Design of water-moderated heterogeneous cores in new STACY facility through JAEA/IRSN collaboration

Izawa, Kazuhiko ; Tonoike, Kotaro ; Leclaire, N.*; Duhamel, I.*

In the post-Fukushima prospect, Japan Atomic Energy Agency, JAEA, intends to re-open its Static Experiment Critical Facility STACY, in order to contribute to the validation of fuel debris calculations in conditions close to those affected by the Fukushima Daiichi Nuclear Power Station accident. The reactor core of STACY is being modified by JAEA from homogeneous solution fuel core to heterogeneous pin-type fuel core. The first step of critical experiments is to establish reference experiments involving lattices of UO rods without fuel debris. A design of such experiments is in progress for the widest range of moderation ratios in the frame of JAEA/IRSN collaboration. For that purpose, perturbation calculation technique and stochastic geometry modeling technique were used with the MCNP5 and the JENDL-4.0 evaluated nuclear data library. The proposed paper will discuss all the aforementioned issues.