Delayed neutron fraction and prompt decay constant measurement in the Minerve reactor using the PSI instrumentation

摘要

The critical decay constant (??/??), delayed neutron fraction (??) and generation time (??) of the Minerve reactor were measured by the Paul Scherrer Institut (PSI) and the Commissariat ?? l'Energie Atomique (CEA) in September 2014 using the Feynman-?? and Power Spectral Density neutron noise measurement techniques. Three slightly subcritical configuration were measured using two 1-g 235U fission chambers. This paper reports on the results obtained by PSI in the near critical configuration (???2??). The most reliable and precise results were obtained with the Cross-Power Spectral Density technique: ?? = 708.4??9.2 pcm, ??/?? = 79.0??0.6 s???1 and ?? = 89.7??1.4 ??s. Predictions of the same kinetic parameters were obtained with MCNP5-v1.6 and the JEFF-3.1 and ENDF/B-VII.1 nuclear data libraries. On average the predictions for ?? and ??/?? overestimate the experimental results by 5% and 11%, respectively. The discrepancy is suspected to come from either a corruption of the data or from the inadequacy of the point kinetic equations to interpret the measurements in the Minerve driven system.