Plasma Cutting in the Multi-Purpose Research Reactor (MZFR) — Underwater use at Steel Thicknesses of up to 130 MM

Remote disassembly of radiologically burdened large components is among the most sophisticated and complex activities in the demolition of nuclear installations. High local dose rates and contamination levels, combined with complicated designs and geometries of the components to be dismantled, plus insufficient accessibility, imply major challenges in the demolition of nuclear facilities. Normally, the shielding effect of water is used in remote dismantling of highly activated components. All processes eligible for this purpose must therefore be suitable for application under water. In underwater (UW) dismantling of the MZFR between 2004 and 2005, plasma cutting has been found to be an efficient method of disassembly with safe remote control capability. Close cooperation in the development of technical solutions among RWE NUKEM, the Institute of Materials Science of the University of Hanover, Kjellberg Finsterwalde GmbH, Industrieanlagen Betriebsgesellschaft (IABG), Studsvik®Ifm, and Forschungszentrum Karlsruhe GmbH contributed to the further development of plasma cutting for use under water in the MZFR, thus making it preferable to all other cutting techniques available for demolition and disassembly. This technique was used in the MZFR for complete disassembly of the geometrically complex moderator tank and most of the thermal shield. The experience accumulated in the hot use of plasma disassembly techniques in the MZFR is presented and assessed in the paper.