RADIOACTIVE CONTAMINATION OF THE ARCTIC OCEAN, BASED ON

OBSERVATIONS IN 1985-1987

A. I. Nikitin, I. Yu. Katrich, A. I. Kabanov, V. B. Chumichev, and V. M. Smagin

UDC 504.4.054(268)

In the process of operating the spent nuclear fuel reprocessing complex at Sellafield, significant quantities of radioactive waste are discharged into the Irish Sea; in particula$ the total release of z37Cs at present has exceeded 1MCi [i]. This is comparable with the radionuclide release during the Chernobyl' accident [2], when the principal mass of radio- active cesium was localized within Soviet territory [3].

On-site research on the transport of wastes discharged at Sellafield [4-6] has shown that the most radioecologically dangerous radionuclides contained in the discharges (134,147Cs, 9~ and transuranic radionuclides) are carried out of the Irish Sea by sea currents within a short time. During the transport process, the concentration of z37Cs, which is the predominant component in the Sellafield discharge, decreases significantly as a result of dilution (thus the z37Cs contamination of water in the Norwegian Sea is I000 times less than in the Irish Sea); however, the total flow of the isotope decreases to a much lesser degree. According to our estimates, approximately 20% of the Z37Cs and approximately 30% of the 9~ discharged at Sellafield enters the Barents Sea. Ultimately the wastes enter the Arctic basin proper, and since only part of the wastes go into the Barents Sea, another nonestimated part enters through the Greenland-Spitsbergen strait.

This article is a continuation of research of the transborder transport of radioactive wastes from Sellafield [5, 6] and their contamination of the Arctic basin proper.

The tracer chosen for these radioactive wastes is Z34Cs, a waste component which was practically absent from atmospheric radioactive fallout prior to the Chernobyl' accident. The atmospheric fallout of products from the radioactive release led to the contamination of sea areas with Z34Cs. This circumstance combined with the significant decrease in the volume of radioactive wastes discharged into the sea at Sellafield [7] complicates further research on their transport using Z34Cs as a tracer.

Studies of radioactive contamination of the waters of the Arctic basin were conducted during the period of drift of the "North Pole-27" station in 1985-1987. The research performed during 1985 was preliminary in nature. It was clearly understood that in the Arctic Ocean, thousands of kilometers from Sellafield, the concentration of the waste tracer Z34Cs would be extremely low. Within the region where work was done in 1985 following the method de- scribed in [8], samples were taken along the depth and the radioactive cesium concentration was determined from a large sample of water (up to i0,000 liters) from three levels: surface (one meter beneath the edge of the ice), a depth of 150 m (the layer of Pacific Ocean water), and a depth of 250 m (the upper portion of the Atlantic layer).

TABLE i. Averaged Depth Distribution of 134,ZSTCs, 9~ and Tri- tium in the 1985 Work Region (81-83~ lat., 150-157~ long.)

Sample Concentration, Bq/m 3 level, m

137Cs 1~Cs 90Sr tritium

0 10,2+_1,0 0,04• 8_+t i 700:i=220 i50 9,6-+-1,3 O, 03!0 ,0t 6=:k~ t300• 250 8,5::k0,5 O,O3_+o,oi 6• i 670=h220

Taifun Scientific and Industrial Association. Goskomgidrometa Arctic and Antarctic Scientific Research Institute, USSR. Translated from Atomnaya ~nergiya, Vol. 71, No. 2, pp. 169-172, August, 1991. Original article submitted May 23, 1990.

0038-531X/91/7102-0687512.50 �9 1992 Plenum Publishing Corporation 687

TABLE 2. Radionuclide Content in the Waters of the Arctic Basin in the Drift Region in 1986-1987

I3~Cs IS4CS

Number of Concentration, Number of Concentration, Depth, m samples Bq/m 3 Depth, m samples Bq/m s

7--20 70

150--i75 250

300--350 400--550

20 50

I00 150 200 250

300--350 400--500

Eastern portion

t3 ,6~0,6 7--20 8,8 70

6,4• t50--175 4, t 200-- 400

5,6~_t,3 3,7~=0,3

Western portion t2,t__A,0 20 ~0,5~0,9 50

7 ,7~t ,2 lO0 4,5/=0,7 200--400 3,4_+_+0,7 4,1~0,4 3,1~0,4 2,5=h0,2

0,tt:i:0,03 0,006

0,05:i:0,(~I O,04•

5 0,08• 4 0,06• I 0,06 5 0,03•

1200

d ~ o .+~.+.I+,+,...~/j }....T,...+ ........ ~, .....................

