When decommissioning nuclear installations, large quantities of metal components are produced as well as significant amounts of other radioactive materials, which mostly show low surface contamination. Having been used or having been brought for a while in a controlled area marks them as ‘suspected material’. In view of the very high costs for radioactive waste processing and disposal, alternatives have been considered, and much effort has gone to recycling through decontamination, melting and unconditional release of metals. In a broader context, recycling of materials can considered to be a first order ecological priority in order to limit the quantities of radioactive wastes for final disposal and to reduce the technical and economic problems involved with the management of radioactive wastes. It will help as well to make economic use of primary material and to conserve natural resources of basic material for future generations. In a demonstration programme, Belgoprocess has shown that it is economically interesting to decontaminate metal components to unconditional release levels using dry abrasive blasting techniques, the unit cost for decontamination being only 30% of the global cost for radioactive waste treatment, conditioning, storage and disposal. As a result, an industrial dry abrasive blasting unit was installed in the Belgoprocess central decontamination infrastructure. At the end of May 2001, after 6 years of operation, 523 Mg of contaminated metal has been treated. 182 Mg of this material was unconditionally released, having been monitored twice by the in-house health physics department. About 303 Mg of the metal, presenting surfaces that could not be measured due to their shape, were melted for unconditional release in a controlled melting facility. The suitability of the abrasive blasting system was verified, and it was proved that there was no intrusion of contamination into the material surface. The paper gives an overview of the experience relating to the decontamination of metal material by abrasive blasting at the decommissioning of the Eurochemic reprocessing plant in Dessel, Belgium.
Belgoprocess started the industrial decommissioning of the main process building of the former Eurochemic reprocessing plant in 1990, after completion of a pilot project. Two small storage buildings for end products from reprocessing were dismantled to verify the assumptions made in a previous paper study on decommissioning, to demonstrate and develop dismantling techniques and to train personnel. Both buildings were emptied and decontaminated to background levels. They were demolished and the remaining concrete debris was disposed of as industrial waste, and green field conditions restored. The main process building is a large rectangular construction of about 80 m long, 27 m wide and 30 m high. About 106 individual cell structures have to be dismantled, involving the removal and decontamination of equipment from each cell, the decontamination of the cell walls, ceilings and floors, the dismantling of the ventilation system. These activities are followed by a complete monitoring of all surfaces in view of the unconditional release of the remaining structures. About 1,500 Mg of metal structures, and 12,500 m3 of concrete with 55,000 m2 of concrete surfaces have to be removed and/or to be decontaminated. The paper presents a status overview of the decommissioning and decontamination activities at the former Eurochemic reprocessing plant on the nuclear site of Dessel in Belgium. The specific Belgoprocess approach will be highlighted, in which the decommissioning activities are carried out on an industrial scale with special emphasis on cost minimisation, the use of technology on an industrial representative scale. The specific alpha contamination of equipment and building surfaces require that the decommissioning work is done with adequate protective clothing. Adapted breathing and cooling air systems have been provided to enable the operators to carry out the decommissioning tasks in acceptable working conditions.
Belgoprocess started the industrial decommissioning of the main process building of the former Eurochemic reprocessing plant in 1990, after completion of a pilot project. Two small storage buildings for final products from reprocessing were dismantled to verify the assumptions made in a previous paper study on decommissioning, to demonstrate and develop dismantling techniques and to train personnel. Both buildings were emptied and decontaminated to background levels. They were demolished and the remaining concrete debris was disposed of as industrial waste and green field conditions restored. Currently, the decommissioning operations carried out at the main building have made substantial progress. They are executed on an industrial scale and will continue till the end of 2005. In view of the final demolition of the building, a clearance methodology has to be proposed. Application of the methodology applied for the storage buildings of the pilot project is complicated for several reasons. Although this methodology is not rejected as such, an alternative has been studied thoroughly. It considers at least one complete measurement of all concrete structures and the removal of all detected residual radioactivity. This monitoring sequence is followed by a controlled demolition of the concrete structures and crushing of the resulting concrete parts to smaller particles. During the crashing operations, metal parts are separated from the concrete and representative concrete samples are taken. The frequency of sampling meets the prevailing standards. In a further step, the concrete samples are milled, homogenised, and a smaller fraction is sent to the laboratory for analyses. The paper describes the developed concrete crushing and sampling methodology.
In the beginning of April, 1998, Belgoprocess started the large scale decommissioning of shutdown facilities at the former waste treatment department of the Belgian Nuclear Research Centre (SCK•CEN). In the second half of 2000, the decommissioning of a former open concrete storage pond was started. It has two parts, one with a volume of 200 m3, the other has a volume of 2 000 m3. In the past, the tanks were used as open cooling reservoir for the scrubber water of an incinerator for low level beta-gamma wastes. As a result, it contained some 126 Mg of sludges that were treated in a bituminisation facility. After emptying and rinsing of the tanks, samples were taken from the inner (brick) and the outer (concrete) wall to define the contamination levels in the material. It was found that the first layer of about one centimetre of the brick wall showed some radium contamination. Samples taken from the outer wall showed no contamination, which does not mean that the entire outer wall should be free of contamination. It was seen that the outer wall had some cracks, and there was no guarantee that a layer of bitumen in between the two walls was still in good condition. Also the top layer of the concrete bottom proved to be radium contaminated. The outer walls of the storage pond were supported by a thick layer of soil, which proved to contain some spots of contamination. The contaminated soil was segregated and evacuated, the remaining part was removed to a temporary storage area, waiting to be monitored for final unconditional release. The paper gives an overview of the decommissioning activities relating to the open concrete storage pond at the former waste treatment department of the Belgian Nuclear Research Centre (SCK•CEN).
BELGONUCLEAIRE has been operating the Dessel MOX plant at an industrial scale between 1986 and 2006. During this period, 40 metric tons of plutonium (HM) have been processed into 90 reloads of MOX fuel for commercial light water reactors. The decision to stop the production in 2006 and to decommission the MOX plant was the result of the shrinkage of the MOX fuel market due to political and commercial factors. As a significant part of the decommissioning project of the Dessel MOX plant, about 170 medium-sized glove-boxes and about 1.200 metric tons of structure and equipment outside the glove-boxes are planned for dismantling. The license for the dismantling of the MOX plant was granted by Royal Decree in 2008 and the dismantling started in March 2009. The dismantling works are carried out by an integrated organization under leadership and responsibility of BELGONUCLEAIRE; this organization includes 3 main contractors, namely Tecnubel N.V., the THV (‘Tijdelijke HandelsVereniging’) Belgoprocess / SCK•CEN and Studsvik GmbH and TRACTEBEL ENGINEERING as project manager. In this paper, after having described the main characteristics of the project, the authors review the different organizational and technical options considered for the decommissioning of the glove-boxes; thereafter the main decision criteria (qualification of personnel and of processes, confinement, cutting techniques & radiation protection, safety aspects, alpha-bearing waste management) are analyzed as well. Finally the progress, the feedback and the lessons learned at the end of August 2013 are presented, giving the principal’s and contractors point of view.
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