Development of an on-line core performance evaluation system for the LMFBR Monju

It is important to know the in-core circumstances precisely in order to operate a reactor core safety and efficiently. The Japanese prototype liquid-metal fast breeder reactor (LMFBR) Monju, which generates 280 MW of electric power and is now under construction, has relatively stable neutron flux distribution. Therefore, the neutron flux level is monitored by ex-vessel neutron detectors, and in-core neutron flux and power distributions are evaluated by an on-line core performance evaluation system. The system is constructed on a process computer placed at the site, which calculates power and temperature distributions and monitors the in-core circumstances and predicts the change of power and temperature distributions due to control rod operations, etc. This paper describes the application programs developed for the system. The models mentioned are expected to offer the prospect that the core performance evaluation system for Monju fulfills their functions from the standpoint of accuracy, calculation time, and computer storage