IEC 61505-1998 PDF

Full title and description

St IEC 61505-1998 — Nuclear reactor instrumentation — Boiling water reactors (BWR) — Stability monitoring. This International Standard gives guidance on which plant parameters to use for monitoring BWR stability, defines analysis methods to relate time-varying plant data to stability figures of merit (for example, decay ratio), and provides technical guidelines for stability-monitoring systems and requirements.

Abstract

IEC 61505:1998 describes methods and recommendations for monitoring the dynamic stability of boiling water reactors. It identifies relevant plant measurements, establishes analysis techniques to derive stability metrics (such as decay ratio and modal damping), and sets out technical guidelines for data acquisition, processing, trending and alarmization used in ongoing stability surveillance programs. The document was published as a guidance/technical standard for operators, I&C engineers and safety analysts responsible for BWR stability assessment and monitoring.

General information

• Status: Withdrawn (withdrawal recorded 22 April 2010).
• Publication date: 10 November 1998.
• Publisher: International Electrotechnical Commission (IEC), TC 45/SC 45A.
• ICS / categories: 27.120.20 (Nuclear power plants. Safety).
• Edition / version: Edition 1.0 (1998).
• Number of pages: 83.

Scope

The standard applies to boiling water reactor (BWR) plant stability monitoring. It defines appropriate plant parameters for use in stability monitoring, specifies analysis methods for relating time‑varying plant measurements to stability figures of merit (for example decay ratio and modal indices), and provides technical guidelines for stability-monitoring requirements including measurement selection, data-recording and processing, analysis frequency, alarm/trip considerations and reporting for long-term surveillance programs. The guidance is aimed at operational monitoring and does not itself set mandatory regulatory limits.

Key topics and requirements

• Identification of plant signals useful for BWR stability monitoring (neutron flux detectors, recirculation flow, core flow, void fraction indicators, reactor power, etc.).
• Definition and calculation of stability figures of merit (decay ratio, damping, modal contributions, frequency content).
• Recommended analysis methods for processing time‑series data (time‑domain and frequency‑domain techniques, modal estimation).
• Guidance on data acquisition, sampling rates, data quality and pre‑processing (filtering, detrending, windowing).
• Operational requirements for periodic stability surveillance, trending, alarm thresholds and operator information presentation.
• Technical recommendations for monitoring-system architecture, redundancy and verification/validation of analysis software.
• Reporting and recordkeeping practices to support long‑term stability assessment and regulatory review.

Typical use and users

Primary users include nuclear utility reactor operations staff, instrumentation and control (I&C) engineers, plant stability specialists, safety analysts, regulator technical reviewers and researchers working on reactor dynamics. Typical uses are establishing or refining plant stability monitoring programs, selecting measurement points and analyses for online or periodic surveillance, and applying consistent methods to quantify stability margins during operation and testing.

Related standards

IEC 61505 sits in the TC 45/SC 45A family of nuclear instrumentation and I&C documents. Documents commonly referenced alongside it include standards on classification and instrumentation for nuclear plants (for example IEC 61226, IEC 60880, IEC 61771) and general I&C system requirements such as IEC 61513. Technical reports and regulatory documents on stability analysis and reactor dynamics (NUREG/CR and CSNI reports) are also commonly used in conjunction with IEC 61505 for detailed methodologies and application examples.

Keywords

BWR, boiling water reactor, stability monitoring, decay ratio, reactor dynamics, instrumentation, I&C, data acquisition, modal analysis, time‑series analysis.

FAQ

Q: What is this standard?

A: IEC 61505:1998 is an IEC international standard titled "Nuclear reactor instrumentation — Boiling water reactors (BWR) — Stability monitoring" that provides guidance on monitoring and analysing BWR stability using plant measurements and defined stability metrics.

Q: What does it cover?

A: It covers the selection of plant parameters for stability surveillance, methods to derive stability figures of merit (e.g., decay ratio), recommended analysis techniques (time‑ and frequency‑domain), data acquisition/processing guidance, and technical recommendations for monitoring systems and reporting.

Q: Who typically uses it?

A: Reactor operators, I&C and instrumentation engineers, stability analysts, plant safety staff, and technical reviewers or researchers concerned with BWR dynamic stability monitoring and trend analysis.

Q: Is it current or superseded?

A: IEC 61505:1998 has been withdrawn (withdrawal recorded 22 April 2010). It does not have a single direct one‑to‑one replacement listed on the IEC webstore; users implementing stability monitoring should consult more recent and active I&C and nuclear instrumentation standards (for example IEC 61513 and current IEC publications) and contemporary technical reports for updated methods and regulatory expectations.

Q: Is it part of a series?

A: It belongs to the body of IEC TC 45/SC 45A publications on nuclear instrumentation and I&C; while not formally a numbered "series" item like IEC 61508/61511 families, it is related by subject area to other IEC nuclear instrumentation standards and technical reports used together for I&C and safety work.

Q: What are the key keywords?

A: BWR, stability monitoring, decay ratio, reactor dynamics, instrumentation, I&C, time‑series analysis, modal analysis, data acquisition.