Editing Radioactive waste (section)

==== Proliferation concerns ====
{{See also|Nuclear proliferation|Reactor-grade plutonium}}

Since uranium and plutonium are [[nuclear weapons]] materials, there are proliferation concerns. Ordinarily (in spent nuclear fuel), plutonium is [[reactor-grade plutonium]]. In addition to [[plutonium-239]], which is highly suitable for building nuclear weapons, it contains large amounts of undesirable contaminants: [[plutonium-240]], [[plutonium-241]], and [[plutonium-238]]. These isotopes are extremely difficult to separate, and more cost-effective ways of obtaining fissile material exist (e.g., uranium enrichment or dedicated plutonium production reactors).<ref>{{cite web |url=http://www.world-nuclear.org/info/inf15.html |title=Plutonium |author=World Nuclear Association |date=March 2009 |access-date=2010-03-18 |url-status=dead |archive-url=https://web.archive.org/web/20100330221426/http://www.world-nuclear.org/info/inf15.html |archive-date=2010-03-30}}</ref>

High-level waste is full of highly radioactive [[fission products]], most of which are relatively short-lived. This is a concern since if the waste is stored, perhaps in deep geological storage, over many years the fission products decay, decreasing the radioactivity of the waste and making the plutonium easier to access. The undesirable contaminant Pu-240 decays faster than the Pu-239, and thus the quality of the bomb material increases with time (although its quantity decreases during that time as well). Thus, some have argued, as time passes, these deep storage areas have the potential to become "plutonium mines", from which material for nuclear weapons can be acquired with relatively little difficulty. Critics of the latter idea have pointed out the difficulty of recovering useful material from sealed deep storage areas makes other methods preferable. Specifically, high radioactivity and heat (80&nbsp;°C in surrounding rock) greatly increase the difficulty of mining a storage area, and the enrichment methods required have high capital costs.<ref>{{cite web |url=http://nci.org/s/sp121495.htm |title=A Perspective on the Proliferation Risks of Plutonium Mines |author=Lyman, Edwin S. |publisher=[[Nuclear Control Institute]] |date=December 1994 |access-date=2015-11-25 |url-status=dead |archive-url=https://web.archive.org/web/20151125225922/http://nci.org/s/sp121495.htm |archive-date=2015-11-25}}</ref>

Pu-239 decays to U-235 which is suitable for weapons and which has a very long half-life (roughly 10<sup>9</sup> years). Thus plutonium may decay and leave uranium-235. However, modern reactors are only moderately enriched with U-235 relative to U-238, so the U-238 continues to serve as a [[Denaturation (fissile materials)|denaturation]] agent for any U-235 produced by plutonium decay.

One solution to this problem is to recycle the plutonium and use it as a fuel e.g. in [[fast reactor]]s. In [[integral fast reactor|pyrometallurgical fast reactors]], the separated plutonium and uranium are contaminated by actinides and cannot be used for nuclear weapons.