Analysis: Nuclear in small packages

Ongoing uncertainty about the future of large-scale nuclear generation in the UK has put the spotlight on the role that smaller, cheaper reactors might play. Tom Grimwood reports.

Large-scale nuclear is having a difficult rebirth in the UK. The Hinkley Point saga was expected to end in July when EDF made its final investment decision.

However, prime minister Theresa May had different ideas, calling for a review and delaying the project yet again.

With the sheer scale of the nuclear power plant, and the massive amount of capital required – £18 billion – it is no surprise that attention is turning to smaller, cheaper alternatives that could be quicker and easier to build.

These alternatives include small modular reactors (SMRs). Proponents say these offer a form of secure, low-carbon energy, the cost of which is comparable to, if not lower than, larger reactors. They come with the bonuses of smaller up-front costs, shorter build times, the option to gradually scale up capacity and even to provide low-carbon heat.

So enticing is this proposition that the government has now launched a competition to find the best value small reactor technology.

However, critics say it is a solution looking for a problem; an attempt to make nuclear seem relevant at a time when alternatives are looking more and more appealing.

If SMRs are to find a future in the UK’s energy mix, they will have to overturn a key principle which has historically underpinned nuclear reactor design – economies of scale.

Building one 400MW reactor rather than two 200MW ones, goes the argument, will not require twice the amount of materials and land to build, or twice the number of staff to operate.

The 3.2GW Hinkley Point C project is a product of this thought process, as are the other reactors proposed for development in Britain at Wylfa Newydd in North Wales and Moorside in Cumbria.

Tony Roulstone, nuclear lecturer in the Department of Engineering at the University of Cambridge, says: “With smaller reactors you’re going against that trend and against that principle.”

SMRs rely on a different form of economies of scale to keep costs down – economies of mass production. The idea is that building them in large numbers in a controlled factory environment will avoid expensive on-site construction issues and enable suppliers to refine the manufacturing process.

“If these small reactors were to try to make up for their losses of economies of scale through this kind of mass manufacture, they would have to be manufactured in the hundreds, if not the thousands,” says MV Ramana an associate research scholar at the Princeton University Nuclear Futures Laboratory. “Are there hundreds of utilities looking to buy the reactors? The answer is no.”

According to Ramana, the idea of SMRs is appealing to utilities; particularly the short build times and lower up-front cost for each reactor. However, they are unlikely to be prepared to place an order until the reactors become cheap enough. That will require any developer to have a large enough order book to build the factories that will produce them. “There’s a chicken and egg problem,” he says.

There is reason to be sceptical that reactors really exhibit economies of scale in terms of the reactor size. “Theoretically it sounds very plausible – but there is almost no evidence of it working,” says Roulstone. He points out that studies from France, Japan, the UK, Canada and South Korea have all shown that these economies of scale are either small or completely absent.

A report looking at the history of the French nuclear programme by Arnulf Grubler, programme director at the International Institute for Applied Systems Analysis, found that costs had actually increased as reactors got bigger.

That being said, academic research at the Department of Nuclear Engineering at Texas A&M University has estimated that each kilowatt-hour of electricity from an SMR would still be at least 15 per cent and up to 70 per cent more expensive than a kilowatt-hour from a large-scale nuclear power station.

Whatever the case, one factor that the Energy Technologies Institute nuclear strategy manager Mike Middleton says is a “game changer” for the economics of SMRs is the potential to use them for district heating.

“[SMRs] have got a more flexible approach to siting. You can find sites to put SMRs where you can’t put big plants,” says Middleton. Not only can SMRs be located closer to urban and developed areas, including industrial sites, “their thermal output is such that they’re a much better match for the amount of heat that will be required by city-scale district heating systems”.

The ETI estimates that revenues from selling heat could match those from power generation for SMRs, and with a 20 to 30 per cent loss to electrical output taken into account, this represents a 40 to 60 per cent increase in overall revenues.

One of the biggest challenges will be persuading the public of the benefits of locating reactors closer to population centres. Roulstone says: “I think that the public’s not ready for it yet. It’s quite a hill to get over.”

SMRs could present a viable future for new nuclear, and one that could complement larger scale nuclear plants and other low-carbon technologies that are being developed.

The main issue the technology faces revolve around finances and whether the savings promised by the theory of economies of mass production can be realised. This will only be known if and when mass orders for SMRs start being manufactured.

To achieve this, a long pipeline of orders is required, and this would stretch beyond the UK’s national boundaries. As the government presses ahead with its competition to find the best value SMR design for the UK, it will have to work with other nations to crack the reactor riddle.


 


The SMR shortlist

The government has named the organisations eligible for the first phase of its competition to find the “best value” small modular reactor (SMR) for the UK. Here are a few of the contenders:

NuScale Power

NuScale’s plant design has up to a dozen 50MW power modules that can be combined to form a larger 600MW plant. The modules will be suspended in a below ground pool, and will each contain a passively cooled integral pressurised water reactor and a steam generator.

The company has been awarded $217 million by the US Department of Energy to develop the design and has plans to install the first module in Idaho in 2024. Earlier this year it commissioned Sheffield Forgemasters to fashion a demo reactor vessel in Britain by the end of 2017.

U-Battery

U-Battery are going small, so small that they’ve dubbed their 4MW reactor design micro nuclear. The Urenco-led consortium says it will be ideal for a number of niche roles: providing combined heat and power (CHP) for heavy industrial users, powering remote towns and villages without grid access, replacing diesel plant as backup generation, and being deployed to power desalination plants.

The design has been optimised for CHP generation, and the consortium says it could also be used to produce hydrogen as well, giving it a ‘tri-gen’ capability. It will be powered by TRISO fuel – small particles of uranium oxide coated in high-temperature ceramics. U-Battery says this will have significant safety advantages over traditional fuel and make a meltdown impossible. It is currently aiming to have a demonstration unit up and running by 2024.

Moltex Energy

Moltex’s design is for a stable salt reactor in which the nuclear fuel – uranium or plutonium chloride – is suspended in a molten salt coolant. The coolant will not be pressurised.

The company says the by-products of fission will form stable compounds rather than gases, so the design will prevent the spread of radioactive material if the core is damaged. Also, there are no high-pressure systems and few moving parts, so it will be relatively simple to build.

Tokamak Energy

Perhaps the most ambitious entrant into the SMR competition, Tokamak Energy is hoping to crack fusion power; something that hasn’t been done at any scale yet. The company is a spin-off from the Joint European Taurus reactor at the Culham Centre for Fusion Energy in Oxfordshire.

The firm believes smaller reactors are the way to go for fusion, because they can achieve a “much higher plasma pressure for a given magnetic field than conventional tokamaks”. Tokamak is planning to build five prototype reactors on the road to achieving fusion power. It has built two so far and has begun work on a third.