ASME BPVC 2017 Section III div. 1 sub NCA — Subsection NCA General Requirements for Division 1 and Division 2

28 10 月, 2026
ASME Standards

☢️ Section III of the ASME Boiler & Pressure Vessel Code — Rules for Construction of Nuclear Facility Components is organized into several subsections. Among them, Subsection NCA (General Requirements for Division 1 and Division 2) is the administrative and managerial backbone of the entire Section III: it establishes the scope of the rules, the classification of components and supports, the responsibilities of the owner, designer, certificate holder, and authorized inspection agency, the quality assurance (QA) program requirements, authorized inspection, code stamping, data reports, and certificates of authorization. This document covers the 2017 Edition of Subsection NCA (issued July 1, 2017, 121 pages), Division 1 scope. In short: while Subsections NB, NC, ND, NE, NF, NG answer how a component is designed, fabricated, and examined, NCA answers who may build it, under what quality system, with what authorization, and how compliance is demonstrated.

NCA-1000 defines the scope. The objects of regulation are called “items,” which include pressure components (reactor pressure vessels, steam generators, pressurizers, primary coolant pumps, valves, and piping), component supports, piping supports, appurtenances, parts, and field installation activities. The rules also cover concrete containments (Class CC) under Division 2, including their prestressing systems. NCA-1150 addresses units of measurement: both SI and U.S. Customary units are acceptable, but a single system shall be selected and used consistently throughout — mixing values from the two systems constitutes nonconformance. The Owner’s Design Specification (NCA-3250) is the starting point of the entire chain: it must define the design basis, load combinations, materials, and acceptance criteria, and for Division 2 a separately certified Design Report is required.

💡 The key to reading NCA is the “chain of responsibility plus the chain of evidence”: the owner prepares and certifies the design specification, the designer certifies the design report, the certificate holder builds and examines under a QA program, the authorized inspector verifies the data report, and ASME issues the Certificate of Authorization based on the review. If any link is missing, the Code Symbol may not be applied.

1. Scope and Framework (NCA-1000) 📌

NCA-1000 establishes what falls under Section III and how the rules are applied. It is not a design-formula book — it contains no wall-thickness equations. Instead, it sets the “rules of the game”: which organizations may participate, what qualifications they need, what documents must be produced and certified, and how conformity is demonstrated. Whenever an item is to bear the N Code Symbol, the substantive design, material, fabrication, and examination requirements come from the appropriate subsection (NB, NC, ND, etc.), but all questions of qualification, responsibility, and quality systems fall under NCA. A complete documentation set for any nuclear component must therefore cite both NCA and the applicable subsection.

⚠️ NCA is not a substitute for the design subsections. A manufacturer referencing Section III without including NCA (e.g., a purchase order citing only “ASME NB” without the NCA edition, addenda, and code cases) has an incomplete, nonconforming document set.

2. Classification of Components and Supports (NCA-2000) 🔧

NCA-2000 establishes the component classification system. Classification is based on the safety function of the item: components that form the pressure boundary of the multiple barriers against release of radioactive material, or that perform safety functions during shutdown, decay-heat removal, and emergency systems, must be constructed to the Code. Division 1 classifies metallic components as Class 1, 2, 3, Class MC (metal containments), and related categories; Division 2 covers Class CC concrete containments.

Class	Typical Items	Safety Function Basis	Governing Subsection
Class 1	Reactor pressure vessel, pressurizer, primary piping, SG primary side	Coolant pressure boundary; failure could cause loss-of-coolant accident	NB (design NB-3000, examination NB-5000, etc.)
Class 2	Residual-heat-removal piping, safety-injection systems, secondary-side pressure equipment	Performs safety functions or retains pressure under accident conditions	NC
Class 3	Cooling-water systems, auxiliary feedwater, general plant pressure items	Generally non-safety but Code-constructed pressure-retaining items	ND
Class MC	Metal containment vessel	Final barrier against radioactive release	NE
Class CC	Prestressed concrete containment (Division 2)	Final barrier (concrete structure)	CC (Division 2)

Classification is performed by the owner in the Design Specification and must be accepted by the certificate holder and the authorized inspection agency. The class determines the applicable subsection, material restrictions, examination percentages, and testing requirements, so a classification error propagates through the entire chain and is one of the most common sources of nonconformities found during certification audits.

💡 Classify conservatively: when one item performs multiple functions pointing to different classes, the most stringent class requirements normally govern. Any classification change must follow the formal document-revision process with designer certification and acceptance by the authorized inspection agency.

3. Responsibilities and Duties (NCA-3000) ⚖️

NCA-3000 is the heaviest part of Subsection NCA, defining the responsibility boundaries of every participating organization:

Owner: prepares and certifies the Design Specification (NCA-3250), reviews the Design Report (NCA-3260), prepares the Overpressure Protection Report (NCA-3270), signs and files the Owner’s Data Report (NCA-3280), and maintains construction records (NCA-3290).
Designer (Division 2): prepares design drawings and construction specifications, prepares and certifies the Design Report (NCA-3360), and controls later revisions.
N Certificate Holder (Division 1): performs construction and quality assurance (NCA-3460), prepares and controls construction documents (NCA-3450); only a certificate holder may sign the data report and apply the Code Symbol.
Authorized Inspection Agency (AIA): assigns commissioned Authorized Nuclear Inspectors (ANIs) to supervise construction, witness required examinations and tests, and certify the data report.