I , I , . I . I . I , i

200 LtPD 600 80g ?'(]00 Depth, m

Fig. I. Averaged profiles of tritium concentration over the "North Pole-27" drift period: o) 81-83 ~ N. lat., 150-157 ~ E. 10ng. (1985); �9 ) approximately 88~ lat., 75 ~ E. long.-3 ~ W. long. (1985-1987).

As a result of the work done in 1985, the content of iZ4Cs in the water of the Arctic Ocean was first determined, and thus the fact of the presence of wastes from Sellafield in the waters of the Arctic basin was confirmed. The depth profile of the concentrations of 134,137Cs, 9~ and tritium, averaged over the 1985 work region, is given in Table i.

In 1986-1987, the station drifted along 88~ lat. approximately from 120~E. long. to 3 ~ W. long., i.e., in comparison with 1985, the work region shifted to the west. Data were obtained on the content of iZ?Cs and 13"Cs in water at various depths (Table 2). The drift area was divided into two portions - eastern (IIi~176 E..long.) and western (75 ~ E. long. -3 ~ W. long.). It can be seen from the tables that the region studied in 1985 is character- ized. by a practically identical concentration of radioactive cesium in water for a depth of up to 250 m; however, further west during the 1986-1987 drift a significant decrease in the content of radioactive cesium with depth was observed in the same layer of water. While the 137Cs contamination of the surface water differed little in the two regions, the 13~Cs content was higher in the western portion. Practically no differences were observed in the depth distribution of radioactive cesium over the whole extent of the 1986-1987 drift (in the western and eastern portions of the dirft area, there is little difference in the levels of contamination). This applies as well to the distribution of tritium (Fig~ i).

The level of global contamination of the surface waters of the northern part of the Atlantic Ocean by 13?Cs is 3-6 Bq/m 3 (~0. i pCi/liter) [9]. For the surface waters of the Arctic Ocean, the characteristic level is approximately twice as high, due to the influxof radioactive industrially contaminated water. It is interesting to estimate the excess in the quantity of 137Cs in the 0~25 m water layer of the Arctic Ocean over the quantity of Z37Cs from the global source.

The averaged depth profiles of the 137Cs concentration in water (Fig. 2) were obtained in the 1985 and 1986-1987 workregions. Calculating in accord with these profiles, the

688

TABLE 3. 137Cs Content in Sus- pended Material in the 1986-1987 Work Region

Concentration, Bq/m 3 Level, range m boundaries

7--20 50--70

t50--t75 195--255 300--355 400--450 500--550

0,01--0,07 0,009--0,05 0,0i4--0,032 0,006--0,04 0,005--0,03 0,018--0,07 0,0t4--0,05

average value

0,03i_0,004 0,022+-0,008 0,020+_0,003 0,020___0,007 0,0t7+--0,003 0,032+-0,008 0,028__+0,605

S

0 I : I i A-.-- 200 ~-00

Depth, m

Fig. 2. Averaged depth profiles of the z3VCs concentration: o) 1985; .) 1986-1987.

average iSTCs concentration in the 0-250 m layer is 9.5 Bq/m 3 (1985) and 7.5 Bq/m a (1986- 1987). Let us take the average of these values, 8.5 Bq/m 3, for the Arctic basin as a whole. If the global contamination of water in the 0-250 m layer is taken as equal to 5 Bq/m 3 (0.14 pCi/liter), the excess in the quantity of la7Cs in the upper 250-m water layer of the Arctic Ocean over the global quantity is 0.35 MCi (the area of the ocean is 14.7"106 km =, the volume of the 0-250 m water layer is 3.7"106 km 3, and the excess radionuclide concentration in the water above the global level is 3.5 Bq/m 3 (0.i pCi/liter). The total radionuclide quantity in this layer is 0.85 MCi. Thus approximately 40% of the Z37Cs in the water mass of the 0-250 m layer of the Arctic Ocean is possibly of industrial origin.

This tentative figure for the excess of the quantity of 137Cs over the global level is comparable with the influx (0.2 MCi) of industrial la7Cs in the Arctic basin (including that entering through the Greenland-Spitsbergen strait).

In addition to determining the total 137Cs content in the water, in the course of the 1986-1987 work the distribution of ~37Cs in a suspension-solution system at various depths was studied (Table 3). Comparing the data in Tables 2 and 3 shows that in Arctic Ocean waters 137Cs is found almost entirely in a dissolved condition. Its content in suspension is tenths of a percent of the total radionuclide content in the water. Further, no signi- ficant differences were found in the radionuclide content of suspended material at different water depths.

