Standard No.:	GB/T 16702.4-2025
English Name:	Design specification for mechanical components in nuclear island of pressurized water reactor nuclear power plants―Part 4: Class 3 components
Chinese Name:	压水堆核电厂核岛机械设备设计规范第4部分：3级设备
Professional Classification:	GB    National Standard
Source Content Issued by:	SAMR; SAC
Issued on:	2025-02-28
Implemented on:	2025-2-28
Status:	valid
Superseding:	GB/T 16702-2019 Design code for mechanical components in nuclear island of pressurized water reactor nuclear power plants
Target Language:	English
File Format:	PDF
Word Count:	14500 words
Translation Price(USD):	435.0
Delivery:	via email in 1~5 business day

GB/T 16702.4-2025 Design specification for mechanical components in nuclear island of pressurized water reactor nuclear power plants―Part 4: Class 3 components English, Anglais, Englisch, Inglés, えいご This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation， self-check， revision and verification) will be delivered upon being ordered. ICS 27.120.20 CCS F 69 National Standard of the People's Republic of China GB/T 16702.4-2025 Partly Replaces GB/T 16702-2019 Design specification for mechanical components in nuclear island of pressurized water reactor nuclear power plants - Part 4 : Class 3 components 压水堆核电厂核岛机械设备设计规范 第4部分：3级设备 (English Translation) Issue date: 2025-02-28 Implementation date: 2025-02-28 Issued by the State Administration for Market Regulation the Standardization Administration of the People's Republic of China Contents Foreword Introduction 1 Scope 2 Normative references 3 Terms and definitions 4 General principles 5 Materials 6 Design 7 Manufacture and inspection 8 Pressure testing 9 Overpressure protection Bibliography Design specification for mechanical components in nuclear island of pressurized water reactor nuclear power plants - Part 4 : Class 3 components 1 Scope This document specifies the requirements for materials, design, manufacture, inspection, testing, and overpressure protection of Class 3 equipment in the nuclear island mechanical equipment of pressurized water reactor nuclear power plants. This document applies to Class 3 pressure-retaining equipment and its components in pressurized water reactor nuclear power plants as specified in GB/T 16702.1-2025. 2 Normative references The following documents contain requirements which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 16702.1-2025 Design specification for mechanical equipment of nuclear island of pressurized water reactor nuclear power plants - Part 1: General principles GB/T 16702.2-2025 Design specification for mechanical components in nuclear island of pressurized water reactor nuclear power plants - Part 2: Class 1 components GB/T 16702.3-2025 Design specification for mechanical equipment of nuclear island of pressurized water reactor nuclear power plants - Part 1: General principles GB/T 16702.7 Design specification for mechanical components in nuclear island of pressurized water reactor nuclear power plants - Part 7: Supports NB/T 20001-2023 Manufacturing code for mechanical equipment of nuclear island of pressurized water reactor nuclear power plants NB/T 20002 (all parts) Welding code for mechanical components of PWR nuclear islands - Part 1:General requirements NB/T 20005.1 Carbon steel and low alloy steel for pressurized water reactor nuclear power plants - Part 1: Class 1, 2 and 3 forgings and rolled products NB/T 20005.2 Carbon steel and low alloy steel for pressurized water reactor nuclear power plants - Part 2: Forgings for class 2, 3 heat exchanger tube plates NB/T 20005.5 Carbon steel and low alloy steel for pressurized water reactor nuclear power plants - Part 5: Class 1, 2 and 3 pressure-retaining castings NB/T 20005.7 Carbon steel and low alloy steel for pressurized water reactor nuclear power plants - Part 7: Steel plates for class 1, 2 and 3 equipment NB/T 20005.9 Carbon steel and low alloy steel for pressurized water reactor nuclear power plants -Part 9: Class 2,3 seamless steel pipes 3 Terms and definitions The terms and definitions defined in GB/T 16702.1-2025 apply to this document. 4 General principles 4.1 Documents to be prepared The documents to be prepared shall be implemented in accordance with Clause 4.2 of GB/T 16702.3-2025. 4.2 Boundaries of components and attachments for equipment and piping 4.2.1 Boundaries of components The equipment design specification shall specify the boundary scope between the component and the connected piping or other components. The boundaries of vessels, storage tanks, pumps, valves, etc., shall not be within the following scopes: a) The groove end face of the first circumferential joint of welded connection (the connecting weld shall be deemed part of the piping); b) The first flange face of flanged connection (bolts shall be deemed part of the piping); c) The first threaded joint of threaded connection. 4.2.2 Boundaries between components and attachments 4.2.2.1 Attachments Attachments refer to elements in contact with or connected to the internal or external of the pressure-retaining part of the component. Attachments are classified by pressure-bearing function into pressure-bearing attachments and non-pressure-bearing attachments, and by structural function into structural attachments and non-structural attachments. Pressure-bearing attachments include: pressure boundary reinforcements, branch pipes, and vessel opening reinforcements. Non-pressure-bearing attachments include: valve bushings, thermowells, rotating blades, component support load path items, vessel saddle supports, supports, shear lugs, brackets, pipe clamps, trunnions, skirts, and other items on the support load path. Structural attachments perform pressure-bearing functions or serve as component load supports. Non-structural attachments do not perform pressure-bearing functions nor serve as component support load paths, including nameplates, insulation supports, positioning blocks, and lifting lugs. 4.2.2.2 Jurisdictional boundaries The jurisdictional boundary between the pressure-retaining component and attachments specified in the equipment design specification shall not be within the component's pressure-retaining boundary as stipulated in a) ~ g) below. Figures 1 ~ 3 detail the boundary and construction requirements of this document. a) Attachments connected to the component by casting or forging, and surfacing on the component surface shall be deemed part of the component. b) Pressure-bearing attachments, welds, and fasteners shall be deemed part of the component. c) Except as specified in d) and e), the boundary between the pressure-retaining part and its non-pressure-bearing attachments shall be the surface of the component. d) If the first weld between a non-pressure-bearing structural attachment and the component is within 2t of the component's pressure-retaining part (t is the nominal thickness of the pressure-retaining material), the weld shall be deemed part of the component. If the aforementioned weld is outside 2t of the component's pressure-retaining part, the weld shall be deemed part of the attachment. e) The first connecting weld between a non-structural attachment and the component shall be deemed part of the attachment. The first weld within 2t of the component's pressure-retaining part shall meet the welding requirements for non-pressure-bearing attachments and pressure-retaining components. f) Mechanical fasteners used to connect non-pressure-bearing attachments to the component shall be deemed part of the attachment. g) When specified in the design document, the boundary may be set further away from the component's pressure-retaining part as defined in a) ~ f). 4.3 Identification Identification shall be implemented in accordance with Clause 4.3 of GB/T 16702.3-2025.