Analysis and comparison of the nuclear safety regulations in the US and the UK

Abstract

The content and topics developed in this TFM are linked with the safety studies I conducted as an analyst intern in the lead development team of NUWARD(tm). NUWARD(tm) is a Small Modular Reactor developed by EDF with the support of several French nuclear industrial companies aiming to reach the international market for 2030. This study has multiple objectives, firstly to provide a clear vision of the US and the UK regulatory framework by giving a historical review of the nuclear regime, a presentation of the structure and responsibilities of the nuclear safety authorities and the main regulations in force. Secondly, to draw a comparison of main regulatory differences and their potential impacts on the safety referential of new reactors. The analysis will focus on fault assessment expectations, safety systems classification and hazards consideration for the licensing of new nuclear reactors in those two countries. The main findings of this study highlight the efficiency thata licensee can gain by analyzing and taking into account national expectations specificity of the targeting countries at the design stage. In the US, the deterministic and conservative design basis requirements and the national codes and standards should be implemented and followed to the letter. Nevertheless, acomplementary risk-informed regulation bring flexibility and adaptability to the US approach to address specificities of new innovative designs. In the UK, nuclear regime aimed to be non-prescriptive, design neutral and goal-setting, showing openness by referring international well-known requirements, codes and standards. But, the high responsibility given to the licensee in the choices of methods came with very high expectations in the level of detailed and evidences that need to be provided for every design criteria. Furthermore, the safety goals in the UK are very ambitious and in some occasionsjust given as targets which are not expected to be reached systematically but taken as incentives for the designer. It is the licensee that should demonstrate through a quantifying process that the residual risk have been reduced As Low As Reasonably Practicable (ALARP). This study highlights both divergence that would just led to assessment differences and the one having a proven impact on the design. The study also takes credit from a work led to identify and highlight those divergences in the frame of the AP1000 certification in the US and UK. First guidance would be made for the NUWARD(tm) certification, which could address those challengesthrough a common design or by incorporation ofadditional variability options.