With around 80 designs of small modular and advanced reactors on the drawing board there is clearly an abundance of creativity across the nuclear industry. That could spark a new nuclear era, bringing all the benefits of low-carbon, energy dense and dispatchable resource to diverse new markets and applications. Some of the SMR designs that are being proposed are generational types of existing power station reactors. However, a lot of the designs are newer technologies, for example molten salt reactor technology or heat pipe reactors. The problem is that for these newer technologies and the types of fuels that are going to be used in them, the regulatory framework is simply not in place.

Simon Chaplin, transport specialist at the World Nuclear Transport Institute (WNTI) outlines some of the issues: “If you’re transporting the fuel for some of the reactors being proposed, this is high assay, low enriched uranium [HALEU]. That’s higher than the enrichment for which the majority of packaging has been designed for, so the regulatory authorities will be need to look at new packaging and then developing the regulations that surround that.”

Another area of regulatory concern is transportation not just of fuel, but of fully fuelled turn-key reactors. “We may have SMRs where they’re transported without fuel involved, which won’t be difficult because there’s no nuclear element to it. It’s just something which is transported, constructed, and then the fuel will be taken to the site where it’s used. This approach would be operated in the same way that they do now with conventional large-scale nuclear power stations.”

He cites the Akademik Lomonosov floating nuclear power plant. ”That’s classed as an SMR but really that’s using established technology in that it’s based on PWRs so it’s technology that’s been around for a number of years,” says Chaplin. However, he adds: “Some SMRs will be constructed in a yard or a factory where the fuel will be loaded at the same time that it’s constructed or shortly after, maybe in that location or in a secondary location. At that point it will need to be transported with fuel which may be HALEU fuel or maybe more conventional fuel but the challenge we will have is that at the moment, if you’re transporting, say, new fuel to go in a power station there are specific types of packaging. If you now have fuel inside the reactor, then are regulatory issues associated with classifying the reactor as a fuel package or as a reactor in operation?”

This is a more complex issue than it may at first appear, as Chaplin explains: “If it’s classified as a reactor in operation, you could look at using the same rules that are in place for, say, the maritime estate for a nuclear-powered ship. In this case the reactor is considered to be just a part of the ship. However, if it’s a module that’s being transported in a turnkey state with fuel on board, it would be cargo. Under those circumstances there are separate rules to consider it as cargo rather than part of a vessel or conveyance but also whether it is classified as a package.”

If it is considered a package then the actual reactor that’s being carried would have to be able to withstand the same sort of conditions that a package would have to, for example a drop test, an immersion test, a stacking test, and a fire test. “All of those conditions would have to be applied to the reactor and that may not be something that’s easy to achieve. That is an immediate challenge to understand how we’re going to do that and how the various regulatory frameworks would apply,” notes Chaplin.

Designing reactors for lifecycle transport

One of the other associated with transportation and that must be established prior to deployment are the rules and regulations concerning the way that SMRs are potentially operated.

Conventional nuclear power stations are generally operated by an entity that regulatory or government authorities usually have quite close control over concerning the operations of a plant. They are also typically large sites that feature lots of physical security with fences and security guards and they’re generally close to a populated area where people can relatively easily respond to emergencies or security incidents that may arise. For an SMR it could be that none of these conditions may apply.

“With an SMR potentially they may be located in a very remote area and there’s also the potential that they may even be operating automatically and therefore maybe unmanned. The operators will have to make sure that things like safety, security and safeguards would need to be considered in the actual design stages. Just as safety by design is already a consideration so there will be security by design and safeguards by design as well,” says Chaplin, who adds: “Designers will need to consider where it is and how it’s going to be operated to make sure that there is sufficient safety, security and safeguards. That will also apply to the transport phases of the operation too, during transport to the site of operation, during operation and then during the decommissioning.”

Indeed, decommissioning is potentially another particular challenge for SMRs. Chaplin expands on this theme: “Within the design of all of the SMRs that are proposed, the decommissioning process must be considered as well. It may not be possible to decommission in the same way as a conventional site where decommissioning is done in situ and components are taken apart. Instead, they may have to consider an SMR with a spent fuel inside it which will need to be transported to another site for decommissioning.”

While it is clear that designers will need to make sure that all SMRs will be suitable for the operations necessary for the entire life cycle, not all are giving sufficient prominence to the transport issue. As Chaplin observes: “Within the WNTI membership we’ve got several companies that have been designing SMRs and transport is something that they definitely think about, whereas others sometimes indicate that transportation is an issue to be considered at some later date. That’s quite remiss because if you can’t transport it, you’re not going to be able to operate it either. In terms of potential barriers to SMR deployment that’s a deal breaker. If you can’t move the fuel or you can’t move the reactor to the site or take it away again, that’s it. It’s dead in the water”.

Establishing regulatory frameworks

In considering SMRs there are potentially two different types that require considerably different approaches. Some designs are delivered as a complete unit or modules that get assembled in a location and which will stay in that location for the entirety of the unit’s operational life. There are also potentially designs which will be very mobile and which feature an easily transportable containerised reactor, possibly with some other containers which would carry the balance of plant. They may be used for disaster relief, for example, as they can be taken to a location, operated for a number of weeks or months and then taken somewhere else. The fact that a reactor could be moved has some profound implications for the regulatory regime.

