AN EFFICIENT AND OPTIMISED TOTAL COMBUSTION METHOD FOR TOTAL H-3AND C-14 IN ENVIRONMENTAL AND DECOMMISSIONING SAMPLES

摘要

Tritium needs to be measured during waste characterization of nuclear decommissioningmaterials since its disposal is subject to the Radioactive Substances Act (1993) Substances ofLow Activity (SoLA) Exemption Order criteria. If the total activity is below 0.4Bq/g it isbelow regulatory concern in the U.K.. During the last five years, the number of total tritiumsamples analysed by GAU-Radioanalytical increased significantly (Table 1). This is mainlydue to the speeding up and expansion of the nuclear decommissioning programme in the UK.One site where GAU-Radioanalytical provided a significant service was at the Winfrithnuclear research site that was home to the prototype heavy-water moderated reactor SGHWR(Lewis et al, 2005). In the UK numerous first and second-generation nuclear facilities areundergoing decommissioning and since April 2005 it has been closely controlled by theNuclear Decommissioning Authority (NDA). Tritium can be measured using direct aqueousleaching technique and dissolution technique. However, there are limitations using thosetechniques since leaching is effective for extracting HTO but does not guarantee quantitativeextraction of all tritium species and very much depends on the sample types. The dissolutiontechnique involves acids which produce liquid wastes and is labour intensive and timeconsuming since additional distillation procedures for H-3 and C-14 are normally required. Inorder to resolve these problems and produce reliable results within short time scale, atechnique using a purpose-designed tube furnace was developed by GAU-Radioanalytical.This paper describes the validation of the technique and comparison of severalintercomparison exercise results.