1. Radioecological research during 25 years after the Chernobyl accident
Sweden Society Radioecology Conference , of March
The Dnieper River Aquatic System Radioactive Contamination; 25 Years of Natural Attenuation and Remediation
Voitsekhovych Oleg
Dear colleagues:
First of all, I appreciate very much an opportunity to give a presentation to the ISCMEM Working Group on modeling and parameter estimation. After my presentation to ASCMEM 3 months ago, I obtained a number of valuable comments and suggestions, which I addressed in a revised version of the proposal.
During the coming years, a management and remediation strategy for the Chernobyl cooling pond (CP) will be implemented. Remediation options include a controlled reduction in surface water level of the cooling pond and stabilisation of exposed sediments. In terrestrial soils, fuel particles deposited during the Chernobyl accident have now almost completely disintegrated. However, in the CP sediments the majority of 90Sr activity is still in the form of fuel particles. Due to the low dissolved oxygen concentration and high pH, dissolution of fuel particles in the CP sediments is significantly slower than in soils. After the planned cessation of water pumping from the Pripyat River to the Pond, significant areas of sediments will be drained and exposed to the air. This will significantly enhance the dissolution rate and, correspondingly, the mobility and bioavailability of radionuclides will increase with time. The rate of acidification of exposed bottom sediments was predicted on the basis of acidification of similar soils after liming. Using empirical equations relating the fuel particle dissolution rate to soil and sediment pH allowed prediction of fuel particle dissolution and 90Sr mobilisation for different remediation scenarios. It is shown that in exposed sediments, fuel particles will be almost completely dissolved in years, while in parts of the cooling pond which remain flooded, fuel particle dissolution will take about a century.
Head of Environment Radiation Monitoring Department.
Ukrainian Hydrometeorological Institute. Kiev Ukraine

2. Scope of presentation Introduction
1. Radionuclide release and deposition
2. Radioactive contamination of the catchments and aquatic environment
physical and chemical forms of radionuclides and its transformation
radionuclides in the aquatic systems
surface waters (rivers and reservoirs),
groundwaters in the Chernobyl exclusion zone
marine system (Black Sea and global context)
3. Assessment of the water protection countermeasure
Initial phase
Intermediate phase
Later phase and current situation
Chernobyl cooling pond decommissioning project
4. Radiation Dose and Risk assessment. Public perception and Assessment of the countermeasure effectiveness.
5. Lesson learned
Key natural attenuation processes
Developments and validation of radionuclide transport model
Environment Radiation Monitoring strategies and methods development
Risk Assessment and Risk management at the radioactive contaminated lands.
Emergency preparedness aspects
Chernobyl Isotopes applications as markers for Environment studies

3. Introduction
Twenty five years ago, an unprecedented large amount of radionuclides were released into the environment due to the major accident at Unit 4 of Chernobyl NPP. As a result, the catchment areas and water bodies of the Dnieper River Basin (third largest aquatic system in a Europe) had been significantly contaminated, primarily due to 137Cs and 90Sr.
In some cases, the level of radionuclides contamination in the water bodies returned to pre-accident conditions within the first decade following the accident, some aquatic ecosystems remained highly contaminated.
This report presents the past twenty five year time-series data of water body contamination in Ukraine and the dynamic impacts caused by natural factors and human activities in the Chernobyl affected areas.
This overview is trying to find answer on a question. What Have We Learned ?, assessing some successes and failures to mitigate water contamination over post-accidental years

4. Media in the first weeks
The information in
Media in the first weeks
since the Accident
did not described
adequately an actual
situation
On April, 26
1986
01:24
Слайд №2 АВАРИЯ
26 апреля в 01:24 произошли взрывы в реакторе. Практически одновременно были разрушены реактор и все барьеры безопасности. РИС.1 Взрыв сопровождался пожаром активной зоны и кровли машинного зала и Ш-го блока. 6

