Core monitoring system for FBR type reactor

Purpose: To determine power distribution ON-line after the change of the insertion degree of control rods by the provision of means for calculating power change coefficient at each of the points due to the change in the insertion degree from the specific change of insertion degree and multiplying the same with the newest power distribution determined periodically by the diffusion calculation. Constitution: The monitoring system additionally comprises a calculation device for power change coefficient that calculates the power change coefficient in a fuel assembly adjacent to a control rod based on the data concerning the operation of the control rod, and a provisional power distribution calculation device that executes multiplication between the power distribution calculated in a periodical power distribution calculation device based on the calculation instruction and stored in the core and the power change coefficient from the power change coefficient calculation device and forecasts the provisional power distribution. Then, based on the result of the foregoing calculations, 2-dimensional power distribution, maximum temperature for the cladding tube of the specified fuel assembly, maximum temperature of pellets in the specified fuel assembly, maximum power density and the like are calculated in various display value calculation devices and displayed on a display device. (Horiuchi, T.)