Chaplin explains: “At the moment the countries that are talking about using SMRs are countries which already have a developed or even an early-stage nuclear industry or a nuclear regulator. However, there are a lot of countries which will be using SMRs which don’t have a nuclear regulator. They may well not have had any reason to develop a nuclear regulatory framework. Inevitably the host nation would need to have some sort of oversight and some way to intervene if necessary but if they haven’t got a developed nuclear regulator, they won’t have the skills to do that. That is a lot to do.”

In that situation, the host nation are perhaps not going to want to have to develop the necessary regulatory bodies or take too much responsibility for oversight of a plant. In which case it’s more likely that the regulatory side will just focus on making sure that operations are being conducted safely while the operator will be responsible for all of the running, maintenance, staffing and also taking the reactors away at the end of the project. However, where those responsibilities lie will need to established in advance, as Chaplin says: “I think another thing which really needs to be considered by the designers and operators long before deployment is to actually work out who will be responsible for what. That is not so difficult with, say, a land-based SMR but for a floating one that could be more challenging. It will need to determined whether responsibility rests with the country that supplied it and is operating it, if they’re going to be responsible for things like safety, security and safeguards, for example, or whether it would be the host state that would be responsible for those. We don’t really know the answer as to how that will work yet.”

These regulatory issues may also have far-reaching implications for market development too. For some SMR designs, from a regulatory stance and an operations perspective, they are not really any different to the large-scale plants that are already in operation or being developed. “For these kinds of designs the actual modules will be transported without any fuel involved so they are just pieces of equipment that will be constructed and operated in the same way as a large-scale PWR. Designs from Westinghouse, Rolls-Royce, and GE Hitachi are essentially smaller versions of conventional designs and so are potentially going to avoid a lot of these transport and regulatory issues because it’s already been done for their bigger cousins. They might actually get ahead of advanced designs just because they already have, for example, transport package approval and all the associated validation and testing,” notes Chaplin.

Progress on regulatory frameworks

Although many issues remain outstanding to develop the right regulatory frameworks that will be appropriate for all the various SMR designs, progress is clearly being made. Chaplin explains: “Within the international Atomic Energy Agency they are beginning to look at all the regulatory environments. Similarly, in the International Maritime Organisation (IMO), because there are similar issues but also additional ones with transporting a nuclear power plant at sea, there aren’t really the rules in place for doing that.”

WNTI have been invited by the IAEA to participate in working groups for transportable nuclear power plants, for example while another working group is being established specifically for floating nuclear power plants to help guide member states as they develop the regulations.

“They do see the importance of industry being involved in these discussions and not just safety, security and safeguards. They realise that they can’t just have the member states sit around the table and start coming up with what’s good, they need to have industry input just so that they can be certain the regulations and the recommendations that they come up with actually work,” says Chaplin.

Considering the IMO rules, fundamental changes will be needed to accommodate SMRs. “At the moment, it looks like one potential solution is to revise the rules within the safety of life at sea convention and specifically chapter eight, which is the code of safety for nuclear-powered merchant ships. That could be revised to encompass floating nuclear power stations as well. A floating nuclear power station has got to be towed somewhere by sea so there will be maritime regulations that will apply to it. At the moment, that regulation was drafted in the 1960s and was released in 1981. It’s hopelessly out of date given it was written at a time when they were only concerned with nuclear-powered merchant vessels which never really took off other than in the Russian Federation and formerly the Soviet Union,” says Chaplin.

Indeed, WNTI is currently conducting an analysis to explore what changes would be needed to those regulations to bring them up to date so that they can encompass not just nuclear-powered vessels, but also floating nuclear power plants and more specifically those that use new technologies like molten salt reactors alongside the more conventional pressurized water reactors. Aside from floating reactors, the shipping of reactors that are designed for terrestrial applications would potentially fall within those same rules or may come under one of the other regulations that cover cargo. Similarly, carrying a fuelled reactor as cargo might come under the International Maritime Dangerous Goods Code (IMDG) or the Irradiated Nuclear Fuels (INF) code, which are the regulations that apply when transporting irradiated fuel plutonium and high-level waste at sea. Those regulations could be expanded to encompass reactors with fuel on board, whether it be for deployment or under the circumstances where it’s being returned with spent fuel on board. Nonetheless, this is a work in progress, as Chapin notes: “At the moment, it’s not been done and no one has shipped a reactor with fuel in it as a cargo. The only time they have been moved at sea they are part of the conveyance so that will be completely new. None of this is actually in place, and the same applies to the packaging and all the other elements that will need to be in place.”

He notes that additional investment is needed in R&D so that drop tests can be conducted on the flasks and process like that will be ramped up as part of this drive to get SMRs built, shipped and deployed.

Chaplin continues: “For molten salt reactors reactors, heat pipe technology or those that will use HALEU fuel, for example, we need to get regulations in place and that can be a frustrating and very slow process where consensus is needed.” However, overall Chaplin is optimistic. He concludes: “SMRs are such a broad and diverse church, but they are coming at a great pace and we are a lot further along than I thought we would have been in just five years. It feels like it’s a monumental task but, like a snowball rolling downhill, it seems to be gathering pace. As more people understand the need for this and also the challenges, I think the faster it will be. There has been talk of deployment of some SMRs using molten salt reactors in the early 2030s. I wouldn’t like to say it’s not going to happen. I think that it’s easily achievable as long as momentum stays there.”