Assessment of individual external dose for members of the MWC from measurements of absorbed dose in teeth by electron paramagnetic resonance (EPR) and dose to red bone marrow by measurement of translocations in peripheral blood lymphocytes with fluorescence in-situ hybridisation (FISH). Comparative analysis of external dose estimates from EPR, FISH and Mayak Doses 2008 for validation of the dosimetry system and identification of system module modifications for an improved external dosimetry system.
Work package 1.1. Validation of Mayak Doses 2008 using EPR and FISH
Task 1.1.1 Development of strategy (HMGU, HPA, ISS, LUMC, SUBI)
A strategy will be developed to determine how the dosimetric system Mayak Doses 2008 can be best validated and improved. The strategy will aim to enhance significantly the power or informative nature of ongoing or planned epidemiological studies. This will not be related only to epidemiological studies performed in the frame of SOLO, but also to studies performed in the framework of Russian-US collaborations in the Southern Urals.
Task 1.1.2 EPR dosimetry for Mayak workers (HMGU, ISS, SUBI)
The objectives of the task are to assess individual external dose for members of the MWC from measurements of absorbed dose in teeth by electron paramagnetic resonance (EPR) using exposure scenarios based on the dosimetry system Mayak Doses 2008, and to add further EPR measurements for selected workers from exposure clusters which currently do not have a sufficient number of cases for comparative analysis.
Task 1.1.3 FISH for Mayak workers (HPA, LUMC, SUBI)
The objective of FISH measurements under WP1.1 is to estimate individual doses from external radiation for the Mayak workers for comparison with doses estimated from film badge dosimeters and EPR measurements. To achieve this goal, a group of Mayak workers has been identified with characteristics of specific exposure scenarios (clusters), who have according to Mayak Doses 2008 estimates of external doses exceeding 0.5 Gy and for whom EPR measurements are available. For these workers, samples of the peripheral blood will be taken, lymphocytes will be cultured and chromosomal slides will be prepared. FISH analysis, based on painting three pairs of chromosomes (i.e. 1, 4 and 8) will be performed in each of the three laboratories (HPA, LUMC, SUBI). Each laboratory will score the yield of translocations per 1000 cells from each worker involved. The laboratory findings will be pooled and the resulting yield of translocations will be converted into dose to the red bone marrow using data on the age dependence and calibration factors.
Task 1.1.4 Evaluation of experimental results and implications for a new dosimetry system (HMGU, HPA, ISS, LUMC, SUBI)
The objectives of this task are to compare external dose estimates based on EPR, FISH and Mayak Doses 2008 as a means of validating the dosimetry system and the identification of system module modifications for an improved external dosimetry system..
Work package 1.2. Validation of TRDS-2009 using EPR and FISH
Validation of external doses of population of the Techa River in the TRDS-2009 system with the use of EPR and FISH, and utilizing simulations of radiation transport by Monte Carlo method
Task 1.2.1 Development of strategy (HMGU, HPA, ISS, LUMC, URCRM)
A strategy will be developed to determine how the dosimetric system TRDS-2009 can be best validated and improved. The strategy will aim at enhancing significantly the power or informative nature of ongoing or planned epidemiological studies. This will not be related only to epidemiological studies performed in the frame of SOLO, but also to studies performed in the frame of the Russian-US collaborations in Southern Urals.
Task 1.2.2 EPR with teeth (URCRM, HMGU, ISS)
The main objective of the task is to evaluate individual external doses for the most exposed members of the Extended Techa River Cohort by EPR spectrometry of teeth supported by assessment of the contribution to enamel dose from strontium incorporated in dental tissues.
Task 1.2.3 FISH with peripheral lymphocytes (URCRM, HPA, LUMC)
The main objective of the task is to extend validation study by FISH measurements of chromosomal aberrations for the persons with high EPR-measured dose and the residents of the upper Techa region with high levels of external exposure.
Task 1.2.4 Evaluation of experimental results and implications for new dosimetry system (URCRM, HMGU, ISS, HPA, LUMC)
Comparative analysis of pooled EPR measurements and FISH data for the residents of the upper Techa will be performed. Individual dose assessments using TRDS-approach will be performed for all Techa residents whose teeth will be measured by EPR method and blood samples will be investigated using FISH method. External doses for the persons investigated using EPR and FISH methods will be calculated using TRDS-2009 based on individual-exposure histories and if possible on the data on individual’s house locations relative to contaminated river shoreline. Dependences of external dose estimates derived from different methods on the distance from the site of release will be compared and analysed. The results of analysis will be used to update and improve the modules for external dose calculations in TRDS-2009. This task will be performed in close cooperation with U.S. colleagues involved in Russian-US JCCRER project 1.1.
