Investigations of the Effects of the Variation of Fuel Assembly Positions in a core of a PWR


Investigations of the Effects of the Variation of Fuel Assembly Positions in a core of a PWR

Konheiser, J.; Müller, S. E.; Seidl, M.

This work shows the impact of possible variations of the core geometry on the signal values of the ex-core instrumentation of a pressurized water reactor (PWR). Based on the potential influence on the signals, neutron fluxes have been determined for selected fuel assembly displacements using stationary Monte Carlo calculations. First, critical calculations were carried out for the chosen core configurations and corresponding surface sources on the core barrel were determined. In a second step transport calculations for the ionization chambers were performed using the surface sources. Typical data of a German PWR were used for the investigations.
Variation of fuel assembly positions in the outer region of the core were studied, which were directly opposite to the ex-core instrumentation. An increase of the neutron flux at the chambers of up to 4% has been calculated for a change in position of 1 mm between some fuel assemblies. The reason is an improved moderation of neutrons because of the larger water gap. This causes an increase in local power which leads to a greater leakage of neutrons over the core barrel. In addition, a dependence of this effect as a function of cycle burnup was analyzed.

Keywords: PWR type reactor; Monte Carlo calculation; safety analysis; ex-core instrumentation

  • Lecture (others)
    17. AAA Workshop, 04.12.2017, Garching, Germany

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Publ.-Id: 26372