What's so good about thorium nuclear reator fuel?

• Availability. Thorium is more plentiful in the earth's crust than uranium (about 3, or 4 times more so). Thorium is 400 to 500 times more plentiful than uranium-235 (which is currently the only fuel we really make use of).
• It doesn't even need to be mined because it's available as waste from the tailings of many rare earth mines. The kind of rare earth mines needed to make wind turbines, and solar panels. There's so much of this waste, we make about 40 times more, per year, than we need to power the world with!
• It does not need to be enriched like uranium, saving considerably on cost and energy.
• The thorium fuel cycle can begin using a blended mixture of plutonium and thorium. Such plutonium can be made from nuclear bombs or reprocessed 'spent nuclear fuel'. Britain has 140 tonnes of such plutonium stored, waiting to be disposed of.
• Thorium is then bred to make uranium-233
• In the thermal neutron reactor range, U-233 has superior neutronics to any other fissile material:

  	Thermal cross-section (barn)			ratio of capture+fission neutrons to capture neutrons
  	Scatter	Capture	Fission
  U-233	12	45	531	12.8
  U-235	10	99	583	6.9
  Pu-239	8	269	748	3.8

  
  With U-233, only one in 12.8 neutrons are wasted. In comparison, 1 in 3.8 Pu-239 neutrons are wasted.
  When Pu-239 absorbs such a neutron, it makes transuranic waste which can't be fissioned, and has a half-life of hundreds to thousands of years. This is radiotoxic, and is a reason reprocessed spent nuclear fuel, called MOX, is so limited - the more it's reprocessed, the more transuranics, the more radiotoxic it becomes. Transuranic waste like this can only be disposed of with time, or a fast reactor. Thorium fuel can be reprocessed avoiding this pitfall. It will make only a small fraction of the transuranics made in Pu-239, and U-235 powered reactors.
• Even when U-233 absorbs a neutron (capture) to make U-234, such U-234 can absorb a second neutron to make U-235, at which point it gets another chance to fission.
• Because so little U-233 is wasted, thorium/U-233 has by far, the best waste profile of any fuel type. It makes the least possible quantity of transuranics.
• A LFTR is a molten salt reactor using thorium fuel. The fuel can be denatured to protect it against the possibility of diversion for weapons making, so making the LFTR proliferation resistant.
• Some of the spent fuel waste is actually valuable. For example it contains considerable amounts of rhodium, one of the rarest elements on earth, which has specialist applications in chemical catalysis.

Reference

1. Revisiting the thorium-uranium nuclear fuel cycle (pdf) [DOI: 10.1051/EPN:2007007], 2007, by Sylvain David, Elisabeth Huffer and Hervé Nifenecker
2. Rethinking the Thorium Fuel Cycle: An Industrial Point of View (pdf), 2007, by Dominique GRENECHE, William J. SZYMCZAK, John M. BUCHHEIT, M. DELPECH, A. VASILE, H GOLFIER
3. Thorium fuel cycle — Potential benefits and challenges (pdf), IAEA, 2005

NORM waste

Here is an example of the stupidity and paranoia over low-level radiation. They are complaining about NORM waste (which is "Naturally occurring radioactive material"). USA defines NORM waste at 5 picocuries/gram. I calculated a 70kg person is about 235135 picocuries (8,300 Bq), or 3.36 picocuries/gram. That makes living people 2/3 radioactive waste. Our ashes certainly must be NORM waste.

How the NRC stopped the U.S. nuclear power industry.

It was the U.S. Congress that created the NRC in 1975 at the behest of the coal industry. Official line was that the Atomic Energy Commission had a conflicting mission of promoting nuclear energy and ensuring safety. The mission of promoting nuclear was given to the DOE and dropped. The NRC was given the mission to “maximize safety”. Orders for nuclear plants were cancelled as electric companies correctly anticipated skyrocketing costs and delays from onerous NRC regulation. In the 40 years since the NRC opened its doors not a single nuclear power plant was built from conception to completion. It will take the proverbial act of congress to reign in the NRC, or better yet, abolish it and replace it with something similar to the Atomic Energy Commission under which about 70 or 80 nuclear reactors were built in 10 or 15 years. That act of congress isn’t going happen as long as the fossil fuel industries own congress.

-- Jerry Nolan (first comment here)

What is the real cost of nuclear power?

Anti nukes will always quote the most expensive projects. Recently a thorough analysis of worldwide nuclear plants show the cost varies a lot. Hinkley C is almost 3½ times the cost of Indian, Chinese and South Korean reactors.

Hinkley C EPR :

US $7018/kW

Indian, Chinese and South Korean reactor, closer to

US $2000/kW

"Historical construction costs of global nuclear power reactors", 2016, Lovering, Yip, Nordhaus

A politician asks: can thorium be profitable for Norway?

