Validation of the Apollo2.8 code package for the calculation of $\beta_{EFF}$ and $\Lambda$ kinetics parameters and the reactivity versus reactor period relationship

P. Leconte (1) , G. Truchet (1) , J.-F. Vidal (1) , A. Santamarina (1) , P. Blaise (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

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%.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

P. Leconte, G. Truchet, J.-F. Vidal, A. Santamarina, P. Blaise. Validation of the Apollo2.8 code package for the calculation of $\beta_{EFF}$ and $\Lambda$ kinetics parameters and the reactivity versus reactor period relationship. PHYSOR 2016, May 2016, Sun Valley, United States. ⟨cea-02438724⟩