Analysis on the Primary System Radiation Control at Tsuruga Boiling Water Reactor Plant

Countermeasures against crud were successfully carried out at Tsuruga Nuclear Power Station. The concentration of corrosion products in the reactor system was extremely reduced, and the radiation dose rate in the primary system was cut in half The behavior of corrosion products was analyzed by means of a mathematical model. The reduction of the radiation dose was explained by considering the following two cases:

1. radioactive decay of the activity deposited on the system surface
2. deposition-release equilibrium between the lowered activity concentration in the coolant and the deposited activity.

It became clear that, in either case, the prevention of the input of impurities from the feedwater system is essential to the reduction of crud activity in the primary coolant system of boiling water reactors.