Monday, 11 April 2016

Small Modular Reactors: wishful thinking on a grand scale

Take a large number of scientists who have grown up with the firm belief that nuclear power is the future of energy, face them with the fact that nuclear power is proving to be undeliverable in anything like the scale, time and cost that has been originally envisaged in UK Government plans, and what do you get? Wishful thinking about 'small modular reactors' or 'smrs'! You can see this in the article in the Times by Lady Judge at :

She says that:
'The plan to focus on building large reactors was originally conceived before Fukushima, while I was chairwoman of the UK Atomic Energy Authority, and when fossil fuel prices were expected to keep going up. Large nuclear plants, however, are expensive and take a long time to build. In the interim, one answer is small modular nuclear reactors. Being small is useful because they can be built in one place and transported to another, such as the site of one of the coal plants that we are in the process of shutting down, or even an industrial park. Modular, in this context, means that more plants can be added easily on an existing site. The flexibility and lower cost of small reactors is a way of getting greater private sector involvement, without the more complex financing arrangements needed for a larger plant'

The impression you get from this is that the idea of large nuclear reactors is some sort of fairly recent deviation, and that somehow there was some golden era when (presumably) smrs were abandoned through some mistake. The advantages of smrs are stated as if there is evidence for this.
There is no evidence at all for this, and indeed the notion that smrs would ever be cheaper than large reactors flies in the face of engineering logic.

Nuclear reactors in the UK (and in the rest of the world) have been steadily scaled up from around 200 MWe in size to begin with, up to around 500 MWe in the 1960s, and then up to over 1000 MWe in the 1980s and 1990s. Contrary to the impression given in Lady Judge's article, this was not a recent decision or trend. And there are sound engineering reasons for this, including one very simple one: for complex machines with moving parts and the need to ensure (safe) functioning of each unit each unit needs much the same input for design as a much larger unit.

By way of comparison, if you want to build a gas fired power station to generate, say, 500MWe of power, people don't lash together dozens of small gas turbines - that would be financial madness. You have smaller gas turbines when the circumstances demand it, you do not do it out of choice because they generate much cheaper power at much bigger scales. To minimise costs developers will prefer to build one large unit, and they can take several years to build, although of course there is much more certainty about the costs and timescale of building gas fired power stations compared to nuclear power plant. Given that nuclear reactor sets will need much more safety care compared to gas fired power plant, there is no way in this universe that the principles applied to gas turbines are suddenly going to be reversed in the case of nuclear reactors - indeed the reverse is likely to be the case - ie there is even more pressure to upscale nuclear reactors compared to gas-fired power plant.

Sometimes we hear talk about the nuclear powered submarines built by Rolls Royce. But these generate no more than a few MWe of power and whilst we don't know how much they cost exactly, the submarines cost billions of pounds each. Rolls Royce may well be keen to get down to earning money through doing research in smrs, but will they be able to contribute to a project that is cheaper than Hinkley C? I think not.

There is of course no comparison to be made with solar pv cells. They are very small, passive items, with no unit specific design costs. They can be assembled along massive production lines allowing big economies of scale and where you can also get very big supply chain economies of scale - on the basis of just 250-300 watts each. You can, and solar pv companies do, produce hundreds of thousands of units a year. This is simply on a different dimension to nuclear reactors.

The moral of this story maybe that it doesn't matter how clever people are, they can still have unlikely beliefs. The fact that so many scientists appear to subscribe to the nonsense about smrs says something about how being clever doesn't protect you from believing in rubbish, not that smrs are somehow a cost-effective prospect. Never in the history of humankind, (so far as I am aware) have so many clever people subscribed to such an inherently ludicrous concept before!


  1. Nice one Dave.
    I have just seen the Lady Judge article via the Claverton digest.

    I will believe in the utility of small nuclear when they ask the Queen to allow one in the back garden of Buckingham Palace. They could easily green the structure with tasteful gardens and use the waste hot water in a district heating scheme for Whitehall and Westminster. (I haven't quite worked out what to do with waste heat in the summer, I have to admit. Perhaps an extended season for covered cropping for salads across the Royal Parks or some giant leisure centres with 'outdoor' heated swimming pools - we used to call them ‘Lidos’ back in the day in suburban London?)

    Should I apply for a slice of the research grant?


  2. There are numerous and powerful reasons for not building any more nuclear reactors. Should we rely on those rather than get diverted into less convincing ones? I’d like to query two of the points raised.

    1) …the notion that smrs would ever be cheaper than large reactors flies in the face of engineering logic.

    Large modular gas boilers are used commercially in cascades. This arrangement is supposed to be more fuel efficient and flexible than using really massive boilers and also benefits from economies of scale to do with mass production. If not, why do they sell? For examples:

    2) Lady Judge wrote: “Being small is useful because they can be built in one place and transported to another” She appears to be referring to the benefits of prefabricating in a controlled factory environment rather than on site which others have claimed in favour of SMRs.

    There are examples in the building industry of more and sometimes large building components being prefabricated in factories rather than on site because of the tighter control that enables. Here are some examples of PassivHaus buildings incorporating sometimes large prefabricated components:

    I am not, however, arguing in favour of SMRs. Given the highly complex technology involved for nuclear power compared to the much simpler technology required for Passivhaus, renewables and pumped storage it is highly unlikely that SMRs could ever compete economically with these alternatives especially if you factor in decommissioning and long term waste 'disposal' (storage). The huge sums of money being spent on SMR research should of course be spent instead on developing energy storage - pumped storage, tidal schemes with lagoon storage, seed grants for Passivhaus - rather than propping up the self-interest of the likes of Rolls Royce. The carbon cycle of uranium mining and its associated environmental degradation and worker health risks, the long term costs, damage and unknown long term ecological effects of major accidents such as Chernobyl and Fukushima, the immorality and fundamentally undemocratic nature of the legacy being left for future generations, unable as yet to have a vote, to clean up the mess we are creating, the fuelling of nuclear weapons and increasing risks of terrorist attack and the inability to get full insurance coverage of the risks all lead to the conclusion that the continued pursuit by our government of nuclear power is the result of powerful lobbying by vested interests rather than any benefit to our society.

    But to argue that modular design and prefabricated construction are per se inevitably uneconomic is, I would suggest, a misconstrued sidetrack. I think it would be better to argue that any financial savings or increase in safety these _might_ engender would be too minimal to overcome the much more powerful reasons for calling an immediate halt to the nuclear programme.

    1. Please read my argument. If you read my argument carefully a central point I made was that nuclear reactors cannot be compared with 'passive' pre-fabricated units that can indeed be mass produced with long production lines and supply chain economies. Nuclear reactors consist of complex parts that have to be carefully coordinated with lots of moving parts - they are not passive units that can be assembled automatically. They require careful individual calibration (you bet with nuclear safety in mind!) which costs a lot of money to produce each unit - you end up spending a lot of time designing each single small unit. They have to be individually designed and thus the advantages of mass production (even this is a non-starter in required numbers) cannot be mobilised. You require a lot of the costs for designing one small unit compared to the costs of designing a much larger unit. Nuclear reactors cannot in any way be compared with building components. I tried to make this distinction in my blog post above by comparison with solar pv panels.