Sunday, April 14, 2019

Take This with More Than a Grain of Salt

A pretty good article on the promise of molten salt nuclear reactors as a solution to long-term carbon dioxide free electrical power at Watts Up With That: Powering the future – with no compromises
A molten salt reactor (MSR) is a class of nuclear fission reactor in which the primary nuclear reactor coolant and/or the fuel is a molten salt mixture. MSRs offer multiple advantages over conventional nuclear power plants, although for historical reasons, they have not been deployed.

Watch the video:

Molten salt reactors operated in the 1960s.
  • They are seen as a promising technology today principally as a thorium fuel cycle prospect or for using spent LWR fuel.
  • A variety of designs is being developed, some as fast neutron types.
  • Global research is currently led by China.
  • Some have solid fuel similar to HTR fuel, others have fuel dissolved in the molten salt coolant.
Molten salt reactors (MSRs) use molten fluoride salts as primary coolant, at low pressure. This itself is not a radical departure when the fuel is solid and fixed. But extending the concept to dissolving the fissile and fertile fuel in the salt certainly represents a leap in lateral thinking relative to nearly every reactor operated so far. However, the concept is not new, as outlined below.

MSRs may operate with epithermal or fast neutron spectrums, and with a variety of fuels. Much of the interest today in reviving the MSR concept relates to using thorium (to breed fissile uranium-233), where an initial source of fissile material such as plutonium-239 needs to be provided. There are a number of different MSR design concepts, and a number of interesting challenges in the commercialisation of many, especially with thorium.

The salts concerned as primary coolant, mostly lithium-beryllium fluoride and lithium fluoride, remain liquid without pressurization from about 500°C up to about 1400°C, in marked contrast to a PWR which operates at about 315°C under 150 atmospheres pressure.

The main MSR concept is to have the fuel dissolved in the coolant as fuel salt, and ultimately to reprocess that online. Thorium, uranium, and plutonium all form suitable fluoride salts that readily dissolve in the LiF-BeF2(FLiBe) mixture, and thorium and uranium can be easily separated from one another in fluoride form. Batch reprocessing is likely in the short term, and fuel life is quoted at 4-7 years, with high burn-up. Intermediate designs and the AHTR have fuel particles in solid graphite and have less potential for thorium use . . .
If you're against fossil fuels because of CO2 production, and the threat of climate change, and you're not pro-nuclear, you're a patsy of a movement that want to cripple the West. I'm not worried so much about climate change, but I'm strongly pro-nuclear power. I'd much rather live close to a big nuclear power plant than a big coal burner, or even a big natural gas plant. In fact, I do.

I was out talking to my neighbor the other day. He works for the Nuclear Regulatory Commission up in Rockville (he was formerly an operator at the local nuke). He was talking about MSRs and how much trouble they were having trying to fit them into the same regulatory structure as the PWRs had been subjected to. He mentioned that they were designed to be "fool proof", with passive safety features not requiring a continual energy input to cooling pumps like PWRs. He sounded a little frustrated.

It's time for the US to get serious about this technology.

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