Field operators' visual inspection practices in the operating Finnish nuclear power plants
Authors: Passi Tomi , Pakarinen Satu , Liinasuo Marja 
Published: June 2024

In nuclear power plants (NPPs), the integrity of the plant is assured, among other safety measures, by regularly conducted field operator (FO) visual inspection rounds. During these rounds, the FOs tour the NPP and inspect the equipment. Despite the term ‘visual inspection,’ other senses are also used in the task. Previously, no systematic information on visual inspection practices in NPPs has been collected.The objective of the study is to gain an understanding of the visual inspection practices. The goal is to systematically document how visual inspection is conducted, expertise developed, and to compare the practices between the different NPPs. Altogether, five FOs and two trainers, representing all operating NPPs in Finland, participated in the semi-structured interviews. We grouped the plants based on their similarities, resulting in three plant groups.All FOs considered the visual inspection as their most crucial task. During the inspection rounds, the FOs examine the integrity of equipment and appropriateness of the facilities. They record readings and make notes about the equipment; one group uses a paper checklist and two others a tablet with a brief history of the process values. Furthermore, looking, listening, touching, and even smelling form an integral part of inspection rounds for all FOs. The inspection rounds are usually performed by one FO at a time, twice in a 12-hour shift. If something deviant is noticed, another FO often participates in the round. In two groups, rounds may have interruptions due to other tasks, such as separations and reconnections. In contrast, one group reported that the rounds are always performed uninterrupted.In general, vision was reported to be the most critical sense for visual inspection. By looking, the FOs get information about the integrity of the surfaces, perceive the meter readings, and evaluate the appropriateness of the facilities. However, hearing was often reported to be as important as vision. With increasing expertise, FOs can collect information by actively listening for indications of faults within the equipment, such as bearing malfunctions. In addition, tactile sense was found important for detecting deviant temperatures of both rooms and equipment and unusual vibrations. Also, smell can be used to detect, for example, oil leaks.All FOs collaborated with the main control room (MCR) operators to whom the round information was delivered. In addition, the FOs were in contact with the maintenance concerning faults and the cleaning personnel regarding the cleaning matters.The initial training for visual inspection is a classroom learning lasting two to three months. However, the most vital part of the training, in terms of the work in practice, is training during working. Then, the FOs perform rounds under the supervision of experienced FOs for approximately one year. After this period, the work is carried out independently.For the most part, all FOs perform the visual inspection rounds similarly. However, some differences are found, which, at large, seem to be explained by the devices used and the structure of the facilities.