What if we could design and build a nuclear reactor :

  • That uses no water and so can’t have high pressure steam or hydrogen explosions,
  • With fuel that can’t have a nuclear melt down, or melt through the reactor walls,
  • That fissions over 99% of its fuel, so there’s no waste needing storage for hundreds of thousands of years,
  • and some designs can consume spent nuclear fuel from other reactors?

Well, we’ve already built one, and we ran it for 5 years! (But you probably never heard about it…)

What Is A Liquid Fluoride Thorium Reactor?

A Molten Salt Reactor, such as Liquid Fluoride Thorium Reactor (LFTR, pronounced “lifter”) produces energy using a liquid (molten) nuclear fuel, not a solid fuel. MSRs also use a coolant that remains liquid at atmospheric pressure.

LFTRs are designed to convert Thorium (Th-232), an inexpensive and abundant material, into Uranium-233 which can then undergo nuclear fission. Other types of MSR can use spent uranium, depleted uranium, or plutonium, eliminating nuclear waste from solid-fueled reactors.

With liquid fuel and atmospheric pressures, MSRs solve the safety and waste disposal problems our current (1970’s design) light water reactors (LWR) have.

With all the attention lately on nuclear waste, nuclear accidents like Fukushima, and producing energy without climate change, we need to look at nuclear energy not from our current type of reactors.

Most safety concerns of LWRs are from using water coolant; LFTR is a molten salt reactor (uses special salt as coolant).

All the nuclear waste problems of LWRs are from using solid fuel (less than 2% of the fuel gets used); MSR uses molten fuel, so can consume all the fuel leaving only short-term waste.

How does a LFTR molten salt reactor use thorium?
from Kirk Sorensen’s presentation slides TEAC3

With a reactor design that is inherently safer, the expensive “engineered in depth” safety equipment of LWRs is not needed, making LFTR smaller and dramatically less expensive than LWRs.

We abandoned MSRs in the 1970s (we decided to go with the liquid-metal-cooled fast breeder reactor (LMFBR) which produced reactor fuel faster). We later dropped the LMFBR due to proliferation concerns and reactor control issues, but never came back to MSR, mainly from political inertia.

A demonstration Molten Salt Reactor (MSR) was developed at Tennessee’s Oak Ridge National Laboratory in the early 1960s and ran for a total of 22,000 hours between 1965 and 1969.

Alvin Weinberg, who ran Oak Ridge National Laboratory (ORNL) while the Molten Salt Reactor Experiment was conducted, was also the original inventor of the Pressurized-Water Reactor PWR used today (got the patent in 1947).

Of the Generation-IV reactors being developed, only the MSR has been built and operated.

People are working on the engineering to bring a full LFTR into production (an MSR with a Thorium “blanket” to convert Thorium to Uranium fuel).

FLiBe Energy in the USA plans to build a LFTR. The Chinese Academy of Sciences has MSR plans — in 2010 they visited Oak Ridge National Laboratory; and Chinese New Year in 2011 they announced they would be starting a Thorium Molten Salt Reactor program (and patenting every advance they make).

MSR modeling and design work is also being done in other countries, incl. Canada, France, Czech Republic.

Liquid: The fuel is Uranium in a molten salt, circulating continuously through the reactor, for over 99% fuel burnup, and easy processing of fission byproducts.

Fluoride: The salt used is made of Fluoride, Lithium and Beryllium, (or similar salts) very chemically stable, very high boiling point (liquid from ~400° to ~1400° C), and essentially impervious to radiation damage. The high heat capacity of fluoride salts lets a LFTR operate safely at temperatures much higher than water-cooled reactors (1000° vs. 350° C) for more efficient electric generation and industrial use. Most fission byproducts chemically bond with the salt.

Thorium: A plentiful metal, probably a couple of grams in your yard. Among the least radioactive elements, commonly discarded as waste from Rare Earth mines. The reactor converts Thorium to Uranium for fuel.

Reactor: LFTRs fission uranium to produce heat. LFTRs are extremely resistant to nuclear proliferation (from mining to disposal) and produce only a very small amount of short-lived, low toxicity waste which is radioactivity-wise completely benign within 350 years.

LFTRs run at atmospheric pressure, so much less expensive construction than LWR, and much less expensive to operate. Passive safety features handle emergencies, even if no water or power is available.

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