Small(ish) is beautiful

This a new article written by Ben Heard and me in the SA Mines & Energy Journal (issue 23, pg 22-23), about the potential for small modular nuclear reactors. (Ben should get the primary authoring credit here — my job was to ‘enhance’ this one rather than lead the writing.) For comments, head over the the BNC Discussion Forum, here.

Also, be sure to check out Ben’s reporting on the Walkerville ‘environmentalists for nuclear energy’ event that was held last Saturday. It was a great success!

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Back in August of last year, ‘born again’ nuclear advocate and long-time environmentalist George Monbiot made a surprisingly harsh call about energy solutions for climate change: “Small is useless”. Since the time of E.F. Schumacher in the early 1970s, we’ve heard the opposite. So what’s the deal?

Home solar PV systems are small. South Australia has easily the highest per capita installation of solar PV with around 15,000 systems, but this only adds up to 19.8 MW of (peak) capacity. It would take around 215 times this level of installation, or over 3.2 million systems just to match the yearly energy generated by the 760 MW of the Northern and Playford coal power stations.

Considering Adelaide has only 500,000 households, you can begin to see Monbiot’s point.

Conceptual drawing of a two module reactor, featuring full underground reactor containment, reservoirs for emergency passive cooling (top left and right) and fully contained below ground spent fuel cooling pond (bottom centre).

We need big solutions, solutions that can scale up. So what could possibly be good about the emergent technology of “small modular reactors” (SMRs) as a zero-carbon power offering?

When people think about nuclear power, they typically envisage something large. Huge, in fact. That’s reasonable, given that today’s global nuclear fleet is made up of plants larger than 600 MW, with the new French EPR coming in at a hefty 1,650 MW. For context, the entire baseload generation capacity for South Australia is around 3,000 MW.

But now, something very different is emerging in nuclear: the small modular reactor (SMR). These units range up from as little as 25 MW to around 180 MW. Their commercialisation will dramatically increase the flexibility and relevance of nuclear power in a range of settings, and South Australia is a good example.

As a mature, industrialised economy with a small population, South Australia’s overall growth in energy consumption is slow. It is difficult to envisage circumstances, any time soon, where there will be a strong case for an additional 1,000 MW of baseload to be added, all at once. So, for meeting new energy needs, nuclear power is on the outer.

Of course, we have a looming need to replace a great deal of baseload generation, starting with the 760 MW of the Northern and Playford coal power stations. That’s more like the size for nuclear. But unfortunately it has been so long since Australia invested in significant quantities of baseload that we are staring down a big “sticker shock”: the upfront price tag is going to be tough to swallow. That will be the case regardless of the technology, but nuclear is on the pricier end before heading into super-expensive solar options (more on the cost of nuclear for our final article). This leaves us stuck with the high greenhouse options of incrementally adding more low-efficiency gas for peaking (with high fuel costs), and smaller modules of higher-efficiency gas for new baseload.

But if nuclear power could be down-scaled… that changes things. What if, instead of purchasing 700-1000 MW all at once, you could buy 200 MW (or less) at a time, and work up from there? That is the promise of the small modular reactor: a compact, energy dense and zero carbon generating option for new power needs and fossil replacement in slow growing economies. Suddenly, the major capital raising challenge replacing 1,000 MW of baseload could be spread over a series of discrete investments, with returns beginning to flow much more quickly.

Here is an example of the technology we are talking about: the Babcock and Wilcox mPower reactor. Each unit is 180 MWe, suitable for modest growth in overall load, or progressive, staged replacement of fossil baseload. Anything up to 10 of these modules can be built in series to form a much larger plant. The mPower reactor is designed to be housed and contained underground. This is both a great safety feature, and a wonderful visual selling point for those concerned about nuclear reactors. Remarkably, it will only require refuelling once every four years, and the design provides provision for on-site storage of spent fuel for 20 years and the module has a service life of 60 years.

Conceptual SMR site plan, with two below-ground reactor modules in the nuclear island (left side, white building).

At the very small end of the spectrum is the Gen4 Energy Power Module at 25 MW. This type of size would be ideal to power around 20,000 homes (equivalent to 115,000 rooftop solar PV systems), especially in remote locations, or provide reliable district power to hospitals and other major precincts. This design is intended to be returned to the factory, intact, at the end of a 7-10 fuel cycle for decommissioning. At this level we can start talking about the notion of nuclear batteries!

All of the new SMR designs have applied the most up-to-date passive safety systems, meaning the safety of the reactor is in no way tied to external power sources. The units themselves will standardised designs, factory made and delivered by ship or rail to the installation site. They are streamlined designs, with both the reactor and the steam generators held within one compact containment. This again makes them very safe. Fewer systems means fewer potential problems.

Cutaway of a single reactor, showing fuel assemblies (bottom), the steam generator (middle) and the pressurizer (top).

This is emergent technology; we cannot pick up the phone and place an order for a small modular reactor. But its potential value has been recognised through the commitment by the United States Department of Energy of $400 million and a federal site at Savannah River National Laboratory to support the design, licensing, commercial demonstration and manufacturing of SMRs. There is huge benefit to be had from these new designs that improve the versatility of nuclear as a provider of zero-carbon baseload electricity while capitalising on major advances in safety and low-cost production. Somewhat perversely, the fact that Australia is currently so far behind in preparedness for nuclear generation (it is currently illegal under the EPBC Act), might mean that we will be well placed to move straight into these designs as they hit the market.

Small may be useless when it comes to tackling climate change. But smallish nuclear reactors, which still manage to pack an enormous energy punch, could play a big role in hastening the costly transition from aging fossil plants to super reliable, super safe and super compact new zero carbon generation.

That is a big deal.

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