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.

---

---