Work package 1.3. Validation of TRDS-2009 using luminescence methods
Validation of external doses to the population of the former Metlino village in the TRDS-2009 system with the use of luminescence measurements of anthropogenic doses in bricks, environmental data and monitoring and simulations of radiation transport by Monte Carlo method
Task 1.3.1. Sampling, field and luminescence measurements (HMGU, SUBI, URCRM)
Field work will be done in summer and winter time in the area of the former Metlino village, mainly focusing on the dam separating ponds No. 4 and 10, where brick buildings or ruins still exist and provide sufficient sampling material for luminescence measurements. The sampling activity in the present project will focus on the former church, which is currently surrounded by boggy areas and hardly-accessible in summer time.
Task 1.3.2. Radiation transport calculations (HMGU)
Radiation transport calculations are needed to assess brick doses and doses in air originated from realistic sources. Such doses will be vitally important in converting brick doses to corresponding integral air kerma values.
To complete successfully this extensive task it is necessary to develop plausible models of the site during various periods. For this, the site geometry and sources’ activity and distribution need to be evaluated based on a variety of data. Plausible mathematical models of the dam area in Metlino need to be time-dependent in order to account for changes occurring in the past.
Based on the developed models, extensive Monte Carlo simulations of radiation transport need to be done to calculate dose responses from sources in the river and on the floodplain to targets in the buildings and in the air at pre-defined reference locations. The simulations have to account for gamma-radiation emitted not only by 137Cs but by other shorter-lived radionuclides. As a result of these simulations, transition matrices to convert anthropogenic doses measured in bricks to integral air kerma values at reference locations will be calculated.
Task 1.3.3. Evaluation of experimental and modelling results and implications for the dosimetry system (HMGU, URCRM)
Based on calculated responses and on adopted time-dependent source strength distribution, integral doses in air at pre-defined reference locations and their distributions will be derived and compared with the key parameters of the TRDS-2009. Uncertainty analysis including consideration of several contamination scenarios will be an important part of the whole assessment.
Work package 1.4. Evaluation of gaseous releases
Assessment of external exposure due to radioactive noble gases in locations near to or on the Mayak production site using luminescence measurements of bricks and Monte Carlo calculations.
Task 1.4.1. Sampling and measurements at sampling site (SUBI)
Suitable buildings on or near to the production site will be identified, from which 10-15 bricks will be sampled from different heights. If plaster is present, it will also be sampled (after measuring average thickness), as well as parts of the mortar between bricks, if possible. If no documented dates of construction of the buildings are available, well-shielded bricks will also be sampled for luminescence dating. Dose rate measurements will be performed at sample locations and above ground in front of sampled building with and without snow cover. Supplementary in-situ gamma spectrometry at 1 m above ground will be performed, if possible, to assess radionuclide content in ground.
Task 1.4.2. Luminescence measurements (HMGU)
The cumulative doses at two distinctive depths in the brick will be assessed by luminescence measurements. For a selected suitable brick sample, a dose-depth profile will be measured up to 10 cm into the brick. Specific activities of natural radionuclides in brick, plaster and mortar will be determined in the laboratory. The background dose will be assessed using documented or measured ages of bricks, activities in ground, plaster, mortar and brick and previously calculated dose conversion coefficients. The anthropogenic dose will be assessed after subtraction of the background dose.
Task 1.4.3. Evaluation of effective dose and implications for dosimetry system for Mayak workers (HMGU, SUBI)
Monte Carlo calculations will be carried out to verify the source distribution, assumed to be a semi-infinite cloud above air-ground interface, using the luminescence results as experimental constraints. Conversion coefficients “dose in brick-air kerma” at reference point(s) in front of building(s) will be calculated. The effective dose will be determined and compared with the model predictions by Glagolenko et al (2008). Implications will be evaluated for determining the background dose for the members of the Mayak Worker Cohort (MWC), taking into account their behaviour patterns in locations on and close to the production site.