Reporting on nuclear safety

Oversight reports of spent nuclear fuel final disposal facility

STUK carries out inspections of the spent fuel encapsulation and disposal facility in Olkiluoto in accordance with the inspection programme during construction. STUK publishes tertial reports on the regulatory oversight of the plant under construction.

Oversight reports for year 2024

Tertial report 1/2024, January–April

During the first tertial of 2024, STUK continued to process the operating licence application of Posiva, supervised the commissioning of the nuclear facility and planned the supervision to be carried out during its use.

As a conclusion to the processing of the operating licence application material, STUK is drawing up a safety assessment, which will be appended to the safety statement prepared on the operating licence application. STUK’s favourable statement on safety is a prerequisite for the Government to grant an operating licence for Posiva’s encapsulation and final disposal facility.

Overall, STUK has progressed well in processing the operating licence application, but the material is still being reviewed. Due to the scope of the material and the processing of updates STUK required of Posiva, the processing in its entirety has taken longer than anticipated.

The Ministry of Economic Affairs and Employment (MEAE), as the licensing authority, originally requested STUK to issue a statement by 31 December 2023, if possible. At the end of 2023, STUK asked MEAE for additional time until the end of 2024 to provide a statement, as STUK is still processing the licence application material.

STUK’s supervision consists of several areas, with the main aspects of supervision described below for the period between the beginning of January and the end of April 2024.

Construction and commissioning

STUK has supervised the manufacture, installation and commissioning of the systems needed at Posiva’s encapsulation and final disposal facilities. The encapsulation and final disposal facility requires lifting and transfer equipment to transfer spent nuclear fuel and the transfer container or canister containing spent fuel. STUK has reviewed the construction plans of this lifting and transfer equipment and carried out structural inspections. The structural inspections verify that the structure has been manufactured and installed in accordance with the structural plans and approved manufacturing and installation methods.

With testing the nuclear facility’s systems, Posiva ensures that the systems function as planned. STUK pays particular attention to the systems that are safety-classified, which means that their operation is important for nuclear and radiation safety. In connection with the supervision of the trial run, STUK has processed the commissioning testing plans of the systems and monitored the trial runs on site.

The number of the above-mentioned system materials being processed by STUK is continuously decreasing, as most of the documents have already been delivered to STUK.

The commissioning of the overall plant began in April with trials of the final disposal facility's ventilation systems, and the trials will continue throughout the summer. The purpose of the trials is to determine that the various systems in the facility as a whole function as designed and that the facility can be operated in accordance with the instructions. STUK reviews the plans for the trials concerning the operation of the overall plant, supervises the trial operation and the validation of instructions in connection with the trials.

Instructions and operation of the plant

Before STUK can make a favourable safety assessment of the encapsulation and final disposal facility and Posiva can start to operate the plant, STUK must also approve the plant’s technical specifications(operational limits and conditions). STUK expects to receive an updated version of the technical specifications for review before the summer.

STUK has reviewed, among other things, Posiva’s administrative instructions and the operating and alarm procedures that are needed when the operation of the plants begins. STUK is still waiting for several sets of operating instructions to be completed and delivered to STUK so that STUK can assess the procedures presented in the operating instructions in their entirety. STUK will assess the status of Posiva’s instructions for use before the actual use of the Posiva plants begins.

Radiation measurements and emergency response arrangements

The commissioning of the radiation and radioactive release measurement systems started in February 2024. Posiva still needs to make changes to some of the release measurement devices. STUK has also required Posiva to supplement the operating licence application material with regard to the measurement and monitoring of releases. Answers to these questions are expected at a later date from Posiva.

STUK is working on an updated emergency plan. Posiva’s plan is shared with TVO Group. With regard to the state of preparedness, the precautionary action zone and emergency planning zone defined for the Posiva nuclear plants correspond to those of TVO. The consequences of possible accidents in the vicinity of the Posiva plants are significantly less than the consequences of a serious reactor accident at the nuclear power plant.

