Diluted -- down to an enrichment level of no more than 5% U-235
Iranhas been enriching uranium to 20 per cent concentration of the fissile U-235
isotope since early 2010, stoking Western alarm over the nature of its nuclear programme.
Iran openly has enriched uranium to 20% U-235
at this underground site.
In addition, the president contended that the administration's latest calculations indicated that supplies of U-235
would be sufficient (Cochran, Felverson, and von Hippel 2009).
Since mined uranium is less than 1% U235, it must undergo expensive and energy-intensive enrichment to reach the concentration of U-235
needed for LWR fuel.
The splitting of a U-235
atom is caused by the addition of an extra neutron.
Sanders explains, "Depleted uranium is essentially U-238, the isotope after the fissionable isotope, U-235
, has been extracted from uranium ore.
While civilian reactor fuel does not contain enough U-235
to make a bomb and the unseparated plutonium found in used reactor fuel cannot be used to make an explosive without considerable reprocessing, civilian uranium enrichment and plutonium production programs can be used to make weapon-grade fissile material.
All LWRs need fuel that is enriched by a factor of six or seven to a level of 4 to 5% U-235
Then, the centrifuge throws the heavier U-238 atoms towards the wall, letting the rare U-235
ones accumulate near the centre.
The percentage refers to the relative amount of the U-235
uranium isotope, which is the necessary ingredient to sustain a nuclear chain reaction.
The point of enrichment is to increase the percentage of U-235
- to the 5% level for fuel for nuclear power plants, and to the 90% level for nuclear weapons.