An Assessment of the Flux of Radionuclide Contamination Through the Ob and Yenisei Rivers and Estuaries to the Kara Sea

Home , Dalmatovo, Iset (river), Miass (river), Ob (river), Salekhard, Techa

NO9700007

THERESA PALUSZKIEWICZ1, LYLE F. HIBLER1, MARSHALL C. RICHMOND2, DON J. BRADLEY2 ''Pacific Northwest Laboratory, Battelle Marine Sciences Laboratory, 1529 West Sequim Bay Road, Sequim, WA 98382, USA . 2Pacific Northwest Laboratory, P.O. Box 999, Richland, WA 99352, USA.

Introduction

Extensive radioactive contamination (about 63,000 PBq) has been discharged to the environment of the West Siberian Basin. The former Soviet Union (FSU) nuclear program has been operating for the last 50 years; most of its facilities are located in the West Siberian Basin. These nuclear facilities include three sites for reprocessing spent fuel from the FSU's production reactors: Mayak, Tomsk-7, and Krasnoyarsk-26 (Fig. 1). These are believed to be responsible for the majority of the radioactive contamination that is in the major river systems, the Ob and Yenisei, which feed into the Arctic Ocean through the Kara Sea. Extensive radioactive contamination has been reported in surface water reservoirs, and large amounts of radioactive contamination have been discharged to injection sites that are adjacent to tributaries of the Ob and Yenisei Rivers. A massive release of radionuclide contaminants could result if floods, reservoir failures, or containment failures were to occur (Foley, 1991; Bradley, 1991, 1992a, 1992b; Bradley and Schneider, 1990).

The Ob River system consists of the contaminant release sites (FSU nuclear defense sites on land), the terrestrial, ground, and surface waters that link the contaminant release sites to the rivers, the Ob River, its tributaries, the estuary, and the confluence region where the estuaries of the Ob and Yenisei mix and flow into the Kara Sea (Fig. 2). The contaminants that we are following through the system are '''Sr, l37Cs, and 239Pu. The basic algorithms governing the adsorption and desorption of a dissolved contaminant with sediments and solids are used in the transport models. We are evaluating the following scenarios over all seasons for both river systems: a steady release of contaminants, and a massive release corresponding to a flood or reservoir failure. The steady release simulations are yielding a baseline for comparison with current samples from the estuary and the shelf taken by other Arctic Nuclear Waste Assessment Program (ANWAP) participants.

38 MATERIALS AND METHODS

We have characterized the study sites—the Ob and Yenisei River systems—by their potential radioactive contamination sources, their hydrology, and the contaminant transport processes. Our method is to collect existing data and literature, to construct conceptual budget models, to estimate radionuclide inventories, and to analyze the baseline and extreme scenarios with riverine and estuarine models. Because no information is available on the amounts of radioactivity released from the once-through cooled Russian production reactors, Bradley and Jenquin (1995) made calculations based on data from similar production reactors in the United States to estimate the releases. In the following sections, we shall concentrate on the Ob River system.

RESULTS

Potential radionuclide sources of the Ob River

Overview of Mayak contamination The releases of radioactivity at the Mayak site have all been to surface water bodies. All of the water systems at Mayak—lakes, reservoirs, streams, and ponds—are hydrologically connected; therefore, this radioactive contamination is mobile and has an outlet to the Techa River system, making transport to the Ob River and to the Kara Sea possible. During operation of the Mayak site, about 3.7 x 10" Bq of wastes was generated. Lake Karachai (Reservoir 9) has received discharges of low, medium, and intermediate level radioactive wastes since 1951; low level liquid wastes continue to be discharged to the lake (Bradley and Jenquin, 1995). The amount of radioactivity originally released to lakes and reservoirs at Mayak is estimated to be 4.4 x 1018 Bq. The decay-corrected inventory as of June 1995 from the discharges of contaminated cooling water from once-through cooled plutonium production reactors at Mayak, based on our calculations, is 4.9 x 10'5 Bq.

