For the purpose of utilizing radiation-induced chromosome aberrations in human peripheral blood lymphocytes as a means of dose evaluation in a criticality accident, a study was made of the relationship between fission neutron+gamma dose and the chromosome aberrations. Human peripheral blood lymphocytes were exposed in vitro to fission neutrons+gamma rays at Japan Research Reactor No. 4 for 5, 10, 20, 30, or 40min at 200kW. The cells were observed at their first mitotic division stage in culture.
The frequency of the chromosome aberrations per cell, Y, was expressed as a power function of exposure time in minutes, t, as follows: Y=0.0018t^1.12.
On the assumption that there was no mutual interaction between chromosome aberrations induced by the neutrons and those by gamma rays and that there was similarity of the effects of the gamma rays produced in fissions and those of Co-60 gamma ays, estimation was made of contribution of the gamma rays to total yields. However, there was a contradiction that the contribution of gamma rays exceeded the total yield.

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The adsorption of radioactive cations to clay minerals, which governs the movement of radioactive cations through saturated zone, was investigated.
In this study we dealt with calcium ion as the only ion in ground water which influenced the adsorption of radioactive cations to clay minerals.
The experiments were carried out with seven radioactive cations (²²Na, ¹³⁷Cs, ⁵⁴Mn, ⁶⁰Co, ⁶⁵Zn, ⁸⁵Sr and ¹³³Ba) and three ion exchangers (Amberlite IR-120B, Green Sand and KUR Sand) in stead of clay minerals.
The distribution coefficient Kd_A of a radioactive cation to a saturated ion exchanger with calcium ion, was investigated experimentally under several concentrations of calcium ion (C_Ca).
On the basis of experimental results, the following empirical equation obtained.
Kd_A=m·(C_Ca)^-n
In this equation, the values of m and n are determined mainly by the type of radioactive cations and ion exchangers.

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