GB/T 46694-2025 Primary coolant system source terms analysis and control criteria for pressurized water reactor nuclear power plants English, Anglais, Englisch, Inglés, えいご
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ICS 13.220.10
CCS H 57
National Standard of the People's Republic of China
GB/T 46694-2025
Primary coolant system source terms analysis and control criteria for pressurized water reactor nuclear power plants
压水堆核电厂主回路系统源项分析及控制准则
Issue date: 2025-10-31 Implementation date: 2026-05-01
Issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
the Standardization Administration of the People's Republic of China
Contents
Foreword
1 Scope
2 Normative References
3 Terms and Definitions
4 Primary System Source Term Analysis Criteria
5 Primary System Source Term Control Requirements
Appendix A (Informative) Primary Coolant Fission Product Main Nuclide Types
Appendix B (Informative) Calculation Methods for Dose-Equivalent 131I and 133Xe Activity Concentrations
Appendix C (Informative) Escape Rate Coefficients
Appendix D (Informative) Calculation Method for Adjustment Factors
Appendix E (Informative) Primary Coolant Activated Corrosion Product Source Term Parameter List
Appendix F (Informative) Equipment Material Cobalt Impurity Content Levels
References
1 Scope
This document specifies the criteria and control requirements for radiation source term analysis of the primary coolant, primary system equipment, and core structural materials during normal operation in the design of pressurized water reactor nuclear power plants.
This document is applicable to the analysis and control of radiation source terms in the primary system during normal operation considered in the design of pressurized water reactor nuclear power plants.
2 Normative References
This document has no normative references.
3 Terms and Definitions
The following terms and definitions apply to this document.
3.1
Normal Operation
[Source: GB/T 13976-2021, 3.2]
3.2
Nuclide
A type of atom characterized by a specific mass number, atomic number, and nuclear energy state, with an average lifetime sufficiently long to be observable.
[Source: GB/T 4960.1-2010, 2.53]
3.3
[Nuclear] Fission
The phenomenon in which a heavy atomic nucleus splits into two (or, in rare cases, three or more) fragments of comparable mass. This process is accompanied by the emission of neutrons, gamma rays, and occasionally light charged particles.
[Source: GB/T 4960.1-2010, 6.1, modified]
3.4
Fission Product
Fission fragments generated by nuclear fission and their decay products.
[Source: GB/T 4960.1-2010, 6.13]
3.5
Activation
The process by which materials are irradiated by neutrons, protons, or other nuclear particles, thereby inducing radioactivity.
[Source: GB/T 4960.1-2010, 7.57]
3.6
Activation Product
Radioactive products generated after materials are irradiated by neutrons, protons, or other nuclear particles.
[Source: GB/T 4960.1-2010, 7.58]
3.7
Activity Concentration
The activity of a radionuclide per unit mass or volume of a substance.
[Source: GB/T 4960.1-2010, 3.58, modified]
3.8
Neutron Fluence Rate
A measure of neutron irradiation intensity within a given neutron energy range.
Note: It is the product of neutron density and velocity.
3.9
Group Cross Section
The weighted average neutron cross section for a specific energy group.
[Source: GB/T 4960.2-2023, 5.64]
3.10
Decontamination Factor
The ratio of the radioactive level before and after decontamination of contaminated materials.
Note: Also known as the decontamination coefficient. It can apply to the removal of a specific radionuclide or total radioactive contamination.
[Source: GB/T 4960.1-2010, 7.29, modified]
4 Primary System Source Term Analysis Criteria
4.1 Primary Coolant
4.1.1 Fission Products
4.1.1.1 The fission product source term of the primary coolant includes the design-basis source term (design source term) and the realistic source term.
4.1.1.2 The selection of fission product nuclides in the primary coolant should generally consider factors such as their production rate, half-life, radioactivity intensity, and impact on the human body. Typically, radioactive isotopes of inert gases, iodine, cesium, etc., are included. Major nuclides are listed in Appendix A.
4.1.1.3 The fission product source term of the primary coolant can be characterized by the dose-equivalent 131I activity concentration (or total iodine amount) and the dose-equivalent 133Xe activity concentration (or total inert gases). The dose-equivalent 131I activity concentration and dose-equivalent 133Xe activity concentration can be calculated using dose conversion factors or characterized using equivalent methods such as empirical formulas. Specific methods are detailed in Appendix B.
4.1.1.4 The calculation and analysis of the design-basis primary coolant fission product source term should consider conservatism, enveloping variations in core fuel management, system design, and operational states.
4.1.1.5 The fission product source term of the primary coolant can be obtained through theoretical calculations or based on operational experience data.
4.1.1.6 For design-basis fission product source term analysis, theoretical calculation methods should simulate the comprehensive processes of fission product generation in the core, release into the coolant, and purification and removal in the primary system. Theoretical calculations can be based on core radioactive inventory, fuel cladding failure rate, escape rate coefficients, and system parameters. Typically, an in-core fuel cladding failure rate of 0.25% can be assumed. Theoretical calculation results should be consistent with the limits specified in the technical specifications of this nuclear power plant or reference nuclear power plants. The escape rate coefficients for fission products in failed fuel assemblies can adopt values from Appendix C or be determined based on other assumptions regarding the number and state of fuel assembly cladding failures during reactor operation, using mature professional software or validated methods and software for calculation and analysis.
4.1.1.7 If the design-basis primary coolant fission product source term is determined based on operational experience data from similar nuclear power plants, conservatism should be applied to account for potential increases in nuclide activity concentration in the primary coolant due to various transients (including anticipated operational occurrences) during nuclear power plant operation. It can be calculated by multiplying adjustment factors based