It will be profitable when done with the right reactor design. Today's PWR, BWR, designs are too expensive. E.g. Hinkley C in Britain is horrendously expensive. ThorCon (a startup company aiming to make molten salt reactors (MSR), using thorium), reckon they can make a safer reactor, within 6 years, for 20% of Hinkley C prices. ThorCon are not unique. There are a host of other startups and molten salt reactor designs: Transatomic Power, Terrestrial Energy, Seaborg Technologies, Flibe Energy, Moltex SSR, Chinese designs, the Russian MOSART, the EVOL MSFR in France, Japanese, and Czech reactors. Bill Gates TerraPower are said to be working on a molten salt reactor too.

Note:

1. There are 3 practical nuclear fuels (fissile materials): plutonium-239, uranium-235, and uranium-233 (Pu-239, U-235, U-233).
2. Uranium consists of a natural mixture of two isotopes: U-238 : U-235, in a ratio of 1000 : 7. Only U-235 is fissile. It must generally be concentrated 5 times (or more) to be used as fuel. In a reactor some of the U-238 "breeds" to Pu-239. U-235 is the only naturally occurring fissile material.
3. There is about 3½ times more thorium available in the world than uranium. Thorium can be 'bred' to make a kind of uranium not found in nature : U-233. (much like Pu-239 is bred from U-238) U-233 performs better than any other fissile material in a thermal nuclear reactor (and 99%+ of reactors are thermal). This is the reason nuclear engineers love it.
4. A molten salt reactor is a very good natural fit for thorium. Molten salt reactors are also:
   • safer - they do not use water compressed at 80 atmospheres. So the possibility of catastrophes like Chernobyl or Fukushima is eliminated.
   • more efficient - because they operate at much higher temperatures (almost 400ºC above a PWR temperature), they convert more heat to electricity
   • potentially less expensive - the intrinsic safety of a MSR allows many expensive safety boondoggles to be dispensed with.
   • for more see: Advantages of molten salt reactors

The magic of thorium is really uranium-233. Poor uranium-233 had all its limelight stolen by the thorium upstart. U-233 has excellent neutronic performance in the thermal neutron spectrum : 90.3% of neutrons hitting a U-233 atom cause fission and release the atom's energy. Only 7.7% of neutrons are wasted (captured and absorbed). The fission : capture ratio (table below) shows that U-233 is 3.1 times better than Pu-239. I'm measuring this performance in terms of fissionable atoms (and neutrons) wasted. The more that are wasted the more difficult it is for nuclear power to be sustainable. To be sustainable we must be able to breed more fissile material from thorium or uranium-238 than we use up in make energy. The couple: thorium and uranium-233 are sustainable in both the thermal and fast neutron spectra.

In practice, uranium-233 can only be made from thorium. That's why thorium is talked about. But it's really about uranium-233.

The relative performance of 3 fissile materials U-233, U235, Pu-239 under thermal neutron bombardment (aka - in a reactor) :

Thermal cross-section (barn)

	capture	fission	total	% fission	fission : capture ratio
U-233	45	531	576	92.2%	11.80
U-235	99	692	791	87.5%	6.99
Pu-239	269	1025	1294	79.2%	3.81

Now it's not so much that plutonium-239 and uranium-238 don't make a sustainable couple too. They do. But it's U-238 + Pu-239 for the fast neutron spectrum only, but thorium-232 + U-233 for either the fast or thermal neutron spectra.

"Hey, these guys had a pretty good idea. Let's go back to it."

Alvin Weinberg MSR Questions (2004). Youtube link

Dr Laurence Miller: One of the things that I considered was the choice between the liquid metal fast reactors and ...

Alvin Weinberg: [Interrupting] Excuse me. How do you increase the volume in here?

Dr Laurence Miller: You mentioned where did we go wrong. And one of your aims was the molten salt reactor and instead of that we went for the liquid metal reactor. Do you think that was a serious mistake?

Alvin Weinberg: Yes I think it was a mistake but, I guess, what I'm talking about goes much beyond the kind of reactor that we're going to build, or that will take over. Because no matter what kind of reactor you build, apprehensive members of the public, or Ralph Nader for that matter, will be able to use this confusion between phantom risk and real risk to scare people out of nuclear energy. So ... I think that that issue overrides the question of whether molten salt is better than liquid metal. I happen to think that molten salt is better than [liquid] metal.

Moderator: I have a follow-on question from cyberspace that we got by email right before today's colloquium and its related to Dr. Miller's question. This question comes from Kirk Sorensen who is with the NASA Marshall Space Flight Center and it has to do with the molten salt breeder reactor. He would like for you to comment on the inherent safety of the molten salt reactor and how we might be able to restart a molten salt reactor programme.

