Validation of Computer Code Based on Nodal Integral Method Against KAPS-2 Phase-B Data

One of the major activities involved in the operation of Indian PHWRs includes commissioning of nuclear reactor before commercial operation of reactor. The commissioning activities can be divided into three principal phases viz Phase-A, Phase-B, and Phase-C. The commissioning program assures that the plant is made operational in a systematic, informative, and safe manner after its construction. It also verifies that the performance criteria, design intent, and quality assurance requirements are satisfied. Phase-B tests are performed up to 0.1%FP, and its objectives are to confirm that the reactor is suitable for start-up and power operation and to check that core characteristics, control systems, reactor physics parameters are satisfactory. Important activities in Phase-B include initial fuel loading, addition of heavy water into PHT and moderator, first approach to criticality, and low power physics tests. Some of the Phase-B results of Kakrapar Atomic Power Station-2 (KAPS-2) commissioned in 2018 are compared with the theoretical estimations carried out by computer code based on nodal integral method (NIM). The variation of neutron count rates during approach to criticality, critical boron and the worth of reactivity devices etc., are compared with the observation at KAPS-2.