# Power coefficient of reactivity used for assessing the results of transients in power reactors

3/23/2018 2018 - #01 Physics and technology of nuclear reactors

Kazansky Yu.A. Slekenichs Ya.V.

https://doi.org/10.26583/npe.2018.1.07

### UDC: 621.039.516

The authors of the article assume that as the contribution of nuclear power to the production of electricity increases, nuclear power plants will be used more in a manoeuvrable mode of operation than in the basic one. In other words, changes in power from the nominal level to that of auxiliary loads will become common and not so rare events as scheduled reactor shutdowns for fuel reloading or preventive works. It would be useful to have a single indicator, weakly power-dependent and fairly simply measurable, which would enable us to reason about the nature of transient processes over the entire power range and estimate the required reactivity to change the power by a given value. Such an indicator can be the power coefficient of reactivity (PCR). An analysis was made of existing definitions and notions of PCR in related literature. It turned out that there is no generally accepted definition of the PCR. Based on the performed study, the following definition was proposed: the PCR is the ratio of the low reactivity introduced into the reactor to the power increment after the end of the transient process. In this case, the reactivity changes are assumed to be due to the energy liberated in nuclear fission but not related to those caused by feedback signals in the automatic reactor power control system.

Taking into account the adopted definition, an analysis was made of the relationship between the PCR and temperature coefficients and technological parameters associated with the static control program. Also, PCR calculations were performed using the simplest model of the VVER-1000 type power reactor. It turned out that PFR is weakly power-dependent.

The purpose of the study is to determine the PCR dependence on the temperature effects of reactivity determined by the temperature coefficients of reactivity and on the technological parameters associated with the static control program of the power unit, using the example of VVER-1000. The PCR influence on the power reactor statics/dynamics is analyzed.

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