Natural circulation characteristics in a loop-type LMFBR

Motivated by the increasing interests in the development of liquid metal cooled fast reactor, the plant dynamics analysis code NETFLOW has been extended to the NETFLOW++ code that can analyze the turbine system coupling with primary and secondary heat transport systems (HTSs). The NETFLOW++ code can calculate whole HTSs not only fast reactors but also light water reactors. The code was validated by a test result of the natural circulation in the secondary HTS without nuclear power at the fast breeder reactor 'Monju', and natural circulation events in the loop-type fast reactor were analyzed by the code. Good agreement was obtained between the test result and the calculation for the natural circulation transient caused by pump heat input and cooling by air coolers in the secondary HTS during half a day. As the representative of the natural circulation in a loop-type reactor, a postulated event such as a loss of on-site power was evaluated. As a result, good coolability of the reactor was confirmed for the power up to the rated condition. (author)