Reactor emergency coolant discharge at fast and slow rates - according to position of primary circuit leak

摘要

A nuclear reactor installation comprises a liquid-cooled, esp. pressurised water reactor, in which the main coolant circuit comprises a pressure vessel and ducting leading out through the surrounding concrete biological shield. The biological shield, together with the reactor pressure vessel, constitutes a close space in which the pressure is monitored in order to actuate equipment for initiating a rapid power reduction if a leak should occur in the main coolant circuit. Pressure measuring devices inside the close space between biological shield and pressure vessel actuate the rapid power reduction equipment only if a leak occurs within the main biological shield, but initiate a slower reduction of power if a leak should occur outside this closed space within the biological shield. Pref. the pressure measuring equipment provides a comparison between the pressure rise inside the closed space and that outside this space. More specifically, the pressure measuring equipment records the difference in pressure between these two spaces. A sudden reduction in pressure by discharge of primary coolant from the circuit is avoided except in the essential cases of a leak within the primary contained space around the vessel. Where a leak occurs in the primary circuit outside the biological shield, a much slower power reduction is possible, and thus the stress loading induced in the primary circuit components can be correspondingly reduced.