Validation of the Apollo2.8 code package for the calculation of $\beta_{EFF}$ and $\Lambda$ kinetics parameters and the reactivity versus reactor period relationship
Abstract
This paper presents the analysis of kinetics parameters experiments performed in the IPEN/MB-01 mock-up
with the deterministic APOLLO2 code. Comparisons of measurements and calculations are presented on the
effective delayed neutron fraction $\beta_{EFF}$ , prompt neutron generation $\Lambda$ and on the relationship between the reactivity and the period. The impact of the calculation scheme and of the input nuclear data library is tested
and discussed. Comparisons with TRIPOLI4 continuous energy Monte-Carlo calculations have been done for
numerical validation purpose.
The study shows the significant impact of uncertainties associated with delayed neutron abundances and
decay constants on the reactivity prediction, ranging from 4 to 6% in the [0 – 0.5] range. One of the main
results is also the overprediction of $\beta_{EFF}$ by 3 $\pm$ 0.7%, using the JEFF-3.1.1 data, consistent with the overprediction of the reactivity of 4-6% over the whole positive period range. The ENDF/B-VII.0, in spite of a better
estimate of $\beta_{EFF}$, leads to an underestimation of the reactivity reaching up to 13%.
Origin : Files produced by the author(s)
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