ISO 20890-1:2020

Guidelines for in-service inspections for primary coolant circuit components of light water reactors — Part 1: Mechanized ultrasonic testing

Scope

This document gives guidelines for pre-service-inspections (PSI) and in-service inspections (ISI) with mechanized ultrasonic test (UT) devices on components of the reactor coolant circuit of light water reactors. This document is also applicable on other components of nuclear installations.
Mechanized ultrasonic inspections are carried out in order to enable an evaluation in case of
— fault indications (e.g. on austenitic weld seams or complex geometry),
— indications due to geometry (e.g. in case of root concavity),
— complex geometries (e.g. fitting weld seams), or
— if a reduction in the radiation exposure of the test personnel can be attained in this way.
Ultrasonic test methods are defined for the validation of discontinuities (volume or surface open), requirements for the ultrasonic test equipment, for the preparation of test and device systems, for the implementation of the test and for the recording.
This document is applicable for the detection of indications by UT using normal-beam probes and angle-beam probes both in contact technique. It is to be used for UT examination on ferritic and austenitic welds and base material as search techniques and for comparison with acceptance criteria by the national referencing nuclear safety standards. Immersion technique and techniques for sizing are not in the scope of this document and are independent qualified.
NOTE Data concerning the test section, test extent, inspection period, inspection interval and evaluation of indications is defined in the applicable national nuclear safety standards.
Unless otherwise specified in national nuclear safety standards the minimum requirements of this document are applicable. This document does not define:
— extent of examination and scanning plans;
— acceptance criteria;
— UT techniques for dissimilar metal welds and for sizing (have to be qualified separately);
— immersion techniques;
— time-of-flight diffraction technique (TOFD).
It is recommended that UT examinations are nearly related to the component, the type and size of defects to be considered and are reviewed in specific national inspection qualifications.