Mass-Spectrometric Studies of Irradiated Uranium-Erbium Fuel

Abstract

The aim of this work was to investigate by means of secondary-ion mass spectrometry the isotopic composition of the matrix and the erbium consumable absorber in RBMK fuel samples in the initial state (enrichment from 2.4 to 2.8% in terms of ²³⁵U) and the state after irradiation in the IVV-2M reactor (to maximum burnup 34.4 MW·days/kg). It is found that burnup growth is accompanied by reduction of the ¹⁶⁷Er concentration and growth of the ¹⁶⁸Er content. The residual concentration of ¹⁶⁷Er in a mixture of erbium isotopes is 11-fold lower than the initial value. An increase of burnup from 0.42 to 34.4 MW·days/kg is accompanied by ²³⁶U and ²³⁹Pu accumulation. The ²³⁵U concentration in fuel with maximum burnup decreases approximately six-fold relative to the initial value. The usual fission products of irradiated fuel – Cs, Ba, Pr, Nd, Sm, and Ce – are found in the range 132–162 amu.