions, but nevertheless the agreement for the other nuclides was very poor. The last intercomparison program, when no standard solutions were shipped, showed much better results, this meaning - in our opinion - that the general standard of the laboratories has improved. Aten: Did the spiked samples (e.g. in Table 2) also contain other activities that might be present? Harley: Yes, they contained fission products at levels comparable to air samples taken at that time.