Environmental radioactivity measurements and measurements assurance programs in Switzerland

Environment International, Vol. 1, pp. 89-96, 1978. Pergamon Press. Printed in Great Britain.

Environmental Radioactivity Measurements and Measurements Assurance Programs in Switzerland J. Czarnecki Federal Office of Energy, Wiirenlingen, Switzerland

The measurement capabilities of the various laboratories involved in radiation protection measurements in Switzerland are described. Intercomparisons of the results of radioactive effluent measurements from Swiss Nuclear-Power-Stations (NPS) show good agreement. The expected additional doses in the neighbourhood of the operating NPS are about 1 mrad/y. Typical measurement methods already used and planned for future use in the vicinity of the NPS are discussed. (Responsibilities; laboratories; capabilities; measurements; results; programs)

Introduction The worldwide use of radioactive material in medicine and industry, and the construction of nuclear power stations (NPS) have created new problems in the field of low-level radiation measurements. The purpose of these measurements is to ensure that the radioactivity in the biosphere due to industrial activities remains low. Here we describe the laboratories involved with such measurements and the measurement programs in Switzerland. The laboratories involved in radiation protection measurements

We can distinguish between two types of laboratories. One is mainly responsible for the control of radioactive discharges from the nuclear industry. The other is involved with the measurement of the amount of these discharged radioactive materials which have found their way into the environment. Figure 1 defines the laboratories and Fig. 2 their responsibilities. Table 1 shows the measurement devices the laboratories use. The nuclear power station laboratories specialize in measurements of gas and liquid effluents. As well as these measurements Nuclear Safety Division of the Swiss Federal Office of Energy (ASK) and Swiss Federal Radioactivity Surveillance Commission (KUER) must specilize in environmental measurements. The laboratories of the Radiation Protection Section of the Federal Office of Public Health in Switzerland (EGA) and the Swiss National Accident Insurance Fund (SUVA) handle problems arising from the use of radioactive substances in medicine and industry. The laboratory of the Swiss Federal Institute for Water Resources and Water Pollution Control (EAWAG) makes control measurements of surface and ground water, including the control of radioactivity in fish, microorganisms and sediment. Therefore this laboratory specializes in 9°Sr, 3H and "gross"/3

measurements. Finally, the KUER laboratory surveys the radioactivity in the environment, i.e. in the whole Swiss biosphere. All laboratories are able to make radiochemical analysis. There is a close cooperation between the laboratories mentioned. Environmental radioactivity measurements

Two types of measurements are carried out in the vicinity of nuclear-power stations: measurements before tile NPS goes into operation (preoperational measurements) and measurements during the whole operational period of the nuclear-power station. The first type of measurements should give the base line radioactivity, the second type the additional radioactivity due to the radioactive release of the NPS. Since for a modern NPS the radioactive releases are very low, the measurement technique used and the measurement problems are the same whether the nuclearpower station is in operation or not. The very low additional doses to the population in the neighbourhood of NPS are negligible. Therefore the measurement of these low doses (about 1 mrad/y at the highest expected ground concentration) seems not to be necessary. Despite, this public opinion has compelled the controlling authorities to survey very carefully the radioactivity in the vicinity of a NPS. This has led to the applicatior/of very elaborate measurement techniques, i.e. ASK

-

NUCLEAR SAFETY DIVISION OF THE SWISS FEDERAL OFFICE OF ENERGY

KUER

-

SWISS FEDERAL RADIOACTIVITY SURVEILLANCE COMMISSION

EAWAG -

SWISS FEDERAL INSTITUTE FOR WATER RESOURCESAND WATERPOLLUTIONCONTROL

SUVA

SWISS NATIONAL ACCIDENT INSURANCE FUND

EGA

-

RADIATION PROTECTION SECTION OF THE FEDERAL OFFICE OF PUBLIC HEALTH IN SWITZERLAND

Fig. 1. 89

90

J. Czarnecki Control of Radiation Protection and Environmental Radioactivity in Switzerland

NPS Releases Laboratories ~

[ \

\

~c

Dispersion " Dilution Impact ..... 1 ~ ' ~ Reconcentration. ~ k , eCm~l~n~,/Biosphere

"--...--"

/i

[pe~onnel expose!

