Many of the operating nuclear power reactors in the world were build in 1970s. Considering that nuclear reactors are licensed for forty years, many reactors have reached the end of their initial license and have applied for and been granted extension of up to twenty additional years of licensed operation. However, some reactors have reached the end of their practical lifespan and, despite being licensed to keep operating, are being shut down because they are too expensive to maintain and operate. When a nuclear reactor is permanently shut down, it must be decommissioned. This means that all spent nuclear fuel must be eventually disposed of and the entire nuclear reactor facility must taken apart and disposed of. Nuclear decommissioning will be a boom business for decades.
Before decommissioning a nuclear power plant, the cooling system must be decontaminated. While a nuclear power plant is operating, oxidic coatings form in the pipes and other components of the cooling system. As the oxide coating forms, radionuclides are incorporated.
The Siempelkamp group is an international technology company based in Germany that has three divisions. The first division is the machine and plant engineering division which supplies whole factories to the wood panel industry, the metal forming industry and the composite and rubber industry. The second division is the foundry division which can cast objects up to three hundred and fifty U.S. tons. The third division is the NIS Ingenieurgesellschaft mbH division which supplies components and services to the nuclear industry.
Siempelkamp NIS Ingenieurgesellschaft has developed what they refer to as “advanced system decontamination by oxidizing chemistry” (ASDOC) to dissolve the oxide layer and remove the radionuclides. Siempelkamp created their ASDOC solution from common and readily available industrial chemical. After initial tests of the solution revealed problems, Siempelkamp added an acid to the solution to stabilize the pH and prevent a precipitate from forming in the solution. Without a stable pH, corrosion can occur in some metals. The final result is the Siempelkamp’s ASDOC_D-MOD procedure.
The Siempelkamp decontaminating solution is injected directly into the existing cooling system and the radionuclides are removed from the cleaning solution with ion exchangers. The use of existing access to the cooling system components means that external equipment does not have to be brought in and erected in a radioactive environment. The dangers of leakage of fluids is reduced by the use of the existing cooling system components to add the cleaning solution.
The Siempelkamp’s ASDOC_D-MOD procedure reduces the radioactive contamination in a reactor cooling system by eighty five percent. This makes it safer to dismantle the cooling system. The metal in the cooling system pipes and components are decontaminated sufficiently for the metals to be melted and recycled.
A spokesperson for Siempelkamp said: “The development of the procedure was very complex and a highly technical and scientific challenge. We suffered some setbacks until we arrived at the point where we could successfully demonstrate the practical use of it, which to date we have done twice.”
Siempelkamp successfully applied their ASDOC_D-MOD procedure in the decontamination of Unit A at the Biblis nuclear power plant in Hesse, Germany in 2016 and in the decontamination of Unit B at the same plant in 2018.
