Critical service in SMR development

Above: While relatively small features within the context of an overall build, valves are critical for keeping certain SMR designs functioning within ideal parameters

Nuclear power no longer has an image problem. The negative sentiment that has driven its decline since the 1990s is changing and many states, according to International Atomic Energy Agency (IAEA) Director General Rafael Mariano Grossi, are now looking to introduce or expand capacity.

In 1996, nuclear accounted for 17% of global energy production. Today, that figure is around 10%, but the direction of travel is clear. More than 50 reactors are under construction worldwide, mostly in China and India, while other countries have reversed planned nuclear phase-outs. Japan, for instance, is bringing nine reactors back online, with 30 due to restart by 2030.

These changes reflect a period of instability. Energy access and security of supply have become major concerns, with some nations having to rethink medium- to long-term strategy. This is a problem because stability is necessary to limit disruption as economies transition from fossil fuels to low or zero-carbon energy sources, not least those that introduce their own degree of intermittency, such as wind and solar.

Given this situation, it’s unsurprising to see attention returning to nuclear as the intermediary. It’s safe, ‘pilotable’, cost-effective when deployed correctly and, most importantly, zero-carbon. Granted, there is a certain irony in returning to a technology pioneered in the last century when many seem fixed on ‘future’ means of power production. However, the benefits offered by Small Modular Reactors (SMRs) – the industry’s most promising concept – are compelling.

Reduced capital costs, grid balancing, and deep carbon reductions are just some of the prizes SMRs offer. This stimulates huge demand and an influx of investment from governments, investors and R&D departments from some of the industry’s most recognisable names. There are also a large number of new entries to the market backed by VCs and consortia, reflecting the transformative power – and considerable profit potential – of a full commercial-scale design.

Reaching this point, however, will be difficult without a series of changes. These changes include a revision to the regulatory landscape but also closer collaboration with manufacturers that have existing knowledge of nuclear engineering and critical service in general.

Getting to grips with standardisation

SMRs are significant because they’re based on proven science. They also tie in with the idea that the vast majority of technologies required to achieve net zero emissions already exist, albeit in varying degrees of maturity.

Maturity is arguably the most obvious problem with today’s SMR market. There are currently over 80 designs at varying stages of completion, using different coolants and reactor types. This level of activity is undeniably positive, though it also hints at a lack of standardisation that will be essential for making SMRs financially viable.

An attractive business model is important for SMRs and the nuclear industry more generally – especially as the ‘all-in’ cost of renewable energy continues to fall. While interest is currently high, it’s not unreasonable to imagine investors moving away from SMRs if they begin to fall foul of the same delays and budget overruns seen at large reactor sites such as Vogtle in the USA, Flamanville 3 in France, and Hinkley Point in the UK.

But standardisation is not just an issue for those in charge of the balance sheet. It also cuts to the very reason why SMRs were proposed in the first place: convenience and reach. Modular reactors allow nuclear power to reach areas that are unfavourable for traditional multiple-hundreds of MW plants. There’s even potential for them to offer ad-hoc power for relatively short periods, deployed as part of an emergency response or in support of regional economic development. These opportunities are impractical, if not impossible, without a safe and reliable design that benefits from economies of scale.

While not standardised in the strictest sense, there are signs of real progress. GE Hitachi, for example, has made inroads with its BWRX-300, a 300 MW water-cooled reactor design based on its ESBWR design, the Economic Simplified Boiling Water Reactor. The ESBWR is already licensed by the US Nuclear Regulatory Commission, using the same equipment and fuel used in other GE Hitachi reactors currently in service across the world. Several engineering changes have taken place, including the reduction of safety relief valves and an increase in the design pressure. If approved, GE Hitachi’s SMR could be grid-connected sometime before the end of the decade. This would be ahead of most estimated timelines for SMRs being developed by established players, which typically lie somewhere in the mid-2030s.

