DETERMINATION OF CORE DESIGN THERMAL SAFETY LIMITS FOR A 2-LOOP PRESSURIZED-WATER REACTOR

Results are given of independent research of core thermal design limit s for the Nuklearna Elektrarna KrSko (NEK) nuclear power plant; proced ures for two-loop pressurized water reactor plant core design safety l imit calculation are used. Emphasis is placed on researching the vesse l exit boiling and the hot-channel exit quality limits and their impac t on the maximum available design safety operating range and thermal o perating margin of the NEK reactor core. For this purpose, the LIMITS computer code is developed. Based on the modified, well-fried COBR4-IV -I computer code, the departure of nuclear boiling ratio core safety l imits are calculated. The original results complement well those of th e NEK Final Safety Analysis Report. The procedures and the methods for determining the reactor core design thermal limits are successfully p roven despite the unavailability of proprietary data, different models , and computer codes. In addition to the acquired capability of in-hou se independent checking of the vendor's results, the bases are set for further independent analyses of the limiting safety system settings f or the NEK core.