PNST 538-2021 PDF

Full title and description

PNST 538-2021 (ПНСТ 538-2021) — "Оборудование и трубопроводы блоков атомных станций. Расчет на прочность на стадии эксплуатации" / "Equipment and piping of nuclear power plant. Calculation of strength at the operation stage". This preliminary national standard sets requirements for strength (mechanical integrity) calculations of pressure‑retaining equipment and piping of nuclear power plant units during operation, including assessment for remaining life and for operation beyond the design life.

Abstract

This document is a Preliminary National Standard (ПНСТ) developed to provide calculation rules and acceptance criteria for strength assessments of equipment and piping of nuclear power plant units at the operational stage. It addresses calculation approaches (linear‑elastic and elastic–plastic/J‑integral where appropriate), treatment of detected defects and as‑found dimensions, effects of the operating environment (including water environment effects on cyclic strength), seismic and dynamic loading considerations, and requirements for residual‑life substantiation and life‑extension justification.

General information

• Status: Preliminary national standard (ПНСТ); introduced for limited time and subsequently withdrawn/expired (document shown as cancelled in registries).
• Publication date: Approved by Rosstandart by Order No. 25‑пнст on 9 March 2021; date of introduction (entry into force) 1 June 2021 (validity stated through 1 June 2022).
• Publisher: Federal Agency for Technical Regulation and Metrology (Rosstandart) — issued as a preliminary national standard.
• ICS / categories: ОКС (OKS) 03.120.01 as recorded in the standard’s front matter.
• Edition / version: 1st (ПНСТ 538‑2021).
• Number of pages: 90 (electronic PDF commercial copies list 90 pages).

Scope

The standard applies to pressure‑retaining equipment and piping of nuclear power plant units with water‑water energetic reactors (PWR), large‑power channel reactors and heterogeneous loop energy reactors with metal temperatures up to 350 °C. It is intended for components assigned to safety classes 1–3 (whose integrity or unacceptable deformation could lead to coolant release to adjacent circuits or the environment or impair function). The standard excludes certain components (for example, some zirconium alloy channel internals and certain reactor vessel shell/weld situations) and does not prescribe methods for deriving loading conditions — it addresses the strength‑calculation and assessment requirements for the operational stage, including life‑extension substantiation.

Key topics and requirements

• Requirements for strength (mechanical integrity) calculations of equipment and piping during operation, including methods and acceptability criteria (linear‑elastic and elastic–plastic approaches such as J‑integral where applicable).
• Consideration of measured (as‑found) geometry, detected discontinuities and defects revealed during manufacture, installation or operation.
• Accounting for material property changes over time and measured material condition in residual‑life assessments.
• Treatment of environmental effects on fatigue/cyclic strength (including reduced fatigue life in water environments at elevated temperature).
• Procedures for checking resistance to progressive deformation, seismic and other dynamic load combinations, and for selection of conservative combination rules and damping values.
• Specification of which components are covered (pressure‑retaining items, bolted joints, etc.) and explicit exclusions; guidance for life‑extension justification and methods for monitoring application.

Typical use and users

Used by structural and mechanical engineers, nuclear plant equipment designers, lifecycle and integrity assessment specialists, plant operators and maintenance organizations, regulatory or technical assessment bodies, and consultants responsible for fitness‑for‑service, residual‑life assessment and life‑extension studies for nuclear power plant pressure equipment and piping. The standard also served as a reference for technical committees and developers of permanent national standards in the nuclear field.

Related standards

References and related normative documents include national rules and federal regulations on the use of atomic energy, ГОСТ Р 58328 (pipeline concept "leak‑before‑break") and other normative documents cited within the standard; the document was prepared under the responsibility of TC 322 "Atomic engineering" and developed by AO NIKIET. Because PNST documents are preliminary, users should consult current permanent standards/requirements and regulatory rules for final binding requirements.

Keywords

nuclear power plant; equipment; piping; strength calculation; operational assessment; residual life; life extension; fatigue; seismic loads; pressure‑retaining equipment; ПНСТ; Rosstandart.

FAQ

Q: What is this standard?

A: PNST 538‑2021 is a Preliminary National Standard (ПНСТ) of the Russian Federation providing rules and requirements for strength calculations of equipment and piping at the operation stage for certain types of nuclear power plant units. It was approved by Rosstandart (Order No. 25‑пнст of 9 March 2021).

Q: What does it cover?

A: It covers strength assessment methodology, acceptance criteria and calculation requirements for pressure‑retaining equipment and piping of nuclear power plant units (PWR and certain channel/loop reactor types) with metal temperatures up to 350 °C, for components in safety classes 1–3, including treatment of defects, as‑found geometry, environmental effects on fatigue, seismic and dynamic loads, and residual‑life justification.

Q: Who typically uses it?

A: Mechanical and structural engineers, integrity assessment specialists, plant operators and maintenance teams, regulatory/inspection personnel, and consultants involved in fitness‑for‑service and life‑extension evaluations for nuclear plant equipment and piping.

Q: Is it current or superseded?

A: PNST 538‑2021 was issued as a preliminary standard with a limited period of validity (entry into force 1 June 2021, with stated duration through 1 June 2022 per the approving order). Registry entries indicate the preliminary standard period has ended and the document is shown as withdrawn/cancelled in some databases; users should therefore verify whether a permanent national standard or other updated normative document has replaced it before relying on it as current regulatory guidance.

Q: Is it part of a series?

A: It was prepared under Technical Committee TC 322 "Atomic engineering" and is one of a set of normative documents addressing strength justification and safety of nuclear power plant equipment and piping; as a ПНСТ it was intended to gather application experience prior to development of any permanent national standard(s).

Q: What are the key keywords?

A: Nuclear equipment; piping; strength calculation; operational stage; residual life; fatigue in water environment; seismic loads; pressure‑retaining equipment; preliminary national standard (ПНСТ).