Experience with the dismantling of three secondary steam generators in unit A in Gundremmingen by the 'ice-sawing' technique

The unit A in Gundremmingen (KRB A), was the first commercial nuclear power plant in Germany. It had an electrical power of 250 MWe and was in operation from 1966-1977. The plant was equipped with a dual cycle boiling water reactor of a former General Electric design and includes three recirculation lines each with a big recirculation pump and a steam generator comparable with those of pressurized water reactors. Therefore dismantling experience is gained for systems and components of boiling water reactors as well as pressurized water reactors. In early 1980, it was decided to decommission the plant. Actual decommissioning work started in 1983 with the removal of the components and systems in the turbine house. Since 1990 the decommissioning activities have been expanded to all primary water systems inside the reactor building. In 1992, KRB A obtained a licence for dismantling the remaining activated components like the reactor pressure vessel and the biological shield. Meanwhile more than 5200 tons of contaminated components have been dismantled. Special cutting and handling tools were tested, developed and optimized for the purpose of working in radiation fields and under water. The dismantling work of the contaminated systems and components ends up in about 6000 tons of material with a rather low amount of waste, especially due to optimized decontamination techniques Eickelpasch et al. (1992). For the dismantling of the three secondary steam generators in the reactor building the 'ice-sawing' technique was developed and patented. (orig.)