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Retrospective Evaluation of the Source-Term for Techa River Contamination

#2841


Retrospective Evaluation of Radioactive Discharges into the Techa River on the Basis of Radioecological Monitoring and Dosimetric Modeling Data

Tech Area / Field

  • ENV-WPC/Water Pollution and Control/Environment
  • ENV-MIN/Monitoring and Instrumentation/Environment
  • ENV-MRA/Modelling and Risk Assessment/Environment

Status
8 Project completed

Registration date
28.07.2003

Completion date
11.11.2009

Senior Project Manager
Kulikov G G

Leading Institute
Ural Research Center of Radiation Medicine, Russia, Chelyabinsk reg., Chelyabinsk

Supporting institutes

  • VNIITF, Russia, Chelyabinsk reg., Snezhinsk\nNPO Mayak, Russia, Chelyabinsk reg., Oziorsk\nInstitute of Plants & Animals Ecology, Russia, Sverdlovsk reg., Ekaterinburg

Collaborators

  • Forschungszentrum für Umwelt und Gesundheit GmbH (GSF) / Institut für Strahlenschutz, Germany, Neuherberg\nPacific Northwest National Laboratory / Environmental Technology Division, USA, WA, Richland\nNational Radiological Protection Board, UK, Chilton\nSENES Oak Ridge Inc. / Center for Risk Analysis, USA, TN, Oak Ridge\nThe University of Utah / Radiobiology Division, USA, UT, Salt Lake City

Project summary

The primary objectives of this project are retrospective investigations of liquid radioactive releases from the “Mayak” weapon plutonium facility (now Mayak Production Association) into the Techa River. Such information on source term (including total amount of radionuclides released, rate of release as a function of time, radionuclide composition, and chemical forms of radionuclides) is very important both for Techa River residents’ dose reconstruction, and for uncertainty assessment.

Dr. D. Ilyin carried out first assessments of source term for liquid radioactive releases into the Techa River in 1956 [1]. These evaluations should be considered as retrospective [2] because major releases were in the period 1950-1951, but the first release monitoring data were obtained in autumn 1951 shortly before the sharp reduction of releases into the Techa River, and have occasional character. Mayak PA experts in 1990s confirmed evaluations by Ilyin without any revision [3]. Later, a hypothesis was made [4] that the total amount and radionuclide composition of releases could greatly differed from preliminary official assessments.

For a more precise evaluation of source term in the case of the Techa River contamination it is necessary to estimate the source term by several different methods including available historic records analysis, operational data use, and independent environmental measurements results application. The basis for these investigations is a large number of scientific and technical reports and other documents related to the Techa River radioactive contamination and contained in Mayak PA and Urals Research Center for Radiation Medicine (URCRM) archives. At present the Mayak PA archive contains several hundred documents related both to historic and operational records, and routine monitoring data for the period from the end of 1951 till 2002. The majority of these documents are still classified and accessible only for a limited number of experts (a large work has been conducted lately to declassify some of the Mayak PA archive documents). URCRM archive contains declassified technical reports on environmental measurement results in the Techa River area since 1953 (investigations carried out by Moscow Biophysics Institute and URCRM staff). Moreover investigators of the Institute of Plants and Animals Ecology (IPAE) obtained detailed monitoring data on the Techa River contamination during the last 12 years.

It is proposed to integrate these data for source term reconstruction and validation of data on radionuclide composition of releases. Additional work on MCNP Monte Carlo modeling of exposure levels for various objects in the Techa riverside is planned for exposure–rate–measurements validation.

The implementation of this Project will allow the validation of assessments of total radioactive releases into the Techa River and their radionuclide composition, and the validation of measurements of exposure rates on the areas. The results obtained will be of scientific and applied importance for both retrospective dosimetry and validation of doses for population living along the Techa River.

The main tasks of the Project are the following:

- Archive search of source term data: new documents (not used for previous analysis) on release dynamics, radionuclide composition, and chemical forms of radionuclides; measuring procedures; additional information on environmental monitoring results;

- Field investigations for enlargement of environmental monitoring period, and receiving additional data on Techa River contamination by long-lived radionuclides (strontium, cesium and plutonium) for validation of radionuclide transport models;

- Analysis of radioecological data available and assessment of the presence of long-lived radionuclides in the Techa River for validation of releases of these radionuclides during 1949-1956; and

- Monte-Carlo modeling of gamma-fields distribution, radiation energy spectra and integral doses on riverside and comparison of model predictions with the results of thermoluminescence dosimetry of ceramic samples and with available results of EPR dosimetry of tooth samples.


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