Release and speciation of14C during the corrosion of activated steel in deep geological repositories for the disposal of radioactive waste

J Mibus,S W Swanton,N Diomidis,E Wieland

doi:10.1017/rdc.2018.138

Abstract

ABSTRACTCarbon-14 (radiocarbon,14C) is an important radionuclide in the inventory of radioactive waste in many disposal programs due to its significant dose contributions in safety assessments for geological repositories. Activated steels from nuclear reactors are one of the major sources of14C. Knowledge of14C release from steel wastes and its chemical form (speciation) is limited giving rise to uncertainty regarding the fate of14C and a conservative treatment in assessment calculations. In this work, we summarize and make a synthesis of selected results from Work Package 2 of the EU CAST project aiming to improve understanding of14C release related to steel corrosion under repository-relevant conditions. The outcome of the experiments is discussed in the context of the long-term evolution of a repository and its potential consequences for safety assessment.

Highlights

In many radioactive waste disposal programs, carbon-14 is an important radionuclide with a potential for significant dose contributions in safety assessments for a geological repository
We summarize and make a synthesis of selected results from Work Package 2 of the EU CAST project aiming to improve understanding of 14C release related to steel corrosion under repository-relevant conditions
We focus on the corrosion, the 14C inventory of and 14C release from irradiated stainless steel to develop a deeper understanding of the likely rates of 14C release from steel wastes during storage and disposal and the fate of the 14C released

Summary

Introduction

In many radioactive waste disposal programs, carbon-14 (radiocarbon, 14C) is an important radionuclide with a potential for significant dose contributions in safety assessments for a geological repository. Of the chemical form of 14C after release from the waste and the migration of the potential carrier compounds. This gives rise to a considerable uncertainty regarding the fate of 14C and a conservative treatment in safety assessment. The principal objective of Work Package 2 (WP2) of the EU CAST (CArbon-14 Source Term) project has been to measure the rates and speciation of 14C release from activated steel under repository-relevant conditions to address these uncertainties. The state of understanding of carbon and 14C release from steels during corrosion at the start of the CAST project is summarized briefly below (Swanton et al 2015)

Results

Discussion

Conclusion