The Experimental Determination of the Spectral Indices 28ρ and 25δ inside of the Fuel Pellet of the IPEN/MB‐01 Reactor

This work presents the measurements of the spectral indices 28ρ and 25δ inside of the fuel pellet. To reach this goal an appropriate gamma‐counting system based on a cylindrical collimator to shield the gammas arising from the outermost ring is employed. The proposed system is shown to be adequate and in principle can be used to measure these spectral indices across the pellet radius. The theory comparison of the spectral indices shows that the currently released library ENDF/B‐VI.8 agrees reasonably well with the measurements.