Abstract

Dose rate conversion factor was calculated to estimate the absorbed effective annual doses for soils for the beta-rays and gamma-rays, which were emitted from <TEX>$^{238,235}U$</TEX>, <TEX>$^{232}Th$</TEX>, and <TEX>$^{40}K$</TEX> isotopes. The most recent data of the emitted energies per decay, half-lifes, and branching ratios, which were obtained from National Nuclear Data Center, were used. When this factor and the effective annual doses for the beta-rays and the gamma-rays of natural radioisotopes were compared with those of Aitken, these of <TEX>$^{238}U$</TEX>, <TEX>$^{232}Th$</TEX> and <TEX>$^{40}K$</TEX> are estimated to have good agreements but a large difference is shown in this for <TEX>$^{235}U$</TEX>. Through the calculations of effective annual doses by using these factor and the measurements of gamma-ray spectra for soils, which were extracted from prehistoric remains (Mansuri) on Osong, Chungchengbuk-do, The annual effective doses were obtained to be 3.8~5.9 mGy/yr. Also, when these doses including decay elements upper Rn were compared with those on all isotopes, the differences within 9~30 % were obtained. The analysis method of the annual effective doses for the beta-rays and the gamma-rays of the natural isotopes of soils was established by this dose rate conversion factor.