Surface dose rate contribution by actinides mixed in uranium-plutonium fuel elements

Nuclear transmutation of actinides is considered a potential method for the solving of the waste problems connected with nuclear energy. Multiple recycling however, changes the isotopic composition of plutonium and actinides, building up significant amounts of higher atomic weight isotopes responsible for the radiation levels. The photon and neutron surface dose rate have been calculated when 1 - 2 - 3 - 5 w/o actinides other than fuel and 5 w/o plutonium from the 1st cycle and in equilibrium are mixed in a LWR fuel element. Because of variable utilisation strategy, 30 w/o plutonium and 1 - 2 - 3 - 5 w/o actinides generated in the 1st cycle of a LWR are considered to be burned in a FBR. Personnel radiation exposure problems arise when isotopic compounds in equilibrium are introduced in a fuel element fabrication plant. The results have shown that the relative dose (the ratio between the dose rate of U-Pu-actinides and U-Pu mixtures for LWR and FBR) increases greatly when actinides in equilibrium are considered. A relative neutron surface dose rate between 4.7 x 104 and 1 x 106 affected by 252Cf has been calculated. The relative dose underlines the extent of shielding necessary to limit personnel exposure when actinides enter in plutonium fuel fabrication facilities