Finding an equivalent of molybdenum in type B shim rods

The goal of this work is finding an equivalent to molybdenum contained in type B shim rods with other isotopes with similar nuclear characteristics, available from the WIMS nuclear data base. Different substitution for molybdenum were achieved with several isotopic combinations, making use of WIMS and SCALE codes. The overall reactivity of the shim control rod system depends 50% on the contribution from type B rods. The steel from the type B shim contains natural molybdenum in an non-negligible concentration (2.19%). The only existing in the WIMS data base molybdenum is the isotope Mo 95 as a fission product. In conclusion, given the important role of the molybdenum in the neutron absorption, a methodology for finding an equivalent is needed