Why interpretation of nuclear regulatory requirements should be harmonised

A neutron in North America is the same as a neutron in Europe – so, what is the problem? While the physics doesn’t change, national regulators interpretation of the risks and how to best manage those risks vary widely which limits the wide scale deployment of standardized nuclear reactor designs.

High-level safety and regulatory requirements have been well implemented and agreed through consensus at international level through the Convention of Nuclear Safety and the International Atomic Energy Agency’s (IAEA) safety standards. Why then is it, we continue to build different versions of the same reactor design in different countries.

In most cases national regulatory requirements were developed using national experiences, and implemented to support national programmes, during which time little thought was put into aligning approaches between different countries. The existing international requirements have been developed from these national requirements at such a high level that they can be applied to all existing national regulatory frameworks.

Various international activities through organizations such as the IAEA, Western European Nuclear Regulators’ Association (WENRA), NEA Multinational Design Evaluation programme (MDEP), and World Nuclear Association’s Cooperation in Reactor Design Evaluation and Licensing (CORDEL) working group, among others, have attempted to further harmonize the application and interpretation of these high-level standards into specific national regulatory standards and guidance. These efforts have not gone far enough, and significant variance between reactor designs deployed in different countries continue.

Gen III reactor deployment

This variability can be best demonstrated by looking at why we don’t have large fleets of Gen III nuclear power plants operating around the world today, and where the same reactor design has been built or licensed in multiple countries, why the design has changed.

The CORDEL report ‘Different Interpretations of Regulatory Requirements’ examines this in detail providing examples of when the national regulatory licensing approach has altered the designs of the Westinghouse AP1000, Hitachi-GE ABWR, EDF / Framatome EPR, and Rosatom’s VVER-1200.

The differences in national regulatory approaches and the subsequent design changes required to be implemented has resulted in what should be Nth-Of-A-Kind (NOAK) projects reverting to  First-Of-A-Kind (FOAK) projects, thus incurring many of the project and licensing risks and costs often associated with such projects. This means that from the project outset there is a great deal of uncertainty regarding the licensing duration and output.

Key conclusions

The newly published CORDEL report discusses a wide variety of safety requirements, from defence-in-depth to Heating Ventilation and Air Conditioning (HVAC) design, and how their implementation varies between national regulations and guidance. The review undertaken found that differences in the outcome of design solutions, are often driven by differences between the way in which national regulators identify fault scenarios / conditions and acceptance criteria, which ultimately define the design provisions.

The differences between the acceptance criteria amongst national regulators can be difficult to distinguish as it is not always part of the established requirements, but in some cases may be strongly influenced by the differing interpretations of national experts.

The report also identified that the method of demonstrating a safety case can vary widely between national regulators e.g., prescriptive vs non-prescriptive approaches. When reactor vendors wish to licence their design in a country with a different regulatory framework, the different levels of prescriptiveness in regulations and guidance can lead to a complete re-framing of the original safety case – and ultimately a significant amount of effort from the reactor vendor to produce new documentation that was not required in other countries.

It would be expected that more prescriptive regulatory frameworks are less flexible and would result in many potential design changes through the licensing process; however this is not necessarily the case. Just because a regulatory regime is less prescriptive in nature, it does not mean that significant design changes will not be required to fulfil the national regulatory requirements.

Implications for new reactor designs

So, what does all this mean for new reactors designs proposed to come to market in the next decade? Well, put simply, if we do nothing and national regulatory approaches continue to drive significant design changes and thus resetting developers to FOAK projects in each new country, many of these designs will never reach market, or will struggle to expand beyond their country-of-origin regulatory framework and supply chain.

It is vital that national regulators and reactor vendors learn the lessons associated with the national approach to regulation of Gen III reactor designs and apply these to the review of emerging technologies, such as SMRs, to facilitate a wider deployment of standard designs, and support deeper decarbonization of our energy systems.

The CORDEL report makes several recommendations for reactor vendors, licensees, and national regulators to be more cooperative and expand upon both the specific safety requirements identified within the report and the key lessons to develop a new streamlined approach to regulation, utilizing risk informed decision making (RIDM) where possible.

To do so, this would require extensive collaboration between governments, national regulators and industry. To facilitate this collaboration, the report points to the suggested outcomes of another CORDEL report ‘Harmonization of reactor design and licensing: lesson learned from transport’ which recommends the formation of a Multi-National Advisory Panel (MAP), whose aim would be to facilitate just such collaboration among national regulators.

However, this cannot be done by national regulators alone. Governments must provide the policy and financial support to allow regulators to support this level of collaboration, and industry must collectively support regulators undertaking efforts to harmonize industrial codes and standards and to develop industry positions on key safety requirements.

It should be noted that this is not a proposal to either challenge national regulatory sovereignty or reduce the required level of safety standards. In fact, through appropriate collaboration, both of these can be maintained and even enhanced.

There is a lot of work to be done if this is to become a reality and it will not be easy, but without the streamlining of approaches to regulation, the ability of emerging designs to achieve NOAK costs would be limited, and there may only be a small number of countries with sufficient capacity to build the requisite number of plants.

It is therefore essential that governments, regulators, and industry alike take on board these lessons and implement a framework to allow a harmonized approach to regulation. Otherwise, there is a risk that in a decade or so from now we may be asking ourselves: “Why aren’t there large fleets of SMRs operating around the world, and why can no-one export Gen IV reactors?”.

This article first appeared in Nuclear Engineering International magazine.