Dosimetry of Mixed Neutron and Gamma Radiation with Paired Fricke Solutions in Light and Heavy Water

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Paired Fricke solutions, made up from light water or heavy water and 0.8N in H_2SO_4 and 1 mM in Fe(NH_4)2(SO_4)_2 and NaCl, were calibrated with ^<60>Co γ rays and with mixed neutron and y radiation from a ^<252>Cf source. Absorbance increases, AL and AH, in light- and heavy-water Fricke dosimeters, respectively, increased with fast-neutron and γ-ray tissue doses, Dn (Gy) and Dγ (Gy), of the mixed radiation as follows: A_L=0.00l78D_n+0.00371D_γ; A_H=0.00121D_n+0.00442D_γ. G-values of 7.2 and 5.5 were obtained for ^<252>Cf neutrons in light- and heavy-water Fricke dosimeters, respectively. When we applied the pair of equations to A_L and A_H values observed after exposure to mixed radiation in a nuclear reactor, resulting D_n and D_γ values agreed within 10% to doses measured with paired ionization chambers. Doses required for Fricke dosimeters were 5 Gy or more. In contrast, we found that micronuclear yields in onion roots can measure the neutron component of mixed radiation fields at the order of 10 cGy with reasonable accuracy even if the neutron to γ-ray dose ratio is unknown.
日本放射線影響学会の論文