ISO 22946:2020

Overview

ISO 22946:2020 - "Nuclear criticality safety - Solid waste excluding irradiated and non‑irradiated nuclear fuel" provides requirements and guidance for managing nuclear criticality safety of solid radioactive waste that contains fissile nuclides. Intended to be used alongside ISO 1709, the standard covers waste generated during normal operations, including solid wastes and any residual liquids or slurries intimately associated with those solids. It explicitly excludes bulk/process liquids and irradiated or un‑irradiated fuel elements. All phases of the waste life cycle (generation, handling, storage, processing, transport and final disposal) are within scope, and the document can be applied to transport outside nuclear site boundaries.

Key topics and requirements

• Nuclear criticality safety strategy: a documented, facility‑level plan is required to manage criticality risk throughout the waste life cycle. Strategy development early in design or as soon as practicable for legacy waste is emphasized.
• Stakeholder consultation: strategy should involve relevant stakeholders (handlers, processors, transporters, disposal operators and regulators).
• Radioactive waste characterization: systematic characterization of fissile inventory, moderators, absorbers and waste matrix is required to inform safety assessments (Annex A example sheet).
• Criticality safety assessments: requirements for deriving criticality safety limits, accounting for inventory variations, radioactive decay and assessing consequences of potential criticality accidents.
• Balancing risks and constraints: guidance on balancing criticality safety with radiological safety, environmental impact, conventional safety, cost and schedule to avoid disproportionate controls.
• Supporting material: informative annexes provide characterization templates and supporting information for assessment and inventory variation considerations.

Applications and users

ISO 22946:2020 is practical for:

• Nuclear facility designers and waste system engineers planning waste management strategies.
• Waste managers and operations staff responsible for storage, processing and packaging of solid nuclear waste.
• Safety assessors and criticality analysts performing criticality safety assessments and deriving limits.
• Transport planners and regulators assessing movement of waste outside nuclear facilities.
• Disposal facility operators and consultants preparing documentation for compliance and audits.

Practical uses include developing documented strategies, performing characterization and criticality assessments, setting package and facility limits, and informing regulatory submissions.

Related standards

• ISO 1709 - Principles of criticality safety in storing, handling and processing fissile materials (to be used alongside ISO 22946).
• ISO 12749‑3 - Vocabulary for nuclear fuel cycle terms (definitions used by ISO 22946).

Keywords: ISO 22946:2020, nuclear criticality safety, solid nuclear waste, fissile nuclides, waste life cycle, radioactive waste characterization, criticality safety assessments.