Posiva’s trial run of final disposal

In the trial run of final disposal, Posiva tests the operation of the final disposal facility with testing fuel that does not include any spent nuclear fuel. The purpose of the test is to practise the transfer of spent nuclear fuel to the encapsulation facility, encapsulation at the encapsulation facility and canister transfer and final disposal at the final disposal facility. Prior to the trial run of final disposal, all systems have been tested and tests have been carried out at the plants for the operation of the overall plant. The trial run test is carried out with Posiva’s own specifications, and only a few regulatory requirements apply to the test.

STUK has planned monitoring of the trial run and expects to have the planning completed during the early summer. In the trial run, STUK assesses the operation of the Posiva organisation, the functionality of the instructions and the seamless cooperation of the various systems. STUK’s objective is to test the methods of monitoring during the operation phase in the trial run so that monitoring during the operation phase is smooth and timely.

Natural and technical release barriers at the final disposal facility

Posiva faces challenges with constructing the disposal holes according to Posiva's accuracy requirements. The disposal holes are where the final disposal containers are ultimately placed. STUK monitors the situation and assesses the potential safety impact of the problem as Posiva delivers materials to STUK for review.

Progress has been made in the qualification of the production methods of the final disposal canister, clay components and other technical release barriers preventing and retarding the release of nuclear waste into the environment. As part of the production qualification, STUK has participated in the supplier assessments carried out by Posiva as an observer. In terms of the production of clay components, the qualification has been completed. STUK has received qualification materials for the production methods of the canister base, lid and bottom welding in the spring. With regard to the production of copper pipes for the final disposal canister, Posiva has faced challenges in producing canisters that meet the set requirements. At the end of April, STUK received Posiva’s material on how Posiva is progressing in qualifying the production of copper pipes.

STUK expects to receive material regarding the qualification of the installation of the final disposal canister and clay components during the summer.

Nuclear material regulation

The safeguards supervision performed by STUK shows that Posiva has fulfilled its obligations in relation to safeguards of nuclear materials. The International Atomic Energy Agency IAEA and the European Commission have continued the installation of international nuclear safeguards monitoring equipment at Posiva's encapsulation plant. The installations will continue in 2024. Some of the safeguards and the reporting practices required for monitoring are intended to be tested during the Posiva cooperation test.

In March, the IAEA carried out a supplementary inspection visit to the Posiva plants. The European Commission and STUK participated in the visit.

Security arrangements

Posiva has made progress in implementing security arrangements. Posiva has also provided STUK with various materials relating to the security arrangements for processing, which can be used to assess the adequacy of the security arrangements. Posival still has some pending requirements that it needs to consider before commissioning. STUK has monitored the effectiveness and adequacy of the security arrangements by reviewing documents and conducting field inspections.

Organisational monitoring

In its monitoring, STUK has paid attention to deficiencies in Posiva’s quality inspection operations and their handling. STUK required that Posiva assesses the adequacy of the current procedures in the nonconformity management audit. In addition, STUK required that Posiva ensure that all procedures are adequately instructed and pay attention to the maintenance of the skills and qualifications of the quality inspection personnel.

STUK has monitored the development of Posiva's use-phase organisational preparedness and the licensee’s own monitoring of preparedness. Posiva has developed procedures for establishing use-phase organisational preparedness. STUK monitors the application of procedures, including the development of safety culture. STUK has found some shortcomings in Posiva’s extensive sets of material and has required Posiva to supplement the material. Based on the monitoring, STUK sees need for improvement in the assessment of the impact of changes in larger concepts and, in part, in the management of the whole. In addition, STUK’s monitoring has revealed some resource-related challenges. STUK will continue to monitor the adequacy of Posiva’s resources.

Assessing long-term safety

STUK has continued the assessment of the safety justification for demonstrating long-term safety submitted as part of the operating licence application. At the beginning of the year, STUK submitted a request for clarification to Posiva, in which it required background documents relating to the replacement of the buffer material surrounding the final disposal canister. During the processing of the operating licence application, Posiva has made design changes to the release barriers, and STUK must also assess the design changes made with regard to long-term safety. This has an impact on the processing time of STUK’s operating licence application material.

As part of the review of the safety justification, STUK has also continued to conduct emissions, transmission and consequence analyses of radionuclides as part of the assessment of the biosphere transmission and doses of radionuclides.