Overview of the Ob System Transport Processes

Transport of radioactive contamination downstream is governed by meteorologic/hydrologic forcing, contaminant decay and sediment partitioning, and the radionuclide release conditions. Russian arctic meteorology and hydrology are characterized by subfreezing conditions during much of the year, giving rise to the presence of permafrost and large, seasonal variations in the mean flow conditions. The extremes in meteorology and hydrology translate to more complex transport processes, such as sediment transport under spring flood conditions, and the presence and effects of river ice. The Ob watershed is 2.95 x 106 km2, extending from 50°N to 68°N and encompassing notable climactic variation; the large latitudinal variation alone causes freeze and thaw time lags within the watershed of up to 2 months. The regional-scale meteorology is governed by high-latitude, continental effects, with extreme cold and heavy snowfall in portions of the study area and more moderate conditions in other portions. The global average precipitation rate in this latitude range is about 20 to 70 cm yr"1 and within the Ob watershed, the average precipitation rate is 45 cm yr"1. Approximately half of this falls while the mean monthly temperature (MMT) is below freezing.

39 The major tributaries of the Ob River, in terms of discharge or in contaminant sources, are the Tom, Irtysh, Tobol, Iset, and Techa Rivers. The discharge, suspended sediment load, and riverine sediment are not well characterized, although limited data indicate that they are quite variable among the different tributaries. The Techa River is a relatively small river that drains the marshy, pond-marked areas around Mayak. It floods in April, when maximum depths range from 2 to 4 m. The Techa River discharges into the Iset River at Dalmatovo, 240 km river distance from Mayak. The annual estimated discharge increases 17 times from Mayak to the confluence of the Techa and Iset Rivers, indicating the influence of swamps and marshes on the hydrologic budget of this area. The Iset, Tobol, and Irtysh Rivers are the major large tributaries that form the part of the Ob River system; they also drain the regions around the nuclear facilities and nuclear test areas (Mayak and Semipalatinsk). The Ob reach between the Irtysh confluence and Salekhard is depositional; 12.2 x 106 metric tonnes (t) are deposited annually, and this figure does not account for washload or maintenance dredging. The Ob River at Salekhard, which is about 2500 km from Mayak, discharges 21,000 times as much water as the Techa at Mayak. The sediment flux number at Salekhard is 1.6 x 1061 yr1, whereas that at Belogor'ye is 28.3 x 1061 yr] (Bobkin and Bobrovitskaya, 1995; Rusinov et al., 1977).

It is important to characterize the sediment and its transport, but given the limited coverage of sediment sampling stations and the thousands of kilometers of river within these systems, it has been necessary to construct crude, empirically based characterizations of this system. These conceptual models are products of this study and of a study by Bobrovitskaya et al. (in press). The annual cycle in sediment transport is closely linked with the seasonal cycle in discharge (Fig. 3), and the relationship between sediment flux and water discharge is shown in Fig. 4. It is not immediately obvious that a system-wide Q-Qs relationship would be appropriate for the Ob system. A traditional, nonseasonal, linear relationship appears to be adequate to describe the Q- Qs relationship in the lower Ob (between Belogor'ye and Salekhard). Conversely, no such relationship appears to be appropriate for the upper system at Kolpashevo on the Ob or at Khanty-Mansiysk on the Irtysh. Further, at Belogor'ye, a seasonal cycle seems to be apparent: the same discharge rate during the early spring yields a systematically greater sediment flux than the same discharge occurring in the fall. Phenomena such as this have been observed on the Fraser River, and they indicate systematic hysteresis (Dyer, 1986). This phenomenon may be due to the effect of the freeze-thaw cycle on sediment, which tends to loosen soil and cause it to be more easily eroded (hence, the overproduction of sediment in the spring). After this supply of sediment is exhausted, sediment flux is reduced and therefore not available during the fall.

