ASDOC_D-MOD test equipment at the technical center of Siempelkamp NIS IngenieurgesellschaftGermany’s Siempelkamp NIS Ingenieurgesellschaft mbH has developed an innovative procedure for the chemical decontamination of the reactor cooling system and subsystems in nuclear power plants, the company said on its website on 26 February.

The development followed the successful decontamination of the reactor cooling system and its subsystems in a German nuclear power plant. The new procedure took four years to develop. The objective of the ASDOC_D-MOD procedure is to detach radioactive contamination adhering to the inner system surfaces by adding specially formulated chemical additives to the reactor cooling system and to subsequently remove them from the system with the help of ion exchangers, said Siempelkamp. This decreases contamination significantly and minimises radiation exposure to personnel undertaking dismantling work.

With the new procedure, the dose rate can be reduced on average by a factor of 85, significantly simplifying the scheduled dismantling of reactor systems. The process specifically considers materials that, when using conventional decontamination solutions, can be susceptible to corrosion and therefore, it prevents impairment of the functional safety and integrity of the power plant systems included in the decontamination process, Siempelkamp notes.

The modified ASCDOC_D-MOD procedure was developed and successfully tested at the technical centre operated by Siempelkamp NIS. One of the goals was to minimise chemical reactions between the decontamination solution and metallic materials so that a safety-relevant formation of hydrogen would not occur. For the current project, the hydrogen levels stayed below or right at the detection limit.

“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,” said Dr Aldo Weber, management spokesperson for Siempelkamp.

Photo: ASDOC_D-MOD test equipment at the technical centre operated by Siempelkamp NIS Ingenieurgesellschaft