Speaker
Description
The extended operation of many pressurized water reactors now exceeds their original design lifetimes, elevating the importance of stringent safety requirements. A central consideration in evaluating the feasibility of further lifetime extension is the accurate assessment of neutron‑induced embrittlement in the reactor pressure vessel (RPV), as this degradation mechanism directly limits long‑term structural integrity.
To support industry‑grade assessments, VTT has developed a comprehensive computational scheme for analyzing RPV ageing under neutron irradiation. The approach combines a two‑stage Monte Carlo–deterministic Serpent/Ants core-follow methodology to characterize the full‑core fission neutron source - optionally refined through additional Monte Carlo transport calculations at specific state points, with detailed Serpent‑based Monte Carlo modelling of neutron attenuation from the core to key locations, including the RPV wall and surveillance capsules. All components of the workflow are implemented within VTT’s Kraken simulation framework, ensuring methodological consistency, reproducibility, and traceability.
To demonstrate the reliability of this ageing‑prediction workflow, the study performs an in‑depth evaluation of the H.B. Robinson‑2 RPV dosimetry benchmark. The results show that the methodology achieves good agreement with reference measurements when the industry‑standard ENDF/B‑VII.1 nuclear data library is used for attenuation calculations. In addition, the study investigates the impact of adopting more recent nuclear data libraries to determine how updated evaluations may influence the overall computational sequence.