Determination of neutron generation time in miniature neutron source reactor by measurement of neutronics transfer function

The prompt neutron generation time Lambda and the total effective fraction of delayed neutrons (including the effect of photoneutrons) beta have been experimentally determined for the miniature neutron source reactor (MNSR) o f Syria. The neutron generation time was found by taking measurements of th e reactor open-loop transfer function using newly devised reactivity-step- ejection method by the reactor pneumatic rabbit system. Small reactivity pe rturbations i.e. step changes of reactivity starting from steady state, wer e introduced into the reactor during operation at low power level i.e. zero -power. Relative neutron flux and reactivity versus time were obtained. Usi ng transfer function analysis as well as least square fitting techniques an d measuring the delayed neutrons fraction, the neutron generation time was determined to be 74.6 +/- 1.57 mu s. Using the prompt jump approximation of neutron flux, the total effective fraction of delayed neutrons was measure d and found to be 0.00783 +/- 0.00017. Measured values of Lambda and beta w ere found to be very consistent with calculated ones reported in the Safety Analysis Report. (C) 2000 Elsevier Science S.A. All rights reserved.