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.
Within the framework of the “Co-ordination Network on Decommissioning of Nuclear Installations Project (2005–2008)” funded by the European Community a first edition of EURSSEM has been developed to promote common understanding of key issues in the development of a strategy, implementation and execution of a programme to remediate radioactively contaminated sites. The objective of EURSSEM is to describe and provide a consistent consensus information and guidance on strategy, planning, implementation and execution of stakeholder involvement, performing, and assessing radiological soil surface and groundwater (final) status surveys to meet established dose- or risk-based release criteria, and/or remediation, restoration, reuse and stewardship objectives, while at the same time encouraging effective use of human, raw material and financial resources. To be able to provide a consistent guidance and leading practices to involved participants (stakeholders) in a remediation programme for radioactively contaminated sites, an extensive literature study has been performed to collect important documents that have been produced in this field by the International Atomic Energy Agency (IAEA), the SAFEGROUNDS Learning Network, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM) and other national and international institutes. EURSSEM incorporates information provided in those and other documents to conduct all actions at radioactively contaminated and potentially radioactively contaminated sites and/or groundwater up to their release for restricted or unrestricted (re)use. Brief descriptions are provided about the background and the need for a document like EURSSEM, about key issues like stakeholder involvement and archiving for future referencing including the follow-up of the further development of EURSSEM.
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.
Various international decommissioning projects have shown that there are substantial variations in cost estimates for individual installations. Studies to understand the reasons for these differences have been somewhat hampered by the fact that different types of cost estimation methods are used, having different data requirements. Although some uncertainty is inevitable in any costing method, an understanding of the costing methods used in particular projects is useful to avoid key uncertainties. Difficulties of understanding can be encountered and invalid conclusions drawn in making cost comparisons without regard to the context in which the various cost estimates were made. The above-mentioned difficulties are partly due to the lack of a standardised or generally agreed-upon costing method that includes well structured and defined cost items and an established estimation method. Such a structure and method would be useful not only for project cost comparisons, but would also be a tool for a more effective cost management. The OECD/Nuclear Energy Agency (NEA), the International Atomic Energy Agency (IAEA), and the European Commission (EC) have ongoing activities addressing various aspects of decommissioning and decommissioning costs. Based on these concurrent activities and common objectives, and on the advantages of standardised cost item definitions, the three organisations agreed to jointly prepare and to publish a standardised list of cost items and related cost definitions, for decommissioning projects. The work was carried out by Belgoprocess (Belgium) in the framework of a shared-cost contract with the European Commission (Nuclear Fission Safety Programme 1994–1998). This paper presents the results of the co-operative work.
Various international and national bodies such as the International Atomic Energy Agency, the European Commission, the US Nuclear Regulatory Commission have put forward proposals or guidance documents to regulate the "clearance" from regulatory control of very low level radioactive material, in order to allow its recycling as a material management practice. All these proposals are based on predicted scenarios for subsequent utilisation of the released materials. The calculation models used in these scenarios tend to utilise conservative data regarding exposure times and dose uptake as well as other assumptions as a safeguard against uncertainties.None of these models has ever been validated by comparison with the actual real life practice of recycling. An international project was organised in order to validate some of the assumptions made in these calculation models, and, thereby, better assess the radiological consequences of recycling on a practical large scale.The validation was proposed to be carried out by comparing the results of dose measurements during a chain of recycling operations to dose values calculated for the same operations using the (US) RESRAD-RECYCLE and the (French) CERISE programmes. The operations were to cover all recycling activities, including the receipt of contaminated scrap at the radiologically controlled melting facility, its segmentation and melting, transport of released ingots to a manufacturing industry for use with other scrap as feed material and production of industrial products (rolls).The project was initiated by the Swedish Radiation Protection Institute and was a co-operation between authorities, research institutes and commercial companies from Sweden, France, USA and Belgium.A first phase of melting of contaminated scrap at Studsvik, release of ingots and transport to Åkers was carried out. The ingots were re-melted along with other (uncontaminated) scrap at Åkers to be used for manufacturing rolls. The doses to workers were measured at Studsvik, Åkers and during ingot transport. Dose calculations were made in parallel with these operations using the RESRAD-RECYCLE and CERISE programmes. However, the results of these calculations could not be compared with the corresponding values of doses taken by workers, because all of the doses were below the limit of detection.Due to this fact, a second phase was executed involving the segmenting and melting of a 3.4 t stainless steel fuel rack with an estimated activity concentration of over 150 Bq/g, mostly Co-60. The fuel rack was melted for volume reduction in the Studsvik facility in the middle of January 2001, in the presence of project team including the dose modellers, who then made code calculations to estimate the dose uptake of the workers.All personnel involved in the project operations were equipped with electronic (display) dosimeters. The measurements showed that segmenting was the work operation that gave the highest dose, almost 65 % of the total dose incurred, while melting itself accounted for only abou...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.