Safety Effects of Light Water Infiltration in the Argonne Research Reactor (CP-5)

In the course of the recent rehabilitation of CP-5, a study was made of the safety problems associated with in-leakage of light water into the primary coolant (heavy water) stream from a tube rupture in the main heat exchanger. The reactivity effects of the light water can be represented by a prompt positive coefficient and a delayed negative coefficient during normal operation. When the rods are pulled out (as during recovery from xenon poisoning), the effects of light water are to decrease the reactivity. The plant is designed to render water in-leakage highly unlikely. Even in the case such in-leakage occurs, the plant protection system is capable of protecting the system against rupture of many tubes in rapid succession.