Study On Organ Dosimetry Of Residents In Yangjiang High Background Area

Research of natural radioactivity radiation and resident health of high background radiation area of Yangjiang has been developed for almost40years, in order to make research on the effect of ionizing radiation of small and low dose upon human health, especially the effect of small dose radiation upon the cancel risk of different parts of the body. The research of radiation dosimetry accompanying with the above research has been made to get much measurement data of radiation dosimetry. This research as the extend of the dosimetry research in high background area of Yangjiang explored the new dosimetry research method of organ dose caused by external irradiation as to make comparatively accurate estimation to analyze the dose-effect relationship.In this research HPGe y-ray spectrum (Product Number:ORTEC DETECTIVE-DX-100T) was adopted to measure the γ-ray spectrometry in the environments of the high background radiation area and the control area. According to the above measurement result, appropriate irradiation model was established after simplification to imitate the radiation of resident in real environment. Then the calibration tails of detection efficiency of prober of y-ray spectrometry in the irradiation model was calculated by the method of efficiency calibration without a radioactive source, and the distribution, composition and activity of nuclides in the model were calculated after the spectrum unfolding analysis of y spectrum(energy calibration: choosing6points of power of natural radioactive nuclides to mark; efficiency calibration:using software of efficiency calibration without a radioactive source to calculate calibration tails in the model). On the grounds of spatial structure of the model and the activity of nuclide, the free air kerma rate of the reference point was calculated (relative to the germ nucleus of HPGey-ray spectrum), then geometric condition of irradiation was determined according to the actual irradiation conditions, appropriate factor of conversion from unit free air kerma rate to absorbed dose of organs was chosen to calculate absorbed dose of different organs.Four villages were chosen from four monitoring teams which were high monitoring team, middle monitoring team, low monitoring team of high background radiation area and monitoring team of control area as research objects. The four villages were separately the village which was the lowest absorbed dose one in control area and the village which was the highest absorbed dose ones in each monitoring team of high background radiation area. The purpose of choosing like this was to widen the differences of each monitoring team. Four buildings built by soil, stone, and brick were chosen in each monitoring team (there were not enough suitable buildings built by soil or stone in some villages because of limitation of physical conditions). Then measuring points were settled in each monitoring team. The measurement of y spectrum was done in46measurement points, including30indoor points and3outdoor points in high background radiation area and12indoor points and1outdoor point in control area. Soil samples from each outdoor point were collected and made y energy spectrum analysis in laboratory to ascertain the constitution of natural radioactive nuclide in the soil. Besides, the measurement of each measuring point was made by portable X/y dose rate instrument (Product Number:6150AD6/h+6150AD b/h), the measurement data were used to test and verify the calculated result of y energy spectrum.Air kerma rate calculated by the method of y spectrum and dose rate measured by X/y dose rate instrument were unified into the same physical quantities to be analyzed statistically. And the analysis result was proved to accord with the consistency of actual irradiation conditions and the established irradiation model. The feasibility of simplifying actual irradiation conditions was verified.In this research the method of y energy spectrum was used to calculate the absorbed organ dose and effective body dose of residents caused by external irradiation in Yangjiang high background radiation area and the control area.