IN-SERVICE INSPECTIONS (ISI)
Prerequisite for safe operation and a high level of availability
Recurrent in-service inspections (ISI) are essential in guaranteeing the compliance of safety-significant components and systems with their specified function. The effectiveness of such inspections is determined decisively by the scope of the individual inspection steps and the employed techniques.
Bearing this in mind, TÜV NORD Nuclear assesses inspection concepts and instructions applicable to safety equipment besides participating in the related inspections.
Scope and type of required inspections (inspection list)
The recurrent tests to be conducted at a nuclear power plant are summarized in an inspection list and defined in the inspection procedures providing details on test objects, types, scopes, instructions, intervals, participants and the plant operational state during the specific inspection. The individual steps to be executed during each inspection are described in inspection procedures.
The inspection list and procedures are assessed routinely by TÜV NORD Nuclear, taking into account system modifications and – if applicable – incidents at other comparable nuclear facilities. Furthermore, inspection procedures are regularly compared to the scientific and technological state-of-the-art, and adaptations recommended wherever necessary.
Performing recurrent ISI
Inspections are carried out on the important safety-related equipment in the presence of experts from TÜV NORD Nuclear. To ensure that the inspection is carried out correctly,
- the validity of the applied inspection procedures
- the compliance with the currently applicable document revision for authorising the inspection as per the respective inspection procedure
- the compliance with the inspection prerequisites for the respective ISI, such as the system condition, activation measures, or proper condition of the inspection equipment
are verified before the inspection starts. When the inspection is completed as specified in the applicable inspection procedure, the inspection result is evaluated and documented.
Any deficiency detected during the inspection is documented along with a detailed description of the cause of the error, and its safety significance is categorised. This also includes errors made by the inspection personnel. In addition, special findings identified during the inspection that are not addressed explicitly in the inspection procedures are displayed. The identified deficiencies and remarkable problems are stored in a database, including the permissible remedial action for further follow-up.
