Instability evaluation of steam generator in a large scale sodium test facility of fast reactors. Modification of BOST code

Instability analysis was carried out using BOST code for a steam generator in a large scale sodium test facility of fast reactors. However, it was found that BOST code gave stable characteristics under the conditions of higher pressure in water-steam system than MONJU conditions, even if the flow ratio of sodium to water was increased as expected to give unstable condition. Here, modification of BOST code was considered and we found some points to be modified. However, main reasons of stable calculation were not resolved. In this report, the current status of BOST code was summarized especially for the stable calculation under the higher pressure condition for further modification and a new code based on current knowledge and coding technique. (author)