Evaluation of the thermal margin in a KOFA-loaded core by a multichannel analysis methodology

A study has been performed to investigate the thermal margin increase by replacing the single-channel analysis model with a multichannel analysis model. A new critical heat flux(CHF) correlation, which is applicable to a 17 x 17 Korean Fuel Assembly(KOFA)-loaded core, was developed on the basis of the local conditions predicted by the subchannel analysis code, TORC. The hot subchannel analysis was carried out by using one-stage analysis methodology with a prescribed nodal layout of the core. The result of the analysis showed that more than 5% of the thermal margin can be recovered by introducing the TORC/KRB-1 system(multichannel analysis model) instead of the PUMA/ERB-2 system(single-channel analysis model). The thermal margin increase was attributed not only to the effect of the local thermal hydraulic conditions in the hot subchannel predicted by the code, but also to the effect of the characteristics of the CHF correlation. 10 figs., 5 tabs., 22 refs. (Author)