Two important experiments for the application of burnable poison in a PWR core

The first experimental nuclear power reactor in China was started up in the year 1970. After operating at full power intermittently for ten years, the reactor was shut down and its fuel unloaded in 1980. Our two important experiments presented here were completed before and after the fuel burn-up in this reactor core. The first experiment is a physical simulation experiment on a 1 : 1 scaled zero power reactor before the reactor's startup, this paper shows the completed testing items; control rod hang-up criterion test, shutdown margin measurement and neutron flux distribution measurement for searching the maximum hot channel factor. This paper shows how to select arrangement patterns of boron-added burnable poison tube in the reactor core, and what can be the best, and the research of the control rod operating mode affecting the maximum hot channel factor. This paper also shows total of 16 neutron flux distribution measurement data from 4 arrangement patterns of boron tube and 4 figure of neutron flux distribution. For the second experiment, we describe the change of the reactor dynamic parameter aC at the end of burn-up, and the measurements of reactivity of 7 batches old boron tubes withdrawn from reactor core, and 5 batches for the ratio of reactivity of the old boron tubes to the new tubes Δρ_∘/Δρ_n. This experiment was completed in a strong radioactive environment. The neutron detector was the anti-gamma composition counter covered with boron. The reactivity measurement used two methods: two detector cross correlation frequency spectra analyses (CCFS) and pulse neutron source (PNS). The reactor dynamic parameter aC at zero burn-up by PNS is 176.8±8 1/s, at the end of reactor burn-up by CCFS is 144.6±2.1 1/s. The reactivity ratio for boron tubes old to new(Δρ_∘/Δρ_n) is within 0.373 to 0.642. The results show the burn-up degree in the reflector area is lower than that in the control rod area; this is beneficial to the reactor protection of radioactivity. (authors)