Oversight reports for year 2023

In 2023, STUK supervised both the installation and test operation of equipment at the spent fuel encapsulation plant and the ongoing rock excavation works in the underground disposal facilities. STUK also inspected the safety arrangements at Posiva's final disposal facility, the safety culture of the organisation and Posiva's readiness to start final disposal operations.

In addition to supervision, STUK prepared the safety assessment of Posiva's licence application and the statement to be submitted to the Ministries of Employment and the Economy.

Tertial report 3/2023, September–December

During the last quarter of 2023, STUK continued to review the operating licence application of Posiva, supervised the commissioning of the nuclear facility and planned the supervision to be carried out during its use.

The Ministry of Economic Affairs and Employment (MEAE), as the licensing authority, has requested STUK to issue a statement by 31 December 2023, if possible. Since the processing of the operating licence application dossier is still pending at STUK, STUK has requested the MEAE to extend the deadline of the statement to the end of 2024.

STUK’s supervision consists of several areas, with the main aspects of supervision described below for the period between the beginning of September and the end of December 2023.

STUK has supervised the manufacture, installation and commissioning of the systems needed at Posiva’s encapsulation and final disposal facilities. The encapsulation and final disposal facility requires lifting and transfer equipment to transfer spent nuclear fuel and the transfer container or capsule containing spent fuel. STUK has reviewed the construction plans of these lifting and transfer equipment and carried out structural inspections. The structural inspections verify that the construction has been carried out in accordance with the structural plans and approved manufacturing methods.

With testing the nuclear facility’s systems, Posiva ensures that the systems function as planned. Some of the systems are safety-classified, which means that their operation is important for nuclear and radiation safety. In connection with the supervision of the trial run, STUK has processed the commissioning testing plans of the systems and monitored the trial runs on site.

STUK inspected the radiation protection arrangements of Posiva’s encapsulation and final disposal facilities during the inspection of the construction inspection programme in November. STUK assesses the situation and readiness of the radiation protection arrangements from the point of view of the in-service operation of the facilities. On the basis of the inspection, STUK came to a positive assessment of the status of Posiva’s radiation protection arrangements. With regard to radiation protection arrangements, preparations for the use of Posiva’s nuclear facilities have come a long way. Not all radiation protection arrangements are ready yet, but STUK did not detect any significant deficiencies in the areas of radiation protection.

The rock construction of the disposal facility has progressed well for the most part, although with regard to disposal holes, Posiva has had challenges in reaching the accuracy they require. To remedy this, Posiva has created an action plan, according to which things should the problem should be more or less resolved in early 2024.

Progress has been made in the qualification of the production methods of the final disposal canister, clay components and other technical release barriers preventing and retarding the release of nuclear waste into the environment. Several results concerning individual canister components are expected to be completed in early 2024, although the final parts will not be completed until summer 2024. The finalisation of the design dossier for the final disposal canister has been delayed, but on the other hand, the quality of the design dossier has improved thanks to measures taken by Posiva.

The safeguards supervision performed by STUK shows that Posiva has fulfilled its obligations in relation to safeguards of nuclear materials. As early as 2023, the International Atomic Energy Agency IAEA and the European Commission started the installation of monitoring equipment associated with international nuclear safeguards at Posiva’s encapsulation plant. The installations will continue at the beginning of 2024.

In September, Posiva hosted the ESARDA (European Safeguards Research & Development Association) final disposal working group meeting in Olkiluoto. The meeting was a good opportunity to present the final disposal to experts from Europe and the rest of the world.

In November, the IAEA, the European Commission and STUK carried out a four-day periodic inspection of the encapsulation and final disposal facility in which laser scanning measurements were used to verify that the premises have been built as announced.

The implementation of Posiva’s security arrangements is progressing well overall. However, there are still some requirements concerning security arrangements that Posiva must meet before the operating licence can be granted. Posiva has provided STUK with material related to security arrangements which helps STUK to better assess the adequacy of the security arrangements. STUK monitors the progress of Posiva’s security arrangements and supervises that they are adequate in accordance with the Nuclear Energy Act.

STUK commissioned VTT to carry out a study on Posiva’s safety culture. Based on the study, the different areas of Posiva’s safety culture are at a good or fairly good level compared to the life cycle phase of the nuclear facility, which is the preparatory phase for the use phase. From STUK’s point of view, the recommendations highlighted in the VTT study were sensible and well-aligned with the observations made by STUK in their supervision effort. STUK’s supervision serves as the basis for Posiva to further develop its knowledge and procedures for managing the human factors of safety.

