Enrichment Measurements of UF4 Unburnts Material from a Former Uranium Conversion Plant in the Republic of South Africa

摘要

The South African Nuclear Energy Corporation (Necsa) possess uranium tetrafluoride (UF4) unburnts material resulting from historical uranium conversion plant which produced uranium hexafluoride (UF_6) for enrichment purposes. Ammonium diurinate (ADU) was used as feed material in the plant. The UF4 unburnts contains thorium inherent from the ADU feed material and during exothermic fluorination of UF_4 to form UF_6. the thorium was concentrated in the UF_4 unburnts. The UF_4 unburnts material must be characterized, quantified and declared in line with the Comprehensive Safeguards Agreement between the South African government and International Atomic Energy Agency (IAEA). In this work, the UF_4 unburnts material will be characterized in terms of ~(235)U, ~(238)U and ~(232)Th masses using high purity germanium detector and In-Situ Object Counting System (ISOCS) efficiency calibration software. The ~(235)U content (i.e. enrichment) of the UF_4 was measured using high purity germanium detector aided by the Multi-Group Analysis of Uranium version 4.2 software (MGAU v4.2). The challenge of thorium interference in the analysis of uraniferous matrix using the MGAU v4.2 software will be discussed as well. This work will provide a critical role in the characterization, quantification and declaration to the IAEA by the state safeguards authority.