The reload transient analysis methodology developed for the Cofrentes boiling water reactor-6, 2894-MW(thermal)-rated nuclear power plant is based on the RETRAN-03/MOD1 code. Cross-section files have been calculated with the CASMO-3/SIMULATE-3/SLICK codes. The system and hot-channel thermal-hydraulic responses have been predicted with the RETRAN-03 code, and the thermal margin for each fuel type has been determined by the TCPUIT code.

Transient analyses are performed under several initial conditions to improve the plant operational flexibility. The two most thermal limiting plant transients were simulated: (a) generator load rejection with concurrent failure of the condenser bypass system and (b) failure of the feedwater flow control system to maximum demand. In addition, overpressure is evaluated with RETRAN-03, i.e., a closure of the main-isolation-valve transient.

The Cofrentes tenth reload licensing analyses are verified against official fuel vendor calculations. The results obtained agree with them and cover the vendor thermal margins for the different fuel types considered.