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CND // DECOMMISSIONING IN EUROPE / DECOMMISSIONING PROJECTS IN EUROPE / KRB-A |
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Decommissioning Projects in Europe The KRB-A (Gundremmingen) Pilot Dismantling Project  The Commission selected KRB-A as a pilot dismantling project for its 1989-1993 RTD programme on the decommissioning of nuclear installations. The Commission, through shared cost in specific parts of the project, intends to promote the use of advanced techniques and the performance of collateral investigations, in order to enhance the generation of useful knowledge and experience to serve in subsequent decommissioning tasks. In particular, the generation of specific data on costs, working hours, job dose as well as on the amount of generated secondary waste, is considered as an important objective of this pilot project. Short history
HistoryThe nuclear power station "Gundremmingen unit A" (KRB-A) is located in Bavaria at the river Danube between Stuttgart and Munich. It was under construction in 1962 - 66 as the first commercial nuclear power plant in the Federal Republic of Germany (FRG) with an electrical output of 250 MW. KRB-A was operated from 1966 until January 1977. The plants average availability was 75 %. It was shut down in January 1977 due to a short circuit in the grid which caused substantial damage to the plant. KRB-A determined that necessary repairs and backfitting measures would create an outage for several years and could not be justified from an economic point of view. In January 1980, the shareholders RWE-Energie AG (75 % Since 1984 two modern boiling water reactors (BWR's) are in operation on the site with an electric output of 1 344 MW each. Fig. 1 shows the nuclear power site of Gundremmingen with the small domed building of unit A on the left. 
Figure 1. Nuclear power site Gundremmingen The planning phase of the decommissioning of unit A began in 1980, actual dismantling work started in 1983 and is scheduled to end in the year 2000. It is foreseen to decommission just the internals of the plant and keep the building as a workshop for the two running BWRs. KRB-A was a dual cycle BWR of the General Electric type. Beside the primary steam (1 000 Mg/h), there was a secondary steam system (360 Mg/h) available for load regulation of the reactor. Each of the three recirculation loops was equipped with a big recirculation pump and a steam generator (Fig. 2). Therefore dismantling experience gained at KRB-A is obviously transferable to BWR and PWR as well. According to the German atomic law, the dismantling of a nuclear power plant needs a licence. In the licensing procedure the planned measures have to be described including a safety report which demonstrates that there is no impact to human beings or the environment. The licensing process and the later work is accompanied by independent technical experts which report to the federal authority. The whole decommissioning project was divided into different phases, starting with the lower contaminated systems and ending with the high activated reactor vessel. This step by step procedure allows to get experience and to collect data on radiation protection measures, cutting and decontamination techniques, waste production and last not least the financial effort of such a project. The components mentioned in the following figure have been dismantled within this EC programme. 
Figure 2. EC pilot project components The decommissioning project was structured in 3 phases as shown on Fig. 3 and in Table 1. It started 1983 with the removal of components and systems in the turbine house (phase I). Since 1990, the dismantling activities have been extended to the primary water system in-side the reactor building (phase II). In 1992 the dismantling of the RPV has started (phase III) with the segmenting of the RPV-head and the steam dryer. 
Figure 3. The nuclear power plant KRB-A
Table 1. Radioactivity and collective dose in the phases of decommissioning The turbine building has been emptied by dismantling 4 500 Mg of material, mainly steel and concrete (phase I). The total activity to be handled was 4.1010 Bq with surface contamination of up to 1 000 Bq/cm2. By using appropriate technologies the collective dose was only 1 Sv. During decommissioning of the primary water affected systems and components (phase II) only 1.4 Sv collective dose will be spent. The contamination was found to be between 1 000 and 50 000 Bq/cm2. Phase III includes the highly activated RPV and its internals and biological shielding. A collective dose of only 1.5 Sv is calculated because of the use of underwater segmenting techniques. The recycling of dismantled material instead of disposing it as radioactive waste is - as long as technically and economically achievable - preferred in KRB-A. For reuse of material 0.5 Bq/cm2 surface contamination and 0.1 Bq/g as specific activity for steel are valid. Steel parts with residual specific activity between 0.1 Bq/g and 200 Bq/g can be prepared for nuclear recycling by melting for restricted reuse within the nuclear industry. Table 2 shows the calculated material balance for decommissioning of KRB-A.
Table 2. Calculated material balance for decommissioning of KRB-A Further information |
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