Characterization of a New Highly Enriched 233U Spike Reference Material

Highly enriched 233 U reference material is one of the most widely used isotopic spikes to measure uranium content by isotope dilution mass spectrometry (IDMS).Herein, the property values, uranium molarity and isotopic abundances, of a newly prepared highly-enriched 233 U candidate reference material (n( 233 U)/n(U)>99%) were characterized according to ISO 33405:2024.The traceable IDMS method was applied to characterize uranium molarity in the 233 U candidate reference material using a homemade 238 U reverse spike, whose uranium molarity and isotopic abundances had been well-characterized and were traceable.Uranium isotope ratios were measured by thermal ionization mass spectrometry using the total evaporation method and corrected using a uranium isotopic certified reference material.The uncertainty budgets were performed based on ISO GUM guidelines.Relative expanded uncertainties (k=2) of 0.18% and 0.00061% for uranium molarity and isotopic abundance of 233 U were achieved, comparable to those of some existing 233 U certified reference materials.This characterization strategy with the IDMS method using a homemade traceable reverse spike has the advantages of less sample consumption and no requirement of a certified reverse spike.It is applicable to the precise and traceable characterization of 233 U spikes with relatively low uranium concentration, which is beneficial for producing isotopic spikes with lower cost, shorter period, and lower radioactive waste production.