NB/T 20003.3-2021 Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 3: Radiographic testing
1 Scope
This document specifies the technical requirements for X-ray and γ-ray testing of mechanical components in nuclear island of nuclear power plants, as well as the requirements for defect evaluation and quality grading of testing results.
This document is applicable to radiographic testing during the manufacture and installation of steel castings and steel welded joints in mechanical components in nuclear island of nuclear power plants. It may also serve as a reference for radiographic testing of other metallic materials.
2 Normative references
The following documents contain requirements 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 of the referenced document (including any amendments) applies.
GB 11533 Standard for logarithmic visual acuity charts
GB 18871 Basic standards for protection against ionizing radiation and for the safety of radiation sources
GB/T 12604.2 Non-destructive testing - Terminology - Terms used in radiographic testing
GB/T 19348.1 Non-destructive testing - Industrial radiographic film - Part 1: Classification of film systems for industrial radiography
GB/T 19802 Non-destructive testing - Industrial radiographic illuminators - Minimum requirements
GB/T 23910 Non-destructive testing - Metal intensifying screens for radiographic testing
GBZ 117 Requirement for radiological protection in industrial X-ray radiography
GBZ 132 Radiological protection standards for industrial gamma defect detecting
JB/T 7902 Non-destructive testing - Specification for wire-type image quality indicators
NB/T 20003.1 Non-destructive testing for mechanical components in nuclear island of nuclear power plants - Part 1: General requirements
ASTM E186 Standard reference radiographs for heavy-walled (2 to 41/2-in. [51 to 114-mm]) steel castings
ASTM E192 Standard reference radiographs for investment steel castings for aerospace applications
ASTM E280 Standard reference radiographs for heavy-walled (41/2 to 12-in. [114 to 305-mm]) steel castings
ASTM E446 Standard reference radiographs for steel casting up to 2 in. [51mm] in thickness
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 12604.2 and NB/T 20003.1 and the following apply.
3.1
penetrated thickness
T
nominal thickness of material in the direction of radiography. In multilayer radiography, it is the sum of nominal thickness of penetrated layers of materials
3.2
object-to-film distance
b
distance between the surface of the workpiece under test on the side of the radiographic source and the film measured along the centerline of the ray beam
3.3
source-to-object distance
f
distance between the ray source and the surface of the workpiece under test on the side of the radiographic source measured along the centerline of the ray beam
3.4
source-to-film distance
F
distance from the radiation source to the film measured along the centerline of the beam
3.5
source size
d
converted size of the radioisotope source or the effective focal size of the X-ray tube
3.6
standard density tablet
calibrated radiographic negatives with different density steps
3.7
rounded defect
welding defects such as porosity, slag inclusion and tungsten inclusion with length-width ratio not greater than 3
3.8
elongated defect
welding defects such as porosity, slag inclusion and tungsten inclusion with length-width ratio greater than 3
4 General requirements
4.1 Testing personnel
The general requirements of radiographic testing personnel shall meet the relevant requirements of NB/T 20003.1.
Radiographic testing personnel shall receive training and assessment on radiation safety knowledge before taking up their posts, and shall obtain corresponding certificates in accordance with relevant regulations. The uncorrected or corrected near vision of radiographic testing personnel shall not be less than 4.8, and the test method shall meet the requirements of GB 11533. Film-assessing personnel shall have a visual acuity test once a year.
4.2 Testing documents
Radiographic testing documentations, including testing procedures, testing process card or other testing documents, shall meet the requirements of NB/T 20003.1. Radiographic testing shall be implemented according to effective testing procedures.
Radiographic testing procedures shall at least include the following content:
——Scope of application: type, size, testing range and material of the workpiece under test;
——Quoted laws, regulations, standards, design documents, etc.;
——Qualification of testing personnel;
——Testing equipment and materials: radiographic source, film, intensifying screen, filter, masking board, image quality indicator, mark, film processing equipment in darkroom, film-assessing equipment, etc.;
——Testing conditions: surface state, testing time, etc.;
——Testing technology: radiography mode; exposure parameter; cassette composition (film type and quantity as well as intensifying screen); model, quantity and arrangement of image quality indicator; and type and arrangement of mark;
——Darkroom processing of films;
——Radiograph quality: radiograph marking, radiograph density, image quality indicator sensitivity of radiograph, etc.;
——Defect evaluation, quality grading and acceptance criteria;
——Content and format of test report.
4.3 Verification of procedures
Verification of testing procedures shall be performed when:
——the testing procedures are used for the first time;
——the specified value or numerical range of important variables in the testing procedure in Table 1 changes;
——specified in relevant product design documents or procurement specifications.
The reference radiographs shall be used as the main basis for procedure verification. The reference radiograph may be taken separately or selected from the qualified radiograph of the workpiece under test. In both cases, the reference radiograph shall be marked.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Main equipment and materials
6 Testing technology
7 Darkroom processing of film
8 Quality of radiograph
9 Evaluation and quality grading of defects
10 Testing report
Annex A (Normative) Radiography modes of full penetration fillet joints
Annex B (Normative) Radiographic testing of steel castings
Annex C (Normative) Characteristic indexes of industrial radiographic film system
Annex D (Informative) Schematic diagrams for typical radiography modes of welded joints
Annex E (Informative) Method for determining the minimum radiography times of circumferential welded joints
Annex F (Normative) Calculation of source size
Annex G (Normative) Placement sites of positioning markers
Annex H (Normative) Radiographic testing technology for special circumstances
Annex I (Informative) Manual processing of the film
