Dose evaluation for the study on biological effects of thermal and epithermal neutron

Characterization of neutron radiation field in heavy water plant of KUR was made by microdosimetric procedures. Measurements were made changing the thickness of heavy water from 0 cm to 90 cm and microdosimetric parameters were determined using a tissue-equivalent proportional counter (TEPC) with an aim to investigate the biological effects of thermal/epithermal neutron. Absorbed dose rate in the radiation field was calculated according to the equation: N = D/(K·yF). Neutron Flux per lethargy was determined in three modes; OO-0000F (mixed irradiation mode), OB-0000F and CO-0000F (epithermal mode). The frequency mean of linear energy (yF) for the mode, CO-0000F was determined changing the thickness. The value of yF was found to rise as an increase in the thickness of heavy water, whereas the dose mean lineal energy (yD) markedly rose as an increase of the thickness. These results were well coincident to those determined by the procedures of activation analysis. (M.N.)