PEL 262 ENVIRONMENTAL RADIOACTIVITY at the NATIONAL NUCLEAR RESEARCH CENTRE, PELINDABA 1977 by B. Goodwin Lynda De Villiers A.S

PEL 262

ENVIRONMENTAL RADIOACTIVITY AT THE NATIONAL NUCLEAR RESEARCH CENTRE, PELINDABA 1977

B. Goodwin Lynda de Villiers A.S.M. de Jesus

ATOMIC ENERGY BOARD m Pelindaba r PRETORIA Republic of South Africa APRIL 1978

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ENVIRONMENTAL RADIOACTIVITY AT THE NATIONAL NUCLEAR RESEARCH CENTRE, PELINDABA 1977

B. Goodwin* Lynda de Villiers* A.S.M. de Jesus*

* Isotopes and Radiation Division POSTAL ADDRESS: Private Bag X2S6 PRETORIA 0001

ISBN 0 86960 678 6 PEL 2622 CONTENTS Page SAMEVATTING 2 ABSTRACT 2 1. PROGRAM 3 1.1 Measurements 3 2. RESULTS AND DISCUSSION 3 2.1 Gamma Survey 3 2.2 Milk 4 2.3 Fish 4 2.4 Water 4 2.5 Sediment 4 3. RELEASES OF RADIOACTIVE EFFLUENT TO THE ATMOSPHERE AND TO THE CROCODILE RIVER 4 3.1 Releases to the Atmosphere 4 3.2 Liquid Releases to the Crocodile River 4 4. CONCLUSIONS 5 5. APPENDIX 5 6. REFERENCES 5 TABLES 7

SAMEVATTING ABSTRACT

Die hersiene omgewingsmoniteerprogram wat gedurende 1970 in werking gestel en op die monitering van kritieke The revised environmental survey program intuduced paaie toegespits is waardeur die algemene publiek aan during 1970 with the emphasis on monitoring of the critical radioaktiwiteit blootgestel kan word, is in 1977 voortgesit. paths of exposure of the general public, was continued in

Die analise van 1311 jn melk is verfyn om sodoende 'n laer 1977. The analytical method for 1311 in milk was improved waarnemingsgrens te gee en die gamma-agtergrondopname to give a lower detection limit, and the gamma background maak nou vir die spesifieke waarneming van 1311 survey now also includes a more specific measurement for voorsiening. 1311. Resultate van bepalings van totale radioaktiwiteit word Results of determinations of both gross radioactivity verstrek, asook van afsonderlike nukliede in monsters van and individual nuclides in samples of fish and water (which vis en water (die kritieke materiate vir vrygelate vloeibare are critical materials for liquid-effluent releases) from the radioaktiewe afval) uit die Hartbeespoortdam en die Hartbeespoort Dam and from the Crorcdile River, are given Krokodilrivier afkomstig. and discussed. Resultate van 1311, 90sr en gammaspektrometriese Results of 1311_ 90sr and gamma-spectrometric analyses ontledings van melk, die kritieke materiaal vir atmosferiese of milk, the critical material for releases to the atmosphere, vrylatings, word aangebied. are presented. Resultate van gereelde ondersoeke na die samestelling Results are also given of regular investigations of the van vrygelate afval word ook verstrek. Sodanige vrylatings composition of "ffluent releases which were well below the was ver benede die toelaatbare vlakke. permissible levels. Die konsentrasies radioaktiwiteit in neerslag en in lug, Levels of deposited and airborne activity from van kernbomtoetse afkomstig, word weergegee. Geen nuclear-bomb tests are reported. No environmental omgewingsradioaktiwiteit as gevolg van NKNS-vrylatings radioactivity resulting from NNRC releases could be kon bokant hierdie waardes waargeneem word nie. detected above the fallout levels. PEL 262 3

