The radiological environment at the Mayak PA site and radiation doses to individuals involved in emergency and remediation operations after the 'Kyshtym Accident' in 1957.

This article assesses the radiological environment at the nuclear site of the Mayak PA, Russian Federation, during and after the accident in 1957, the so-called 'Kyshtym Accident', and the radiation doses to those who participated in the eradication of its consequences. Based on numerous archival documents, this paper presents the radiation data for 1957-1960, including individual dosimetry monitoring data and estimated doses to the Mayak workers, as well as the to personnel in supporting organisations and the military involved in the remediation operations. From 1957-1959 some 38 500 individuals took part in the clean-up actions and remediation of contaminated areas of the Mayak PA industrial site after the accident, including individuals exposed at the time of the accident: Mayak PA employees, militarypersonnel, and civil construction workers. External equivalent doses to 10 500 individuals were estimated in the range of 220 to 265 mSv, while there were cases of doses up to 950 mSv and higher. The collective dose received during the accident and its aftermath was in the region of 7300 person-Sv. By October-December 1957, the collective dose was about 4500 person-Sv. Collective doses recorded in 1958 and 1959 amounted to 2250 person-Sv and 480 person-Sv, respectively.

Mayak worker dosimetry study: an overview.

The Mayak Production Association (MPA) was the first plutonium production plant in the former Soviet Union. Workers at the MPA were exposed to relatively large internal radiation intakes and external radiation exposures, particularly in the early years of plant operations. This paper describes the updated dosimetry database, "Doses-2005." Doses-2005 represents a significant improvement in the determination of absorbed organ dose from external radiation and plutonium intake for the original cohort of 18,831 Mayak workers. The methods of dose reconstruction of absorbed organ doses from external radiation uses: 1) archive records of measured dose and worker exposure history, 2) measured energy and directional response characteristics of historical Mayak film dosimeters, and 3) calculated dose conversion factors for Mayak Study-defined exposure scenarios using Monte Carlo techniques. The methods of dose reconstruction for plutonium intake uses two revised models developed from empirical data derived from bioassay and autopsy cases and/or updates from prevailing or emerging International Commission on Radiological Protection models. Other sources of potential significant exposure to workers such as medical diagnostic x-rays, ambient onsite external radiation, neutron radiation, intake of airborne effluent, and intake of nuclides other than plutonium were evaluated to determine their impact on the dose estimates.

Mayak film dosimeter response studies, part I: measurements.

The Mayak Worker Dosimetry study is a joint Russian/U.S. project to evaluate doses received by workers at the Mayak Production Association facilities from 1948-1972. A key investigation in this project is the characterization of responses of the three types of film dosimeters used to monitor workers during this time period. Experimental irradiations of the dosimeters were performed in the radiation calibration laboratories at the National Research Center for Environment and Health (GSF) in Munich, Germany. The irradiations used photon sources from x-ray beams with ten different energy distributions and with Co and Cs isotopic gamma sources. Irradiations were performed with the dosimeters on phantoms and free-in-air. The dosimeters and phantoms were also positioned at varying angles to the radiation beam. The result of the experiments was a thorough characterization of the dosimeter response as a function of photon energy and as a function of angle for energy and angular ranges that cover the conditions encountered in the Mayak workplaces. The characterization data were then available for use in developing correction factors, which could be applied to worker dosimeter readings to provide a more accurate assessment of worker dose and estimates of doses to organs.

Mayak film dosimeter response studies, part II: response models.

A study was performed of energy and angular responses of the film dosimeters that were used for worker monitoring at the Mayak Production Association (Mayak PA) in 1948-1992. The study used experimental data from tests with three types of individual film dosimeters, and the data were used to determine the dosimeters' energy and angular response characteristics in the range from 9 keV to Co energies, with the dosimeters exposed both free-in-air and on-phantom at horizontal and vertical rotation. Mathematical models of the dosimeters were developed to calculate the response characteristics of the dosimeters. The models of the film dosimeters were validated by comparing calculations to measurements. The models were then used as the basis for individual dose reconstruction in realistic photon spectra and worker exposure geometries at the Mayak PA workplaces. Reconstructed individual doses have been included in the Mayak worker database "Doses-2005" that is used for epidemiological studies of the Mayak workers' radiation exposures and subsequent health effects.