Canister project proceeds to procedure qualification test phase

Posiva’s disposal canister project people at the central office in Olkiluoto. Around the table from leftto right Tomi Prihti, Terhi Glas, Petri Koho, Oskari Piepponen, Anssi Myllymaa, Jouko Lammi, Tiina Jalonen, Timo Salonen ja Esa Koivula.

Orders for the manufacture of the tubes for procedure testing have been placed with two different suppliers and the project now proceeds along both of the two paths. For the forging of the copper lid and bottom, the qualification test phase has already started. In addition, a procedure qualification test for the welding of the copper tube's bottom inside the canister is to be conducted in the Oskarshamn canister laboratory of the Swedish Nuclear Fuel and Waste Management Company SKB.

- Posiva is looking into two different manufacturing procedures for the production of the copper tube. Copper tubes manufactured with each of the two procedures is planned to be provided to SKB's canister laboratory where a bottom will be welded to the tubes. The final contract for this is in process to be signed in the near future, says Programme Manager Petri Koho from Posiva.

- The price will naturally also be a factor in the final selection of the manufacturing procedure and the manufacturer of the copper tubes.

According to the schedule for the procedure qualification tests, the qualification test for the manufacture of the copper lid and bottom and the welding procedure test for the copper tube's bottom will be completed by the end of 2022.

A set of three test tubes manufactured by the extrusion procedure will also be available during the year 2022. This set is used to verify that the manufacturing procedure is ready for the actual qualification test which will be conducted also on three tubes during the first quarter of 2023.

The qualification test on two tubes produced by the forging procedure will also be conducted by the end of March 2023, probably before the extrusion procedure qualification test.

- This phase has been preceded by 10–20 years of background work. The procedure qualification test is designed to demonstrate that the copper tube manufactured using the approved procedure will meet requirements, Mr. Koho elaborates.

The approved qualification test is one precondition for the start of the manufacture of production components. The procedure qualification test plan, which provides a detailed description of the manufacturing procedure, shall be approved by the Radiation and Nuclear Safety Authority of Finland (STUK) before the qualification test can begin.

- It is possible that STUK will request further clarification on some points, so there are still some moving parts. It is not an easy task for the regulatory authority, either, to approve the canister and all its internal parts as the first authority in the world.

Significant threshold phase

The procedure qualification tests form a significant threshold phase in Posiva's canister project. After the completion of the tests, i.e., after the first quarter of 2023, there still remains work to be done in studying matters related to the inspections of the tubes as well as metallurgy, such as the creep of the metal. The creep tests are also a part of the final approval of the procedure qualification tests.

According to estimates, the creep tests will be finalised in all respects during the last quarter of 2023.

- Preliminary tests have already been carried out with good results, which makes us confident that the tests can be completed successfully. The issue of the canister is the critical line for the start of final disposal, Koho says.

Once the manufacturing procedure and the final product are proven to meet the requirements, Posiva can start to award production contracts and launch the manufacture of production components.

- We are talking about one year before the components will be ready and on the site. This means that the final disposal project of Posiva could start in mid-2020s, as planned.

Text: Pasi Tuohimaa
Photos: Tapani Karjanlahti