Impact assessment of the integration of a generic PEM electrolyser facility into Rivne nuclear station

Abstract

This manuscript presents the outcomes from the impact assessment applied to the onsite integration of a 40 MW hydrogen production plant (HPP) into the protected area of Rivne nuclear power plant (NPP) in Ukraine. The scope of this work is limited to frequency estimation and blast loading characterization applied to three cases of study, representative of the worst-case scenario at different HPP locations. In the framework of the Euratom NPHyCo project, the NPP operator has proposed integration locations and provided corresponding distances to nearby structures with corresponding fragility criteria. The presented study assumes HPP operation at full capacity with allocated NPP electricity as a feedstock.

Hazardous points within the HPP are identified through HAZID (HAZard IDentification) methodology, which is assisted with system reliability analysis based on component failure rates. The identification of accident sequences in the HPP and frequency estimation is accomplished by means of event tree analysis (ETA). The study identifies as the worst-case scenario within the HPP a hydrogen explosion due to the destructive potential over far-range distances via shock wave propagation. In the electrolyser system, an unintended release of hydrogen may trigger a vapour cloud explosion (VCE), whereas in the adjacent hydrogen buffer tank a physical explosion may trigger a shock wave with subsequent projectile generation. The results show that the highest frequency of a hydrogen VCE is in the order of ${10}^{-7}$ per year following a 1% leak in the separator vessel upstream flange within the gas processing area.

The blast load characterization shows that a hydrogen VCE within the electrolyser facility would not exceed the 10 kPa fragility criterion of nearby safety-related structures. Contrarily, a physical explosion in the 30 kg buffer tank may lead to projectile generation with the potential to reach the standby diesel generators, cooling towers, and turbine building at a distance up to 500 m. The vessel fragments are deemed as soft missiles with high deformability upon impact. Nevertheless, means of protection are proposed to reduce the risk of the coupled facility. The outcomes of the study are meant as recommendations for a subsequent comprehensive safety assessment by the NPP operator.