The Ob System near Mayak

We have modeled the Ob and Yenisei Rivers using conceptual (budget) models and a one- dimensional sediment-contaminant interaction model that assumed steady flow under high- and low-flow conditions. The motivation for modeling these simple cases was to evaluate the sensitivity of the model to empirical parameters in the sediment-contaminant algorithms and to provide initial estimates of residence times in the system. The results indicate that residence times for the dissolved contaminants under high-flow conditions are 36 days in the Yenisei River and 120 days in the Ob River. These values were in agreement with the simplest checkpoint calculations made with the conceptual model.

40 The initial quantification has been made of the contaminant inventory at nuclear facilities, primarily Mayak, Tomsk-7, and Krasnoyarsk-26, in order to provide contaminant source terms for the modeling. At Mayak, the contaminant inventory present in surface waters (the reservoirs, the Techa River, and the Asanov Marsh) is a more available (potential) supply of radionuclides to the Ob River and the Kara Sea than the sources at the other nuclear facilities. An analysis of basic residence times under simplified conditions was used to establish that the models were configured properly for each river system. Using a conceptual model that considered dilution alone, we analyzed the concentration levels at Salekhard for possible release scenarios from the Mayak nuclear facility. The contaminant inventory contained within the reservoir system at Mayak is sufficiently large that there would be elevated levels of 90Sr and of I37Cs at Salekhard on the Ob River (exceeding '"Sr concentrations set by the U.S. Environmental Protection Agency's drinking water standards) if these inventories were released uniformly throughout the year. Given this screening of release scenarios, we have then configured the time-dependent river model to fully explore the flux and distribution in the water column and the sediments along the Ob River from releases of contaminated reservoirs.

We are modeling the time-dependent hydrodynamics and sediment/contaminant transport for areas of the Ob and Yenisei Rivers using the PNL-CHARIMA model (Holly et al., 1990). PNL- CHARIMA is a one-dimensional, finite-difference model that simulates unsteady flow (flood wave) hydraulics, nonuniform sediment transport, and contaminant transport in open channel systems, such as rivers and canals. The model has the capability to simulate branched and looped channel systems, the operations of dams and reservoirs, heat transport with surface heat transfer, dissolved contaminant transport, sediment-sorbed contaminant transport, and the accumulation and/or resuspension of contaminants sorbed to sediments in the river bed.

The application of the PNL-CHARIMA model to the Ob River system is currently in progress. This section of the river model begins at Reservoir 11 on the Techa River and ends just downstream of the confluence of the Iset and Miass Rivers (Fig. 5). This covers a distance of approximately 362 km (225 miles). The topographic data and cross-sectional shape for the Ob River system were developed from 1:50000 scale Russian topographic maps and supplemental field surveys. The model grid uses a resolution of approximately 5 km to represent this portion of the river. To illustrate preliminary model results, a test simulation corresponding to a constant release of dissolved 90Sr for 1985 hydrologic conditions is presented. Using streamgage records for the Iset (Bobkin and Bobrovitskaya, 1995; Rusinov et al., 1977), monthly average input flows for the model were specified for the Techa, the Iset above the confluence with the Techa, and the Miass Rivers. The flows were apportioned based on the respective subwatershed areas. A constant input concentration of'"Srat Reservoir 11 and the Asanov Marsh of 30 Bq L"1 and 15 Bq L'1, respectively, were assigned based on source term data reported by Trapeznikov et al. (1993) and Bradley and Jenquin (1995).

