Which factors are important for plutonium production?

[vifteovn]

As far as I understand plutonium production is mainly a function of the spesific burn-up. A low burn-up of under 1000 MWd/tU is preferred to produce weapongs-grade plutonium. The higher the burn-up the more pu-240 and other plutonium isotopes that makes production of weapons a bit more difficult and increases the risk of a fizzle.

How does the enrichment level play into this? A reactor fueled with natural uranium will have more u-238 available for neutron capture than a reactor fueled with LEU. Will a LEU reactor produce a better/worse composition of plutonium isotopes compared to a NU reactor if their burn-up levels were equal?

 

[Kritmiss]

A reactor fuelled with natural uranium would be your choice to make weapons grade plutonium. The design of fuel and moderator (which needs to be heavy water or graphite) is such that it maximises the production of plutonium, the irradiation time will determine the isotopic composition of your plutonium.