Decommissioning and Remediation of the Chernobyl Nuclear Power Plant Cooling Pond Department of Environment Radiation Monitoring Ukrainian Hydrometeorological Institute. Kiev. Ukraine Centre for Monitoring Studies and Environment Technologies LLd Oleg Voitsekhovych Waste Management WM-2010 Phoenix 7-11 March 2010

Outline This Case Study based on the number of recently implemented national and international studies funded by UA Government ( ), EC (In-Copernicus -2004)and TACIS-NNC and IAEA (2009) Current focus of the interest for Chernobyl Cooling Pond Roadmap for Decommissioning and Remediation was initiated as a part of the IAEA Project UKR “Chernobyl NPP Units Decommissioning and Radioactive Waste Management at the Site Including Shelter Workshop” The task : Assessment of the Current Status and Challenges of ChNPP Cooling Pond Decommissioning and CP Legacy Site Remediation

Facility characterization The Chernobyl cooling pond is an artificial water reservoir that was created in first chain and in (1982 –second chain) to cool down the heat exchangers of four (6) nuclear reactor units at the Chernobyl NPP The CP is situated in the northern part of Ukraine, on the right-bank flood plain of Prypiat River. Banks of the Cooling Pond are formed by both an above-land terracing of the river and a protecting dike of 25 km in length. ChCP Area ~ 22 km2; volume ~ 0.15 km3; length ~ 11 km; width ~ 2 km; mean depth ~ 6.6 m; and the max depth ~ 18 m. The water elevation of the CP is about 5-7 m over the Prypiat river level. The main factors of the water loses are filtration to the Pripyat Rier and evaporation

To compensate for water losses due to leakage and evaporation, water is continuously pumped from the Prypiat River to the Cooling Pond. The existing area of the CP significantly exceeds the current needs. The annual maintenance cost are rather high. Engineering risk of the dam safety is high. The Government decided to stop pumping, to eliminate water level. As the pumping stops, the water level in the CP will decline and highly radioactively contaminated sediments will be exposed Thus, the present ecological situation of the Cooling Pond is not risk free, requiring the development of an appropriate strategy for safe decommissioning of the pond. The problem of draining the pond is complex and not straightforward, as it requires the consideration of linked problems of safety, public health, ecosystem management, risk assessment and remediation. SCOPE OF THE PROBLEM

Mainly dispersed fuel particles settled on the water surface. Heavily contaminated water (~5,000 m3) from the reactor basement released to the lagoon Heavily contaminated soils removed from the nearby sites dumped into the lagoon. Estimates of the total radioactivity in the lagoon range from 2,200 to 13,000 TBq Initial assessment for Long-lived radionuclides in the sediments: 170TBq 137Cs, 35TBq 90Sr and 0.8TBq 239,240Pu. Recently more accurate assessment have be done for site contamination study Primary Sources of Contamination Сs-137 in soils at the surrounding areas Kashparov et al. 2001

Radionuclides in the bottom sediment (UHMI, 2005) Сs-137Sr-90 Pu-239,240

Specific feature of the bottom sediment contamination is still high contribution of the “hot particles” 2-5 µк, which potentially can be exposed to the wind re-suspension, while in the neighboring areas the hot particles in the soils are almost dissolved ( Kashparov, at al. 2004)

RISK Analyses ( considered) E ngineering risk (dam sustainability, water pump station, needs to repair drainage systems and possible accidents) E conomical risks (annual budged of CP management is up to US$ + long-term institutional control and needs for sustainable management of infrastructure. R adiological Risks (dilution of significant amount of radionuclides in the environment, possible exposure of people due to dispersion of radionuclides and possible access to the site) E cological Risks (eutrophication and ecosystem degradation, long term ecosystem effects S ocial risks (stress depended risk factors, inadequate tenses, uncertainty in the regulatory provisions, research Environment Reserves

The dam failure were considering (Zheleznyak M.2004) In case of CP is full of water and dam may be broken, the water from the CP will cover the neighboring floodplain, and will inlet to the cascade of the Dnieper reservoirs. However even for worst scenario the existing doses due to water consumptions can not be significantly increased for the critical group of population living along the Dnieper cascade (10-15 % above the existing post-Chernobyl level, which is less 0,1 mSv a year)

