Key words :
Civil plutonium can be used to make effective nuclear weapons
15 Dec, 2008 10:02 pm
Can the plutonium recovered from spent civil nuclear-power reactor fuel elements (civil plutonium) be used to fabricate nuclear weapons with significant explosive powers?
The plutonium produced in nuclear-power reactors operated for the most efficient generation of electricity, called reactor-grade plutonium, contains a higher proportion of the isotope plutonium-240 than that preferred by nuclear-weapon designers. Typical reactor-grade plutonium contains 1.3 per cent plutonium-238, 56.6 per cent of plutonium-239, 23.2 per cent of plutonium-240, 13.9 per cent plutonium-241, and 4.9 per cent plutonium-242. Nuclear-weapon designers prefer plutonium containing, typically, 0.012 per cent of plutonium-238, 93.8 per cent of plutonium-239, 5.8 per cent of plutonium-240, 0.35 per cent of plutonium-241, and 0.022 per cent of plutonium-242, called weapon-grade plutonium. The major difference is that weapon-grade plutonium is richer in plutonium-239 and poorer in plutonium-240 than weapon-grade plutonium.
As J.Carson Mark explained there are two major problems with using reactor-grade plutonium in a nuclear weapon (1). Mark is undoubtedly an expert on the subject. He headed the Theoretical Division at the US Los Alamos National Laboratory for decades; was intimately involved in the design of both nuclear fission weapons and thermonuclear weapons.
The first problem is that plutonium-240 has a high rate of spontaneous fission so that the device will continually produce many neutrons. One of these background neutrons may set off the fission chain reaction prematurely, called pre-initiation, causing the device to have a relatively low explosive yield. The spontaneous emission rate of reactor-grade plutonium is about 360 neutrons/second/gram. The figure for weapon-grade plutonium is about 66 neutrons/second/gram. The probability of pre-initiation using reactor-grade plutonium is, therefore, much larger.
The second problem described by Mark is the heat produced by the alpha-particle decay of plutonium-238. The amount of plutonium-238 in reactor-grade plutonium is about one or two per cent. This contributes 10.5 watts of heat per kilogram of reactor-grade plutonium, compared with 2.3 watts per kilogram of weapons-grade plutonium. The design of a primitive nuclear explosive using reactor-grade plutonium would have to incorporate a method of dispersing the heat – such as the use of aluminium shunts. Otherwise, the plutonium would get very hot and become distorted or even melt.
Mark explained that, in spite of these problems, nuclear weapons could be fabricated using reactor-grade plutonium. “The difficulties of developing an effective design of the most straightforward type is not appreciably greater with reactor-grade plutonium than those that have to be met for the use of weapons-grade plutonium”.
More reactor-grade plutonium than weapon-grade plutonium would be required for a nuclear weapon. The bare sphere critical mass of reactor-grade plutonium is about 13 kilograms; that of weapons-grade plutonium is 10 kilograms.
Mark’s analysis was supported by Richard L. Garwin, another leading American nuclear-weapon expert expert, who wrote that reactor-grade plutonium is usable in nuclear weapons, whether by unsophisticated proliferators or by advanced nuclear-weapon states (2). Garwin was a consultant for the Los Alamos National Laboratory from 1950 to 1993, mostly involved with nuclear weapon design,manufacture and testing.
He was an author of the report by the Committee on International Security and Arms Control of the US National Academy of Sciences that concluded: “In short, it would be quite possible for a potential proliferator to make a nuclear explosive from reactor-grade plutonium using a simple design that would be assured of having a yield in the range of one to few kilotons, and more using an advanced design”. (3).
At a conference at the International Atomic Energy Agency in June 1997, Matthew Bunn, of Harvard University, discussed the value of reactor-grade plutonium for the fabrication of nuclear weapons, stating that countries with advanced technologies "could, if they chose to do so, make bombs with reactor-grade plutonium with yield, weight, and reliability characteristics similar to those made from weapon-grade plutonium”. He went on to point out that “in some respects if would actually be easier to make a bomb from reactor-grade plutonium (as no neutron generator would be required)" (4).
A detailed description of the nuclear physics involved in the design of nuclear weapons was given by Amory B. Lovins in the British scientific journal Nature in 1980 (5). It gives the physical basis for understanding the scope for using reactor-grade plutonium in nuclear-fission weapons and shows that plutonium from nuclear-power reactors “can produce powerful and predictable nuclear explosions”.
