Wedoany.com Report-Jun 26, Finnish radioactive waste management company Posiva has successfully produced the first copper casting blank for a final disposal canister at the Onkalo used nuclear fuel repository. The casting process began earlier in June 2025 at Luvata’s Pori foundry, a subsidiary of Japan’s Mitsubishi Materials, under the supervision of Finland’s Radiation and Nuclear Safety Authority (STUK).

The initial blank, weighing over 17 tonnes, was completed in a single shift. Preliminary analysis samples were taken before the blank was measured and weighed. It will now undergo sawing to trim its front and rear ends, with sample slices cut for material analysis. Jouko Lammi, Posiva’s canister manufacture coordinator, stated: “The casting process was a great success. A good casting quality is important for the subsequent canister production phases. New investments have been made in the foundry to improve the quality and the processing of the casting. One of the most important accomplishments has been the increase in the diameter of the casting with a larger gravity die.”

After sawing, the blank will be machined to precise dimensions, followed by non-destructive testing, visual inspection, and dye penetrant inspection. Posiva will then conduct a final review of the casting and its documentation. Once approved, the blank, weighing approximately 12 tonnes, will be packaged and sent to the canister manufacturer.

The Onkalo repository, located 430 meters deep in the bedrock, is designed to store used nuclear fuel from TVO’s Olkiluoto and Fortum’s Loviisa nuclear power plants. The disposal system includes a sealed iron-copper canister, a bentonite buffer, tunnel backfilling with swellable clay, and sealed rock enclosures. The copper canister, formed from the casting blank with a welded bottom and cover, features 5cm-thick walls to serve as a corrosion barrier for the cast iron insert, which holds 12 fuel assemblies.

Upon receiving its operating license, Posiva will begin final disposal operations, expected to continue for about 100 years before the repository is sealed. This milestone in canister production supports Finland’s commitment to safe and sustainable nuclear waste management, ensuring long-term environmental protection and operational reliability.