Small break model: calculative methods for the C-E small break LOCA evaluation model

The document provides a description of the improvements to the CEFLASH-4AS blowdown code which is employed by C-E for analysis of the small break loss-of-coolant accident. The modifications include development of a new steam generator model and improvements to the phase separation model. Sensitivity studies and comparisons with experimental data with the new models are provided. Analysis of the small break spectrum employing the new models is also presented. Also documented in the report is a change made to the core heat transfer logic to prevent the return to nucleate boiling. The inclusion of this modification makes the small break evaluation model consistent with the change that NRC required in STRIKIN-II