5. Chernobyl Accident is the Highest Single Release of Radionuclides into the Global Environment
Europe
Ukraine
Airborne radionuclide transport >200,000 km2 of Europe with 137Cs >37 kBq/m2 (1 Ci/km2).
Fuel particles—finely dispersed, low volatility, settled primarily within the ChEZ
Condensed components—from radioactive gases, settled primarily along the atmospheric flow pathways
Hot particles—fuel particles, uranium dioxide, with a specific activity >105 Bq/g, size 1 to 100 µm, surface density ~ 1,600 per m2, to ~0.5 m depth
Chernobyl is located in the Northern Ukraine near the border with Belarus and Russia.
The Chernobyl nuclear reactor accident at the Chernobyl Nuclear Power Plant in the former Soviet Union was the worst nuclear power plant accident in history and the only instance so far of level 7 on the International Nuclear Event Scale, resulting in a severe release of radioactivity into the environment.
Most of the strontium radioisotopes were deposited within 100 km of the destroyed reactor, because they were released as large-size fuel particles, and then precipitated not far from the reactor.
Cesium was released in the form of radioactive gases, which were distributed by wind long distances from Chernobyl. More than 200,000 km2 of European territory received levels of 137Cs1 above 37 kBq m2 (1 Ci km2). Over 70% of this area was in the three most affected countries, Belarus, Russia and Ukraine. No more than 20% of the radioactive release spread beyond Europe (De Cort et al., 1998).
Immediately after the accident, the exclusion zone within the radius of 30 km from the ChNNP was established to prevent further access after the accident. However, as more measurements of the level of contamination over a larger territory were made, the boundary of the exclusion zone was adjusted to prevent access to highly contaminated areas. Its total area within the Ukrainian borders, except for part of the Kiev reservoir, is 2,044 km2
Another typical feature of the Chernobyl accident is the release of so called hot particles, which are mostly fuel particles of uranium dioxide.
Note that climate in the Chernobyl Region is humid with mild, short winters having frequent thaws, and warm summers.
Average annual precipitation from 550 to 750 mm/year
Average annual temperature from 5oC to 7oC
min monthly average -35oC
max monthly average 39oC
Groundwater depth is 2-3 m 5

6. Uncertainties in Assessment and needs for experimental verification of the accidental consequences.
Radionuclide transport studies due to Runoff, sampling at the contaminated lands and water bodies

7. Specific phenomenon of the Chernobyl radioactive release --- significant amount of nuclear fuel particles were dispersed to the environment and deposited on catchment’s soils and bottom sediment of the affected water bodies
UOx matrix fuel particle
Fuel particle X-ray microanalysis spectrum of Zr-U-O fuel particles (Ahamdach 2000)
U-Zr-O matrix fuel particle
Median size of fuel particles ~ 4-6 m
Till 2000 about 70% of radionuclide activity was associated with hot particles particles (2000)
In 2008 most of particles in the soils of river water catchments have been destroyed due to weathering impact and chemical leaching, while significant amount of the “hot particles” still remained in the bottom sediment of lakes around ChNPP.
from Kashparov at al, 2003

8. Geochemical Conceptual Model of the fuel hot particles behavior in soils and bottom sediment
Low DO and high pH cause a very slow dissolution of fuel particles in bottom sediments.
Weathering effects, vegetation and microbiological are causing significant effects onto the hot particles physical structure In soils and dried wetlands increasing its dissolution rate.
Fuel particle dissolution will take ~15–25 years in exposed sediments, and ~100 years in flooded areas
The physical and chemical form of radionuclide transformation in the catchments' soils and bottom sediment allow to achieve significant progress developing radionuclide water transport models from the contaminated watersheds and river systems
J Environ Radioact Apr;100(4):p
Fuel particles in the Chernobyl cooling pond: current state and prediction for remediation options.
Bulgakov A, Konoplev A, Smith J, Laptev G, Voitsekhovich O.
Before showing the results of predictions of contaminant transport, I’d like to briefly discuss the geochemical processes affecting contaminant transport.
Low DO and high pH cause a very slow dissolution of fuel particles in the cooling pond sediments.
After the sediments are exposed, vegetation and microbiological activity will acidify newly formed soils, causing the dissolution rate to increase.
It is expected that dissolution of fuel particles will take ~15–25 years in exposed sediments, and ~100 years in flooded areas.

