The Mudcat Café TM
Thread #100266 Message #2009311
Posted By: The Fooles Troupe
28-Mar-07 - 07:29 AM
Thread Name: US bombs Aust / Vets proven DU affected
Subject: RE: US bombs Aust / Vets proven DU affected
"material that has ever seen the inside of a reactor"
... contains NEW radioactive elements (created during the radioactive breakdown of uranium) that make uranium look like cold porridge...
From Wiki (no bl;ickies - just copy and paste!)
Uranium-238 (U-238), is the most common isotope of uranium found in nature. When hit by a neutron, it becomes uranium-239 (U-239), an unstable element which decays into neptunium-239 (Np-239), which then itself decays, with a half-life of 2.355 days, into plutonium-239 (Pu-239).
Around 99.284% of natural uranium is uranium-238, which has a half-life of 1.41 × 1017 seconds (4.46 × 109 years, or 4.46 billion years). Depleted uranium consists mainly of the 238 isotope, and enriched uranium has a higher-than-natural quantity of the uranium-235 isotope.
http://en.wikipedia.org/wiki/Uranium_238
Only around 0.72% of all natural uranium is uranium-235, the rest being mostly uranium-238. This concentration is insufficient for a self sustaining reaction in a light water reactor; enrichment, which just means separating out the uranium-238, must take place to get a usable concentration of uranium-235. Pressurised Heavy Water Reactors, other heavy water reactors, and some graphite moderated reactors are known for using unenriched uranium. Uranium which has been processed to boost its uranium-235 proportion is known as enriched uranium, different applications require unique levels of enrichment.
The fissile uranium in nuclear weapons usually contains 85% or more of 235U known as weapon(s)-grade, though for a crude, inefficient weapon 20% is sufficient (called weapon(s)-usable); even less is sufficient, but then the critical mass required rapidly increases. However, judicious use of implosion and neutron reflectors can enable construction of a weapon from a quantity of uranium below the usual critical mass for its level of enrichment, though this would likely only be possible in a country which already had extensive experience in developing nuclear weapons. The Little Boy atomic bomb was fueled by enriched uranium. Most modern nuclear arsenals use plutonium as the fissile component, however U-235 devices remain a nuclear proliferation concern due to the simplicity of the design.