Determination of Uranium, Plutonium, Neodymium, Gadolinium and Their Isotopes in UO2-Gd2O3 Spent Nuclear Fuels

Abstract

Determination of U, Pu, Nd, Gd and their isotopes in UO₂-Gd₂O₃ spent nuclear fuels by isotope dilution mass spectrometry has been studied. The spent fuel samples were dissolved in 8 M HNO₃ at 90 ºC for 16 h under reflux. This method involves two sequential anion exchange resin (AG 1X8 and 1X4) separation procedures and a Gd purification procedure with a cation exchange resin (AG 50WX8) separation. Each fraction isolated was analyzed by thermal ionization mass spectrometry. The contents of U, Pu, Nd, Gd and their isotopes (²³⁴U, ²³⁵U, ²³⁶U, ²³⁸U, ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu, ²⁴²Pu, ¹⁴³Nd, ¹⁴⁴Nd, ¹⁴⁵Nd, ¹⁴⁶Nd, ¹⁴⁸Nd, ¹⁵⁰Nd, ¹⁵²Gd, ¹⁵⁴Gd, ¹⁵⁵Gd, ¹⁵⁶Gd, ¹⁵⁷Gd, ¹⁵⁸Gd and ¹⁶⁰Gd) in the spent fuel samples were determined by isotope dilution mass spectometric method (IDMS) using quadruple spikes (²³³U, ²⁴²Pu, ¹⁵⁰Nd and ¹⁵⁸Gd). The results obtained from IDMS were applied to burnup determination as a destructive method using ¹⁴⁸Nd isotope monitor.