GB1341131A - Methods of operating nuclear reactors - Google Patents

Abstract

1341131 Controlling reactors SIEMENS AG 19 April 1971 [19 Feb 1970] 21867/71 Heading G6C In the power regulation of a pressurized water nuclear reactor, in particular in the control of load cycles, using a power control-rod bank, the compensation of the Doppler effect, occurring with load variations and caused by variation of the fuel temperature, is carried out by means of a Doppler control-rod bank, while the power control-rod bank has a constant entry depth. The rods of the power bank are generally inserted only into the upper region of the core, even if the desired power output is quite low. The number of rods in the Doppler bank, which may consist of a partial group of the power bank, is selected such that it fully enters the reactor core at the minimum load in order to compensate for the effects of the fuel temperature variation and in order that it should absorb uniformly over the entire core height. At larger partial loads, a smaller number of rods will be selected for the Doppler bank, which would fully enter the core for the larger partial loads also. Owing to the initially rising coolant temperature when the load is reduced, the control rods of the Doppler bank at first receive entry command to provide adequate rod effectiveness, accompanying entry ofthe control rods of the power bank being necessary since the Doppler bank works slowly. After adequate regulation of coolant temperature, the power bank receives upwards command to its former working position, while the Doppler bank alone takes over the compensation. On the load being restored, the Doppler bank returns to its full load position corresponding to the working position of the power bank. It is advantageous for the rods of the Doppler bank to be exchangeable at relatively long time intervals with the rods of the power bank to avoid long-term different burnup effects.