ISO 10645-2022 PDF

Full title and description

St ISO 10645-2022 — Nuclear energy — Light water reactors — Decay heat power in non-recycled nuclear fuels. This international standard provides calculation methods and data to determine the decay heat power produced by non‑recycled nuclear fuel in light water reactors (pressurized and boiling water reactors), covering contributions from fission products, actinides and isotopes formed by neutron capture in fission products, for decay times from 0 s to 10^9 s.

Abstract

This document specifies procedures to calculate decay heat power for light water reactor fuels composed of 235U and 238U (non‑recycled fuels). It separates and quantifies contributions from fission products, actinides and neutron‑capture products in fission products, and is intended for decay heat periods from immediate post‑shutdown up to about 10^9 seconds. The standard is not applicable to recycled fuels (for example MOX or reprocessed uranium) unless other contributions are determined specifically for that reactor/fuel type.

General information

• Status: Published.
• Publication date: April 2022 (Edition 2).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 27.120.10 (Nuclear energy — reactor physics / decay heat).
• Edition / version: Edition 2 (2022).
• Number of pages: 20 pages (ISO publication).

Scope

Defines calculation methods and tabulated contributions for estimating decay heat power from non‑recycled uranium fuel in light water reactors (PWR and BWR). The scope explicitly covers fuel composed of 235U and 238U and the decay heat contributions from fission products, actinides and neutron‑capture products in fission products for times between 0 seconds and 10^9 seconds after shutdown. Use for recycled fuels (e.g., MOX) is not permitted without additional, fuel‑specific treatment.

Key topics and requirements

• Calculation models and procedures for decay heat power from non‑recycled LWR fuel (PWR/BWR).
• Separation of decay heat contributions: fission products, actinides, and products from neutron capture in fission products.
• Applicability limits: fuel composition restricted to 235U/238U mixtures; recycled fuels excluded unless treated separately.
• Time range of validity for calculations: from immediate shutdown (0 s) up to 10^9 s (~31.7 years).
• Guidance for applying fission‑product results to other thermal reactor types only when actinide and neutron‑capture contributions are determined for that reactor.

Typical use and users

Primary users include nuclear reactor designers, safety analysts, thermal‑hydraulics engineers, spent fuel management planners, regulatory authorities, research organizations, and vendors of nuclear fuel and reactor simulation software. The standard is used to support safety analyses, shutdown and decay‑heat removal system design, spent fuel handling and storage planning, licensing documentation, and validation of decay‑heat models in neutronics and system codes.

Related standards

National and international documents on decay heat, reactor fuel behaviour and reactor physics may be used in conjunction with ISO 10645:2022 (for example national adoptions and related technical reports). Historical and national standards addressing decay‑heat calculation and fuel‑specific methods (such as national standards and related DIN/BS adoptions) provide complementary methodologies and implementation details. The standard was prepared under ISO/TC 85/SC 6 (nuclear fuel cycle and materials).

Keywords

decay heat; decay heat power; light water reactor; LWR; PWR; BWR; non‑recycled fuel; uranium fuel; fission products; actinides; neutron capture; reactor safety; spent fuel; ISO 10645:2022.

FAQ

Q: What is this standard?

A: ISO 10645:2022 is an international standard that specifies methods to calculate decay heat power for non‑recycled uranium fuel in light water reactors (pressurized and boiling water reactors).

Q: What does it cover?

A: It covers calculation procedures and component contributions (fission products, actinides, and isotopes formed by neutron capture in fission products) for decay heat from 0 s up to 10^9 s for fuels composed of 235U and 238U; it excludes recycled fuels unless additional reactor‑/fuel‑specific contributions are determined.

Q: Who typically uses it?

A: Reactor designers, safety and licensing analysts, fuel vendors, spent fuel storage planners, regulators and researchers — essentially professionals involved in reactor thermal analysis, safety cases, code validation and spent‑fuel management.

Q: Is it current or superseded?

A: ISO 10645:2022 is the current published version (Edition 2, April 2022). It replaces the earlier edition (ISO 10645:1992) which was withdrawn.

Q: Is it part of a series?

A: It is a standalone ISO standard focused on decay‑heat calculations for non‑recycled LWR fuels, prepared under ISO/TC 85/SC 6. It is related to other national and international documents on decay heat and reactor fuel calculations but is not formally numbered as a multi‑part series. National adoptions and related national standards (for example DIN and BSI adoptions) may exist.

Q: What are the key keywords?

A: Decay heat, light water reactor, non‑recycled nuclear fuel, fission products, actinides, neutron capture, PWR, BWR, reactor safety.