This study evaluates the capability of the independently developed SPRUCE2.0 code to simulate core thermal-hydraulic behavior during severe accidents. Numerical models were established for the CORA-13 (ISP-31) heat-up experiment and the QUENCH-06 (ISP-45) reflood experiment, and the calculated temperatures and hydrogen generation were compared with measurements and international benchmark calculations. Nodal-refinement effects and the sensitivities to convective heat-transfer and oxidation-rate factors were also examined. For CORA-13, SPRUCE2.0 predicted a second-ring fuel peak temperature of 2486 K, within 1.2% of the SCDAP/RELAP5 result, and a total hydrogen production of 182 g, 10.78% below the measured 204 g; however, the simulated hydrogen-generation peak occurred 568 s too early. For QUENCH-06, the code reproduced the heat-up and reflood-cooling trends of the cladding and shroud, but underpredicted the peak temperature of the corner rod at 950 mm by 23.4% and overpredicted the total hydrogen production by 26.4%, yielding 45.0 g compared with the measured value of 35.6 g. Nodal refinement changed the selected responses by less than 1%. The convective heat-transfer factor had a comparatively weak effect, whereas the oxidation-rate factor strongly controlled hydrogen production. The results demonstrate that SPRUCE2.0 captures the principal heat-up, quench, and zirconium-steam oxidation phenomena, while identifying oxidation heat-release, high-temperature melting, and hydrogen-timing models as priorities for continued development and severe-accident safety analysis.

SPRUCE2.0; severe accident; core thermal hydraulics; CORA-13; QUENCH-06