Evaluation of SFR Deformed Core Reactivity
Résumé
In the framework of the development of the Sodium Fast Reactor technology (SFR) the analysis of all possible scenarios leading to perturbation of nominal operating condition is exploited. Among these scenarios attention is being paid on reactivity modification due to core assemblies bowing and deformation, and to lattice readjustments consequent to earthquakes. A computational scheme based on the spatial projection method fulfilling a good compromise between the accuracy of stochastic codes and the quick runtime of deterministic codes has been developed and used to determine the reactivity changes issued from core lattice deformations and irregularities. The calculation of reactivity changes induced by core deformation is achieved by modifying the isotopic concentrations of assemblies concerned by displacements, by projecting the deformed lattice geometry on that corresponding to regular reference case. This methodology was validated by comparison with stochastic codes, and good agreements between the results achieved and those obtained by the Monte Carlo code TRIPOLI4 are observed. The deterministic code available at CEA for fast reactors, i.e. ERANOS/PARIS, has been used to solve neutron transport equation in a full 3D core representation and to calculate the reactivity changes due to core flowering and compaction. In this work, such a method has been used to determine the maximal positive/negative reactivity insertion corresponding to a postulated mechanical energy supplied to an SFR core, as much as the lattice deformation causing it. The results presented in this paper, represent a first step in the assessment of a favourable calculation scheme that can be easily scaled-up to large-sized core and used for the future application in core design and safety analysis.
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