Development of a measurement method of doppler reactivity coefficients of PWRs

Doppler reactivity coefficient is a very important factor for inherent safety of PWRs. Doppler reactivity coefficients for test assemblies were measured by direct measurements of fuel temperatures and core reactivity. However, the measurement for Nuclear Power Plants has not been performed so far, because the direct temperature measurement of tens of thousands of fuel rods in the core is practically impossible. In this study, a measurement method of Doppler reactivity coefficients of PWRs based on five estimation processes has been developed. In this method, Doppler reactivity coefficients can be measured only using neutron flux and average moderator temperature which are measured in a low power transient during reactor physics tests. For these data, we have got a measured Doppler coefficient and the results show good agreements with our designed results. (author)