Tuesday, 30 June 2015

Case study in anti-nuclear power FUD

I noticed it here: Tas Uni academic less than “abundantly clear” about Generation IV nuclear reactors. An article by Dr Jim Green, the national nuclear campaigner with Friends of the Earth, Australia. It's purpose is to discredit pro-nuclear activist Barry Brook. It has a few misleading claims but the standout false claim is:

France has used a fast reactor to produce plutonium for weapons.

No such thing ever happened. France did have fast reactors which made plutonium, but they were never used to make nuclear bomb material. When challenged on this point, eventually a friend of the author (Dickie) narrowed down the claim:

Fact: The fast-neutron reactor Phénix, which operated at significant power level until the late 1990s, produced about 340 kg of plutonium for WMD.
- Dickie, Comment no. 17
, and sourced it to a website: International Panel of Fissile Materials. That website had 3 documents claiming Phénix made weapons grade material but only one claim mentioned 340 kg:
Global Fissile Material Report 2010, page 91

The claim begins:

To estimate the contribution of Phénix to the French stockpile of weapons plutonium, it is assumed that only the surplus plutonium—not the total amount of weapon-grade plutonium—extracted from the blankets was transferred to the weapons program.

So we're really dealing with guesswork here (to estimate, it is assumed), rather than fact, as was originally claimed. What of the guesswork? Is it likely, or even possible? No, not likely at all. There are several reasons to avoid using fast reactors to make weapons grade plutonium. First, let's figure out what ideal weapons grade plutonium contains. It is defined as being predominantly Pu-239, typically about 93% Pu-239. Additionally, three particular radionuclides pose a problem:

  • First and most important, plutonium-240, Pu-240 has a high rate of spontaneous fission, meaning that the plutonium in the device will continually produce many background neutrons, which have the potential to reduce weapon yield by starting the chain reaction prematurely.
  • Second, the isotope plutonium-238, Pu-238 decays relatively rapidly, thereby significantly increasing the rate of heat generation in the material.
  • Third, the isotope americium-241, Am-241 (which results from the 14-year half-life decay of plutonium-241 and hence builds up in reactor-grade plutonium over time) emits highly penetrating gamma rays, increasing the radioactive exposure of any personnel handling the material.
- Weapons-Grade Plutonium ... U.S. DoE

To summarize: people trying to make weapons grade plutonium want 93% Pu-239, with as little as possible Pu-238, Pu-240, and Am-241.

How to get there?

An obvious first step is to avoid fast reactors. A fast reactor has (n, 2n) reactions in addition to the normal absorption and fission reactions found in thermal reactors. To quote:

A side reaction chain also produces Pu-238:

U-238 + n -> U-237 + 2n
U-237 -> (6.75 days, beta) -> Np-237
Np-237 + n -> Np-238
Np-238 -> (2.1 days, beta) -> Pu-238

Pu-238: This isotope has a spontaneous fission rate, 1.1x10^6 fission/sec-kg (2.6 times that of Pu-240) and a very high heat output (567 W/kg!). Its very high alpha activity (283 times higher than Pu-239) makes it a much more serious source of neutron emission from the alpha -> n reaction. In high-burnup commercial reactor fuels it makes up no more than one or two percent of plutonium composition in extracted plutonium, but even so the neutron production and heating can make it very troublesome.

- Nuclear Weapons FAQ

A reactor may produce several kinds of plutonium. For example: Pu-238, Pu-239, and Pu-240, among other things. I'll concentrate on the plutonium made and particularly upon these 3 varieties. The kind required for nuclear bombs, and the two others most to be avoided. These 3 versions of plutonium are practically impossible to separate from each other. We can't use chemical means because they all have identical chemistry. We can't use physical means because they're nearly the same atomic weight. Once we've made too much Pu-238 and/or Pu-240, we must accept that our plutonium is bad for making bombs with. The smart A-bomb maker avoids Pu-238, Pu-240 and other such junk in the first place. They ensure their plutonium is nearly all Pu-239. They make plutonium under carefully controlled conditions, using thermal reactors, with slow burnups. Phénix was a fast reactor with a high burnup - the opposite of what a sensible person would choose.

Slow burnup is preferred because its plutonium has the least amount of spontaneous neutrons:

Type Composition Thermal power w/kg Spontaneous neutrons /s/g Origin Use
Weapons-grade Pu-239 with less than 8% Pu-240 2-3 60 From military 'production' reactors with metal fuel operated for production of low burn-up Pu. Purex separation. Nuclear weapons (can be recycled as fuel in fast neutron reactor or as ingredient of MOX)
Reactor-grade from high-burnup fuel 55-70% Pu-239; more than 19% Pu-240 (typically about 30-35% non-fissile Pu) 5-10 200 Comprises about 1% of used fuel from normal operation of civil nuclear reactors with oxide fuel used for electricity generation As ingredient (c. 5-8%) of MOX fuel for normal reactor
IFR-grade actinide Pu + minor actinides + U, 50% Pu fissile 80-100 300,000 From fast reactor used metal fuel by pyroprocessing recycle
- Plutonium, World Nuclear Association

Notice that two of the villains in plutonium atom bomb material are Pu-238, Pu-240. A fast reactor makes the most of this junk and a military reactor makes the least.

All this information used to find how not to make plutonium bombs has been readily available on the internet for decades. It's hard to understand how an august body such as the International Panel on Fissile Materials, with their swanky, plausible looking reports could've missed all this. It's almost as if they never did Nuclear Physics 101, but only write their reports to spread FUD. Perish the thought!

This blog has a lot of cut'n'paste in it. That's deliberate. I did it to show that you don't need a lot of know-how to decipher FUD. You just need to ask someone who knows, and do the obvious research (wikipedia)! The FUD promoted by Friends of the Earth and the International Panel on Fissile Materials misses out basic research. It begins with supposition (to estimate, it is assumed) and cross-references itself, claiming to be fact. A classic FUD technique that one.


  1. Plutonium, World Nuclear Association
  2. Nuclear Weapons Frequently Asked Questions (internet FAQ)
  3. Tas Uni academic less than “abundantly clear” about Generation IV nuclear reactors, by Jim Green
  4. Wikipedia: Weapons-grade_plutonium
  5. Global Fissile Material Report 2010, page 91
  6. "Reactor-Grade and Weapons-Grade Plutonium in Nuclear Explosives", Nonproliferation and Arms Control Assessment of Weapons-Usable Fissile Material Storage and Excess Plutonium Disposition Alternatives (excerpted). U.S. Department of Energy. January 1997. Retrieved 5 September 2011.
  7. Dickie, Comment no. 17

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