Abstracts and Available Papers Presented at the 1999 International RERTR Meeting
ACCURACY OF WWR-M CRITICALITY CALCULATIONS
WITH CODE MCU-RFFI
Yu.V.Petrov, A.N.Erykalov, and M.S.Onegin
Petersburg
Nuclear Physics Institute RAS
188350
Gatchina, St.Petersburg, Russia [email protected]
ABSTRACT
The scattering and deviation of
fuel element parameters by manufacturing, approximations of the reactor
structure in the computer model, the partly inadequate neutron cross sections
in the computer codes etc. lead to a discrepancy between the reactivity
computations and data. We have compared reactivity calculations using the MCU-RFFI
Monte Carlo code of critical assemblies containing WWR-M2 (36 enriched)
and WWR-M5 (90%) fuel elements with benchmark experiments. The agreement
was about Dr±0.3%. A strong influence of the water ratio on reactivity
was shown and a significant heterogeneous effect was found. We have also
investigated, by full scale reactor calculations for the RETR program, the
contribution to the reactivity of the main reactor structure elements: beryllium
reflector, experimental channels, irradiation devices inside the core, etc.
Calculations show the importance of a more thorough study of the contributions
of products of the (n,a) reaction in the Be reflector to the reactivity. Ways of improving
the accuracy of the calculations are discussed.