Establishing the suitability of products important to nuclear safety from start to finish
The nuclear industry operates with an unwavering focus on safety, which is reflected in the rigorous processes and standards applied to the selection, design, manufacturing, and testing of equipment important to nuclear safety (ITNS). These processes aim to ensure that all equipment meets the stringent requirements for performance and reliability in the challenging conditions found in nuclear power plants. This post will provide a look at the flow of activities involved in the assessment of the suitability of ITNS from the perspective of the customer, encompassing various aspects such as general suitability of the item, approval of the supplier, qualification, dedication, and receiving the item.
The following discussion is informed by various international regulatory frameworks, including the Finnish nuclear regulatory guidance document Valves of a Nuclear Facility, published on 20.1.2020 (YVL E.8). This document serves as an example of how the regulatory requirements and industry best practices are translated into practical steps and considerations for ensuring equipment suitability.
Overall flow of activities to ensure the suitability of equipment important to nuclear safety (ITNS)
1. General suitability of the item
Review technical drawings, data sheet, performance specifications.
Review industry operating experience.
Assess potential impact to host-equipment or to system in which the item would be installed.
2. Approval of supplier
Perform pre-qualification and verify supplier interest. Use questionnaire when possible and review quality program documentation if available.
Perform industrial supplier approval and registration. Inform supplier of result.
For complex items or manufacturing processes: visit supplier’s premise as a part of the approval process.
3. Qualification (suitability of item design and capability according to plant specification)
Verify that the design is capable of performing its safety function(s) when necessary and in the specified range of postulated service conditions.
Do this by type testing a representative specimen, analysis or by using operating experience. Document this.
After qualification, any major changes to design or manufacturing should be reviewed to determine if they impact the qualification.
4. Dedication (verification that manufactured item quality is sufficient for use according to the qualification)
Verify the quality of the manufactured item prior to use. Quality is the degree to which the manufactured item meets its requirements.
Do this by selecting some characteristics which are relevant to the item’s safety function(s) and verify those during or after manufacturing.
The supplier’s own quality management system might already be sufficient to verify the chosen characteristics, visit supplier and review quality management program to determine this.
5. Receiving and storing the item
Perform standard receipt inspection, verify that documentation confirms the product fulfills the procurement requirements.
If storing: make sure storage conditions are suitable and conform to the specification.
If using: retain records related to the procurement, especially those evidencing critical characteristics were verified (quality records).
Another way to look at it
The following approach to the entire equipment suitability process is derived from the Finnish nuclear regulatory guidance document Valves of a nuclear facility, 20.1.2020, YVL E.8
View the entire YVL E.8 regulatory guide on stuklex
Manufacturer:
The management system of a valves manufacturer in Safety Class 3 shall be appropriately certified. Otherwise, the licensee may separately apply for approval for other management system assessment performed by an independent third party.
manufacturer report (part of ‘construction plan’)
manufacturing procedures (part of ‘construction plan’)
Design requirements:
The structural design and dimensioning of (safety class 3) valves is based on a generally applied valve design standard.
If the standards applied present different requirement levels for design and dimensioning requirements, the requirement levels applied shall be relative to the valve’s safety class. [Graded Approach]
The same standard series shall apply in valve design and manufacturing.
The valve shall maintain its design basis integrity, leak-tightness or performance even in the event of a limit switch failure if the switch-off inoperability is the valve’s design basis.
The valve’s design solutions shall employ proven technology.
The structural materials of the valve’s pressure-retaining parts and parts essential for operation shall be standardised materials, which have been proven suitable in practice for the intended applications.
Material thickness, thermal expansion, seal solutions, etc.
Design analysis:
design bases (part of ‘construction plan’)
design data (part of ‘construction plan’)
calculations: Pressure dimensioning of the valve’s pressure-retaining body parts, Operability analysis, Strength calculations for other parts (large valves only) (part of ‘construction plan’)
Equipment qualification (by testing):
The conformity of the valve’s design solutions shall have been demonstrated with a type test that allows confirming the valve’s design basis performance.
Type testing shall be implemented in conditions corresponding to the design basis operational, transient and accident situations using such testing parameters by which the valve’s conformity can be unambiguously demonstrated based on the test results.
operating experience and type test data (part of ‘construction plan’)
Quality assurance/quality control:
The valve shall be manufactured and manufacturing quality controlled in accordance with an approved construction plan and the associated inspection plan.
The machines, equipment and facilities used in manufacturing shall facilitate achievement of a quality compliant with the requirements. The machines and equipment shall be periodically tested and calibrated as required by the manufacturer’s quality management system. The test results shall be recorded so that they can be presented on request.
Within the scope of the inspection plan, a third party shall:
witness the sampling, stamp transfer and destructive testing of materials and confirm the results with a certificate of type 3.2 under standard SFS-EN 10204 [13],
witness and confirm procedure and personnel qualifications
witness and confirm the manufacturing of the component, such as welding, forming and non-destructive testing.
The licensee shall request from STUK or an AIO a construction inspection to establish the acceptability of the valve’s manufacturing documentation, to conduct the inspections and to witness the tests in the scope of the approved inspection plan.
In Safety Class 3 at least one of identical valves in the delivery batch shall be inspected when dismantled after factory testing. The scope of dismantling shall comply with the accepted construction plan.
inspection plan and procedures. (part of ‘construction plan’)
Final thoughts
These practices not only demonstrate the importance of collaboration between manufacturers, suppliers, and regulatory bodies, but also underscore the significance of quality assurance, design analysis, and equipment qualification in the pursuit of a secure and reliable nuclear industry.
