The MAAP v5.03 computer program was modified to incorporate the unique features of the VVER plant design to provide a state-of the-art severe accident analysis code for the VVER plants. The MAAP5-VVER code is applicable to the VVER-440, VVER-1000, and VVER-1200 plant designs and is capable of accurately modeling scenarios with in-vessel melt retention (IVMR), which is a crucial VVER accident management strategy, and PRISE accidents (large primary-to-secondary leaks) which are key contributors to plant risk. The MAAP5-VVER code version is intended to be applied to accident management analyses as well as Level 1 and Level 2 PRA analyses.

To ensure that the MAAP5-VVER code adequately addresses phenomena and capabilities important to the expected VVER applications, the MAAP5-VVER code is undergoing verification and validation (V&V) testing prior to final code release. The V&V test plan is designed to provide complete coverage of the MAAP5-VVER specific models and important modeling capabilities. Additionally, the validation exercises consist of data for both the VVER-440 and VVER-1000 plants designs obtained from scaled experiments, full scale plant tests, and other detailed code calculations.

This paper provides an overview of the MAAP5-VVER modeling capabilities, discusses the MAAP5-VVER V&V testing program, and presents preliminary results for a benchmark against the IAEA-SPE-3 test performed at the PMK-2 scaled test facility.