Effects of CASMO-5 models and delayed neutron data on simulate-3K reactivity initiated accident predictions

The total energy released during a Reactivity Initiated Accident (RIA) is closely related to the fuel safety parameters like the fuel centerline temperature, fuel enthalpy and fuel enthalpy rise. Point kinetic models with prompt energy feedback relate the total energy release to the fuel temperature coefficient (Doppler coefficient), the delayed neutron fraction and the reactivity of the control rod. The fuel temperature coefficient and the delayed neutron fraction depend primarily on the models and the data used by the lattice code that generates the cross sections and other nuclear parameters for the 3-D kinetics code. The objective of this paper is to evaluate the influence on RIA of the following CASMO5 models and data: (a) the resonance up scatter correction, (b) the effective Doppler temperature and (c) the kinetic parameters set. For this purpose, a comparison of the CASMO5/Simulate-3K results against the Special Power Excursion Reactor Test III E-core experiments is provided. The calculations using the asymptotic scattering kernel and the effective Doppler temperature predict higher peak powers because the fuel temperature coefficient predicted using the asymptotic scattering kernel and the effective Doppler temperature is less negative than the fuel temperature coefficient predicted with the exact scattering kernel and no effective Doppler temperature. Calculations performed using the Tuttle kinetic data will predict lower peak powers compared to ENDF/B-VII. 1 data if the control rod is ejected from a known position (e.g. from its insertion limit). Otherwise, the Tuttle kinetic data will predict higher peak powers. (Author)