In its inspections, STUK has paid attention to how Posiva’s management monitors the organization’s readiness to start operating the nuclear facility. STUK requires that Posiva develop the organization’s readiness and monitoring indicators towards greater transparency and clarity. In addition, STUK has required Posiva to make more extensive use of the information generated by the licensee’s own operations in order to develop the organization’s operations. STUK has verified that the resource planning of Posiva’s key functions is proceeding as planned for the production phase of Posiva.

STUK has continued to review the long-term safety justification that is part of Posiva’s operating licence application. On the basis of the review, STUK made a third request for clarification to Posiva in 2023. STUK has also carried out comparative analyses on Posiva’s calculations on the transport of post-release radionuclides in the near and far field. In addition, STUK has started to assess the transport of radionuclides in the biosphere and the associated dose estimation.

Tertial report 2/2023, May–August

During the second third of 2023, STUK continued to review the operating licence application of Posiva, supervised the commissioning of the nuclear facility and planned the supervision to be carried out during its use.

As a conclusion on the processing of the operating licence application material, STUK draws up a safety assessment, which will be appended to the safety statement prepared on the operating licence application. STUK’s positive statement on safety is a prerequisite for the Government to grant an operating licence. The Ministry of Economic Affairs and Employment (MEAE), as the licencing authority, has requested STUK to issue a statement by 31 December 2023, if possible. The current estimate is that by the end of the year STUK will propose that the Ministry of Economic Affairs and Employment postpone the deadline.

STUK’s supervision consists of several areas, with the main aspects of supervision described below for the period between the beginning of May and the end of August 2023.

STUK has supervised the manufacture, installation and commissioning of the systems needed at Posiva’s encapsulation and final disposal facilities. The encapsulation and final disposal facility requires lifting and transfer equipment to transfer spent nuclear fuel and the transfer container or capsule containing spent fuel. STUK has reviewed the construction plans of these lifting and transfer equipment and carried out structural inspections. The structural inspections verify that the construction has been carried out in accordance with the structural plans and approved manufacturing methods.

The construction of the underground premises of the final disposal facility are almost complete. STUK has processed a few updates to the rock construction design materials.

The final disposal canister, the bentonite buffer to be installed around it and the filling material for the disposal tunnels are technical release barriers to the release of radioactive substances from the spent nuclear fuel. As part of the approval of the plans for technical release barriers, Posiva must demonstrate that the planned release barriers can be manufactured. Therefore, Posiva must carry out methodological tests for the manufacture of these components.

The capsule consists of several parts and the methodological tests for their manufacture have been started, but the results will take several months to complete. Methodological tests for the manufacture of the bentonite buffer have been carried out and STUK has processed report on the methodological test the tunnel backfilling.

The safeguards supervision performed by STUK have shown that Posiva has fulfilled its obligations in relation to safeguards of nuclear materials. In early 2023, the International Atomic Energy Agency IAEA and the European Commission started the installation of international nuclear safeguards monitoring equipment at Posiva’s encapsulation plant. Equipment installations have been continued in July, and once the installation work was concluded, STUK verified that the installations were appropriate. There are many new issues related to the nuclear safeguards of the final disposal, and it is important to clearly define Posiva’s reporting obligations and supervisors' control activities. This definition has been continued in a workshop organised in August between STUK, Posiva, the IAEA and the European Commission.

The implementation of Posiva’s security arrangements is progressing well overall. However, Posiva has some matters related to security arrangements that must be completed before the nuclear facility is commissioned. During the autumn of 2023, Posiva will provide STUK with security arrangement material that can be used to better assess the adequacy of security arrangements.

STUK has also supervised the preparation of Posiva’s organization for the use phase of the nuclear facility. During the second third of 2023, STUK approved Posiva’s rules of procedure and quality management programme for the use phase as part of the operating licence application. Posiva describes the safety-critical tasks, decision-making forums and the powers and responsibilities of the key roles. The quality management programme presents the principles of quality management in the use phase along with the main processes and the procedures related to them. STUK monitors the progress of Posiva’s guidance work and validation of the instructions.

