Off-line vs. semi-implicit TH-TH coupling schemes: A BEPU comparison

• Published in: Annals of nuclear energy 2022-12, Vol.178, p.109344, Article 109344
• Main Authors: Casamor, M., Avramova, M., Reventós, F., Freixa, J.
• Format: Article
• Language: English
• Subjects: BEPU; Coupling; DNBR; PWR
• ISSN: 0306-4549; 1873-2100
• DOI: 10.1016/j.anucene.2022.109344

•Comparison of coupling schemes through BEPU methodologies.•Application of a BEPU methodology to system induced transients in coupled calculations.•Influence of boundary contitions on MDNBR in coupled calculations. Several TH-TH code coupling methods are used in the nuclear industry to model the core thermal–hydraulic conditions and the system behaviour. In some cases, the boundary conditions obtained by system codes are applied to sub-channel codes by table (off-line coupling). Even though this approach is in general considered valid, some boundary parameters will present inconsistencies. Alternatively, system and sub-channel codes are coupled using different coupling methods (semi-implicit coupling). Recent studies have shown a strong influence of the boundary conditions uncertainty on the sub-channel code results. The present study aims to evaluate the differences produced by the coupling methods by performing a best-estimate plus uncertainties (BEPU) comparison to the following cases: a complete loss of forced flow and a pressurizer relief valve opening. Results show that BEPU analysis presents good agreement with some discrepancies that can be explained and correlated to the boundary conditions deviations between codes.