National foreword

This British Standard is the UK implementation of ISO 4233:2023.

The UK participation in its preparation was entrusted to Technical Committee NCE/9, Nuclear Installations, Processes & Technologies.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

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Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 March 2023.

Foreword

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This document was prepared by Technical Committee ISO/TC 85, Nuclear technology, nuclear technologies, and radiological protection, Subcommittee SC 6, Reactor technology.

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Introduction

Hot helium leak testing can realize more reliable leak tightness assessment than the conventional cold helium leak testing for components that run at elevated temperatures. It gives the total leakage rate of a component at its operating temperature and pressure, and could greatly reduce its operational leak risk.

1 Scope

This document specifies the methods and techniques for leak tightness assessment of a metallic component at high temperature by measuring its total leakage rates in a vacuum chamber with a tracer gas leak detector and high-pressure helium gas or the gas mixture flowing out of the component as tracer gas during its thermal and pressure cycles at its operating conditions. The minimum detectable leakage rate can be as low as 10^-10 Pa·m³/s, depending on the dimension, external configuration complexity and materials of the component, and is strongly related to the test system and the test conditions.

This document is applicable for the hot helium leak test of in-vessel components as per its normal operating conditions in nuclear fusion reactors, which operate at elevated temperatures in an ultra-high vacuum environment down to 10^-6 Pa and with inner flowing-coolant at operating pressure. It is also applicable to the overall leak tightness test of welds in other metallic components and equipment that could be evacuated and pressurized, such as pressurized tanks, pipes and valves in power plants, aerospace and other nuclear reactors.

2 Normative references

3 Terms and definitions

4 Symbols

5 Principles and techniques of detection

5.1

5.2

5.3

5.4

5.5

5.6

5.7

6 Personnel

7 Apparatus

7.1 General

7.2 Test component and vacuum chamber

7.3 The vacuum pumping system

7.4 Heating and temperature control system

7.5 Temperature uniformity requirement

7.6 Reference leak

7.7 Tracer gas leak detector

7.8 Other equipment

8 Test component preparation

8.1 Preliminary tests before hot helium leak test

8.2 Vacuum baking

9 Calibration

9.1 General

9.2 Response and cleanup time measurements

9.3 Leak detector validation and determination of minimum detectable leakage rate

10 Testing procedures

10.1 Installation of the component into the test system

10.2 Initial set-up of the leak testing system

10.3 Initial helium leak testing

10.4 Helium leak testing at elevated temperature

10.5 Cyclic hot helium leak testing

10.6 Final cold helium leak testing

11 Test report

BS ISO 4233:2023

Reactor technology. Nuclear fusion reactors. Hot helium leak testing method for high temperature pressure-bearing components in nuclear fusion reactors

Current

Published:

31 Mar 2023