In 1953, the British exploded a nuclear weapon at the nuclear test site in South Australia made from plutonium of a quality considerably below that of weapons-grade (6). In 1962, the United States conducted a similar nuclear-weapon test (7). The actual amount of Pu-239 in the plutonium used in these tests has not been made public but it was apparently about 19 per cent. The tests were made to prove that reactor-grade plutonium can be used in an effective nuclear weapon.
Given all this evidence, it is, to say the least, surprising that some people still deny that reactor-grade plutonium can be used to fabricate nuclear weapons with significant explosive powers?
1. J. Carson Mark, Explosive Properties of Reactor-Grade Plutonium, Science and Global Security, Vol.4, pp.111-128, 1993.
2. Richard L. Garwin, Reactor-Grade Plutonium Can be Used to Make Powerful and Reliable Nuclear Weapons: Separated plutonium in the fuel cycle must be protected as if it were nuclear weapons, Federation of American Scientists, August 26, 1998.
3. Committee on International Security and Arms Control (CISAC) of the National Academy of Sciences, The Management and Disposition of Excess Weapons Plutonium, National Academy Press, Washington, DC (1994), pp32-33,
text is available at
American Nuclear Society, Protection and Management of Plutonium, Special Panel Report, August 1995, p. 25.
4. Bunn, M, The US Program for Disposition of Excess Weapons Plutonium, Paper to International Atomic Energy Agency Conference, Vienna, June 1997.
5. Lovins, A. B., "Nuclear Weapons and Power-Reactor Plutonium", Nature, 28 February 1980, pp.817-823 and typographical corrections, 13 March 1980, p.190.
6. Arnold L., ‘A Very Special Relationship: British Atomic Weapon Tests’, Chapter 4, HMSO.
7. U.S. Department of Energy, Additional Information Concerning Underground Nuclear Weapon Test of Reactor-Grade Plutonium, Office of the Press Secretary, Washington, DC apollo.osti.gov/html/osti/opennet/document/press/pc29.html
Key words :
Â“Peak OilÂ” is NonsenseÂ… Because ThereÂ’s Enough Gas to Last 250 Years.
Threat of Population Surge to "10 Billion" Espoused in London Theatre.
Current Commentary: Energy from Nuclear Fusion Â– Realities, Prospects and Fantasies?
The Oil Industry's Deceitful Promise of American Energy Independence
Shaky Foundations for Offshore Wind Farms
In this case, all the sources are at least ten years old. The author even cites a 1980 article written by the famous college dropout, Amory Lovins. Is there no better information than this?
A casual googlehunt shows that anti-nuclear political groups have commandeered the bombs-from-reactor-fuel position. However, there is a technical article that shows the subject not to be so one-sidedly simple, which can be found here. This more current article shows that adjustments to the fuel cycle can render spent fuel unusable even for the low-yield bombs this author is concerned about.
This leaves us where we started. There are three ways a country can make an atomic bomb and there is nothing the rest of the world can do to stop it beyond economic sanctions or possibly bombing the facility. A country can make it from natural uranium or by building a production reactor or by managing the fuel cycle of a power plant. None of this is changed by the presence or absence of civil power programs in countries that presently have them.
Hans Blix was head of IAEA, the UN agency responsible for preventing proliferation. Here's what he has to say:
"A phasing out of nuclear power in some or all states would not lead to the scrapping of a single nuclear bomb.
"States can have nuclear weapons without nuclear power though it is not common today. Israel is a case in point. It has no nuclear power but is assessed to have some 200 nuclear warheads. For a long time China had only the weapons. Indeed, most nuclear weapons states, including the US, had weapons before they had power. " ( Blix )
Dr. DiVolpe argues:
"Despite common agreement that a modern nuclear-weapons design could conceptually be fueled with reactor-grade plutonium, it would not be without severe degradation and uncertainty in explosive yield. The qualification ?conceptually? included because, from all available evidence, such a implausible design has not been tested."
"While modern designs might deal with the inherent problem of pre-initiation, they would have to be modified to deal with the short-term and long-term effects of excessive heat from reactor-grade plutonium."
Dr. DiVolpi after carefully reviewing the testing records of plutonium based nuclear devices staged by the bovernments of the United Kingdom and the United States has concluded that there has never been a test of a plutonium device that used reactor grade plutonium, and without such tests there can never be assurance that such weapons would work.
Voilpi was a peer of Carson Mark, and points out that Mark did not view reactor grand plutonium as a a practical material for nuclear weapons. Mark's views would seem to point to the practical impossibility of building a storable nuclear weapon from reactor grade plutonium.
