Cables for nuclear power generating stations, 3

The construction of nuclear power generating stations has been energetically pushed ahead in recent years. In view of the growing importance of providing improved safety measures against possible nuclear reactor accidents, IEEE-STD-383 was established in 1974 stipulating for the implementation of severe environment condition tests based on a presupposed accident at a nuclear power station due to the loss of the reactor coolant and vertical tray flame tests simulating a fire on various types of cables. In Japan, cables for use in nuclear power generating stations have been required to withstand such tests in the wake of enforcement of this rule. The environment condition tests as specified in the regulation is conducted under high temperature and high pressure conditions employing a specially designed pressure vessel. Through intensive researches, new cables with a high degree of resistance to radioactive rays and incombustibility have been developed, demonstrating excellent properties against a series of required tests. Meanwhile, the findings of a study conducted to identify the effect of various processes of an environment condition tests on the sample cable have indicated that the properties of heat-resistant polyvinyl chloride showed a marked degradation during the LOCA process while those of other materials deteriorated remarkably during the process of radioactive rays application. (auth.)