1. PROGRAM Mossambica, from the Hartbeespoort Dam and Crocodile River. Bulked samples of a particular The survey of environmental radioactivity in and around species are measured for gross beta activity, 90&r and the National Nuclear Research Centre (NNRC) at Pelindaba gamma-emitting nuclides. was started in 1964 and earlier results have been published in a series of Pelindaba reports [ 1 —10. 23-25]. The 1.1.4 Monthly sampling of drinking water from the procedures for sample taking, sample preparation and Kosmos/Schoemansville area: analyses for residual activity measurements are described in these reports, as well beta activity (gross beta minus 40K activity); 90Sr as in a paper by Fourie et al [11 J. A review article by Van analyses; gamma-spectrometric analyses on As and Basson [12| has been published, discussing the semi-annually bulked samples. purpose, extent and value of the environmental monitoring program. More detailed results on fallout radioactivity in 1.1.5 Monthly sampling of water from the Crocodile River South Africa are reported in articles by Basson, Van As, at a point above the NNRC effluent-release point, Van der Westhuizen and Vleggaar (13, 14], by Van As and with analyses as for drinking water. Basson [ 15| and by Basson, Van As and Vleggaar [16). In the report for 1969 [6], a revised program was Because of the problems encountered in trying to suggested which places the emphasis on the monitoring of obtain . epresentative fish samples from the only those materials which, due to their properties of River/Dam complex, indicator materials (e.c* concentrating hazardous nuclides and their use and/or plankton) which are easier to sample or which have consumption by the population, would constitute the higher concentration factors, may also be gathered principal routes, i.e. critical paths, through which human and analysed. beings would be exposed. This program was introduced 1.1.6 Quarterly sampling of water from the Hartbeespoort during 1970. Results obtained from January to December Dim from four representative points, with analysis 1977 are given in the present report. for residual beta activities on individual samples, and As critical paths may vary according to the composition 90Sr ana" gamma-spectrometric analyses on of releases to the environment, monthly bulked samples of semi-annually bulked samples. liquid effluent were analysed to determine the presence of individual nuclides. Weekly samples of airborne effluent 1.1.7 Annual sampling and analyses of sediment found at released through the Reactor stack and the Waste the inflow to the Hartbeespoort Dam of the Treatment Plant stack were collected by means of May Crocodile River, and in the Crocodile River itself. packs |17J. Individual elements of this monitoring system were measured for gross alpha activity, gross beta activity 2. RESULTS AND DISCUSSION and 1311. Whenever appreciable amounts of gross activity are detected, more detailed analyses for individual nuclides Gross alpha activity is expressed as the equivalent are carried out. 24lAm activity, and gross bpta activity as the equivalent

The concentrations of most fission products from 4u 204j| activity, i.e. 2,3 times the equivalent K activity. nuclear-bomb tests have decreased in the biosphere to levels which can no longer be measured by means of direct 2.1 Gamma Survey gamma spectrometry. Due to their long half-lives and buildup over many years, 90Sr and 137c$ are still present The gamma survey serves the purpose of establishing a in measurable concentrations. The accumulated levels of network of points of known background activity which, in some 10mCi 9°Sr/km2 and some 18mCi 137cs/km2 in case of an emergency, can be used for a rapid delineation of soil are responsible for a reduced but continuous uptake in the contaminated area. various food chains. During 1977 the gamma survey monitors ,. aman type 332) were re-calibrated, following resetting of the 1.1 Measurements discriminators discussed in the previous report |25|..131| The present environmental program consists of the sources were arranged in a grid covering an area of 16 m2. following : Concentrations of b nCi/m? and 10/uCi/m2 (nominal) were used. The C2 setting on the instruments was adjusted to 1.1.1 Annual measurement of gamma radiation at 91 measure the 3651 80 keV energy region, i.e. the 1311 points inside the exclusion area, and at 99 points on photopeak, and a calibration factor of 4 /jCi/m2 per nine routes in the vicinity of the NNRC, up to 100 cps for C2 was found. distances of 30 km from the Reactor. As the calibration of the instruments has remained stable since re-setting, close agreement has been obtained 1.1.2 Weekly monitoring of milk from 10 farms in all wind between the present set of background readings and those directions, up to distances of 8 km from Pelindaba. reported in the previous report in |25|

Bulked samples are analysed for 1311. Quarterly Standard souros of mock 131| (a mixture of 133ga ancj bulked samples are measured for 90Sr and 137cs. 13?C$ 'n an approximate ratio of 9:1, simulating the gamma spectrum of 1311 and with a half life of 7,2 years) 1.1.3 Quarterly sampling of the general edible fish species, are used regularly to check the sensitivity of the viz. Tilapia Mossambica, Cyprinus Carpio and Clarios instruments. PEL2624 2 2 Milk Gamma-spectrometric analyses on bulked samples of water from the Dam and from the River, and of drinking 1311 determinations in milk are done on bulked weekly water, showed only natural *0K and traces of 137cs in the samples (TABLE II). A 500 mii sample of milk, with 2 mg case of water from the Crocodile River. The measured 9C*Sr, Nal carrier added, is passed through an ion-exchange 137c$ and ^K concentrations are given in Table IX. column containing 10 g Dowex AG2X-8, 20-50 mesh in NO3 form at a rate of 5 mt/min (18]. The column is eluted 2.5 Sediment with 510 mli of 2N NaNC>3 and then converted to iodine which is extracted into CCI4. Back-extraction into NaOH Sediment samples from the Hartbeespoort Dam and the solution is followed by acidification and final precipitation Crocodile River were collected during December 1977 to as Agl, with AgN03_ A lower detection limit of 0,5cpm, indicate the possible sedimentation of released activity. The with a counter efficiency of 39 %, is equivalent to gross beta activities were normal and were comparable to approximately 0,5 pCi and allows the measurement of 1311 the values for previous years. No gamma-emitting nuclides