🚨 Responsibility cannot be delegated away: a certificate holder may subcontract work, but the control of the QA program, final examination, and use of the Code Symbol remain fully with the certificate holder. Subcontractors must be drawn into the holder’s program; treating a subcontractor as an independent “certified party” to escape liability is not acceptable under the Code.

4. Quality Assurance Program (NCA-4000) 📋

NCA-4000 requires every certificate holder to establish and execute a documented quality assurance program covering everything from design and procurement through fabrication to handling, storage, and shipping. The program elements correspond one-to-one with the 18 criteria of 10 CFR 50 Appendix B and of ASME NQA-1, including organization, QA program documents, design control, procurement document control, instructions/procedures/drawings, document control, control of purchased items, identification and control of materials, control of processes, inspection control, test control, control of measuring and test equipment, handling/storage/shipping, nonconforming items, corrective action, QA records, and audits.

Program Element Area	Core Requirement	Typical Evidence
Organization and procedures	Responsibility matrix, personnel training and qualification, program document approval	Organizational charts, QA manual, qualification records
Design and procurement control	Design-basis review, supplier evaluation, Code clauses in purchase documents	Design specification, approved supplier list
Item control	Material identification, traceability, transfer of identification	Material test reports, transfer records
Inspection and testing	Inspection plans, witness/hold points, performance and evaluation of tests	Examination reports, NDT reports, test records
Nonconformances and corrective action	NCR disposition, verification, preventive action	NCR log, corrective-action reports

The retention periods, formats, and signature requirements for QA records are set out in NCA. These records are repeatedly retrieved during regulatory reviews and the licensing phase, so the operating philosophy “records equal requirements, signatures equal commitment” is a fundamental work ethic in the nuclear industry.

5. Authorized Inspection, Stamping, Certificates, and Data Reports 🛠️

NCA also establishes the authorized inspection and Code Symbol stamping system. Authorized Nuclear Inspectors must be individually qualified and commissioned; their duty is to independently verify that the item has been constructed in accordance with the approved design, the Code, and the QA program. Without ANI certification, the data report is invalid and the Code Symbol may not be applied. Certificate types available under the rules include N (nuclear components), NPT (nuclear parts), NV (nuclear safety-related pressure relief valves), NA (field assembly of nuclear components), N3 (concrete containments), and NS (nuclear component supports); materials organizations hold a Quality System Certificate (QSC). Certificates are typically valid for three years and are renewed after a joint review by an ASME-recognized team including AIA representatives.

Upon completion, the certificate holder prepares the applicable Code data report forms (e.g., N-1/N-2/N-3/N-4, NV-1) and the Owner’s Data Report. After ANI certification, the reports are distributed with the component or installation records and the owner files them with the regulatory body in accordance with NCA-3280.

💡 A certificate’s scope defines what it legally permits. Even a manufacturer holding an N Certificate may not stamp a product category not covered by its certificate scope (for example, valves). Always verify that the supplier’s certificate scope covers the product class and type you are purchasing, and check the publicly posted ASME certificate information before contracting.

6. Engineering Practice Essentials 🛠️

🔍 Pre-certification self-audit: compare your QA program item-by-item against NCA-4000, and check that purchase documents cite the full package — “ASME Section III NCA + applicable subsection + edition + addenda + code cases.”
🔧 Units declaration: select one system of units in the Design Specification and construction documents, and never mix values across systems.
📊 Witness-point management: define hold points (H) and witness points (W) in the inspection and test plan, and notify the ANI in advance to avoid rework from missed inspections.
📋 Records closure: include material certificates, welder qualifications, heat-treatment curves, NDT films, and reports in the QA records and keep them for the NCA-required retention periods.
🔄 NCR closure: repair, concession, or reject dispositions must be Code-permitted and accepted by the authorized inspector before release.

7. Frequently Asked Questions ❓

❓ Q: What is the relationship between NCA and Subsections NB/NC/ND?
A: NCA is the general requirements subsection handling qualification, responsibility, and quality systems, while NB/NC/ND provide the specific design, material, fabrication, and examination rules for Classes 1/2/3. Both are required whenever code construction is cited.

❓ Q: Can a non-certificate-holder supply components for a nuclear project?
A: Pressure components generally must be constructed by organizations holding the appropriate certificate (e.g., N). Materials must come from QSC holders or suppliers qualified under the Code. Applying or implying ASME acceptance without the corresponding certificate is misuse of the Code symbols.

🔍 Q: What does the Data Report do?
A: It is the formal document showing that the item was constructed and examined under the Code. Once certified by the ANI, it becomes part of the regulatory and equipment-life record — the legal basis for traceability and acceptance, usually filed by the owner.

❓ Q: May a Class 2 component use the less restrictive Class 3 requirements?
A: No. The class is set by the owner on the basis of safety function and written into the Design Specification; the full set of requirements for that class must be applied. Upgrading to a stricter class is permitted (“when in doubt, go higher”), but downgrading is not.