Modeling of LVRF critical experiments in ZED-2 using WIMS9A/PANTHER and MCNP5

The accuracy of WIMS9A/PANTHER and MCNP5 in modeling D2O-moderated, and H2O-, D2O- or air-cooled, doubly heterogeneous lattices of fuel clusters was demonstrated using Low Void Reactivity Fuel (LVRF) substitution experiments in the ZED-2 critical facility. MCNP5 with ENDF/B-VI (Release 5) underpredicted keff but gave excellent coolant void reactivity (CVR) bias values. WIMS9A/PANTHER with JEF-2.2 overpredicted keff and underpredicted the CVR bias relative to MCNP5 by 100–200 pcm. Both codes reproduced the measured axial and radial flux shapes accurately.