~

/ ;

,,

}

]

I

Dose

',

ASK EGA SUVA

ponslbdlty field of the KUER

Fig. 2 the measurement of the dose rate with pressure-ionization chambers and the identification of the contributing radioactive nuclides with Ge (Li) -detectors. Such measurements are carried out at a few selected points in the vicinity of the plant. The measurement time varies from a week to a few months. The program starts about one year before the NPS goes into operation and is then repeated each year. Many publications describing the measurement technique and the achieved results can be found in the literature (Black, 1972; Auxier, 1973). The main difficulties connected with these measurements are the following: (i) The dose rate at a point caused by the natural background radioactivity can differ from the mean value by + 20%. In Switzerland this is equivalent to a dose-rate variation of + 20 mrad/y. The variation is caused by changing soil humidity, by washout of radon daughters, by different thicknesses of the snow cover during the winter months, etc. (ii) The dose rate caused by natural background radioactivity is not the same at two points separated by several kilometers. Therefore a reference point for the background radiation cannot be determined, and the measurements must give the absolute dose rate value. (iii) The calibration of the ionization chambers and the Ge (Li) -detector for the in situ measurements must be done with an appropriate accuracy of about -+ 5-10%. Table 2 shows results of dose-rate measurements using a pressurized ionization chamber and a Ge (Li) spectrometer. The agreement between the dose rate values measured with these instruments is very good (Beck, 1972; Cardinale, 1971). Such results should be achieved in routine measurements. The laboratories of the controlling bodies (ASK, KUER) have five pressurized ionization chambers. In the newest models magnetic cassettes are used to record data. In our laboratory the information is fed from the cassettes into a mini-computer (ND-812). Calculations performed by the computer should allow us to determine the dose-rate contribution of the radon daughters (slow component in comparison with the gaseous effluent plume component) (Gogolak, 1974). We hope that we can measure hourly

dose-rate variations, due to radioactivity released from the nuclear-power stations, as low as 0.1 gR/h using the chambers and the computer. For in situ 7-ray spectrometric measurements we use Ge (Li) detectors and a ND-100 pulshight analyser. The field experiments started two months ago. Together with simultaneously measured meteorological data, the use of another computer program allows the determination of atmospheric diffusion factors. These are used to supplement the diffusion calculations. Such experiments are under way at the NPS of Mtihleberg (BWR). The 133 Xe concentrations in air are measured using on-site sampling, followed by laboratory low temperature adsorption on charcoal. Special equipment was developed for this purpose. The 133 Xe measurements are done by the Lab of Low Level Counting of the University of Bern and KUER. Measurement assurance program

The assurance program for monitoring radioactive effluents is based on the following approach: Comparison between laboratories Four times a year samples of gaseous and liquid effluents, as well as air-filter samples, are taken from each NPS. The laboratories of the nuclear power stations and of the controlling bodies, ASK and KUER, analyse these samples. Table 3 gives as an example the results of such a comparative analysis. A good agreement between the results was achieved for many nuclides. But a difference in the measured activity concentration up to a factor 5 exists for some nuclides. The causes of these differences are not yet quite clear. It should be mentioned that the sampling, treatment and analyses of the samples were carried out during the routine measurement program of all the laboratories. Some errors arise due to different nuclear data given in different Tables of Nuclides and also to the different energy peaks used in various laboratories to disentangle, e.g. the 6SSkeV (11°rnAg) from the 662 keV (137Cs-laTmBa); o/her errors arise from the standards used for the' calibration of the counting equipment. These standards have

Environmental radioactivity measurements

91

Table 1. I. Lab:

MEASUREMENT EQUIPMENT

No

1.

Type o f measurement

Input/Output

Apparatus

Dot. type

ND-4420

Spectroscopy

ASK/EIR

8 ADC, ND-812 Computer: 16 k ND-4420 B u f f e r : 16 k

32 k

Josslble use Lab Field

Teletype Faclt (HSP) Remex (HSP) Plotter

1.1

y

Ge(Li) 10 % rel. elf,

N0-4420

X

X

1.2

y

Ge(Li) 10 & re1. elf.

