ISO 27468:2011 PDF

Nuclear criticality safety — Evaluation of systems containing PWR UOX fuels — Bounding burnup credit approach

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Title (English):

ISO 27468:2011

Nuclear criticality safety — Evaluation of systems containing PWR UOX fuels — Bounding burnup credit approach

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 10
Publication date:: July 5, 2011
Edition:: ISO IS 27468 edition 1 version 1
ICS:: 27.120.30

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Description (English):

ISO 27468:2011 establishes an evaluation methodology for nuclear criticality safety with burnup credit. It identifies important parameters and specifies requirements, recommendations, and precautions to be taken into account in the evaluations. It also highlights the main important technical fields to ensure that the fuel composition or history considered in calculations provides a bounding value of the effective neutron multiplication factor, keff. ISO 27468:2011 is applicable to transport, storage, disposal or reprocessing units implying irradiated fissile material from pressurized water reactor (PWR) fuels that initially contain uranium oxide (UOX). Fuels irradiated in other reactors (e.g. boiling water reactors) and fuels that initially contain mixed uranium-plutonium oxide are not covered in ISO 27468:2011. ISO 27468:2011 does not specify requirements related to overall criticality safety evaluation or eventual implementation of burnup credit.

Technical details

Technical committee: ISO/TC 85/SC 5 - Nuclear installations, processes and technologies
SKU: ISO 27468:2011

Abstract

Overview

ISO 27468:2011 - "Nuclear criticality safety - Evaluation of systems containing PWR UOX fuels - Bounding burnup credit approach" establishes a structured methodology for applying burnup credit in nuclear criticality safety assessments. The standard is focused on irradiated Pressurized Water Reactor (PWR) uranium-oxide (UOX) fuels and specifies how to ensure that the assumed fuel composition or history produces a bounding value of the effective neutron multiplication factor (keff). ISO 27468:2011 applies to transport, storage, disposal and reprocessing of irradiated PWR UOX fuel; it explicitly excludes fuels from other reactor types (e.g., BWR) and mixed oxide (MOX) fuels. The document provides requirements, recommendations and precautions but does not itself set overall criticality safety or implementation rules.

Key Topics

Bounding burnup-credit methodology - stepwise approach to produce conservative keff estimates.
Main evaluation steps:
- Choose and justify a burnup distribution (axial and radial profiles).
- Perform depletion calculations to obtain post‑irradiation nuclide concentrations (including cooling time).
- Select absorber and actinide nuclides to include in keff calculations.
- Perform validated criticality calculations and document results.
Burnup distribution considerations - axial and radial gradients, end effects, flat-profile justifications and uncertainty treatment.
Irradiation parameters that affect nuclide inventories - boron concentration, coolant temperature/density, burnable poisons, control rod insertion and neighboring fuel types (e.g., MOX).
Cooling time - choose bounding cooling time for depletion calculations (keff behavior varies with decay of Pu, Am, fission products).
Validation and documentation - require validation of depletion and criticality codes (Annex A references post-irradiation examination) and documented justification of input assumptions.
Operational guidance - Annex B offers considerations for implementing burnup credit in operations.

Applications

ISO 27468:2011 is practical for:

Criticality safety engineers performing safety analyses for transport casks, storage racks, reprocessing facilities and disposal systems handling irradiated PWR UOX fuel.
Licensing and regulatory submissions where conservative, auditable burnup-credit approaches support higher-fidelity keff estimates.
Facility designers and operators seeking to reduce unnecessary conservatism (increase cask capacity or reduce handling operations) while maintaining subcritical margins.
Nuclear analysts validating depletion codes and deriving bounding nuclide inventories for criticality models.

Related Standards

ISO 1709 - Principles of criticality safety in storing, handling and processing.
ISO 14943 - Administrative criteria related to nuclear criticality safety.
ISO 27468 references additional technical literature and measurement/validation practices (e.g., post‑irradiation examination guidance).

Keywords: ISO 27468:2011, burnup credit, nuclear criticality safety, PWR UOX fuels, keff, depletion calculations, burnup distribution, irradiation parameters.

Related standards

Standards mentioned in the description

Abstract

Overview

Key Topics

Bounding burnup-credit methodology - stepwise approach to produce conservative keff estimates.
Main evaluation steps:
- Choose and justify a burnup distribution (axial and radial profiles).
- Perform depletion calculations to obtain post‑irradiation nuclide concentrations (including cooling time).
- Select absorber and actinide nuclides to include in keff calculations.
- Perform validated criticality calculations and document results.
Burnup distribution considerations - axial and radial gradients, end effects, flat-profile justifications and uncertainty treatment.
Irradiation parameters that affect nuclide inventories - boron concentration, coolant temperature/density, burnable poisons, control rod insertion and neighboring fuel types (e.g., MOX).
Cooling time - choose bounding cooling time for depletion calculations (keff behavior varies with decay of Pu, Am, fission products).
Validation and documentation - require validation of depletion and criticality codes (Annex A references post-irradiation examination) and documented justification of input assumptions.
Operational guidance - Annex B offers considerations for implementing burnup credit in operations.

Applications

ISO 27468:2011 is practical for:

Criticality safety engineers performing safety analyses for transport casks, storage racks, reprocessing facilities and disposal systems handling irradiated PWR UOX fuel.
Licensing and regulatory submissions where conservative, auditable burnup-credit approaches support higher-fidelity keff estimates.
Facility designers and operators seeking to reduce unnecessary conservatism (increase cask capacity or reduce handling operations) while maintaining subcritical margins.
Nuclear analysts validating depletion codes and deriving bounding nuclide inventories for criticality models.

Related Standards

ISO 1709 - Principles of criticality safety in storing, handling and processing.
ISO 14943 - Administrative criteria related to nuclear criticality safety.
ISO 27468 references additional technical literature and measurement/validation practices (e.g., post‑irradiation examination guidance).

Keywords: ISO 27468:2011, burnup credit, nuclear criticality safety, PWR UOX fuels, keff, depletion calculations, burnup distribution, irradiation parameters.

ISO 27468:2011 PDF

Technical details

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

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Nuclear fuel technology — Administrative criteria related to nuclear criticality safety

Nuclear criticality safety. Evaluation of systems containing PWR UOX fuels. Bounding burnup credit approach.