9. Radioactive contamination of the catchments and aquatic environment as versus of fallout formation date, its physical and chemical forms and also the landscapes at the deposited river watersheds
Calculated plume formation according to meteorological conditions for instantaneous releases on the following dates and times (GMT): (1) 26 April, 00:00; (2) 27 April, 00:00; (3) 27 April, 12:00; (4) 29 April, 00:00; (5) 2 May, 00:00; and (6) 4 May, 12:00
(Borsilov and Klepikova 1993).
137Cs activity concentration in different rivers per unit of deposition, Smith, 2004

10. Radionuclides in Rivers
Ratio of 90Sr and 137Cs in soluble forms in Pripyat River near Chernobyl
Annual fluxes of 137Cs in the Dnieper River
1012 Bq Radionuclide inlet to the Kiev reservoir. Pripyat River
Desna River
Rain flood
Winter ice jam
Spring flood
Spring flood
Data of Ukr. Hydromet. Institute

11. Return water running off from floodplain and drainages
Wash-out phenomenon for 137Cs and 90Sr
Pripyat River Flood 1999
Return water running off
from floodplain and drainages
90Sr
Wash-off Snow
melting effect
Radionuclides runoff budget in the Pripyat river show 10-20% of Cs and 40-70% of Sr have contributing by contaminated waters washed out from the ChNPP zone
90Cs

12. Pripyat River Floodplain around Chernobyl NPP was most heavy contaminated and identified as most significant source of the Dnieper system 90Sr-90 secondary contamination
1986
Flood protective dam has been constructed
Site characterization studies and modeling results show that most efficient water protection strategy will be to control water level and to mitigate inundation of the most contaminated floodplains by the flood protection sandy dykes constructed at left and right banks of the Pripyat river
1993
1999

13. Annually averaged 90Sr activities in water of the Pripyat River downstream of Chernobyl town and effects of water contamination reduction due to construction of the protective dams, preventing flooding of the most contaminated floodplain area near NPP riverside in 1993
Before protective dam constructed
1987
1993
After protective dam constructed in 1993
2009

14. Radionuclides in the closed lakes of the most contaminated areas around Chernobylа
137Cs and 90Sr in Gluboky lake near Chernobyl NPP
Radionuclides in water of the Chernobyl cooling pond,
Data of Chernobyl Ecocenter

15. TRWDS Temporary Radioactive Waste Disposal Sites
are significant sources of the shallow ground water contamination
Its characterization and step by step removal to the specially organized places for long-term safe storage at the Radioactive Waste Reprocessing Plant become significant element of Environment Remediation Strategy at the Chernobyl Exclusion zone reducing their influence on further long-term ground waters contamination
NNC,2001

16. Schematic trench cross-section
Chernobyl Pilot Site – “worst case” scenario of near-surface radioactive waste disposal
Trench Studies TRWDS (PVLRO “ Red Forest)
Bugay at al, 2003.
Schematic trench cross-section

17. Monitoring and Simulation of 90Sr Distribution in Groundwater
In some places 90Sr activities concentrations in the ground waters adjacent to TRWDS are continuing to growth.
Those, its moving toward the Pripyat river are very slow (1-10 m per year).
90Sr will reach the Pripyat River in ~50-60 yr from now,
However, even in case contaminated groundwater front will reach the river its flux contribution will be insignificant to the Pripyat River radioactive contamination at this time.
In any case observations on the groundwater regime and its contamination trends will be continued for a long time
90Sr in the groundwater TRWDS “Sand Plato” near Pripyat River (Kiereev et al. 2006)
Based on the results of modeling, Sr flux in groundwater is expected to be different at different locations witin the ChEZ, and it is expected that Sr will reach the Pripyat river in~800 years, so that its concentration will reduce to an ind=significant level by that time. I’d like to note that these predictions are not conservative, as the aquifer heterogeneity was not taken into account.
Bugai et al. 1996

