Your website seems pretty factual, but it makes little distinction between plutonium produced for weapons and plutonium produced by reprocessing spent fuel. This latter reactor grade fuel is not used for making nuclear weapons. I understand reactor grade plutonium would make a poor nuclear weapon because the Pu-240 contamination causes enough spontaneous fission to destroy a fabricated nuclear device prematurely, making the explosive force relatively small. Granted, we need to guard reactor grade plutonium stocks so that terrorists do not attempt to make a low yield "dirty" bomb to terrify the public. But this reactor grade plutonium is certainly not a source of nuclear weapons that might be used in wars between nations. I think you dilute your message by not focusing specifically on weapons materials.

Reactor-grade plutonium is, indeed, not an ideal material for a bomb, but it can be used to build an explosive device. Then, the reprocessing technology that is used to separate plutonium from power reactor fuel is the same that is used for separating weapon-grade plutonium. So, while reactor-grade plutonium is in a separate category, it still has to be considered along with "true weapon-grade" materials.

I agree that the reprocessing technology is the same, but the distinction between the resulting weapons-grade plutonium or reactor-grade plutonium arises from the source of the plutonium. That plutonium contaminated with Pu-240 from its long exposure to neutrons in a commercial power reactor is is reactor-grade -- not used in military weapons. That plutonium from purpose-built weapons-grade plutonium production reactors with frequent fuel exchange to avoid long neutron exposure of the plutonium is the source of the material for weapons. I believe the distinction is important to assessing nuclear weapons proliferation risk.

Pavel Podvig, A reactor grand plutonium device would not be deliverable by military means, could not be kept in storage, would require skilled scientists, engineers, and workmen to assemble, would require a the sort of equipment found in a weapons laboratory like Los Alamos, would require detectable testing, and would produce an explosion that would be no more powerful than that produced by $100,000 worth of conventional explosives. Not only would the explosives be far less expensive, and require far less technological skills, and far less special equipment, but they would be more difficult to detect. Why would anyone prefer the RGP approach? [...]

I don't think there is much disagreement about whether reactor-grade plutonium is a weapon material of choice. It is certainly not. However, that does not make it irrelevant in the context of nuclear proliferation or disarmament. It's been shown that building an explosive device out of reactor-grade plutonium would be possible, even if highly impractical (I would emphasize "highly" to avoid a lengthy discussion here - the arguments are well known). Regardless of whether reactor-grade plutonium is suitable for weapons or not, there is the issue of the spread of reprocessing technology and facilities, which is a serious proliferation concern.

(I edited out part of the comment to make sure the discussion stays on relevant technical matters. I would very much appreciate if we could keep it that way. Thank you.)

To follow on, a colleague sent me this very useful quote from a 1997 U.S. Department of Energy report:

"[V]irtually any combination of plutonium isotope ... can be used to make a nuclear weapon ... reactor-grade plutonium is weapons-usable, whether by unsophisticated proliferators or by advanced nuclear weapon states ...

...At the lowest level of sophistication, a potential proliferating state or sub-national 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 weapon-grade plutonium."

I read that same report prepared in 1977 at the same time that President Carter "revealed" that there had been a 1962 test of a "reactor grade plutonium" weapon. We now know that the vague statements were to disguise the fact that the test used nearly weapons grade plutonium from the UK Magnox reactors that were originally designed for plutonium production.

I think your exaggerated concerns about plutonium in spent LWR fuel are expressions of a deep prejudice against the use of nuclear power.

For a more complete, revealing analysis than that 1977 report please visit http://depletedcranium.com/why-you-cant-build-a-bomb-from-spent-fuel/

I would just note that the quote is from a different report - the 1997 one, not 1977.