To take a case study, let’s look at those HTGR and try and prepare one for mass production. Firstly I’d recommend dropping the core temperature down to 650 °C. We’d still likely require at least a Nickel alloy lining of the core, but the outer casing of the pressure vessel and the turbogenerator kit can now be made out of Stainless steel alloys. We would of course be sacrificing superior energy efficiency and the ability to make hydrogen thermally, but this drop in core temperature would solve so many problems it would be worth it. I’d also recommend shrinking it in size to around 20 – 40 MWth, that way we end up with a pressure vessel that’s easily forged or cast and yet still light enough to be moved around by a small crane and hoist system and that is also easily road or rail transportable (I’ll admit to WEG’ing it on that point though!).
I’d also probably ditch the whole “pebble bed” idea, as the mechanics of that while not impossible to mass produce “complicate things” and could lead to maintenance issues further down the line. Again, that graphite core, I would also investigate whether some alternative to that can be used, ideally something easier to dispose of afterwards and less of a fire hazard. I’d also likely drop any ideas about using Thorium, at least until any market for it, and the technology to make it work, have both been firmly proven.
10.4.3 – Design for Manufacture, the LWR
In another example we could take an off the shelf naval BWR or PWR reactor and civilianise it. Firstly, we’d need to ditch the highly enriched fuel and use something less “terrorist friendly”. We’d also need to beef up safety systems, ideally make the core capable of cooling by natural convection and fit some form of last ditch Boric acid injection system to shutdown reactions in an emergency. The individual parts of the reactor would likely need to be redesigned for mass production.
10.4.4 – Design for Manufacture, the implications
Looking at the two proposals above it is clear that in all likelihood the mass production of small reactors would result in a reactor design that is less energy efficient and thus burns more fuel per kWh than current reactors. So if we planned on using these to replace our existing nuclear capacity, we’d be increasing the burn up rate of our global fuel stocks, and increasing the amount of nuclear waste being generated. So we just made a failing grade on two of our important criteria!
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