41 CONCLUSION

Recent data (Bradley and Jenquin, 1995) indicate that there are potentially large sources of radionuclide contamination on the Ob River system. To quantify the existing radionuclide contamination and the potential contamination from a possible catastrophic event, we are using data and models to quantify scenarios. Using a compilation of Russian data on the radionuclide contamination (Bradley and Jenquin, 1995), hydrologic data (Bobkin and Bobrovitskaya, 1995; Rusinov, et ai, 1977), and Russian studies on the sediment transport processes (Bobrovitskaya, 1967, 1968, 1994; Litsitsyna et al, 1979), we have developed a conceptual model of the Ob system and applied a numerical model to estimate the radionuclide flux to the Kara Sea. We are continuing to apply the numerical model to other portions of the Ob River system and to include, explicitly, the Irtysh River up to Semipalatinsk and the Asanov Marsh. The initial results of the river modeling in the Mayak region show how important the watershed flow from the marshes are to the hydrologic budget of the area. Our preliminary analysis of the sediment flux indicates the need to consider the depositional (storage) regions such as the Asanov Marsh. In order to consider the flux of contaminants overland and through the Techa floodplain and the Asanov Marsh, we are linking a watershed model to the river model. We have begun work on the estuarine model for the Ob and Yenisei Rivers. The inclusion of this watershed model component then provides a complete representation of the water- and sediment-bome pathways that could be important to the transport of radionuclides from inland sources to the Kara Sea.

ACKNOWLDEGEMENT

The authors would like to thank Dr. Susan Thomas for her assistance in preparing this abstract, and to acknowledge the support of our work by the Department of the Navy, Office of Naval Research, Arctic Nuclear Waste Assessment Program under contract number 21584.

REFERENCES

Bobkin, V.I. and Bobrovitskaya, N.N. (1995). SHI/USGS Database. State Hydrological Institute, St. Petersburg, Russia.

Bobrovitskaya, N.N. (1967). Discharge of suspended sediments as a function of hydrologic characteristics. Soviet Hydrology: Selected Papers 6(2): 173-183.

Bobrovitskaya, N.N. (1968). Determination of the normal annual discharge of suspended sediments and its cyclic fluctuations. Soviet Hydrology: Selected Papers 7(5):447-462.

Bobrovitskaya, N.N. (1994). Assessment of trends to sediment discharge variations in the rivers of the Former Soviet Union (FSU). In Proceedings of the International Symposium, East-West, North-South Encounter on the State-of-the-Art in River Engineering and Design Philosophies, 16-20 May 1994, pp. 32-39. State Hydrological Institute, St. Petersburg, Russia.

Bobrovitskaya, N.N., C. Zubkova and R.H. Meade. (In press for 1996). Discharges and yields of suspended sediment in the Ob' and Yenisei Rivers of Siberia. In Erosion and Sediment Yield:

42 Global Perspectives (D.E. Walling and B.W. Webb, eds.). International Association of Hydrological Sciences Publication. (Cited in R. Meade, U.S. Geological Survey, personal communication, April 17, 1995).

Bradley, D.J. (1991). Radioactive Waste Management in the USSR: A Review of Unclassified Sources, Volume II. PNL-7645, Pacific Northwest Laboratory, Richland, Washington.

Bradley, D.J. (1992a). Radioactive Waste Management in the Former USSR: Volume III. PNL- 8074, Pacific Northwest Laboratory, Richland, Washington.

Bradley, D.J. (1992b). Radioactive Contamination of the Arctic Region, Baltic Sea, and the Sea of Japan from Activities in the Former Soviet Union. PNL-8292, Pacific Northwest Laboratory, Richland, Washington.

Bradley, D.J. and U.P. Jenquin. (1995). Radioactive Inventories and Sources for Contamination of the Kara Sea by Riverine Transport. PNWD-2316, Prepared for the Office of Naval Research by Pacific Northwest Laboratory, Richland, Washington.

Bradley, D.J. and K.J. Schneider. (1990). Radioactive Waste Management in the USSR: A Review of Unclassified Sources, 1963-1990. PNL-7182, Pacific Northwest Laboratory, Richland, Washington.

Bulatov, V.I. (1993). USSR's 200 Nuclear Test Sites: Geography of Radiation Catastrophes and Contamination. Presented at Fourth ex-USSR Nuclear Society Meeting, June 28-July 2, 1993. Nizhniy Novgorod, Russia.

