[en] We present the results of our computational studies on the possibility of using graphite and heavy water as moderating media for nested neutron spectrometer. The effectiveness of these alternate moderating media is explored by comparing the unfolded spectra with the actual spectra for typical fluxes of thermal and fast reactors. (author)

[en] We present the calculation methodology and the results of our computational studies on the estimation of isothermal temperature coefficient of reactivity (ITCR) of Fast Breeder Test Reactor (FBTR). Thermal expansion of core components due to change in the core temperature viz. radial expansion of grid plate, axial expansion of core and change in sodium density are considered in the study. Core configurations were chosen such that the study would encompass all the major core changes that were made during the evolution of FBTR from its first core configuration to the 30th campaign core configuration for operating the reactor at designed target power of 40 MWt. The calculation methodology was validated by comparing the computational results against that of experimentally measured values for various core configurations of FBTR and found that they were in good agreement. (author)