Despite the fact that the volume of radioactive waste discharged at Sellafield is now significantly decreased in comparison with the maximum detected in 1974-1977, research on the level of radioactive contamination of the waters of the Arctic basin and the mechanisms

689

of its formation is as topical as it was previously. At present, radioactive cesium re- leased by the accident at Chernobyl' is in the process of being removed from the Baltic Sea~ This radionuclide is first carried into the North Sea, and its further transport is analog- ous to the transport of the Sellafield radioactive wastes. In addition, nuclear-powered ships operate in the waters of the Arctic basin. The continuing radioactive contamination of the waters of the Arctic Ocean and its seas point to the need to develop an international agreement which would reflect the interests of all the countries whose waters are subject to radioactive contamination.

LITERATURE CITED

I. W. Templeton and A. Preston, "Ocean disposal of radioactive wastes," Intern. J. Radio- active Waste Management and the Nuclear Fuel Cycle, 3 (i), 75-113 (1982).

2. "Information prepared for the IAEA on the Chernobyl' nuclear accident and its con- sequences," At. Energ., 61, No. 5, 301-320 (1986).

3. V. G. Asmolov, A. A. Borovoi, V. F. Demin, et al., "Report of the USSR at the Inter- national Conference on Indicators and Nuclear Power Safety, IAEA, Vienna, 9/28-i0/2/ 1987, Vienna: IAEA, SN'48/63," ibid., 64, No. i, 3-23 (1988).

4. H. Kautsky, "The North Sea region taken as an example for the behaviour of artificial radioisotopes in near shore sea areas," in: Proc. 3rd NEA Seminar Mar. Radioecol., Tokyo, 1979, Paris (1980), p. 283-287.

5. S. M. Vakulovskii, A. I. Nikitin, and V. B. Chumichev, "The effect of the influx of radioactive industrially contaminated North Sea Water on the radiation level in the Baltic Sea," At. Energ,, 62, No. 2, 104-108 (1987).

6. S. M. Vakulovskii, A. I. Nikitin, and V. B. Chumichev, "The contamination of Arctic seas by radioactive wastes from West European radiochemical plants," At. Energ., 58, No. 6, 445-449 (1985).

7. "Doses from aquatic radioactivity decrease," Nucl. Energy, 28, No. I, 4-5 (1989). 8. S. M. Vakulovskii (ed.), Methodological Recommendations on Determining the Radioactive

Contamination of Aquatic Objects [in Russian], Gidrometeorizdat, Moscow (1986). 9. S. M. Vakulovskii, I. Yu. Katrich, Yu. V. Krasnopevtsev, et al., "Contamination of the

Atlantic Ocean and its seas by radioactive products," Okeanologiya, 21, No. 2, 257-265 (1981).

EFFECT OF A LEAD TARGET ON THE CHARACTERISTICS OF AN

ELECTRONUCLEAR REACTOR

V. S. Barashenkov, A. N. Sosnin, V. N. Sosnin, and S. Yu. Shmakov

UDC 621.039.5

A significant part of the heat in an electronuclear reactor is emitted in a narrow central region along the path of the primary proton beam, as calculations have shown [i]. In this region it is advisable to use a liquid target, which would serve as an efficient converter of the proton beam and at the same time could be used as a coolant. However, this is possible only if there is no substantial decrease in the plutonium output (or the neutron flux, if the electronuclear installation is used as a neutron source).

Here we study how introducing a cylindrical lead beam with dp = 3 and 8 cm (see Fig. I) into a electronuclear reactor changes various reactor characteristics. The reactor consists of thin fuel elements with enriched uranium (2~sU/23SU = 0.3%). The interstices between the steel cladding of the fuel elements is filled with liquid sodium.

For the calculations, the reactor was divided arbitrarily into zones - the target and the homogenized five-component medium surrounding it: 22.7% 238U, 0.069% 23~U, 17.7% 56Fe, 13.8% 23Na, and 45.8% IsO. The same calculational method was used as in [i], except that

Joint Institute of Nuclear Research (OIYal), Dubna. TranslatedfromAtomnaya Energiya, Vol. 71, No. 2, pp. 172-175, August, 1991. Original article submitted June i, 1990.

690 0038-531X/91/7102-0690512.50 �9 1992 Plenum Publishing Corporation