Radioecological research during 25 years after the Chernobyl accident Sweden Society Radioecology Conference , 22-23 of March. The Dnieper River Aquatic System Radioactive Contamination; 25 Years of Natural Attenuation and Remediation. Voitsekhovych Oleg.
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Sweden Society Radioecology Conference , 22-23 of March
Head of Environment Radiation Monitoring Department.
Ukrainian Hydrometeorological Institute. Kiev Ukraine
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
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
Media in the first weeks
since the Accident
did not described
adequately an actual
On April, 26
Chernobyl Accident is the Highest Single Release of Radionuclides into the Global Environment
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
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
J Environ Radioact. 2009 Apr;100(4):p.329-32..
Fuel particles in the Chernobyl cooling pond: current state and prediction for remediation options.
Bulgakov A, Konoplev A, Smith J, Laptev G, Voitsekhovich O.
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
Ratio of 90Sr and 137Cs in soluble forms in Pripyat River near Chernobyl
Annual fluxes of 137Cs in the DnieperRiver
1012 Bq Radionuclide inlet to the Kiev reservoir. Pripyat River
Winter ice jam
Data of Ukr. Hydromet. Institute
Pripyat River Flood 1999
Return water running off
from floodplain and drainages
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
Pripyat River Floodplain around Chernobyl NPP was most heavy contaminated and identified as most significant source of the Dnieper system 90Sr-90 secondary contamination
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
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
After protective dam constructed in 1993
137Cs and 90Sr in Gluboky lake near Chernobyl NPP
Radionuclides in water of the Chernobyl cooling pond, 1986-2009
Data of Chernobyl Ecocenter
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
Trench Studies TRWDS (PVLRO “ Red Forest)
Bugay at al, 2003.
Schematic trench cross-section
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)
Bugai et al. 1996
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
90Sr in the reservoirs of the Dnieper cascade is still above of its pre-accidental levels observed in 2010 in range 40-100 Bq m-3 ( the same levels as were observed during 2002
137Cs activity concentration in water at the lowest reservoir returned to its pre-accidental level still in 1996-1998.
In 2010 137Cs activities in Kiev (upper reservoir) in a cascade were observing in range 10-20 Bq m3, while in Kakhovka (lower reservoir) -- 0,5-1,0 Bq m3
Upper part of Kiev Reservoir
Low part of Kiev Reservoir
Kremetchug reservoir bottom, 1994
Dam near Kiev
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
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
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.
For 1-st year about 47 %
For 10 years about 80%
From I.Los, O.Voitsekhovych, 2001
Public perception about
Food product, milk water external inhalation
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).
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
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 reached3000 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 approximately1000 man Sv.(Voitsekhovich et al. 1996).
Water level above the sea
Days after start point
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)
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
According to UHMI report in the CP is currently accumulated about
280 TБк 137Cs, 42 TБк 90Sr and 0,75 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
Preliminary assessment show that combination of OPTIONS
International Conference 25 Years after Chernobyl, Kiev
What has been changed ?
137Cs activity and 238Pu/ 239,240Pu activity ratio profiles in deep-sea sediment core BS2K-11 (water depth 1880 m), 2002
137Cs in core BS98-03illustrate a history of sedimentation typical of riverine suspended particles deposited near the Danube River Delta
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.Resolution of the core cutting method is 5-7 slices for 1 cm of the bottom sediment core
Black Sea Cruise 1998
DPSIR = Drivers, Pressures, States, Impacts and Responses
Schematic of Monitoring Wells
Chernobyl Ecocenter, S. Kireev.
After Bugai et al.
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.
Kd depends on the N ammonia concentration (M. Zheleznyak et al., (2005)—INTAS-2001-0556 Project Report “Radionuclide and Sediment Transport Modelling Within the Cooling Pond Ecosystem“)
Zheleznyak et al., 2002; Maderich et al, 2005
Processes Affecting Radionuclide Transport in the lake-reservoir systems
Radionuclides in bottom sediments
Modified after M.Zheleznyak
Do We Have Reliable Monitoring and Modeling Tools?
Modeling of Cooling pond Dam Break and Sr-90 release
M. Zheleznyak et al. 2005
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)
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
UHMI, Nauki prospect, 37. Kiev 03028. Ukraine