concentrations in excess of 1 pCi/C; delay in sample other than 137c$( 40K, natural uranium and thorium were collection and analyses restrict the actual limit to 2 pCi/ï. detected. The results of these determinations are presented The detection limit is 0,5 % of the derived working limit for in Table X and XI and show no significant changes from the 1311 concentration in milk, i.e. 400 pCi/K (19). previous years. 90Sr levels in milk were not significantly different from previous years, while 137QS levels have decreased to the 3. RELEASES OF RADIOACTIVE EFFLUENT extent that they are below the detection limit of direct TO THE ATMOSPHERE AND TO THE gamma spectrometry (2pCi/C); they now require chemical CROCODILE RIVER separation of the 137cs and beta counting on a low-background beta counter. 3.1 Releases to the Atmosphere 90sr in soil is fairly mobile and is taken up in grass and forage, with the result that the 90Sr levels in milk are fairly Releases to the atmosphere are monitored in the constant. In contrast, accumulated 137QS becomes bound Reactor stack and the Waste Treatment Plant stack by to soil particles and is not freely available for uptake. The means of May packs (17| which are changed and measured 137cs levels in milk are therefore dependent on fresh for gross alpha, gross beta and 1311 (particulate and fallout rather than accumulated fallout, and have decreased gaseous) activities on a weekly basis. Whenever normal significantly due to the low levels of fresh fallout. background levels are exceeded, gamma spectroscopic analyses are performed. No quantitative monitoring is 2.3 Fish normally done for gaseous activity other than that of 1311. This monitoring program was officially approved in Samples of fish from the available edible species in both April 1972 by the National Committee of Control over the Hartbeespoort Dam and the Crocodile River were Radioactive Waste Disposal, on the basis of a special obtained only during February, June, October and scientific investigation (20]. The Committee also approved December. The species Cyprinus Carpio and Clarius revised levels for the disposal of airborne radioactivity, Mossambica could be obtained from the river only once. based on calculations using measured dispersion and The gross beta activities in the fillets of various species are transfer parameters. The permissible levels for releases to given in Table IV. the atmosphere under normal conditions are as follows: Bulked samples from the River and Dam were analysed by gamma spectioscopy. Only the fission product 13/Cs Alpha activity - 1,0mCi/a, provided 0,1 mCi'wk is not (originating most probably from deposited fallout) and the exceeded;

3 naturally occurring 40« could be observed. The Beta activity - 1 000 mCi/a (excluding n ancj concentrations of 90Sr, 137cs and 40« are given in Table radioactive noble gases), provided V in units of pCi/kg fresh weight. 100 mCi/wk is not exceeded.

2.4 Water The measured releases are given in Table XII |211 During 1977 the releases of alpha and beta activity The gross beta activities in drinking water from the amounted respectively to 1,0% and 18,6 "-> of the Kosmos/Schoemansville area, in upstream water samples permissible levels. from the Crocodile River, and in water from the Hartbeespoort Dam, are given in Tables VI, VII and VIII 3.2 Liquid Releases to the Crocodile River respectively. Generally, 40« constitutes approximately 80 % of the gross beta activity. Releases to the Crocodile River are reported in The anomalously high residual beta-activities found in accordance with permits No. 220 B and No 2b0 B of the the river water in August and October 1977 are not Department of Water Affairs. According to these permits,

reflected in results of analyses for individual nuclides. The all alpha activity is calculated as being due to 226R3 ,,n(| average of the residual beta activities on rejection of these all beta activity as being due to 90Sr, unless analyses for the two hiqh values is 2,8 pCi/V, 24 % of the gross activity. No individual nuclides are performed. The total equivalent obvious reason could he found for the high results. activity released is calculated as follows: PEL 262-5