18. Effects of the Groundwater level drawdown
ChNPP NSC
Predicted 90Sr concentrations in the aqueous phase without NSC after 100 yr.
Distance toward the Pripyat River from NSC
The groundwater water table will be reduced at mane places around the ChNPP Cooling pond from 1 to 7 m of present since it will be decommissioning
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 lowering inundation levels at Chernobyl NPP NSC (New Safe Confinement) site
Bugai D., Skalsky A. 2001

19. 90Sr in the waters of the Dnieper’s reservoirs
90Sr in the reservoirs of the Dnieper cascade is still above of its pre-accidental levels observed in 2010 in range Bq m-3 ( the same levels as were observed during 2002

20. 137Cs in the waters of the Dnieper reservoirs
137Cs activity concentration in water at the lowest reservoir returned to its pre-accidental level still in
In Cs activities in Kiev (upper reservoir) in a cascade were observing in range Bq m3, while in Kakhovka (lower reservoir) -- 0,5-1,0 Bq m3

21. 137Cs in the bottom sediments of Reservoirs
Dnieper
Upper part of Kiev Reservoir
Pripyat River
2009
Low part of Kiev Reservoir
1994
137Cs
Kremetchug reservoir bottom, 1994
Dam near Kiev

22. 137Cs in freshwater fish and other aquatic biota
137Cs in predatory and non predatory fish species in Kiev reservoir. (after I.Ryabov et al., 2001)
Gudkov, et al. 2008)
137Cs and 90Sr in predatory and non-predatory fish species. Gluboky Lake

23. Gluboky Lake Published by D.Gudkov et al. 2008
Absorbed dose rate caused by incorporated radionuclides in the algae and non-predatory fishes.
Published by D.Gudkov et al. 2008
Averaged chromosome aberration rates in the fresh water lake mussels in the lakes of the ChNNP area and in the reference clean lakes near Kiev

24. Summary. Long-term doses from aquatic pathways.
Human exposure via the aquatic pathway took place as a result of consumption of drinking water, fish catch in reservoirs and agricultural products grown using irrigation water from Dnieper reservoirs.
In the middle and lower areas adjacent to the Dnieper reservoirs, which were not significantly subjected to direct radionuclide contamination in 1986, a significant proportion (10–20%) of the Chernobyl exposures were attributed to aquatic pathways.
Estimates were that individual doses via aquatic pathways would not have exceeded 1–5 μSv y-1.
Furthermore, in some closed lakes, the concentration of 137Cs remains high and high levels of contamination are found in fish species. People who illegally catch and eat contaminated fish may receive internal doses in excess of 0,5-1 mSv per year from this source.
The most significant individual dose was from 131I and was estimated to be up to 0.5–1.0 mSv for the citizens of Kyiv during the first few weeks after the Chernobyl accident.

25. Aquatic pathway of Radiation Risk forming and its Public perception
Dose realization (%) during a 70 years for children born in 1986
Aquatic pathway of Radiation Risk forming and its Public perception
For 1-st year about 47 %
For 10 years about 80%
From I.Los, O.Voitsekhovych, 2001
Years
In spite of doses were estimated to be very low, there was an inadequate understanding of the real risks of using water from contaminated aquatic systems.
This created an (unexpected) stress in the population concerning the safety of the water system. This factor made reasonable to provide assessment of collective commitment doses as a basis for justification of some water protection actions
Actual dose
Public perception about
Food product, milk water external inhalation

26. Long-term probabilistic assessment of the Dnieper River contamination -- as a basis for collective dose simulation
Estimates were made of the collective dose to people from these three pathways for a period of 70 years after the accident, i.e. from 1986 to 2056
A long-term hydrological scenario was analysed using a computer model (Zheleznyak et al 1992).
Historical data were used to account for the natural variability in river flow.
Dose-assessment studies were carried out to estimate the collective dose from the three main pathways (Berkovski et al 1996),.
Concentration of 90Sr (1 pCi = 3,7 *10-2 Bq) in water of the upper and downstream reservoirs for the worst (top) and best probabilistic hydrological scenarios to be possible expected at the Dnieper reservoirs (Zheleznyak et al., 1997).

