RETRAN applications in pressurized thermal shock analysis of Turkey Points Units 3 and 4

A methodology to assess the impact of overcooling transients on vessel wall integrity with respect to pressurized thermal shock conditions has been developed at FPL for the Turkey Point Nuclear Units. Small break loss-of-coolant and small steamline break events have been simulated with the RETRAN code. Highly, conservative assumptions, such as engineered safeguards with minimum temperature and maximum flow have been made to maximize cooldown and thermal stress in the vessel wall. Temperatures and pressures obtained with RETRAN provide input for stress and fracture mechanics analyses that evaluate reactor vessel integrity. The results of the RETRAN analyses compare well with generic calculations performed by the Westinghouse Owners Group for a similar type plant