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Executive Summary of the
third project year
Subproject 1 is aimed at quantifying external dose values for
Mayak PA workers by EPR and FISH dosimetry, in order to validate or improve the
Mayak worker cohort (MWC) external dosimetry system.
Subproject 1 consists of
three workpackages (WP). WP1.1 EPR for Mayak PA workers will apply EPR
spectroscopy of tooth enamel to determine the external dose of selected members
of the MWC. EPR spectroscopy will be combined with measurements of spectral and
angular characteristics of radiation fields at work places and with results on
dose due to strontium in tooth enamel from WP3.5 Dosimetry for 90Sr
in teeth. WP1.2 FISH for Mayak PA workers will estimate individual
red bone marrow dose by the fluorescence in-situ hybridisation (FISH) method.
Both workpackages are supporting WP1.3 Improvement
of the Mayak PA dosimetry system and individual dose calculations which aims
at the establishment of improved dose estimates for the MWC, Mayak Doses 2008
and will provide external dose values to WP2.2
Improvement of the Mayak dosimetry system and individual dose calculations.
WP1.1 EPR for Mayak PA workers
Workpackage Leaders:
Evgeni Vasilenko (ZAO) and
Albrecht Wieser (GSF)
The
workpackage is planned for 3 years after start
of the project. The aim of the
work is to provide
independent external occupational dose values for members of the MWC by
measuring the absorbed dose in teeth with EPR spectroscopy. It will contribute
to improve or validate external dose values for the MWC that are derived from
occupational dose monitoring with film dosimetry and which will be an input to
Mayak Doses-2008. Reconstruction of occupational dose from absorbed dose
in tooth requires as input numerical simulated irradiation condition at work
place and background dose in tooth. Objectives
of the workpackage are verification
of numerically simulated irradiation conditions by gamma spectroscopy
measurements at the main work places at Mayak PA,
reconstruction of background dose in teeth of Mayak workers on the basis of EPR
measurements with residents of Ozyorsk, and to expand data on dose values in
teeth from earlier projects by further measurements with groups of workers
selected according to the type of film dosimeter used for monitoring of
occupational dose.
First Project
Year's results: Workpackage 1.1
(WP1.1) EPR for Mayak PA workers is aimed at an
assessment
of the external doses received by members of the MWC, with the help of electron
paramagnetic resonance (EPR) measurements of absorbed dose in teeth. In order to
evaluate the measurements, the characteristics
of radiation fields at work places and non-occupational exposures at the living
place in Ozyorsk are being studied. In the first 12 months of SOUL,
70 tooth samples of
Mayak workers and 25 samples of Ozyorsk residents were measured. A data base
including results from previous projects was established. It contains EPR
results for 205 teeth from 142 MWC members, together with information on
occupational history, characteristics of radiation fields at work areas and
medical exposures. In order to prepare an experimental validation of the
calculated characteristics of radiation fields, in situ gamma-ray
spectrometers of two participating laboratories (AUTH, ZAO) were intercalibrated.
Based on 85 EPR measurements for inhabitants of Ozyorsk with no occupational
exposures, age-dependent background doses were assessed.
WP1.2 FISH for Mayak PA workers
Workpackage Leaders:
Alan Edwards (HPA) and Tamara Azizova(SUBI)
This work package is planned to last
for 4 years. The objective of this work package is to provide independent
experimental evidence to validate or improve the present recorded estimates of
dose to persons in the Mayak worker cohort. The method chosen is to measure
stable chromosomal aberrations, that is translocations, in blood lymphocytes.
The translocation yield can then be related to dose to the individual. The
lymphocytes in peripheral blood when the blood sample is taken, were stem cells,
presumably in the bone marrow when they were irradiated many years previously.
Thus the measured dose is essentially that to the bone marrow. The end product
of this work package is to produce a table for selected individuals of the doses
based on personal monitoring and the cytogenetic bone marrow dose. Whether or
not the recorded doses have been validated or improved may then be judged.
First Project
Year's results:
Fluorescence in-situ hybridization
(FISH) measurements of chromosomal aberrations
(translocations) in peripheral blood lymphocytes are
performed in the framework of WP1.2 FISH for Mayak PA workers, in order
to assess bone marrow doses of MWC members. Dose based on the
translocation yield frequencies will be compared with individual exposure doses
based on Mayak Doses-2005. A first study group containing 50 workers of
Mayak PA was defined during the first year. 35 persons signed an “Informed
consent” form. FISH measurements and assessments of bone marrow doses were
performed for 25 persons.
WP1.3
Improvement of the Mayak PA dosimetry system and
individual dose calculations
Workpackage Leaders:
Evgeni Vasilenko (ZAO), NN
The
workpackage is planned for 2 years,
from the
19-th
till 42-nd
months after obtaining
preliminary results from WP1.1. The main
objective of the workpackage is integration of integral estimates of individual
external doses, including critical
organ doses, for all members of
MWC into the database Mayak Doses-2008.
As for the
external exposure, estimates of energy and angular distributions of the photon
fields at different work places obtained in the framework of WP 1.1. will be
summarized;
these data will be classified.
A special module (computer
program structural unit) for reconstruction of individual external doses on the
basis of the data obtained with different methods will be developed for
improvement of external dose estimates.
Individual doses will be
reconstructed on the basis of film dosimeters and EPR-measurement results.
This program module will
require criteria optimization for integration of workplaces and working areas
with similar radiation field parameters and exposure conditions into groups.
Neutron field
characteristics necessary for dose reconstruction will be presented for certain
workplaces.
These data will be obtained in the
framework of the joint American-Russian Projects. For reconstructed
doses critical organ doses due to external exposure will be determined taking
into account spectra and exposure geometry. These estimates will be included
into the database Mayak Doses-2008.
A special program module
will be developed;
doses will be assigned
approximately to 17%
of Mayak PA members not subject to
external exposure monitoring.
Database
Mayak Doses–2008 will be compiled integrating external doses estimated under
this WP for all members of MAYAK worker cohort.
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