Around Semipalatinsk Nuclear Test Site: Progress of dose Estimations Relevant to the Consequences of Nuclear Tests

The paper is an analytical overview of the main results presented at the 3rd Dosimetry Workshop in Hiroshima(9-11 of March 2005), where different aspects of the dose reconstruction around the Semipalatinsk nuclear test site(SNTS) were discussed and summarized. The results of the international intercomparison of the retrospective luminescence dosimetry(RLD) method for Dolon\u27 village(Kazakhstan) were presented at the Workshop and good concurrence between dose estimations by different laboratories from 6 countries (Japan, Russia, USA, Germany, Finland and UK) was pointed out. The accumulated dose values in brick for a common depth of 10mm depth obtained independently by all participating laboratories were in good agreement for all four brick samples from Dolon\u27 village, Kazakhstan, with the average value of the local gamma dose due to fallout (near the sampling locations) being about 220mGy(background dose has been subtracted). Furthermore, using a conversion factor of about 2 to obtain the free-in-air dose, a value of local dose ~440mGy is obtained, which supports the results of external dose calculations for Dolon\u27: recently published soil contamination data, archive information and new models were used for refining dose calculations and the external dose in air for Dolon village was estimated to be about 500mGy. The results of electron spin resonance(ESR) dosimetry with tooth enamel have demonstrated the notable progress in application of ESR dosimetry to the problems of dose reconstruction around the Semipalatinsk nuclear test site. At the present moment, dose estimates by the ESR method have become more consistent with calculated values and with retrospective luminescence dosimetry data, but differences between ESR dose estimates and RLD/calculation data were noted. For example mean ESR dose for eligible tooth samples from Dolon\u27 village was estimated to be about 140mGy(above background dose), which is less than dose values obtained by RLD and calculations. A possible explanation of the differences between ESR and RLD/calculations doses is the following: for interpretation of ESR data the "shielding and behaviour" factors for investigated persons should be taken into account. The "upper level" of the combination of "shielding and behaviour" factors of dose reduction for inhabitants of Dolon\u27 village of about 0.28 was obtained by comparing the individual ESR tooth enamel dose estimates with the calculated mean dose for this settlement. The biological dosimetry data related to the settlements near SNTS were presented at the Workshop. A higher incidence of unstable chromosome aberrations, micronucleus in lymphocytes, nuclear abnormalities of thyroid follicular cells, T-cell receptor mutations in peripheral blood were found for exposed areas (Dolon\u27, Sarjal) in comparison with unexposed ones(Kokpekty). The significant greater frequency of stable translocations (results of analyses of chromosome aberrations in lymphocytes by the FISH technique) was demonstrated for Dolon\u27 village in comparison with Chekoman(unexposed village). The elevated level of stable translocations in Dolon\u27 corresponds to a dose of about 180mSv, which is close to the results of ESR dosimetry for this village. The importance of investigating specific morphological types of thyroid nodules for thyroid dosimetry studies was pointed out. In general the 3rd Dosimetry Workshop has demonstrated remarkable progress in developing an international level of common approaches for retrospective dose estimations around the SNTS and in understanding the tasks for the future joint work in this direction. In the framework of a special session the problems of developing a database and registry in order to support epidemiological studies around SNTS were discussed. The results of investigation of psychological consequences of nuclear tests, which are expressed in the form of verbal behaviour, were presented at this session as well

Interlaboratory comparison of tooth enamel dosimetry on Semipalatinsk region:Part 1,general view

For intercomparison of methods of dose determination using electron paramagnetic resonance (EPR) spectroscopy of tooth enamel, the same sets of enamel samples were analyzed in different laboratories using similar recording parameters. The sets of samples included calibration samples irradiated in known doses, test samples irradiated to doses unknown to the participants and accidental dose samples prepared from teeth of humans affected by radioactive fallout from nuclear tests in the Semipalatinsk Nuclear Test Site in Kazakhstan. The test samples were analyzed to determine the differences in the resulting doses using different spectrometers and different spectra processing methods. The accidental dose samples were analyzed in order to test the precision of doses determined by EPR spectroscopy and to obtain more accurate values by averaging the results from different laboratories

A gradient of radioactive contamination in Dolon village near the SNTS and comparison of computed dose values with instrumental estimates for the 29 August, 1949 nuclear test

金沢大学環日本海域環境研究センター地球環境計測研究部門Spatial distributions of soil contamination by 137Cs (89 sampling points) and 239+240pu (76 points) near and within Dolon village were analyzed. An essential exponential decrease of contamination was found in Dolon village: the distance of a half reduction in contamination is about 0.87-1.25 km (in a northwest-southeast direction from the supposed centerline of the radioactive trace). This fact is in agreement with the available exposure rate measurements near Dolon (September 1949 archive data): on the basis of a few measurements the pattern of the trace was estimated to comprise a narrow 2 km corridor of maximum exposure rate. To compare computed external doses in air with local dose estimates by retrospective luminescence dosimetry (RLD) the gradient of radioactive soil contamination within the village was accounted for. The computed dose associated with the central axis of the trace was found to be equal to 2260 mGy (calculations based on archive exposure rate data). Local doses near the RLD sampling points (southeast of the village) were calculated to be in the range 466-780 mGy (averaged value: 645+/-70 mGy), which is comparable with RLD data (averaged value 460+/-92 mGy with range 380-618 mGy). A comparison of the computed mean dose in the settlement with dose estimates by ESR tooth enamel dosimetry makes it possible to estimate the "upper level" of the "shielding and behavior" factor in dose reduction for inhabitants of Dolon village which was found to be 0.28+/-0.068