(226Ra x 200) + (other a-activity x 2,86) + (9°Sr x 20) 7. REFERENCES + (otherfi-activíty x 1). [I] Van As. D. Environmental radioactivity at the According to the permit of the Department of Water National Nuclear Research Centre, Pelindaba: Report Affairs, the total equivalent activity released may not until 1964, PEL-89. Jul 1965. 75 p. exceed 4,54 Ci per 13 consecutive weeks. ISBN 0 86960 024 X. Total equivalent activities released to the Crocodile River in 1977 are given in Table XIII [22]. [2] Idem. Report for the year 1965. PEL-123. Oct. This method of calculating releases to the Crocodile 1966. 60 p. ISBN 0 86960 058 3. River is convenient for administrative purposes, and is very conservative as far as the control of permissible levels of [3) Van As, D.; Fourie, H.O.; Jordaan, CM. various radioisotopes in drinking water is concerned. Environmental radioactivity at the National Nuclear However, drinking water need not necessarily be the critical Research Centre, Pelindaba: Report for the year path. Because the composition of effluent may vary due to 1966. PEL 160 Aug 1967. 51 p. differences in reactor operation or the research activities on ISBN 0 86960 079 6. the Site, it is imperative that the different individual isotopes present in the effluent be known, in order that 14] Van As, D.; Fourie, H.O.; Vleggaar, CM. possible critical paths can be identified in advance of a Environmental radioactivity at the National Nuclear critical situation. Research Centre, Pelindaba: Report for the year Representative samples of the monthly releases of 1967. PEL 181. Sep 1968. 20 p. effluent were analysed gamma spectroscopically for all ISBN 0 86960 095 8. gamma-emitting nuclides, as well as chemically for 90$r; the results are given in Table XIV. (5] Idem. Report for the year 1968. PEL-192. Sep 1969. 26 p. ISBN 0 86960 105 9.

(6] Idem. Report for the year 1969. PEL-205. Oct 1970. 4. CONCLUSIONS 37 p. ISBN 0 86960 118 0.

The continued absence of atmospheric testing of nuclear (7] Van As, D.; Vleggaar, CM. Environmental weapons in the Southern Hemisphere has resulted in further radioactivity at the National Nuclear Research reduced levels of fission products in the environment of the Centre, Pelindaba: Report for the year 1970. NNRC. Except for 90Sr and 137Cs, no other fission PEL 216. Oct 1971. 21 p. ISBN 0 86960 122 9. products could be detected. These long-lived nuclides are remnants of previous tests and stratospheric fallout. (8] Idem. Report for the year 1971. PEL 208. Dec 1972. Releases from the NNRC showed no measurable 21 p. ISBN 0 86960 380 9. increases in the environment of Pelindaba. [9] Idem. Report for the year 1972. PEL 229. Nov 1973. 20 p. ISBN 0 86960 464 3.

