Dose loading of the personnel of atomic power station (APS) Kozloduj from incorporated radioactive nuclides

Based on indirect dosimetry data, radiation exposures to NPP Kozloduj personnel were estimated for work at nominal reactor power, during partial nuclear refueling, and during planned preventive repair. Measurements covered the period 1977-1981 and involved a group of 30 subjects occupied in the strictly controlled areas of the plant. Collected 24-hour urine samples were processed and assayed for contents of tritium, strontium 90, iodine 131, and cesium 137. Absorbed dose equivalents resulting from strontium 90 to bone tissue, from iodine 131 to the thyroid, and from tritium and cesium 137 to the whole body were calculated using the mathematical model proposed by Shamov (1972) for tissue dose assessment. Maximum absorbed dose equivalents in individual subjects were not found to exceed 1.3 x 10-3 Gy for tritium, 9.5 x 10-5 Gy for strontium 90, 5.8 x 10-5 Gy for cesium 137, and 1.9 x 10-3 for iodine 131, indicating thus an insignificant level of internal exposure to NPP personnel. Urinary contents of the radionuclides investigated were seen to increase upon refueling operations. Since 1979, there has been declining trend in radiation exposure from radionuclide intake by personnel engaged in controlled areas of strict regimen. (authors)