It’s Rolls Royce, however, that offers the best example of why it’s important to keep commercial realities in sight during SMR development. The company is currently engaged in a partly UK government-funded programme to develop 470 MWe pressurised water units. The initial £500m (US$634m) of programme funding is due to run out before the end of 2024, which has caused Rolls Royce’s CEO to publicly request the drafting of a government deployment plan before the end of 2023. These SMRs are projected to cost around £1.8bn (US$2.3bn) – a huge saving when compared to the £9bn (US$11.4bn) that could be needed for one unit of Sizewell C. Whether that cost is achievable remains unclear until its Generic Design Assessment is completed.

The Promise of harmonised regulation

It’s difficult to overlook the regulatory maze surrounding SMRs and how this affects roll-out. Licences are needed for both design and operation. This applies to both the vendor where an SMR is being developed and to the end user. In most cases, these two parties will be in separate countries with different regulatory stipulations.

Given the number of proposed SMR designs in development, progression through licensing has become a slow and intimidating process. Regulators are unfamiliar with many SMR designs, especially those relying on innovative reactors and novel manufacturing methods.

Some of the more mature SMRs use established coolants, such as pressurised water, whereas others rely on relatively newer approaches using liquid metal, helium, and molten salts. Any deviation or change from what is already known or approved will need thorough testing evidence to guarantee safety.

This is understandable and should not be regarded as an obstacle to commercial success. After all, public confidence will be a requisite as local authorities bring nuclear power much closer to the places where people live and work. SMRs benefit from smaller reactor cores and, therefore, smaller radioactive inventories that, in theory, reduce shielding requirements and the size of emergency planning zones. Some also include an integral steam supply system in which the steam generator is directly connected to the reactor. These built-in passive safety systems provide SMRs with greater and, in some cases, indefinite coping times in the event of an offsite power failure.

Still, the industry recognises the complexities of cross-border regulation. In 2022, for example, the IAEA announced a Nuclear Harmonisation and Standardisation Initiative, which aims to simplify the process that would see SMRs readied for deployment worldwide. This also includes a framework for accepting factory-assembled parts that, once passed, would create a global production network based on a set of agreed manufacturing principles shared by the regulatory bodies of each participating nation. The idea would follow something similar to the regulatory landscape that is now established best practice in global shipping and aviation.

This would be a significant step forward, allowing a large number of parts to be licensed for production in multiple countries, creating the type of coordinated supply chain necessary to drive down costs. However, this solution also introduces its own set of challenges. Modular construction and fabricated parts built according to consistent codes and standards will require legal scrutiny, especially when it comes to logistics. For example, international nuclear liability regimes for transportable plants are still unclear, as is the applicability of environmental protection and public participation legislation.

The role of critical service

Given the long regulatory approvals process – even for businesses that are further ahead with their design – opting for what’s known to meet existing standards is clearly sensible. Not just to prove the overall SMR concept, but also to give economies a pragmatic way to complement the variable nature of renewables without creating a major shortfall.

Valves offer a good case in point. While relatively small features within the context of an overall build, they are critical for keeping certain SMR designs functioning within ideal parameters. IMI Critical Engineering is helping to accelerate progress in this area by assisting with the application and design of several core components, including all safety relief valve types. This includes main steam safety valves, main steam and main feed-water isolation valves, turbine bypass valves, and also emergency core cooling system strainers.

All these products have been previously approved for service in large-scale reactors. While they cannot be applied like-for-like in an SMR, they nevertheless have thousands of hours of operations proven in critical service, easing some of the unfamiliarity regulators will face with bespoke engineered parts. This is particularly important given the passive safety systems inherent to many SMR designs, which lower the barrier of entry for new, inexperienced operators.

This is not to say components can be overlooked or fast-tracked during development. Every part, irrespective of where it’s manufactured, must go through the same robust testing procedure that has underpinned decades of safe product design and engineering in nuclear. But, if simplicity and speed are necessary aspects of making SMRs a success, then it’s prudent for developers to work with existing components and companies with knowledge of how they perform in critical service. This is just one aspect of a much larger puzzle, though no less important for introducing a technology that can legitimately decarbonise the grid and wider industry at a meaningful pace.

Author: Luc Todo, President of Global Strategic Projects in Nuclear for IMI