Dose assessment for public resulting Dnieper water contamination from collapse of the dam The considered exposure groups are fishermen and other populations, using water from the Pripyat and Dnieper Rivers. As a result of the dose calculations it is shown that the collective dose from all pathways (drinking water, fish, irrigated products) for 1 year after dam break of considering scenario can be assessed about 20 man-Sv (18.5 man-Sv from Sr-90 and 1 man-Sv from Cs-137). The Annual individual doses from consumption of fish contaminated by Sr-90 and Cs-137 from Kiev reservoir for fisherman compose 7.35E-2 mSv, that is one order of magnitude lower than radiologically safe limits

Natural condition of the water level declining The water level drawdown will due to natural factors (filtration and evaporation) will take 5-7 years depend of climatic mode of the year to be selected for water decline implementation strategy. Forecast of water level in the Cooling Pond under the conditions of natural drainage (Dry and Normal Scenarios) Days after start point Water level in H, meter above the sea

Normal Climate Scenarios The forecasts of eventual water levels in the water bodies created in place of dried-up Cooling Pond for the «normal» and «dry» scenarios ( Bugay et al. 2004) Dry Climate Scenarios

Chernobyl CP water level declining mode 1-st year later 108,5 m 2-nd year later 107,5 m 4-th year later m End point after 6 year Declining m CP state for the dry year chain conditions Starting point 110.5m m m

Forecast of the final water levels during Cooling Pond drying-up For a years with normal humidity and temperature characteristics, the hydrogeological conditions at the CP drying-up are simulated by means of a filtration model. The location of the shoreline of separate water bodies and water levels in them are determined by way of iterations under the conditions of balance between the water income (with precipitation and groundwater recharge) and outcome by way of evaporation and filtration into Pripyat River. The hydrogeological conditions typical for the dry year (atmospheric precipitation constitute mm/year, infiltration replenishment is low, the evaporation is high, the levels of Pripyat River are low) are simulated with a filtration model.

Structure of the radionuclides in the bottom sediment at the different depth and type Most of radionuclides are associated with fine particles deposed at the deepest locations. Shallow areas are relatively self-cleaned If to decline water level on 7 m below the present there still about 32% of the bottom sediment territory will be remained below the resulted water level. About % of Cs-137 and Sr % of Pu will be remained under the water layer at the averaged climate conditions and will not be exposed for wind re-suspension

As the result of the water level decline the area covered about % of the bottom sediment territory may be dried and exposed for wind human access. The new artificially forming bottom sediment relief will be created by the 3 types - always dry - always covered by water - intermediate wetland (dried or wet) depend of water mode and climate conditions) Bottom landscape transformation The geochemistry of the wetland lakes will be transformed. рН will be reduced and NH 4 will be increased The radionuclides in the water column will be increased

Effects of the Groundwater drawdown The groundwater water table will be reduced at mane places around the cooling pond from 1 to 7 m of present The ground water flow directions will be also changed. The effects of the groundwater level declining in the CP will create positive effects in regarding of the number of temporary waste disposal sites situated around and also is beneficial for Chernobyl NPP New Safe Confinement Bugai D., Skalsky A. 2001

The effects of re-suspension at the different simulated wind effects resulting as to be local and may increase contamination of the surrounding areas no more then 5-10 % of existing contamination level Possible effects of particles atmospheric dispersion Cs-137 Fall out effects Kashparov et al. 2004

Radiation expose effects NO significant effects for personnel, working at the Chernobyl NPP site due to effect of wind re-suspension or grass fire at the CP (less 1 mSv a year)

Evaluation of the remediation strategies 8 different remediation strategies were considering in case of water declining at the CP 5 level of score evaluation were applied ( «0» – not acceptable -- «5» fully acceptable) The three time frame period were considered 1.From present until water level will be declined (4-6 years) 2.From the end of period 1 to the year when bottom sediment will be stabilized due to natural succession ( natural attenuation – 7-12 years after starting of water declining) 3.From after years and for the all period of institutional control.