Dyer, K.R. (1986). Coastal and Estuarine Sediment Dynamics. John Wiley and Sons, New York. 342 pp.

Foley, M.G., P.E. Long, D.J. Bradley, L.M.G. Ballou and D.W. Wester. (1991). Regional Geohydrologic Framework of Selected Soviet Sites. PNL-777, Pacific Northwest Laboratory, Richland, Washington.

Holly, F.M., Jr., J.C. Yang, P. Schwarz, J. Schaefer, S.H. Hsu and R. Eeinhellig. (1990). CHARIMA: Numerical simulation of unsteady water and sediment movement in multiply connected networks of mobile-bed channels. IIHR Report No. 343, Iowa Institute of Hydraulic Research, The University of Iowa, Iowa City, Iowa.

Kazakhstanskaya Pravda. (January 4, 1992). History of Radiation Safety at Semipalatinsk Detailed, p. 1.

Kononovich, A.L., V.A. Luppov, V.I. Makovskii, M.G. Nifontova, I.I. Koltik and E.M. Rafikov. (1991). Effect of Radioactive Contamination Deposited in a Swamp on the Radiological Situation in the Adjacent Region. Atomnaya Energiya 71(3):249-254.

43 Kuznetsov, Yu., N. Rakov and L.W. Tishkov. (1994). An Assessment of the Contribution by Different Contamination Sources into the Total Radioactive Contamination of the Kara Sea. Radium Institute, St. Petersburg, Russia.

Lagovskiy, V. (1994). Number, Purpose of Non-Military Nuclear Explosions in Former Soviet Union. Rabochaya Tribuna 86-87(985-896): 1.

Lisitsyna, K.N. (1974). Stok vzveshennikh nanosov rek sibiri. Gosudarstvennyi gidrologicheskii institut Trudy 210:48-72. Unpublished English translation by V.G. Yanuta (1994).

Milliman, J.D. and R.H. Meade. (1983). World-Wide Delivery of River Sediment to the Oceans. The Journal ofGlaciology 91(1).

Nilsen, T. and N. Bohmer. (1994). Sources of Radioactive Contamination in Murmansk and Arkhangel'sk Counties. Bellona Report, Vol. I. Published by the Bellona Foundation, Oslo, Norway.

Nuclear Safety and Cleanup Report. (1994). East, Central European Radwaste Detailed in ANS Directory/Report. 3(5):43-45.

Nuclear Waste News. (October 10, 1991). Revelations of 20 Years of Improper Sea Disposal Causes Concern in USSR, p. 397.

Raisbeck, G.M., F. Yiou, Z.Q. Zhou, L.R. Kilius and H. Dahlgaard. (1993). Anthropogenic 129I in the Kara Sea. In Environmental Radioactivity in the Arctic and Antarctic (P. Strand and E. Holm, eds.), pp. 125-128. Proceedings of the International Conference on Environmental Radioactivity in the Arctic and Antarctic, August 23-27, 1993, Kirkenes, Norway.

Rusinov, M.I., M.L. Ruppert and T.I. Yakovleva. (1977). State water Cadaster, its purpose and structure. Soviet Hydrology: Selected Papers 17(3):176-185.

Sivintsev, Yu. (Chairman). (1992). Conclusion of the Expert Commission for State Ecological Examination of the Russian Federation Ministry of Ecology Concerning Investigative Materials on the Novaya Zemlya Archipelago and Adjoining Territories. October 13, 1992. Moscow, Russia.

Trapeznikov, A., A. Aarkrog, N. Kulikov, S.P. Nielsen, V. Pozolotina, G. Polikarpov, V. Trapeznikova, M. Chebotina, V. Chukanov and P. Yushkov. Radioactive contamination of the Ob River system from the nuclear enterprise "Majak" in the Urals. In Environmental Radioactivity in the Arctic and Antarctic (P. Strand and E. Holm, eds.), pp. 135-142. Proceedings of the International Conference on Environmental Radioactivity in the Arctic and Antarctic, August 23-27,1993, Kirkenes, Norway.