ND-4420

X

X

Ge 16x5 mm

ND-4420

X

X

Teletype Facit (HSP) Remex (HSR) Plotter

X

X

1.3

X ,Y

1.4

c:

Surface B a r r i e r Diode: 330 mm 2

ND-4420

1.5

(~

Surface Barrier Diode: 330 mm 2

ND-4420

1.6

(x

Surface B a r r i e r Diode: 300 mm2

ND-4420

Surface Barrier Diode: 2000 mm 2

ND-4420

1.7

1.8

c~

Surface Barrier Diode: 2000 mm 2

ND-4420

1,9

y

NaI{TI); WBC 4"x4"

ND-IOO/4K

1.10

y

NBI(TI); 131 1 1-x1" [ T h y r o i d )

S i n g l e Channel PHA

Printer

X

1.111

y

NaI(TI); 1251 l"xlmm (Thyroid)

S i n g l e Channel PHA

Printer

X

1,12

y

Ge(Li) 6 % rel.

1.131 Spectroscopy + Personal Ooslmetry

:2.

6 - Spectroscopy

ND-4410

1ADC, ND-812 Computer: 8 k ND-4410 B u f f e r : 4 k

Teletype/Tape Cassette

X

ND-4420

2 ADC, ND-812 Computer: 16 k ND-4420 B u f f e r 8 k

Teletype/HSP-HSR/DOS

X

Minicomputer,

X

elf.

Records

Liquid Sc. Oet.

4 ADC ( w i t h Router)

Betaszlnt BF-5000

Printer

3.1

B - Total

GM-Antlcolncldence

Scaler

Printer

X

3.2

8 - Total

GM-Anticolncldence

Scaler

Printer

X

4.1

e - Total

Proportional Chamber 300 cm 2

4.2

~ - Total

Proportional Chamber 7 cm 2

5.1

Oosarate (pR/h)

High-pressure Ionlsation Chamber

RSS-111

Paper Tape recorder, Tape cassette system Interface to ND-B12

X

X

5.2

Doserate (pR/h)

High-pressure Ionisatlon Chamber

RSS-111

Paper Tape recorder

X

X

5.3

Ooserate [pR/h)

Scintilation Detector

Szlntomat

L i n e a r ranges from 2 pR/h - 3000 m R/h

X

X

92

J. Czarnecki

MEASUREMENT

No

1.

Type oF measurement

Pet.

EOUIPMENT

ND-4420 or Elsclnt Meda

1.1

y'

Ge(LI) 9 . I % t e l , eFf.

1.2

y

Ge(Li) 18 % r e l . e l f .

1.3

y

NaI(TI) 3"x3"

1.4

y

NaI(TI) 3"x3"

y

2.1

cL

2 ADC,

ND-2200/4K

KUER

Input/Output

N0-812 Computer: 16 k ND-4420 Buffer : 8 k 24 k

I ADC

~osslble use LaP Field

Teletype, HSP-HSR Plotter, Tape cassette system

X

X

Printer, Plotter HSP Card-punch

RCL-512 or Elsoint

NaI(TI) 1V2"xIV2"

Meda

PHA

Single Channel

RCL-512 or Elsclnt Meda

Chamber 2.2

Lab:

Apparatus

type

Spectroscopy

1.5

2.

