First phase of central channel completed – Project still delayed

The fabrication of the central channel is being pursued with the highest priority. Despite considerable progress, delivery has been postponed until 2025.

The lowest section of the 3.5-meter-long central channel has been completed in its raw form: The so-called mounting flange with welded plug. However, one of the unresolved challenges in the production of the central channel is finding a suitable heat treatment to achieve the prescribed uniform expansion of the weld seam of the expansion joint. Technical Director Dr. Axel Pichlmaier is nevertheless optimistic: “Together with our partner companies and under the scrutiny of the experts, we have developed special processes so that completion of the expansion joint is finally in sight.”

Quality assurance officer Britta Pollom from FRM II with the finished mounting flange of the central channel. © Dr. Axel Pichlmaier, FRM II / TUM

Quality assurance officer Britta Pollom from FRM II with the finished mounting flange of the central channel. © Dr. Axel Pichlmaier, FRM II / TUM

More than a dozen companies involved in manufacturing
Only when all of this has been fulfilled and completed can the production of the remaining central channel begin. More than a dozen companies are involved in the production. The project is being coordinated by FRM II employees, with the independent expert from the nuclear supervisory authority involved at all times.

Damage discovered in 2022
Damage to the compensator of the central channel was discovered during maintenance work in 2022. The central channel is the most central component of the FRM II. It is located vertically in the moderator tank and supports the fuel element. It separates the primary cooling circuit from the heavy water in the moderator tank. As it cannot be repaired, it must be replaced with a new part. In the course of production, the company commissioned to manufacture the replacement part was forced to outsource key manufacturing steps to other project partners, who in turn first had to be certified by the FRM II. Manufacturing techniques were developed from scratch to the required quality.

The structure for welding the mounting flange is a unique prototype, fully tested and approved. © AIT Austrian Institute of Technology, LKR Light Metal Competence Center Ranshofen GmbH

The structure for welding the mounting flange is a unique prototype, fully tested and approved. © AIT Austrian Institute of Technology, LKR Light Metal Competence Center Ranshofen GmbH

Many small delays
“Unfortunately, despite considerable progress in all areas of the project, various small delays have accumulated to such an extent that we now have to assume that the central channel will be delivered in 2025,” says Pichlmaier. After delivery, it will take around six months before scientific operations can be resumed.

Skills shortage and loss of expertise
Pichlmaier sees the following reasons for the delay: “The production of the central channel requires intensive administrative support from the FRM II, as the industrial partners are no longer familiar with the nuclear regulations. In addition, the FRM II and this procurement process, like the entire German industry, is suffering from an ever-increasing shortage of skilled workers.” The production of a single unit, prototypes, is usually of little economic interest to the manufacturing companies.

Additional modernization work
Moreover, the employees at FRM II have made significant progress in the preparatory work that is a prerequisite for the operation of FRM II. The cranes in the experimental hall and reactor hall, which are required for changing the central channel and loading the Castor with spent fuel elements, have been converted. Further modernization work is underway. These include the cleaning lines of the primary circuit, parts of the tertiary circuit, irradiation facilities for radioisotope production, experimental facilities, fire protection systems and ventilation components.