DiVolpi points to a statement by David Hafemeister of the United States DoE,
" [Advanced] nuclear-weapon states such as the United States and Russia, using modern designs, could produce weapons from reactor-grade plutonium having reliable explosive yields, weight, and other characteristics generally comparable to those of weapons made from weapon-grade plutonium."
"I suggest a discriminating reader would see that the quote is limited to ?advanced nuclear-weapon states,? confined to ?modern designs,? and qualified by terms such as ?could produce,? ?reliable yields,? and ?comparable characteristics.? Since official declarations (hedges) are usually the product of a careful inter-agency vetting. His statement, thus, pretty much excludes reactor-grade plutonium as source material under a number of realistic circumstances: less-advanced nuclear-weapon states, less-sophisticated designs, less-than-assured yields, and other sub-marginal situations. In other words, neither advanced weapon states, nor less-advanced weapon states, nor threshold weapon states are likely to produce weapons from reactor-grade plutonium (for reasons validated by Hafemeister?s carefully chosen omissions)."
From the viewpoint of this statement, the claim that "Civil plutonium can be used to make effective nuclear weapons" is poorly informed, hysterical nonsense.
Nascent nuclear weapons producers have shown a clear penchant for enriching natural uranium vice wading through an entire technological develoment project that is decades in the making and radioactively messy at that.
Less sophisticated terroists are more prone to stealing moisture density sensors containing nuclear material from any number of road construction projects. Whether such material will work well or not as a bomb is irrelevant..... the scare is in thanks to rampant fear-mongering such as is evident in the article above. The author of this one-sided pseudo-scientific screed shows absolutely no perspective. Just more of the same old anti-nuclear obstructionist harem scarem.
The LFTR is a very simple, efficient, and elegant type of reactor. It can use any kind of nuclear fuel, bomb material, or nuclear waste product to produce very high temperature heat and at the same time breed more fuel in the bargain. This thrifty approach to nuclear energy greatly appeals to me, but I became even more interested in the LFTR when the details of a new patent were revealed by Dr LeBlanc (see below @ minute 53). It opens up the possibility of building a reactor that can run for 30 years without refueling in an unattended mode sited underground while it breeds new fuel within the thorium structure of the reactor itself.
In order to get to this U233 that has been produced inside the very walls of this 200 ton reactor containment vessel, a proliferator must destroy and disassemble the reactor, lift its heavy reactor core out of a 100 meter deep reinforced aircraft crash proof hole in the ground, then cut the thorium up into small pieces while enduring heavy gamma radiation exposure, next reprocess these reactor pieces using isotopic separation since the U233 is denatured with enough U238 to make chemical separation of bomb grade U233 impossible, and do all this without being detected. Now, this is a tall order for any proliferator and may just be an impossible assignment.
At the end of the service life of the Lftr, the reactor vessel is sent back to the factory where it is reduced to liquid fluoride salts that become the feedstock of a next new Lftr. This feedstock can only be used by the new Lftr and not for bombs. The waste products are held at the factory for a few hundred years to cool down before they are mined for the many precious elements contained within like platinum and iridium. Now that?s what I call a safe, efficient and thrifty mode of operation!
For more information see the following:
What Fusion Wanted To Be
Liquid Fluoride Reactors: A New Beginning for an Old Idea
His interpretation (and that's all it is, since he lacks a published relevant hands-on technical background in the subject matter), about the weaponizability of reactor-grade plutonium runs counter to a half century of now-consummated facts. Of the ten states that have weaponized fissile materials, it is rather evident that none have utilized the readily available but inferior reactor-grade plutonium, and there are plenty of technical reasons that can be deduced and inferred to recognize its deficiencies.
Barnably, like other wishful alarmists, has attempted to validate the weapons potency of reactor-grade plutonium by relying in part on highly misleading and reprehensible information derived from from statements, press releases, and inferences about a so-called explosive test in 1962. There are far too many technical, historical, and deductible reasons to give any credibility to that line of thinking.
Dr. Barnaby also wonders why terrorists have not so far resorted to "dirty bombs." Again, there are (fortunately) good technical reasons why it is a poor choice of weapon.
Just because something is academically and theoretically conceivable hardly makes it practical. After all, more than a half century without nuclear weapons made from civilian plutonium, without radiological terror weapons -- but with highly productive nuclear power throughout the world should count for something.