RCL-512 SurFace Barrier Detector, 200 mm 2 lot Elscint Made

e

2.3

(X - Total

3.1

8-Spectroscopy

Scintilatlon Detector

Scaler/Timer

(T)

Scaler

5oaler/Conicidence

Scaler/Printer

2x RCA 8850 PM 4.1

8 - Total

4.2

8 - Total

5.1

Ooserate

5.2

Ooserate

GM-Counter

Scaler

GM-Antlooincldence

Scaler

(pR/h)

High-pressure Ionlsatlon Chamber

RSS-111

Paper Tape recorder

X

X

(~R/h)

Sclntilatlon Detector

Szlntomat

Linear ranges from 2 pR/h - 3000 m R/h

X

X

MEASUREMENT

No

Scaler/Prlnter

Type of measurement

3, Lab:

EOUIPMENT

Oat, type

Input/Output

Apparatus

(PWR)

possible use Lab Field

!1.1

y - Spectrometry

Gs(Li);BOxlO -6 m"

JN 90

1.2

y - Spectrometry

Ge(Li);33x10 -6 m"

JN Didac 4000

1ADC

Printer

1,3

y - Spectrometry

Ge(Lt);45x10

JN Oidac

I ADC

Printer

X

X

1.4

y - Spectrometry

various

Single Channel PHA

Scaler

X

X

2.

a /8 - Total

Prop.

FrSeseKe + HSpfner

Scaler

X

3,

B - Total

Liquid

Scaler

X

4.

Doslsrate

Scintilation Detector

-6

NaI

counter sclnt.

m~

(48 K)

Nuclear Power Station - 8aznau

800

Panex Szlntomat

x 2

2 ADC

Floppy Disk TJJ Silent 700

Linear ranges from 2 pR/h - 3000 m R/h

X

X

93

Environmentalradioactivitymeasurements

MEASUREMENT EQUIPMENT

No

Type o f measurement

4.

Lab:

Nuclear Power Station - MOhleberg (BWR)

Apparatus

Oct. type

1,1

y - Spectroscopy

G e ( L i } ; 4 4 x 1 0 -6 m3

Hlstomat

1.2

y - Spectroscopy

Nal (TI)

Leben

Input/Output

(2000)

I ADC

(BOO)

possible u s e Lab Field

Teletype

I ADC

Printer,

Plotter

3"x3" 1.3

y - Spectroscopy

2.1

B - Total

2.2

B - Total

NaI (T1) 3"x3" GM-Anticoincldence Proportional Counter

MEASUREMENT

No

Type o f measurement

I.

y - Spectroscopy

!2.

B - Spectroscopy

3.

~ * B - Total

4.

8 - Total

5.

Doserate

S i n g l e Channel PHA NE SR3

Scaler

Landis and Gyr

Scalar

Frieseke

Scaler

+ H6pfner

EQUIPMENT

Det. type

NsI(TI)

Liquid Sc. Proportional Counter 180 cm 2 GM

5.

Type o f measurement

SUVA

Apparatus

Input/Output

)osslble u s e Lab I Field

Printer / S c a l e r Timer

Landis and Gyr Single Channnel PHA Packard C 2425

Teletype

Herfurt

Herfurt

Ionisation Chambers

6.

I No

Lab:

Pet. type

L~b:

Low Level Counting Lab of the University o f Bern

Apparatus

I1.1

Spectroscopy

Proportional Counte~s from 10×10" m3 t o 2 . 8 x 1 0 -6 m3

1.2

Spectroscopy

Ge(Li)

ND Multlchannel

PHA

1,3

Spectroscopy

NaI (T I)

ND Multlchennel

PHA

Input/Output

possible usa Lab Field

NO Multichannel PHA

neither the proper radionuclide compositon nor the proper relative nuclide activity as the "rad" waste from lightwater-cooled nuclear-power stations. Furthermore all the laboratories involved use different geometries (containers and different measurement configurations). The controlling body cannot demand that all laboratories use the same containers and measurement configurations. Recommendations from the ICRM would perhaps be helpful in this matter. A further reason for the differences could be the dissimilar chemical properties (pH value, solubility, etc.) of the reactor sample and the sample used to the cross-

checking measurements. Adsorption on the bottle wall and precipitation of undissolved components can affect the results. A typical example of such problems is shown in Table 4. The pH value of the sample was unusually high. Differences between the first measurement in all three laboratories were probably caused by the differences in the measurement geometries used in particular laboratories.