27. Kremetchug reservoir as a function of years after 1986
Collective effective dose for Kyiv region population due to water consumption from Kiev reservoir usage pathways as a function of years after 1986
Collective effective dose for Poltava region population due to water usage pathways from
Kremetchug reservoir as a function of years after 1986

28. COLLECTIVE DOSE COMMITMENT (CDC70) CAUSED BY 90SR AND 137CS FLOWING FROM THE PRIPYAT RIVER (BERKOVSKY ET AL. 1996)
Dose estimates for the Dnieper system show that if there had been no action to reduce radionuclide fluxes to the river, the collective dose commitment for the population of Ukraine (mainly due to Cs and Sr) could have reached 3000 man Sv.
Protective measures, which were carried out during 1992–1993 on the left-bank flood plain of the Pripyat River and later on right bank (1999) decreased exposure by approximately 1000 man Sv. (Voitsekhovich et al. 1996).

29. Water protection and Remediation
Many remediation measures during initial period after the accident ( ) were put in place, but because actions were not taken on the basis of dose reduction, most of these measures were ineffective.
Because of the importance of short lived radionuclides, early intervention measures, particularly changing supplies, can significantly reduce doses to the population, mainly because 131I. However this opportunity has been missed during first month since the accident.
During first months after the accident restrictions on fishery and irrigation from the contaminated water bodies have been established. The number of water regulation actions at the small river in the Chernobyl exclusion zone were applied.
Numerous countermeasures put in place in the months and years after the accident to protect water systems from transfers of radioactivity from contaminated soils were, in general, ineffective and expensive and led to relatively high exposures to workers implementing the countermeasures.
The water regulation at the most contaminated floodplains and water runoff regulation from the wetlands in the close zone around ChNPP only can be considering as effective.

30. Decommissioning of the Chernobyl Cooling Pond
Decommissioning means:
Restore Monitoring network
Stop water pumping from the river
Separating the inflow and outflow channels (to use as fire reservoir)
Construct alternative source of cooling water--groundwater pumping wells
Declining water from the CP (filtration)
Remediation of the remained bottom area if needed. Institutional control.
ChNPP
Pripyat River
Water level above the sea
Of particular interest to scientists and engineers is the problem of decommissioning and remediation of the Chernobyl Cooling Pond. The pond is located within the watershed of the Pripyat River--between the CHNPP and the river. Its areal extent is ~ 22 sq km.
To maintain the water level in the pond, water is continuously pumped from the river to the pond. The released particles precipitated at the pond water surface, resulting in severe contamination of water and bottom sediments, mainly by Sr, Cs, and plutonium.
The pond decommissioning will involve stopping pumping water to the pond, and separating the NPP inflow and outflow channels from the pond. It is clear these actions will cause the decline in the water level in the pond and exposure of fine-structure highly contaminated bottom sediments.
Days after start point 30

31. Bottom Sediment landscape transformation
The geochemistry of the wetland lakes will be transformed.
рН will be reduced and NH4 will be increased
The radionuclides in the water column will be increased
As the result of the water level decline the area covered about 60-70% 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)

32. Radionuclides in the bottom sediment (UHMI, 2005)
90Sr
239,240Pu
According to UHMI report in the CP is currently accumulated about
280 TБк 137Cs, TБк 90Sr and ,75 TБк Pu
The major activities of these radionuclides accumulated at the depth deeper of 7 meters and will remain flooded in a new transformed water ecosystem

33. Possible effects of soil particles atmospheric dispersion and fire
The effects of re-suspension to be local and may increase contamination of the surrounding areas no more then 5 % of existing contamination level.
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)

34. Conclusions
Radiological Risks associated with decommissioning of ChNPP for population living along the Dnieper River is negligible.
Transition period of the water infiltration may take 5-7 years, since the current CP will be transformed in to the new ecosystem
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 km2 by removing them and placing in the waste disposal site can be reasonable .
Natural attenuation process such as natural vegetation covers of the exposed sediment to be most reasonable selected remediation strategy.
New transformed ChNPP cooling pond ecosystem will pose a unique natural ecosystem laboratory.
It is still uncertain understanding how fast new transformed ecosystem will be restored as wetlands with a new sustainable conditions

