Verification of a Nuclear Analysis System for Fast Reactors using BFS-62 Critical Experiment

Abstract

Critical experiments have been analyzed to verify a nuclear analysis system for fast reactors used in Japan Nuclear Cycle Development Institute (JNC). The experiments were performed in a collaboration work between JNC and the Institute of Physics and Power Engineering of Russia to dispose Russian surplus weapons plutonium, focusing on the effect of the introduction of uranium-plutonium mixed-dioxide (MOX) fuel and stainless steel reflector into the current BN-600 core that is comprised of UO 2 fuel and blanket.The analysis results agreed well with measured values on most of the nuclear characteristics. The accuracies are comparable to those obtained for the conventional MOX fueled fast reactors. It suggests that the JNC analysis system can analyze accurately nuclear characteristics in uranium fueled cores as well.A significant improvement was achieved on the sodium void reactivity by employing an ultra fine group cell calculation system. A change in adjoint neutron spectrum mostly contributes to the improvement.A discrepancy of more than 20% was found on the fission rate distribution of 235 U or 239 Pu in stainless steel reflector regions, which cannot be solved by introducing continuous Monte Carlo calculation or different nuclear data sets.

Uranium-235 Neutron Capture Cross Section at keV Energies

“…In order to evaluate an impact of this revision on the nuclear characteristics of the BFS cores, we estimate the k eff and sodium void reactivities of the BFS cores measured in the BFS-62 critical experiment 23) using relative sensitivity coefficients S ij , which are calculated from the derivative of the reactor characteristic I with respect to the cross section ij :…”

Development of a Fine and Ultra-Fine Group Cell Calculation Code SLAROM-UF for Fast Reactor Analyses

“…Such an example has been reported in BFS-62 critical experiment as 0.3% increase in criticality and 30% increase in the non-leakage component of sodium void reactivity. 29) …”