Round-robin measurements To make round-robin measurements a laboratory prepares

94

J. Czarnecki Table 2. Examples of field measurements made with GE(LI) detectors, NAI(TL) detectors and ionization chambers ~IRIH DETECTOR LOCATION TYPE

K

U

T

CS

ZR-NB

OTHER

SUM

ION CHAMBER

JOLIET. Ill 1971

GE(LI) NAI(TL)

2.8 2,7

1,2 i,i

2.5 2,4

0,2 0,3

0,3 0,2

0.i

7,I 6,7

7,8

CHANNAHAN, 111 1971

GE(LI) NAI(TL)

2,6 2,4

1,0 1,1

1,9 1,8

0,2 0,2

0,3 0,2

0,1

6,1 5,7

5,9

MORRIS. Ill 1971

GE(LI) NAI(TL)

2,2 2.2

1,4 1.2

1,7 1,8

0,i 0,i

0.3 0,2

< 0,i

5,7 5,5

WATERFORD. CONN, 1971

GE(LI) NAI(TL)

1.7 1,7

1,7 1,4

3,0 3.4

0,6 0,4

0,2 0,I

7,2 7,0

7.6

WATERFORD. CONN, 1971

GE(LI) NAI(TL)

2,4 2.4

1,6 2,1

2,9 3,1

0,7 0,4

0.2 0,i

7,8 8.1

8,0

FORKED RIVER, N,J, GE(LI) 1971 NAI(TL)

0,2 0,2

0,8 0,9

L~,9 0,8

0,6 0,7

0,2 0,2

2,7 2,8

2.6

FORKED RIVER, N,J, GE(LI) 1971 NAI(TL)

0,3 0,3

0,5 0,5

0,6 0,5

0,8 0,8

0,1 0,1

-

2,3 2,2

2,1

DENVER, COLO, 1965

NAI(TL)

3,4

2,4

7,4

0,3

0,2

13,7

13.8

BIKINI, ATOLL 1967

NAI(TL)

0

0

0

19,0

5,8

24,8

24.0

Table 3. Liquid effluent measurement comparison LABORATORIES

ASK,

SAMPLE

LIQUID WASTE FROM NPS-BEZNAU

COLLECTING DATE

20, 6, 1975

TABLE OF NUCLEAR DATA USED

NPS-BEZNAU

CEN,

~SK

JUELICH 1971

KUER

VARIOUS

(PWR) AND KUER

11,45 H LARA-1975

NANOCURIES PER LITER

UNITS NUCLIDE

NPS-BEZNAU

NPS-BEZNAU

ASK

KUER

144Ce

ii0

112

90

141 Ce

22

23

17

103 Ru

120

%

104

51Cr 137Cs

560

360

438

99

27

125Sb 95Zr 95Nb 58Co 54Mn

66 120

75

55

177

90

180

119

146

340

22~

231

42

29

60Co

310

194

198

124Sb 131I

880

841

807

134Cs 110mAg 65 Zn 106Rb 1/,0La

29,7

24.8

6

2,0

5

5,1

7

1,4 6,4

163 22

127 1,0

95

Environmental radioactivity measurements Table 4. "Rad" waste 3' -analyses from waste disposal tank NPS-Beznau, 9 June 1976 (units: nCi/l)

NPS-BEZNAU

ASK

KUER

GE(LI)[ G** 3

PART OF THE ORIGINAL SAMPLE *) 260 cc DILUTION TO 550 cc (SHAKEN) G** 3

9,6,1976

14,9,1976

15,9,1976

13,9,1976

268

78

108

85

ORIGINAL SAMPLE 500 cc G*"

DATE

G~

1

9,6,1976

2

9,6,1976

54Mn

i00

cc

AFTER i DAY SEDIMENTATION G**

3

(SHAKEN) G** 4

58Co

40

6O

429

113

156

117

60Co

250

38O

3421

877

1360

875

134Cs

1400

2100

6590

1865

2100

2220

137Cs

3200

4100

14840

4200

4760

4680

* From the original sample 170 cms was taken for SR-90 and T-measurements. ** Measurements geometry Table 5. Interlaboratory comparison

LABORATORIES:

EIR-ASK,

KUER,

NPS-BEZNAU (PWR),

NPS-MUEHLEBERG (BWR) DATE

MARCH, 1975

SAMPLE TYPE :

DRIED SOLUTION

UNITS

NANOCURIES

(PREPARED BY ASK/EIR LAB)

NUCLIDE

EXPECTED

ASK/EIR

KUER

NPS-BEZNAU

241Am

39,63

46,2

52,8

97,0

24,0

57Co

23,8

29.5

28,0

28,0

23,0

134Cs

34,8

33.4

33,4

39,0

51,0

137Cs

56,63

55,0

57,5

59,0

74,0

60Co

41,2

43,9

39,4

40,0

56,0

a sample composed o f a selected number o f radionuclides. The activity of the nuclides is carefully chosen. All the other laboratories have to measure the sample and report the results. Round-robin measurements were made two to four times a year. Table 5 shows some results of such measurements. The agreement between the results is good except for 241 Am.

Calibration of the counting equipment using laboratory standards The precision of the measurement results is a function of the type and quality of laboratory standards. In most of

NPS-MUEHLEBERG

our standards from well established foreign laboratories are used (IAEA, Saclay, NBS, Amersham, Brookhaven, etc.).

Conclusions

1. The measurement problems arising due to the necessity to control the radioactive effluents can be treated with a satisfactory accuracy by the nuclear-power-station laboratories. 2. Representative standards should be available in respect o f the measurements of the effluents from NPS.

96 3. The Labs o f the NPS laboratories should be traceable to the laboratories o f the control organizations. 4. The laboratories o f the control organizations (ASK, KUER, SUVA, EGA) should be traceable to internationally "well-known" laboratories. 5. To realize our environmental measurement program we look for standards (a) composed o f natural matrices and containing only natural radioactivity in various concentrations, and (b) composed o f natural matrices and containing natural and artificial radionuclides.

Acknowledgements - I wish to express my thanks to Mr. H. Voelkle, KUER; Mr. H. Loosli and Mr. R. Schleicher, University of Bern; Mrs. M. Bezzegh, EAWAG; Mr. E. Kaufmann, SUVA; Mr. W. Goerlich, Swiss Reactor Research Institut; Mr. M. Heise, NPS-Beznau; Mr. J. P. Ghysels and Mr. G. Schriber, NPS-Miihleberg; for their assistance in the measurements and the information about the capabilities of their laboratories. The critical review of the manuscript by Mr. W. Jeschki, ASK and the editorial work by Mrs. S. Segat and Miss Wyssmann when typing the manuscript are also much appreciated.

J. Czarnecki

References Auxier J. A., Christian D. J., Jones T. D., Kerr G. D., Perdue P. T., Shinpaugh W: H. and Thorngate J. H. (1973) Contribution of natural terrestrial sources to the total radiation dose to man, Oak Ridge National Laboratory-TM--4323, Oak Ridge, TN. Beck H. L., De Campo J. A. and Gogolak C. (1972) In Situ Ge (Li) and NaI (T1) gamma-ray spectrometry, Health and Safety Laboratory-258, New York. Beck H. L., Lowder W. M., Bennett B. G., and Condon W. Y. (1966) Further studies of external environmental radiation, Health and Safety Laboratory-170, New York. Cardinale A., Fritelli L., Lembo G., Gere F. and Ilari O. (197t) Studies of the natural background radiation in Italy, Health Physics 20, 285. De Campo J. A., Beck H. L., and Raft P. U. (1972) High pressure argon ionization chamber systems for the measurement of environmental radiation exposure rates, Health and Safety Laboratory (USA)-260, New York. Gogolak C. and Miller K. M. (1974) Method for obtaining radiation exposure due to a boiling water reactor plum from continuously monitoring ionization chambers, Health Physics 27~ 132. International Atomic Energy Agency (1974) Environmental survaillance around nuclear installations, Proceedings of a Symposium, Warsaw, 5 - 9 Nov. 1973. Jkaya M. (1976) Natural radiation dose in Akiyoshi Cavern and on Karst Plateau, Health Physics 3 It 76.