Regulation( ONR) who produce guidance including the Safety Assessment Principles( SAPs). Nuclear sites must produce safety cases, including for managing radioactive waste, which include criticality safety assessments where appropriate.
When Something Goes Wrong A criticality accident( uncontrolled chain reaction in the supercritical region) produces a rapid release of radiation, which could result in a harmful or lethal dose to personnel nearby, and / or contamination of the area by fission products.
Notable criticality accidents include: the JCO Tokaimura Fuel Fabrication Plant criticality accident in 1999 in which there were two fatalities and one significant exposure, and the 1953 Mayak product receiving tank criticality accident in an interim storage vessel in which there was one serious exposure and one significant exposure.
The report“ A Review of Criticality Accidents”, published in 2000, detailed 22 criticality accidents during process operations, and 38 from reactor and critical experiments. These categories of accident resulted in 9 and 12 fatalities respectively.
Managing Criticality Safety in Radioactive Waste Transport The relevant international regulations and guidance come from two IAEA safety documents: the ' Specific Safety Requirements, SSR-6 ', and the ' Specific Safety Guide, SSG-26 '. Regulations require transport packages to be designed with robust safety margins( including application of the MAGIC MERV parameters), with additional consideration for circumstances such as the prevention of ingress of neutron moderator( lowering incident neutron energy) or leakage of material.
Radiation Protection Today Winter 2025
Criticality transport assessments are prescriptive and consider a set of scenarios and accident conditions( such as a drop from height or a fire). Waste material is modelled with pessimistic assumptions, which lead to conservative criticality limits such as the mass of fissile material allowed per package, or how many packages are allowed per consignment.
Future of Criticality in Radioactive Waste Management Criticality assessment is a fundamental part of assessing radioactive waste packages for eventual disposal in the UK Geological Disposal Facility( GDF), and is required for the demonstration of safety during transport, handling, emplacement and long-term disposal. Robust procedures are already in place through the Nuclear Waste Services( NWS) Waste Package Specifications and the Environment Agencies ' Guidance on Requirements for Authorisation( GRA), which require disposers to undertake conservative criticality safety analyses, apply appropriate safety margins, and demonstrate compliance with relevant regulatory expectations. These arrangements provide confidence to regulators that criticality risks are effectively controlled prior to waste acceptance into the GDF.
A Master Slave Manipulator( MSM) used for handling materials( Copyright Cerberus Nuclear)
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