5. APPENDIX f 10] Idem. Report for the year 1973. PEL 240. Sep 1974. 18 p. ISBN 0 86960 532 1. Measurement of Nuclear-Bomb Fallout in Air and in Deposition. [II] Fourie, H.O.; Ghijsels, J.P. Radiostrontium in As radioactive debris from nuclear-bomb tests biological material: A precipitation and extraction contributes to the environmental background radioactivity, procedure eliminating the use of fuming nitric acid. these concentrations have been taken into consideration Health Phys. (Nov 1969) v. 17(5) p. 685-689. when investigating the contribution from the NNRC to the environmental levels of radioactivity. [12] Van As, D.; Basson, J.K. Study of radioactivity in the Monthly measurements of individual nuclides measured environment of the National Nuclear Research in air samples collected at Pelindaba are given in Table XV. Centre. S. Afr. J. Sci. (Jan 1969) v. 65(1) p. 3 16. The levels of all fission products have decreased below the detection limit of our gamma-spectrometric system. ?Be, an [13] Basson, J.K.; Van As, D.; Van der Westhuizen, M.; activation product of natural origin, is the most prominent Vleggaar, CM. Measurement and analysis of radioactive isotope in air samples. Although radioactive fallout over South Africa and its gamma-spectrometric investigation of air samples will be biological uptake. S. Afr. J. Sci. (Jul 1970) v. 66(7) continued in order to detect any fresh fallout, quantitative p. 214-224. analyses will be limited to chemical separation and beta counting ot quarterly bulked samples of 90Sr and 137cs. [14] Van As, D; Vleggaar, CM.; Van der Westhui/en, M,; Quarterly levels of 90Sr and of various gamma-emitting Basson, J.K. Measurement of radioactive fallout over nuclides in deposited fallout, as well as of the total rainfall, South Africa during 1965-1973. PEL 239. Sep are given in Table XVI. No fresh fallout was detected. 1974. 64 p. ISBN 0 86960 531 1. PEL 2626 [15] Basson, J.K.; Van As, 0. Fallout over South Africa [20] Van As. D.; Vleggaar, CM., Basson, J.K. Derivation from nuclear weapons tested by France in 1966. of safe continuous releases of airborne radioactivity Health Phys. (Apr 1968) v. 14(4) p. 307-309. from the National Nuclear Research Centre, Peiindaba. IRPA regional conference on radiation protection, Jerusalem, 5-8 Mar 1973, v. 1 [16] Basson, J.K.; Van As, D.; Vleggaar, CM. Airborne p. 523-542. and deposited fallout over Southern Africa and resulting biological uptake of 90Sr, 13?Cs and 1311. [21 ] Kruger, J. Private Communication, 27/5/1/3/0. IRPA regional conference on radiation protection, Jerusalem. 5-8 Mar 1973. v. 1 p. 259-278. [22] Van der Westhuizen. H. Private Communication, 30/1/2/5, [17] Kruger, J.; Keet, G.M. The monitoring of gaseous [23] Van As, D.; Vleggaar, CM. Environmental radioactive waste at Peiindaba. PEL 223. Jun 1972. radioactivity at the National Nuclear Research 17 p. ISBN 0 86960 384 1. Centre, Peiindaba: Report for the year 1974. PEL-246. Jul 1975.18 p. ISBN 0 86960 570 4. [18] Saiki, M,; Omomo, Y. Determination of iodine-131 in milk. Quick methods for radiochemical analysis. [24] Van As, D.; Vleggaar, CM.; Goodwin, B.; Ockerse, IAEA Technical Reports Series No. 95. 1969. 62 p. E.C Environmental radioactivity at the National Nuclear Research Centre, Peiindaba: Report for the year 1975. PEL-254. Jul 1976. 18 p. [19] Morley, F.; Bryant, P.M. Basic and derived ISBN 0 86960 643 3. radiological protection standards for the evaluation of environmental contamination. FAO, IAEA and [25] Van As, D.; Goodwin, B. Environmental radioactivity WHO. Seminar on environmental contamination by at the National Nuclear Research Centre, Peiindaba: radioactive materia'.*, Vienna, 24-28 Mar 1969, Report for the year 1976. PEL-256. Jun 1977.18 p. p. 255-272. ISBN 0 86960 660 3. PEL- TABLE i

GAMMA SURVEY

1. Area enclosed by Secuiity Fence

7-counts/s 7-counts/s 7-counts/s 7-counts/s Point Point Point Point T T T T C2 C2 C2 c2

100 8 40 108** NM NM 116 6 35 126 6 30 101 15 60 109** NM NM 117 7 40 127 6 30 102 6 24 110** NM NM 118 6 35 128 10 60 103 6 20 111 4 20 119 10 60 129 8 40 104 4 28 112" NM NM 120 6 35 130 8 50 105 6 27 113 NM NM 121 5 30 131 6 15 106** NM NM 114** NM NM 122 6 30 132 6 20 107 6 30 115 8 sO 123 8 15 133 4 30 124 6 30 134 8 50 125 6 35 135 6 25 136 6 25

2. Exclusion Area

7-counts/s 7-counts/s 7-counts/s Point Point C2 T C2 T C2 T

1 15 70 34 7 30 56 6 25 3 8 45 35 7 45 57 8 50 5 9 70 37 6 35 59 4 15 6 8 49 38 7 35 60 9 50 7 8 50 39 6 30 61 10 50 10 9 50 40 7 40 64 6 35 11 7 35 41 7 35 65 8 65 16 5 20 43 6 25 68 8 45 19 6 35 44 6 25 69 10 60 20 11 55 45 6 30 70 10 60 21** NM NM 46 6 25 73 4 15 22 9 60 47 5 20 /G 11 60 23 11 70 48 5 25 76 7 35 24 14 70 49 6 25 77** NM NM 27 14 2u 50 5 20 78 9 55 29** NM NM 53 6 30 80 ; 40 30** NM MM 54 7 35 82 6 25 31 4 25 55 7 45 93** NM NM 32 6 30 94** NM NM - . ,„ ...... ** inaccessible NM not measured PEL-262 8 3. Routes Route A Pretoria — Skeerpoort