Uncertainty Evaluation of Effective Delayed Neutron Fraction βeff of Typical Proto-type Fast Reactor

• Published in: Journal of nuclear science and technology Vol. 36; no. 1; pp. 61 - 80
• Main Authors: ZUKERAN, Atsushi, HANAKI, Hiroshi, SAWADA, Shusaku, SUZUKI, Takayuki
• Format: Journal Article
• Language: English
• Published: Tokyo Taylor & Francis 01.01.1999; Atomic Energy Society of Japan
• Subjects: Applied sciences; delayed neutron constant; delayed neutron yield; effective delayed neutron fraction; Energy; energy dependences; Energy. Thermal use of fuels; Exact sciences and technology; fission cross sections; Fission nuclear power plants; Installations for energy generation and conversion: thermal and electrical energy; MeV range; reaction kinetics; reaction rates; sensitivity; uncertainty; uranium 238; Neutron flux; Uncertainty; Uranium; Fast reactor; Plutonium; Cross section (collision); Nuclear reactor
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/18811248.1999.9726182

Uncertainty of effective delayed neutron fraction β eff is evaluated in terms of three quantities; uncertainties of the basic delayed neutron constants, energy dependence of delayed neutron yield v m d in the low energy side below about 50keV and in the high energy side above about 4MeV, and the uncertainties of the fission cross sections of fuel elements. The uncertainty of β eff due to the delayed neutron yield is expressed by a linearized formula assuming that the delayed neutron yield does not depend on the incident energy, and the energy dependence is supplemented by using the detailed energy dependence proposed by D'Angelo and Filip. The third quantity, uncertainties of fission cross section, is evaluated on the basis of the generalized perturbation theory in relation to reaction rate ratios such as central spectral indexes or average reaction rate ratios. Sensitivity coefficients of the reaction rate ratios to fission cross sections are obtained by generalized perturbation code. Resultant uncertainty of β eff is about 4 to 5%, in which primary factor is the delayed neutron yield, and the secondary one is the fission cross section uncertainty, especially for 238 U. The energy dependence of v m d systematically reduces the magnitude of β eff about 1.4 to 1.7%, depending on the model of the energy vs. v m d correlation curve.