Reply #28: You figured it out wrong

[bananas]

IEER Plutonium Factsheet:

It is important to remember that this classification of plutonium according to grades is somewhat arbitrary. For example, although "fuel grade" and "reactor grade" are less suitable as weapons material than "weapon grade" plutonium, they can also be made into a nuclear weapon, although the yields are less predictable because of unwanted neutrons from spontaneous fission. The ability of countries to build nuclear arsenals from reactor grade plutonium is not just a theoretical construct. It is a proven fact. During a June 27, 1994 press conference, Secretary of Energy Hazel O'Leary revealed that in 1962 the United States conducted a successful test with "reactor grade" plutonium.

National Academy of Sciences, 1994:

In short, it would be quite possible for a potential proliferator to make a nuclear explosive from reactor-grade plutonium using a simple device that would be assured of having a yield in the range of one to a few kilotons, and more using an advanced design. Theft of separated plutonium whether weapons-grade or reactor-grade would pose a grave security risk.

Marvin Miller and Frank von Hippel, 1997 letter to APS:

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... reactor-grade plutonium can be used to make nuclear weapons at all level of technical sophistication.

In what follows, we briefly outline the technical basis for this conclusion within the limits of classification.

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These considerations underlie the recent and most explicit declassified government statement on the usablility of reactor- grade plutonium in weapons:

"At the lowest level of sophistication, a potential proliferating state or subnational group using designs and technologies no more sophisticated than those used in first-generation nuclear weapons could build a nuclear weapon from reactor-grade plutonium that would have an assured, reliable yield of one or a few kilotons (and a probable yield significantly higher than that). At the other end of the spectrum, 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 weapons-grade plutonium. <snip> Proliferating states using designs of intermediate sophistication could produce weapons with assured yields substantially higher than the kiloton-range possible with a simple, first-generation nuclear device."

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Ivan Oelrich, 2006, Nuclear Engineering International Magazine and Federation of American Scientists:

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Second, the GNEP proposal states that the envisioned separation technologies are ‘proliferation resistant’. (The DoE is very careful not to claim that anything is ‘proliferation proof’.) There have been various proposals for new separation techniques, for example, Urex, Urex+, UREX+1, and now Urex+1a. As the names imply, they are variations on a theme. In the longer term, other techniques, such as pyroprocessing might become available on an industrial scale. When GNEP proponents say that these techniques are ‘proliferation resistant’, they mean they are when compared to the Purex process. Purex was developed during the Manhattan project specifically to provide plutonium for the first atomic bombs. The claim is, then, that Urex variants are less proliferation prone than a process that was specifically designed for bomb manufacture, a very low hurdle indeed. But none of these processes is more proliferation resistant that what we are planning to do now, that is, disposal of sealed, intact fuel rods in a geologic repository.

Part of the alleged proliferation resistance comes about because some variations on Purex – for example Urex+ – intentionally leave radioactive contaminants in the plutonium to make them more difficult to steal and handle if stolen. Frank von Hippel and Jungmin Kang at Princeton University have calculated the radiation doses from Urex+ and pyroprocessed fuel and found them falling short of meeting the standards of ‘self protection’. Moreover, even if impurities are intentionally left in the plutonium, nothing prevents a thief from using a simplified version of the 60-year-old Purex technology to get pure plutonium out. Some approaches, such as leaving in chemically similar radioactive rare earth elements make self protection more robust but substantially increase the final fuel fabrication costs. Finally, as pointed out by Richard Garwin recently in Congressional testimony, spent fuel from a nuclear reactor is about 1% plutonium, while Urex+ fuel would be more than 90%, so a thief would need to steal only about 9kg of Urex+ fuel to get an 8kg critical mass of plutonium but would have to steal approximately 800kg of lethally radioactive spent fuel to get a critical mass.

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