STUK has paid attention to Posiva’s quality management in the manufacture of individual system components and has monitored Posiva’s corrective actions. In its oversight, STUK monitors that Posiva comprehensively identifies the reasons behind the deficiencies and improves its operations.

STUK has commissioned VTT to carry out an independent safety culture study on Posiva, which will be completed in September 2023. The purpose of the report is to assess Posiva’s readiness to move to the use phase from the perspective of safety culture.

Review of safety of Posiva’s final disposal facility after it is closed has continued. In connection with the inspection, requests for clarification and information have been made. In addition, Posiva and STUK have gathered to discuss some of the issues raised during STUK’s inspection. In addition to review of the materials, STUK has promoted comparative modelling, with the objective of gaining a deeper understanding of the cases and consequences calculated by Posiva.

Tertial report 1/2023, January–April

In the first third of 2023, STUK continued to process Posiva's operating licence application material. STUK stated that not all of the material delivered to STUK fulfilled the requirements set for the operating licence application material.

As the processing progresses, STUK will prepare requests for clarification concerning the incomplete materials to Posiva, on the basis of which Posiva must update the materials and resubmit them to STUK for processing. In the first third of the year, STUK sent requests for clarifications on the final safety analysis report and the assessment of the safety case concerning long-term safety.

STUK found shortcomings especially in the system descriptions of the final safety analysis report. In the final safety analysis report, Posiva must present information on nuclear facilities that describes the facilities before the start of nuclear fuel encapsulation. At present, some of the information presented does not describe the final facilities, but rather how they are designed. In addition, STUK observed that the final safety report did not present in sufficient detail all the information that STUK requires to be presented in the final safety report on the basis of the YVL Guides. The requirements set out in the request for clarification relate to the supplementing of these matters.

When inspecting the assessment of the safety case concerning long-term safety prepared by Posiva, STUK made some inspection observations and remarks on the basis of which STUK requires additional information. In the first request for clarification, STUK asks questions concerning, among other things, the initial state after the closure and related deviations as well as the long-term behaviour of the system. STUK has also initiated the preparation of the next request for clarification concerning the safety case in the first third of the year.

During the first third of the year, Posiva was manufacturing, installing and commissioning the systems needed for encapsulation and final disposal. The encapsulation and final disposal facility requires lifting and transfer equipment to transfer spent nuclear fuel and the transfer container or capsule containing spent fuel. STUK has reviewed the construction plans of these lifting and transfer equipment.

STUK also oversees the manufacture of lifting and transfer equipment. STUK has carried out construction inspections for equipment whose manufacture has progressed sufficiently. The inspections verify that the construction has been carried out in accordance with the plans and approved manufacturing methods.

The commissioning of the Posiva nuclear facility involves the testing of systems. With these tests, Posiva ensures that the systems function as planned. Some of the systems are safety-classified, which means that their operation is essential for nuclear and radiation safety. STUK oversees the test runs of such systems, reviews the commissioning testing plans for the systems and monitors test runs on site. During the first third of the year, Posiva carried out the first safety-classified system test run. Plans for the following test runs are being processed by STUK.

STUK carried out two inspections as part of the construction inspection programme, the first of which focused on the management of changes in Posiva's project and organization for operational purposes. Based on the inspection, Posiva's change management procedures appear to be appropriate and mainly meet the relevant safety requirements. The organizational change related to the transition to the operating phase is significant from the point of view of safety, and Posiva will prepare an assessment of the impact of the organizational change on safety. The requirement issued by STUK during the inspection concerns the procedures for the assessment of a future organizational change.

The second inspection of the construction inspection programme focused on the operating instructions of Posiva's nuclear facility, the training of plant operators and the management of human factors. The inspection found that Posiva is still in the process of drafting the operating instructions for the nuclear facility and the procedures necessary for their management.

The inspection showed that the approval procedures for the operators of the Posiva nuclear facility are not fully completed. STUK monitors the development and completion of the approval procedures. The inspection covered the management of human factors in planning as well as the improvement and monitoring of the reliability of human activities. The inspection found that Posiva's plan for integrated system validation does not sufficiently include disturbances and emergencies. During the inspection, STUK made a request to rectify the matter.