NB/T 20003.8-2021 Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 8: Leak testing
1 Scope
This document specifies the technical requirements for leak testing adopted by mechanical components in nuclear island of nuclear power plants.
This document is applicable to leak testing during the manufacture and installation of mechanical components and parts in nuclear island.
2 Normative references
The following documents contain provisions 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 (including any amendments) applies.
GB/T 12604.7 Non-destructive testing - Terminology -Terms used in leak testing
NB/T 20003.1-2021 Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 1: General requirements
NB/T 20003.7 Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 7: Visual testing
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 12604.7 and NB/T 20003.1-2021 and the following apply.
3.1
standard leak
calibrated leak with known leakage rate to dry air (dew point temperature below -25℃) under specified conditions (inlet pressure: 100kPa ± 5kPa; outlet pressure: less than 1kPa; temperature: 23℃±7℃)
3.2
calibrated leak
leak providing a known mass flow rate for a specified gas under specified conditions
3.3
background signal
indication of stable or fluctuant output signal produced by the leak detector due to the presence of residual tracer gas or other factor that may cause response of the testing element, when no tracer gas is applied
3.4
Bourdon tube type pressure gauge
high-precision differential pressure gauge with the function of zero compensation
4 General requirement
4.1 Qualification of testing personnel
The requirements specified in 5.1 of NB/T 20003.1-2021 shall apply.
4.2 Testing documents
The testing procedures, testing process cards or other testing documents shall meet the requirements of NB/T 20003.1-2021. The leak testing shall be implemented according to effective testing procedures.
The testing procedures shall cover at least the following contents:
——scope of application: type, size, testing range and material of the workpiece under test;
——quoted laws, regulations, codes, standards, design documents, etc.;
——qualification of testing personnel;
——information of the testing piece, such as name, shape, size, testing area and volume;
——testing equipment and devices, such as leak detector, pump, pressure gauge, vacuum gauge, standard leak, calibrated leak and tracer gas;
——testing requirements, such as testing time, surface preparation requirements and testing methods used;
——testing process and testing technique;
——evaluation, recording and acceptance standard of testing results;
——content and format of testing report.
The supplementary requirements of different leak testing methods to testing procedures shall meet the relevant requirements specified in A.1, B.1, C.1, D.1, E.1 and F.1.
4.3 Procedure demonstration
4.3.1 Scope of application
The testing procedure demonstration shall be performed under the following conditions:
——the workpiece is subjected to the leak testing for the first time;
——the testing conditions and/or technical requirements (specified value or numerical range of essential variables in the annex) change;
——specified in relevant product design documents or purchase specifications.
4.3.2 Implementation of procedure demonstration
Under the testing conditions specified in the procedure, the testing personnel shall conduct leak testing on the demonstration specimen containing calibrated leak according to the requirements of the procedure. If the leakage of calibrated leak is detected, the procedure shall be considered as valid.
The above procedure shall be recorded and documented.
4.4 Testing scope and proportion
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General requirement
5 Equipment and devices
6 Testing method and technique
7 Testing report
Annex A (Normative) Bubble testing - Direct pressure method
Annex B (Normative) Bubble testing - Vacuum box method
Annex C (Normative) Testing by helium mass spectrometer - Sniffing probe method (Sniffing method)
Annex D (Normative) Testing by helium mass spectrometer - Tracer probe method (helium spray method)
Annex E (Normative) Testing by helium mass spectrometer - Hood method
Annex F (Normative) Pressure change testing
Annex G (Normative) Demonstration block for bubble method
Annex H (Normative) Helium leak testing of steam generator tube-tube plate seal welding
