Yasuo Kusama

Radiation resistance of ethylene-styrene copolymers

A study on the radiation resistance of two types of ethylene-styrene copolymers, random and graft, is described. It is shown that the random copolymer is highly resistant to gamma -rays in the aspects of carbonyl group formation, gel formation, and elongation. It shows even better resistance when proper additives are compounded in. The tensile strength of the graft copolymer did not show a decrease under gamma -irradiation even at a high dose of 10 MGy.<<ETX>>

Effect of a simulated LOCA testing period on durabilities of insulating and jacketing materials for reactor cables

In the typical examples of LOCA (loss-of-coolant-accident) simulation, presented by IEEE Std 323-1974, the test period was estimated to be three months for BWR and one year for PWR. We studied test conditions which were expected to influence the deterioration of elastomeric materials used in a nuclear reactor, such as heating or cooling rate in the first transient part of a LOCA profile, dose rate effect, and effect of oxygen in the LOCA environment. Studies have progressed since 1979 in JAERI to verify an adequacy of qualification testing method. In this report, we present the effects of an exposure length in a simulated LOCA environment on the degradation of insulating and jacketing materials for reactor cables. In addition, the effect of temperature on the degradation rate of these materials during the cooling phase after a LOCA which follows the first transient phase.