Nuclear analyses of neutron activation system for Indian TBM

•Suitable location for nuclear measurement in LLCB TBM is middle part of TBM.•Proposed NAS arrangements inside LLCB TBM are perturbing the neutronic responses.•The perturbation in nuclear responses due to proposed NAS arrangements are more than 10%.•Assessment of radioactivity in candidate foils and materials for NAS capsule was also done to assess the irradiation time & handling of capsules. Measurement of neutronic responses in Lead Lithium Ceramic Breeder (LLCB) Test Blanket Module (TBM) is an essential part of Test Blanket Module Program in ITER. It contributes to the validation of neutronic design and the estimation of uncertainties associated in neutronic calculations. Selection of neutronic measurement locations inside LLCB TBM has been made in consideration of two criteria. First, the location of measurements should be such that the spatial variation of neutronic responses in TBM is minimum. And second, the number of measurement locations should be based on the neutron spectra variation along with the radial depth of TBM. The Neutron Activation System (NAS) is proposed for measuring the neutronic responses inside LLCB TBM. It measures the absolute neutron flux with information on the energy spectrum at selected locations in the TBM. The nuclear analyses have been carried out for NAS arrangement inside LLCB TBM. The paper covers the identification of suitable location & neutronic measurement points inside TBM by estimating the 3D neutronic responses mapping inside LLCB TBM and radial profile of neutron flux. The impact of NAS arrangement inside TBM on the neutronic responses is analyzed by estimating the neutronic responses at the particular locations inside TBM with and without NAS arrangements. To conceptualize the NAS design, estimations of activity and reaction rates in candidate activation foils & materials have been done. The neutronic analyses have been performed using the MCNP radiation transport code and FENDL-2.1 nuclear cross section data library. The activation code FISPACT-2007 has been employed to estimate the activation responses.