Results and recommendations of the Canadian Nuclear Safety Commission Workshop on Microbial Issues Related to the Disposal of Low- and Intermediate Level Waste in Deep Geologic Repositories

An abstract of a technical paper presented at:
Canadian Nuclear Safety Commission Workshop on Microbial Gas Generation From Low- and Intermediate-Level Waste Disposed in Deep Geologic Repositories
January 20–23, 2013

Prepared by:
Richard R. Goulet, Ph.D.
Canadian Nuclear Safety Commission (CNSC)

Abstract

The Canadian Nuclear Safety Commission (CNSC) regulates the management of nuclear waste. In this capacity, CNSC staff consulted with Canadian and international experts on gas generation from low- and intermediate-level waste in deep geologic repositories (DGRs). The objectives were twofold: to learn more about microbial processes that affect the long-term stability of the waste and to provide recommendations on microbial research areas.

The workgroup indicated that, first, likely only a small fraction of the waste material would be converted to gas, thus leading to lower gas pressures than predicted from typical precautionary gas modelling exercises where all the waste is converted to gas. (Lower pressure leads to a reduced possibility of gas phase transitioning into supercritical fluids.) Second, dissolution of acid-generating gases would be reduced, which might decrease the extent of rock and cement deterioration. Finally, re-saturation of the DGR would persist longer. Some radioactive gases would likely diffuse slowly out of the DGR while radionuclides in water would diffuse out laterally or downward. Dissolved radionuclides would diffuse or migrate through the damaged shaft seal/excavation zone only once the DGR had become re saturated.

Regulatory decisions are made based on cautious scenarios that yield a higher dose when uncertainty prevails, which sometimes raise public concern. As a result, recommended research areas are as follows: potential occurrence of supercritical fluids; gas generation occurring inside waste containers; conversion of sulphur in the host rock into acids; and use of methods to pinpoint the parameters influencing gas generation from the waste and to create a model that applies to repositories.

To obtain a copy of the abstract's document, contact the CNSC. When contacting the CNSC, please provide the title and date of the abstract.