Nuclear facility operations

Regulatory oversight during the operation of the nuclear facility includes continuous safety assessments. By conducting supervision during operation, STUK aims to ensure that the nuclear facilities are and will remain in a condition according to requirements, function as intended and that they are used in accordance with regulations.

Supervision is targeted at nuclear facilities’ operations, systems, equipment and structures, facility modifications as well as the organizations’ activities. STUK’s assessment of the safety of a nuclear power plant during operation comprises operational occurrences, annual maintenance, inspections, key figures, reports, meetings, resident inspectors, document reviews, projects, modifications and inspection programmes. 

The operational inspection programme for nuclear facilities

The Operational Inspection Programme is a safety supervision tool used to systematically check the ability of licensees to ensure the safety of their plants. The inspections cover safety management, the main processes of operations and procedures and the technical acceptability of the systems. The inspections ensure that the safety assessment, operation, maintenance and protective measures of the plant comply with the requirements of the nuclear safety regulations.

Nuclear facility operating condition

STUK conducts the surveillance of technical operating conditions in nuclear facilities by assessing whether facility operations are in accordance with the safety technical requirements in the licence conditions, by supervising annual maintenances, facility maintenance and ageing management, radiation safety, security arrangements and emergency preparedness.

In regulatory oversight, STUK uses periodic and event-specific reports submitted by licensees. Based on the reports, STUK gains an insight into the use of the facilities and the facility operators’ activities. STUK also assesses the safety in nuclear facilities by conducting inspections at facility sites and equipment manufacturers as well as using operating experiences and safety studies. Based on safety assessments during operation, both the licensee and STUK assess the need and possibilities for improving safety.

Local on-site STUK inspectors conduct daily surveillance of the use of facilities. The local inspectors assess faults, monitor repairs of faults and testing of important safety equipment.

Regulatory oversight of facility modifications

Different modifications are carried out in nuclear facilities. The purpose of these modifications may be to improve safety, renew ageing systems and equipment, facilitate operations or maintenance in the facility or to enhance energy production. 

STUK regulates nuclear facility modifications from design to implementation. STUK inspects plans for extensive safety-significant modifications and supervises the modifications based on documentation submitted by the licensee as well as inspections on site or at manufacturers.

Operations of organizations

Regulatory oversight of operations of organizations is a part of ensuring safety in facilities. STUK monitors operations in organizations by assessing safety management, management and quality management systems, nuclear facility personnel qualifications, training and operating experience. The goal of the supervision is to ensure that the organizations of the nuclear facility and its key suppliers function in a way that facility safety is secured on all levels. 

In order to continuously improve the safety of nuclear facilities, scientific and technical developments and operating experience must be taken into account. Operating experience from abroad must also be analyzed systematically, and measures for improving safety must be taken when needed. STUK oversees that operating experience feedback from nuclear facilities is used to effectively prevent recurrence of incidents. STUK pays particular attention to the licensee’s ability to detect and identify the reasons for the incidents and to correct the underlying vulnerabilities in the organization’s activities. In addition, STUK analyses domestic and international operating experiences and sets requirements to improve safety when needed. 

If necessary, STUK will also establish an investigation team if the licensee's own organization has not acted as planned in connection with the incident. An investigation team may also be established if the incident is estimated to lead to significant changes in the technical structure of the facility or in the facility's instructions. STUK appoints its own investigation team if the licensee has not sufficiently investigated the root causes for the incident.

Safety analyses

Safety analyses are tools for assessing the safety in nuclear facilities. Safety analyses are conducted in order to assure that the nuclear facility is designed to be safe and can be used safely. The deterministic and probabilistic approaches of the analyses complete each other.

STUK assesses the safety of nuclear facilities and develops tools and methods for identifying accident risks, assessing their magnitude and eliminating or reducing risk factors. STUK also inspects deterministic safety analyses and probabilistic risk analyses relating to the construction licence, operating licence and operation of nuclear facilities. If necessary, STUK carries out its own independent comparison analyses to ensure the reliability of the results.

Deterministic safety analyses refer to disruption and accident analyses required to justify the technical solutions of nuclear facilities. Licensees update the analyses when renewing operating licences, at regular safety assessments and whenever extensive modifications are made in the facility.

Probabilistic risk analyses (PRA) refer to quantitative evaluations of threats to the safety of nuclear facility, the probability and adverse effects of a series of events. PRA can be used to assess major risks in the nuclear facility, as a tool for designing nuclear facilities as well as for developing the facility’s operations and technical solutions. Licencees use PRA for maintenance and continuous improvement of the technical safety in nuclear facilities.