44 Vakulovsky, S.M., A.I. Nikitin, V.B. Chumichev and S. Malyshev. (1993a). Radioactive Contamination of the Barents and Kara Seas. Presented at an IAEA meeting on Assessment of Actual and Potential Consequences of Dumping of Radioactive Waste into the Arctic Seas. February 1-5, 1993. Oslo, Norway.

Vakulovsky, S.M., A.I. Nikitin, V.B. Chumichev and I.Yu. Katrich. (1993b). Radioactive contamination of Russian Arctic Seas from results of observations during the years 1960-1962. In Environmental Radioactivity in the Arctic and Antarctic (P. Strand and E. Holm, eds.), pp. 177-179. Proceedings of the International Conference on Environmental Radioactivity in the Arctic and Antarctic, August 23-27,1993, Kirkenes, Norway.

Zhou, Z Q., G.M. Raisbeck, F. Yiou and L.R. Kilius. (1993). I29I as a Tracer of European Reprocessing Emissions in the North Atlantic and Arctic Oceans. Presented at the conference on Radioactivity and Environmental Security in the Oceans: New Research and Policy Requirements in the Arctic and North Atlantic. June 7-9, 1993. Woods Hole, Massachusetts.

45 Latvia Estonia \ : felst. / ^J Petersburg Lithuania t^vBu

JwTTBelarusl ™ V <~

S9411O24.1 • Cities • Weapons Design Laboratories Test Sites • Weapons Production Facilities • Production Reactor and Reprocessing Sites Uranium Enrichment

Figure 1. Map of the Former Soviet Union illustrating the sites of interest to this study (Bradley and Jenquin. 1995).

46 60' 70' 80° 90°

• -aft*

iJ ara Sea* \ * ?0. \ A* y t\ I i\\\\ \ I V\\ / SalekbJd

•-..

/ L i fObR. / | \ / \Belj gorye X Obi .60° 60'. •». <•* tw-MansiyskV L "V / lievo \ a* K)asnoyardt^ 1 L Tomsk l N jvosibirsk I ' •^iT ^ d / ) 1 > AyaK~~Mi5!l7 < u2= 60° 70' 80° 90°

Figure 2. Map of the Ob and Yenisei River systems.

47 50000 7000 (a) Salekhard (b) Kolpashevo -Q 40000 MOO

^ 30000 4200 DO

or 2oooo zaoo or

10000 1400

50000 7000 }(c) Belogorye S (d) Khanty-Mansiysk Q 40000 eooo

« 90000 4200 00

20000 2800 gr

10000 1400

1986 1987 1989 1991 1986 1987 1989 1991

Figure 3. River water discharge (Q) and sediment flux rates (Qs) for 1985-1992 at (a) Salekhard, (b) Kolpashevo, (c) Belogor'ye, and (d) KJianty-Mansiysk (Q is shown as solid line, corresponding to the left axis; Qs is shown as dashed line, corresponding to the right axis) (data from Bobkin and Bobrovitskaya, 1995).

48 10* : (a) Salekhard : : (b) Kolpashevo :

• / •

:V:* • •

101 t • : (c) Belogorye^ : : (d) Khanty-Mansiysk :

- /if :

10* lofo* Q (m.3a/s) Q

Figure 4. Relationship between sediment flux (Qs) and water discharge (Q) for 1985-1992 at (a) Salekhard, (b) Kolpashevo, (c) Belogor'ye, and (d) Khanty-Mansiysk (data from Bobkin and Bobrovitskaya, 1995).

49 PNL-CHARIMA River Model Configuration Junction Location

61° E 62

-56! N

KASU

Approximate Scale

Figure 5. Configuration for the PNL-CHARIMA river model in the Mayak region. The dots indicate junction locations; resolution of the model grid varies between junction locations with an average resolution of 5 km.