Accurate determination of delayed neutron emission rate based on in pile kinetic measurements

by Yanai Yedvab

at Astrophysics and Cosmology Seminar

Wed, 29 Jun 2016, 11:15
Physics building (#54) room 207

Abstract

Delayed neutrons result from radio active decays of highly excited fission products following a fission event They account for 1 of the total number of neutrons which are emitted in fission and the timescale for their emission ranges between 0 1 and 100 seconds after the fission event Delayed neutrons are of interest in various applications in astrophysics and nuclear physics They play a critical role in reactor physics where they are responsible for controlling the reactor and balancing the chain reaction Consequently several hundred scientific works have been published in the last seventy years aiming to measure their characteristics and primarily their rate of emission following a fission event Surprisingly in spite of the vast number of publications and the significant improvements in measurement equipment over the years the discrepancies in the expected emission rate between the most popular and widely spread compilations exceed a factor of 2 and no convergence in the agreement between the measurements is observed In this work a novel idea for measuring the time dependence of delayed neutron emission is employed based on integral measurements in a critical nuclear reactor and relying on Boltzmann s transport equation as a strict physical constraint Though a nuclear reactor is a very complex engineering system and in spite of the fact that the Boltzmann equation depends on a large number of different physical parameters careful measurements performed in two different nuclear reactors Dimona amp Soreq and detailed uncertainty analysis resulted in evaluated uncertainties which are smaller by an order of magnitude from the discrepancies between popular compilations in the literature This uncertainty decrease is critical for the accurate prediction of the behavior of a nuclear reactor away from equilibrium and in severe accidents scenarios Accurate measurements of delayed neutron emission rate may potentially be of interest also as a benchmark for calibrating radio active isotopes decay which are relevant in some astrophysical applications

Created on 26-06-2016 by Bar Lev, Yevgeny (ybarlev)
Updaded on 26-06-2016 by Bar Lev, Yevgeny (ybarlev)