Loss-of-Coolant Accident Aspects of the Combustion Engineering Advanced Light Water Reactor—System 80+

Combustion Engineering’s advanced light water reactor, System 80+, is an evolutionary upgrade of the proven System 80® nuclear steam supply system design. While both plants are rated at 3817 MW(thermal), System 80+ incorporates a number of design enhancements, including direct vessel injection for the safety injection (SI) system and other changes to the reactor cooling system. The results of a best-estimate small-break loss-of-coolant accident (LOCA) study that addresses utility investment protection concerns is presented. Specifically, the size piping break that can be tolerated without the liquid or two-phase fluid level falling below the top of the active core is addressed. Using best-estimate analytical procedures, and assuming no single failure, the active core remains covered with substantial margin for breaks up to 0.254-m (10-in.) diameter. This reduces the possibility of core damage due to a small LOCA. A large-break, cold-leg LOCA licensing analysis is also presented that addresses the reflood capability after the end of SI tank discharge without credit for a low-pressure SI pump system. This analysis confirms that the improved high-pressure SI system provides adequate reflood capability to satisfy the U.S. Nuclear Regulatory Commission LOCA licensing criteria.