Question 24 of 24: Treatment and Ultimate Disposal of Liquid Radioactive Wastes

Question 24: Treatment and Ultimate Disposal of Liquid Radioactive Wastes (3 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

Liquid radioactive waste is first segregated by isotope half-life and activity level, since the appropriate management path differs sharply between short-lived and long-lived radionuclides. Short-half-life liquid waste (common in medical/research use) is typically held in shielded storage for radioactive decay — generally ten or more half-lives — until its activity falls below the regulatory discharge limit, after which it can be released as ordinary liquid effluent (dilute-and-disperse within the regulated limit). Long-half-life or higher-activity liquid waste is instead concentrated using ion exchange, evaporation or chemical precipitation to separate the radioactivity into a much smaller volume of concentrate, minimizing the volume that must go to final management; the resulting concentrate is then solidified (cementation or vitrification) and the treated, decontaminated liquid fraction is released within permitted limits. The solidified concentrate is placed in engineered, licensed long-term storage or a geological disposal facility, isolated from the biosphere for a period matched to its decay time. All of these steps in Canada are carried out under the Canadian Nuclear Safety Commission (CNSC)'s licensing and regulatory framework, which sets the discharge limits, storage/shielding requirements, and ultimate-disposal criteria at every stage.