The Development of the Canister Production

In the development of the final disposal canister, the production of both the exterior made of copper and the insert made of cast iron will be tested.

Manufacturing the Copper Exterior

Manufacturing the copper canister starts with manufacturing the ingot which, in this case, is a large block of copper. The copper block measures 86 cm in diameter and weighs between 13 and 17 tons.

Further processing involves piercing the block, widening its diameter, lengthening it and thinning down the walls. Three different techniques are used during further processing: piercing and drawing, extrusion and forging.

Piercing and drawing produces an exterior where the base is already attached. In this way, no separate welding phase for the base is required. Piercing and drawing is tested with equipment located in Germany.

Extrusion means that the copper section of the canister is extruded. As a consequence, the material in this method comes out very finely structured. When using this method, the base has to be separately attached by welding. This method, however, produces a finished canister with only a few working phases. Extrusion has been tested in Scotland.

Forging is also an option for manufacturing a copper canister. Forging is the manufacturing method with the largest number of working phases. Nevertheless, this method is also suitable for producing a made-to-measure canister. There are a number of eligible forging mills in Europe, the nearest of which is located in Sweden.

All three methods are appropriate for manufacturing a final disposal canister that meets the requirements. Even when the final disposal begins, at least two methods and two separate manufacturers are required to be obtainable at any time.

Manufacturing the Cast Iron Insert

The final disposal canister interior is made of spheroidal graphite cast iron and manufactured by casting. During the casting, molten iron with a temperature of almost 1,400°C is poured into a mould. After casting, the insert is allowed to cool down, which can take as long as a fortnight. Then it is cleaned, sawn and machined into its correct measures.

The canister insert manufacturing is tested with test casts. The purpose of the test casts is to help in finding exactly the correct cast settings and to ensure that they can be used in manufacturing a canister insert that, by its mechanical and other features, meets the demands set for a final disposal canister. Mechanical properties, such as resilience and strength, of the sample pieces taken from the casts are measured with tensile strength tests. Their matrix – for instance, the forming of nodes by the graphite – is examined with a microscope.