Estimation of 177 Lu activity produced from direct and indirect routes in Indian research reactors

177 Lu can be produced by neutron irradiation of 176 Lu (direct route) or 176 Yb (indirect route). In direct route, the thermal neutron capture cross-section of 176 Lu does not vary as 1/v and shows strong temperature (temperature of medium as well as that of the thermalized neutrons) dependence, resulting in added complexities in radioactivity estimation. We use an analytical model to estimate the activity of 177 Lu produced from direct as well as indirect routes. For direct route, we have used both Westcott convention-based method and one-group effective cross sections generated using multigroup cross-section library. Our estimations are also validated against known experimental results and compared to measured activity produced in Indian research reactors.