35. From Chernobyl Forum, 2005 to 2011
International Conference 25 Years after Chernobyl, Kiev
Идея информации на этом слайде предполагает обратить внимание Board на то, что на Чернобыльском Форуме 2005 к 20-летию Чернобыльской аварии, эксперты всего мира, изучив проблему совместно с МАГАТЭ подготовили рекомендации, относительно развития реабилитационных программ, будущего восстановления зоны отчуждения ЧАЭС.
Некоторые выдержки из этих рекомендаций приводятся на слайде.
В частности, отмечается, что еще далека до совершенства практика обращения с РАО в зоне ЧАЭС и окончательно ясной стратегии обращения нет.
Так же были затронуты вопросы будущей стратегии обращений и использования объектов окружающей среды и самой территории ( это все на слайде)
В связи с тем, что приближается 25 годовщина, а очередной Форум состоится весной 2011 в Киеве, разумно было бы с использованием экспертов сети ENVIRONET провести международную оценку, насколько за последние 5 лет мы продвинулись в решении этих проблем и возможно пересмотреть некоторые рекомендации, подготовленные экспертами 5 лет назад.
Следует отметить, что к сожалению, большинство ранее активных международных программ по изучению долговременных радиоэкологических последствий для окружающей среды аварийного загрязнения ЧАЭС в последнее десятилетие были свернуты.
Важно восстанавливать сотрудничество. ENVIRONET может помочь и, в частности, используя эту территорию для тестирования реабилитационных стратегий и технологий. Это обсуждалось на предыдущем слайде
What has been changed ?

36. Radionuclides in the Black Sea
After Chernobyl 137Cs inventory in the 0-50 m layer increased by a factor of 6-10 and the total 137Cs inventory in the whole basin increased by a factor of at least 2 ( pre-Chernobyl value of 1.40.3 PBq)
137Cs input from the Danube and the Dnieper rivers (0.05 PBq in the period ) was insignificant in comparison with the short-term atmospheric fallout.
The contribution of Chernobyl-origin 137Sr from atmospheric fallout was estimated at PBq.
At the same time, a relatively important input of 90Sr from the Dnieper and Danube Rivers was observed.

37. Sediments/Water Fluxes
137Cs and 90Sr vertical distributions in the Western Black Sea deep-water basin (1998 and 2000)
Sediments/Water Fluxes
137s

38. Vertical profile of Radiotracers
137Cs activity and 238Pu/ 239,240Pu activity ratio profiles in deep-sea sediment core BS2K-11 (water depth 1880 m), 2002
137Cs in core BS98-03 illustrate a history of sedimentation typical of riverine suspended particles deposited near the Danube River Delta

39. The result illustrates the low sedimentation rates, the upper peak of 137Cs corresponding to the Chernobyl input (1986) and the lower one to the time of maximum input from global fallout in the early 1960s.
Black Sea Cruise 1998
1986 (89)
ChNPP
NW Tests
1963 (66)
Resolution of the core cutting method is 5-7 slices for 1 cm of the bottom sediment core

40. Environment Radiation Monitoring Findings
ERM should be a tool for decision making
ERM should be Task and Site specific
Sampling programs to be based on screening assessment and also have adequately designed according to the tasks, expected way of the data utilization and regulatory requirements
Parameters for analytical measurements have to be corresponded with source term analyses and strategies for Safety or Environment Assessment .
QA/QC principles to be obligatory for all partners of the ERM programs
Data reporting and Data management should be well coordinated, agreed and based on DPSIR principles
DPSIR = Drivers, Pressures, States, Impacts and Responses

41. Network of Monitoring Stations and Wells in the ChNPP close-in zone.
Schematic of Monitoring Wells н н и и й й ” ”
40 cross sections and aerosol pump stations;
138 wells, 2 water supply stations;
4 stations of surface water and bottom sediments
Chernobyl Ecocenter, S. Kireev.