Alvin Weinberg: The molten salt people, who included most famous figures nuclear energy, in particular Eugene Wigner, are all dying off and once they're dead then I suppose you can reinitiate a program on molten salt. Are molten salts inherently safer than liquid metal fuel pin reactors? I think they are, as much as anything, because you don't have supercritical amounts of uranium involved in the system. You add uranium, bit by bit, as you need it because the material is molten. But I'm much impressed with the fact that, despite molten salt reactors having in a sense been a failure in that we don't have people building molten salt reactors now, the molten salt reactor experiment, which produced seven and a half megawatts of heat was one of the most important, and I must say brilliant achievements of the Oak Ridge National Laboratory. And I hope that, after I'm gone, people will look at the dusty books that were written on molten salts and will say "Hey, these guys had a pretty good idea. Let's go back to it."

Radon is not nearly as scary as the authorities make it out to be.

Under normal circumstances, radon is not a threat to your health. No matter what the EPA tell you. There's no positive correlation between lung cancer rates and the distribution of background radiation. Radon-222 is a decay produce of radium-226, which is a decay product of uranium-238. Radon is a heavy gas which accumulates in homes and offices. According to the EPA it is a huge threat to life. In reality it is not such a big threat. It can easily be demonstrated that the effect of other background radiation on the lungs (e.g. from carbon-14 and potassium-40 decay) greatly exceeds the effect of radon-222 by about 100 to 1. So according to EPA logic there should be 100 times as much lung cancer due to potassium-40 and carbon-14 (compared to their projected radon cancers). There's not. There is no good evidence that, at the low doses found, radon-222 causes any measurable lung cancer. The EPA's worry about radon is based upon a projection of a bad mathematical model.

If anything, a map of the USA shows a negative correlation between radon concentration and lung cancer!

Perhaps better described as a positive correlation between radon concentration and no lung cancer!

For an average 70kg person:

• Your lungs weigh approximately 1.3 kg; 1.86% of your body.[1]
• We experience about 8300 Bq of radiation (mostly K-40 and C-14).[2]
• It follows, our lungs experience about 158 Bq (mostly K-40 and C-14).
• When doing mild activity, we breath about 14 litre/minute = 2.3 × 10^-4 m³
• US average radon air concentration is 37 Bq m^-3 (EPA).[4]
• It follows that a US citizen's lungs are exposed to 37 × 2.3 × 10^-4 = 0.00863 Bq radon

When accounting for the effect of that radon on the body we should assume it follows the main decay chain. That's because the other branches of the decay chain have very low probabilities. The main radon decay chain is shown below. It has 4 alphas in it [5]:

		energy (MeV)	½-life
Rn-222 → Po-218	(alpha)	5.59	3.8235 d
Po-218 → Pb-214	(alpha)	6.002	3.1 min
Pb-214 → Bi-214	(beta, gamma)	1.024	26.8 min
Bi-214 → Po-214	(beta, gamma)	3.272	19.9 min
Po-214 → Pb-210	(alpha)	7.687	164.3 µs
Pb-210 → Bi-210	(beta)	0.064	22.2 y
Bi-210 → Po-210	(beta)	1.163	5.012 d
Po-210 → Pb-206	(alpha)	5.305	138.4 d

To convert to millisievert we need to weigh the decays. I won't convert to millisievert but we will weight radon far more heavily than other natural radiation experienced in our lungs. Comparing the effect of radon with other radionuclides we experience: mostly potassium-40 and carbon-14. When converting from grays to millisievert the weighting is normally:

alpha	beta	gamma
20	1	1

Because the EPA are so worried about radon, I'll assume they must know something I don't. So I will weight it twice and also assume every decay in the main decay chain counts. The main radon decay chain is worth 86 according to normal weighting. 4 alphas, 4 betas, and 2 gammas = 20 x 4 + 4 × 1 + 2 × 1. I'll double that to 172. Let's compare the lung radiation contribution of radon with K-40 and C-14:

radon	= 172 × 0.00863	= 1.5
K-40 and C-14		= 158

The effect of K-40 and C-14 combined is about a hundred times that of radon. [even after I weighed radon twice as much as I should have!]

The following table shows the radioactivity found in a typical adult human body of 70,000 grams (about 154 pounds)[2]:

Nuclide	Total Mass	Total Activity (Bq)
Uranium	90 µg	1.1
Thorium	30 µg	0.11
Potassium-40	17 mg	4,400
Radium	31 pg	1.1
Tritium	0.06 pg	23
Polonium	0.2 pg	37
Carbon-14	20 pg	3,840
Total:		8,302
Source: Radionuclides in the Ocean

References

1. Lungs (Wikipedia)
2. Radionuclides in the Ocean
3. Radon decay chain
4. Radon (Wikipedia)
5. Radioactive series of radium-226
6. EPA: The National Radon Action Plan
7. Mohan Doss comment on radon at 'The Conversation'

Postscript

I said "perhaps better described as a positive correlation between radon concentration and no lung cancer!". Here it is: