Recent neutron physics investigations on the incineration of plutonium and other transurania elements

In early strategic considerations for the production of nuclear energy in fission reactors, plutonium should become the main fissile material in fast breeder reactors (FBR) in order to achieve a high utilization of the uranium resources. The startup of breeder reactors should be realized with available plutonium, An improvement of the startup was considered by enhanced plutonium production rates in high converting light water reactors (HCLWR). However, political and economical aspects have lead to a significant delay in the market introduction of FBRs. So, instead of enhanced plutonium production in LWRs, the incineration of plutonium of present reactors is now the main objective of strategic studies. Moreover, the considerable amounts of "weapons-grade" (WG) plutonium must be disposed in the most useful way. The paper will discuss recent FZK neutron physics investigations on plutonium incineration in three types of nuclear systems: Pressurized water reactors (PWR), liquid metal cooled fast reactors (LMFR) and accelerator driven systems (ADS). All systems need a closed fuel cycle with sufficient capabilities, The use of mixed uranium and plutonium oxide (MOX) in PWRs is proven technology in several countries. Strategic investigations for plutonium multi-recycling in PWRs will be presented for pools of PWRs with full UOX and full MOX core-loadings. It will be shown, that for a ratio of UOX/MOX approximate to 5/3 after about 80..100 years a near to equilibrium constant plutonium inventory may be reached at a level of about half the value of the case of direct spent fuel disposal, First investigations for the use of WG-plutonium in PWRs also will be discussed. Plutonium incineration in fast spectrum reactors is studied within the common European CAPRA project. Especially the consequences for the buildup of neptunium and americium will be discussed in some detail. For the more advanced accelerator driven systems, suitable nuclear data libraries and calculational procedures have been established and validated. First results of studies for plutonium incineration with a fast spectrum ADS will be presented.