The Attributes A - Dose to normal members of the public, from normal operations B - Dose to normal members of the public, as a result of a low probability event such as tornado or dam break. C - Dose to people working at ChNPP industrial zone, from normal operations D - Dose to people working at ChNPP industrial zone, as a result of a low probability event such as tornado or dam break. E - Dose to workers implementing remedial action on the pond, from normal operations F - Dose to people working at ChNPP industrial zone, as a result of a low probability event such as tornado or dam break. G - Local ecology H - Ease of implementation I - Sustainability i.e. the need for future human action J - Ukrainian legal requirements K - Cost

Selection of the best practicable option The Options Option 1Maintenance of the current pond water level Option 2Do nothing, stopping the pumps and allowing the natural drainage of the pond Option 3Planting of the exposed area with the appropriate vegetation, i.e. phytoremediation Option 4Spray the exposed area with a chemical dust suppressant Option 5Transfer the contaminated sediment into the remaining pond using high pressure water sprays, bulldozing or dredging Option 6Cap the contaminated sediment with sand taken from the Pripyat flood plain Option 7“Partial Remediation”, i.e. remediation of the most contaminated sediments by removing them and placing in the waste repository. The most contaminated sediments are located in an area of approximately 1 km 2. Option 8“Complete Remediation”, i.e. the removal and disposal of all contaminated sediments.

Multi-Attributive analyses matrix ATTRIBUTES OPTIONS A – Public dose – Normal B – Public dose – Accident C – Worker dose – Normal D – Worker dose – Accident E – Implementer dose – Normal F – Implementer dose – Accident G – Environmental impact H – Ease of implementation I – Sustainability J – Ukrainian legislative requirements 53 (Uncertain); K – Cost 0 53 (There is a significant uncertainty) 0 0 Not at all acceptable 1 Significant disadvantages or problems 2 Many disadvantages or problems 3 Some disadvantages or problems 4 Acceptable but with slight disadvantage 5 Perfectly acceptable

Conclusions Radiological Risks associated with decommissioning of ChNPP for population living along the Dnieper River is low. Engineering and economical Risks to keep the status-quo option for CP are feasible. Once the ChNPP has no further requirement for the Cooling Pond in its current capacity, the carried out studies concludes that the decommissioning of the Cooling Pond should begin. This involves simply stopping supporting the water level, by halting water pumping from the Pripyat River. Transition period of the water infiltration may take 5-7 years, since the current CP will be transformed in to the new ecosystem

Conclusions and Recommendation Preliminary assessment show that combination of OPTIONS Do nothing and “Partial Remediation”, i.e. remediation of the most contaminated sediments ( relatively small areas 0,1-0,5 km 2 by removing them and placing in the waste repository can be reasonable. The cheapest option should be selected to prevent re-suspension from the exposed sediments before natural vegetation covers the exposed sediment, The regulatory provisions and establishing requirements for remediation strategies and long-term institutional control to be harmonized with Chernobyl NPP exclusion zone prospective New transformed ChNPP cooling pond ecosystem will pose a unique natural ecosystem laboratory. Therefore radioecological studies should be initiated with involvement of the international cooperation and funding

Flow Chart Summarizing Recommended Actions in the Feasibility Study of the Cooling Pond Decommissioning

Potential projects in Support of Chernobyl CP Decommissioning

Cooperation challenges The Ch.CP can be used as Investigation Reserve areas Unique Case study (Analogue Sites) Hot particle speciation (long-term speciation) Succession process and self-remediation Ecosystem transformation and Radiobiological long term biological and ecosystem effects Natural attenuation process as an effective element of the waste management practice Regulatory provisions (radiological and ecological) and Institutional control practice (experience and training) Remediation and clean-up technology can be tested Best experience can be transferred (Savanah-River, Hanford site and other)

Acknowledgements All partners from the previous national and international projects contributing their efforts and data to this study: D.Bugay, A.Skalsky, V. Kanivets, S. Kireev, G. Laptev, V. Kashparov, A. Konoplev, A. Bulgakov, M.Zheleznyak, J.Smith, Y.Onishi, B.Faibishenko et.al. Many thanks to Chernobyl NPP authority and Administration of the Chernobyl Exclusion zone for supporting of the pre-FS on future CP remediation project and monitoring programs at the Chernobyl Cooling pond Special thanks to IAEA supported IAEA Workshop Summary and Recommendations of the IAEA Expert Group Related to the Chernobyl Cooling Pond Roadmap for Decommissioning and Remediation and participation in WM-2010

Thank you for attention UHMI, Nauki prospect, 37. Kiev Ukraine