42. Groundwater Modeling VisualModflow and MT3D96 codes
Regional model of the Chernobyl exclusion zone and a 2D cross-section model
Pond
Modeling was conducted using well known codes Modflow and MT3D96 for different environmental scenarios, using both regional and 2D vertical cross-section groundwater flow models.
The models area is ~3 by 3 km, the mesh was from 30 by 30 m to 500 by 500 m.
Here is an example of the results of modeling showing the spatial distribution of infiltration/water loss over the modeled area. Witin the pond area, infiltration is from 200 to 250 mm per year, which is the same
Infiltration model
After Bugai et al.

43. Surface Water Modeling
Radionuclide transport modeling codes RIVTOX, COASTOX and THREETOX developed in IMMSP of the National Academy of Sciences of Ukraine
Water Quality Analysis Simulation Program (WASP)--EPA framework for modeling contaminant fate and transport in surface water.
Now about the surface water modeling.
WASP is a dynamic compartment-modeling program for aquatic systems, including both the water column and the underlying benthos. WASP allows the user to investigate 1D, 2D, and 3D surface water systems, and a variety of pollutants with the time-varying processes of advection, dispersion, point and diffuse mass loading and boundary conditions, along with hydrodynamic and sediment fluxes.
Kd depends on the N ammonia concentration (M. Zheleznyak et al., (2005)—INTAS Project Report “Radionuclide and Sediment Transport Modelling Within the Cooling Pond Ecosystem“)
Zheleznyak et al., 2002; Maderich et al, 2005

44. Processes Affecting Radionuclide Transport in the lake-reservoir systems
Microbial communities
Suspended sediments
Advection
Uptake
Adsorption
Radionuclides in
suspended sediments
Diffusion/Dispersion
Dissolved radionuclides
Desorption
Resuspension
Adsorption
Desorption
Sedimentation
Radionuclides in bottom sediments
Modified after M.Zheleznyak
Do We Have Reliable Monitoring and Modeling Tools?

45. Modeling of Cooling pond Dam Break and Sr-90 release
Floodplain
Chernobyl NPP
Cooling
pond
Extensive work was performed for assessing the contaminant transport during floods.
M. Zheleznyak et al. 2005

46. Some conclusive comments
Basic knowledge of geological, hydrological and ecosystem peculiarities at the area of potential radiation impact allows to select right strategy on imitative and environment protection
Any countermeasure and remediation planning must be based on detailed monitoring data and exhausting site characterization results.
Scientifically defensive assessment tools and required data must be developed and applied
Countermeasure and remediation selection must be based on a cost-risk analyses that directly connects the main physical and chemical processes to environment (ecosystem) or human heath risks and costs
Decision makers must be knowledgeable on phenomena being evaluating, they should efficient use expert’s experience and expert’s analytical and modeling systems, which can help to accept right and reasonable decisions aiming to mitigate or prevent expose of people and also allow to safe as always limited resources available , when measures can not be justified or may be postponed.
Decision makers must communicate facts quickly and honestly to the affected public

47. Acknowledgements
This this comprehensive overview is based on the results taken from number of previous national and international projects, which have been implementing with contribution of many people during recent 25 years.
Special thanks to:.
G. Laptev, V.Kanivets, A. Kostezh, L.Pirnach, S.Todosienko (UHMI)
and also appreciate to our colleagues:
D.Bugay, A.Skalsky (Institute Geological Sciences)
S. Kireev ( Chernobyl Centre),
V. Kashparov (Institute agriculture radioecology)
Konoplev, A. Bulgakov, (SPA, “Typoon”)
M.Zheleznyak, (IPMMS)
V.Berkovsky ( IRP)
O.Nasvit and D.Gudkov (IGB)
Many thanks to all analyst, engineers and technicians, which contribution to field and analytical studies make possible this syntheses and analyses
Many thanks to Chernobyl NPP authority and Administration of the Chernobyl Exclusion zone for supporting remediation projects and monitoring programs at the Chernobyl exclusion zone

48. Thank you very much for your attention
UHMI, Nauki prospect, 37. Kiev Ukraine