In the nuclear industry, licensing and qualification documentation is usually divided into three levels: plant, system and component level. This article explores the component-level documentation. The component level licensing and qualification requirements are presented in the E series of the YVL Guides, for example, the requirements for the design, manufacturing, installation, commissioning, operation, condition monitoring and maintenance of valves and pumps are presented in the Guides YVL E.8 and YVL E.9, and detailed safety requirements pertaining to electrical and I&C equipment and cables of nuclear facilities, as well as procedures related to STUK’s supervision and inspections, are described in Guide YVL E.7.

According to the Radiation and Nuclear Safety Authority (STUK), “Qualification is normally used as a synonym for “validation” in YVL-guides. Qualification shall refer to confirmation, through the provision of objective evidence, that the requirements for a specific intended use or application have been fulfilled.” Outside Finland, qualification is often related to environmental conditions, but in Finland qualification refers to broader scope. This should be taken into account especially when working with foreign suppliers and manufacturers.

Mechanical components and structures

With regard to mechanical components and structures, compliance with the requirements shall be demonstrated in construction plan documentation. The construction plan can be drawn up in two parts, the manufacturing construction plan and the installation construction plan, but they can also be combined into a single construction plan. The requirements for the construction plan content are presented in the E-series Guides related to mechanical components and structures (e.g. YVL E.3, YVL E.6, YVL E.8 and YVL E.9). The construction plans shall be reviewed and approved by STUK or an authorised inspection organization (AIO) in accordance with the division of inspection responsibilities presented in the YVL Guides; In general, STUK inspects components and structures in the highest safety class, an AIO inspects equipment in lower safety classes. It should be noted and kept in mind that STUK inspects and approves the documentation of all pressure equipment (safety-classified and class EYT). The requirements for pressure equipment and piping are presented in Guide YVL E.3.

A separate manufacturer approval shall be applied for the manufacturer of mechanical component if special processes are used in the manufacturing or installation of parts relevant to the operability of the component. The requirements for approval and oversight procedures are presented in Guide YVL E.3. The acceptability of other manufacturers is assessed in connection with the construction plan by a manufacturer report. Structural material shall also be approved in accordance with Guide YVL E.3 if the structural material is not based on a material standard generally known in Finland.

Mechanical components and structures are subjected to construction inspections both after manufacture and installation. The manufacturing construction inspection shall provide evidence that the materials, manufacture, structures and operation of the component comply with the construction plans. The valve (manufacturing) construction inspection shall have been successfully completed before the valve is installed. The installation construction inspection carries out inspections within the scope of the approved inspection plan and determines the acceptability of the installation final documentation. In addition, the installation construction inspection shall provide evidence that the valve installation work and the quality control of the installation work have been carried out in accordance with the installation construction plan. The (installation) construction inspection shall have been successfully completed prior to the commissioning inspection of the valve.

Electrical and I&C equipment

The demonstration of the suitability of safety-classified electrical and I&C equipment (incl. software, radiation monitoring equipment and cables) requires the preparation of both a preliminary and a final suitability assessment. Suitability assessments can be combined into a single document if the qualification of the device does not involve type approval, software assessments, tests or factory tests and the suitability assessment can be prepared directly in connection with the equipment selection process. Suitability assessments are not required for serially manufactured installation accessories which will be used in normal operating conditions. Suitability assessments should only be carried out by an expert who is familiar with the requirements of the place of use of the device. As a rule, the qualification requirements for electrical and I&C equipment (e.g. the content requirements for suitability assessments) are presented in Guide YVL E.7.

In connection with the preliminary suitability assessment, STUK shall be provided with the requirement specification of the equipment as well as the quality and qualification plans, unless these matters have already been discussed in connection with the system-level, i.e. pre-inspection documentation. A qualification plan is necessary for the approval of the equipment because it includes a plan of the documentation, estimates, tests and documentation required for validation, as well as a roadmap with timelines and dependencies.

In connection with the final suitability assessment of safety class 2 components, an independent assessment of the acceptability of qualification measures shall be presented. In addition, a requirement specification review shall be carried out as part of the qualification of safety class 2 components to demonstrate that the requirements of the product are consistent with the higher-level requirements.

Type approval is required for certain safety class 2 components and cables and components qualified for accident conditions (instrumentation of requirement 5214 of Guide YVL B.1 and radiation monitoring equipment of requirements 402 and 402a of Guide YVL C.6). Components requiring type-approval are listed in requirement 569 of Guide YVL E.7.The type-approval process requires a third-party assessment with regard to the design, implementation and durability of the component to environmental conditions. On the basis of that assessment, a third party shall draw up a type-approval certificate.

If safety-classified pressure equipment is permanently installed in conjunction with electrical and I&C equipment or it has a pressure equipment interface, its design, manufacture, installation and supervision shall be implemented in accordance with Guide YVL E.3. The strength calculations of power-transferring or load-bearing parts and structures of electromechanical, safety class 2 and non-serial manufactured components, and the coverage of in-manufacture inspections shall be demonstrated. In addition, a capability analysis shall be performed on the mechanical interfaces of safety-classified rotating electrical machinery and electromechanical valve actuators in accordance with Guides YVL E.8 and YVL E.9.

KELPO-projekti

The KELPO project, a development project related to the suitability of components used in Finnish nuclear power plants, was launched by Fortum, Teollisuuden Voima Oyj and Fennovoima in 2018. The main task of the KELPO project was to reform the licensing and approval procedures for procurements. In addition, the goal was to ensure an extensive supplier network and to make better use of serially manufactured, standardised devices and components. The Radiation and Nuclear Safety Authority (STUK) was also closely involved in the project. More information about the KELPO project can be found e.g. Finnish Energy’s website.

How can Platom help?

The suitability of the systems of nuclear facilities and the related mechanical components as well as electrical and I&C equipment for their purpose and location shall be ensured on the basis of objective evidence. Platom’s experts have strong expertise in the qualification of electrical and I&C equipment as well as mechanical components, and Platom is able to support the customer in the following areas:

• pre-studies
• identifying the real scope and amount of  qualification work
• preparation of required documentation, e.g. construction plans and suitability assessments
• preparation of test programs and plans related to environmental qualifications.