Development of Advanced Loop-Type Fast Reactor in Japan: Progress of Design Study Based on Preliminary Assessment Results

The Japan sodium-cooled fast reactor (JSFR) is an advanced loop-type reactor concept which is investigated in the Fast Reactor Cycle Technology Development project in Japan. This paper describes some important progress on the JSFR design study and R&D discussed in a preliminary assessment for the first milestone of this project. As for the reactor system design, structural integrity against both thermal stress and seismic force was investigated. Then, the specification of the reactor vessel was established. Also, investigation of design options to extend a design margin against seismic force has been suggested. Regarding thermal hydraulics issues in the reactor vessel, design measures against cover gas entrainment and vortex cavitations have been introduced to the reactor system design based on R&D results. Further investigation is in progress for design optimization or improvement of preventive effect. The hot-leg piping design of primary cooling circuit was also established taking “Type-IV” damage into account.