[en] In the decommissioning of unusual nuclear structures the health physics safety requirements have often been underestimated. The structure may have ceased operation many years ago and been left to allows radioactive decay. This can create problems with structural deterioration of components which are contaminated with radioactive material. The particular problems associated with the planned initial decommissioning of the Windscale Pile Chimneys are used as an example. (author)

[en] Reliable cost estimating is one of the most important elements of decommissioning operation. Reliable cost estimating is one of the most important elements of decommissioning planning. Alternative technologies may be evaluated and compared on their efficiency and effectiveness, and measured against a baseline cost as to the feasibility and benefit derived from the technology. This principle ensures that the cost consideration is economically sound and practical for funding. This paper provides a list with basic review of cutting and dismantling techniques, including some typical characteristics if available, as well as aspects of implementation, parameters of cutting and dismantling techniques in decommissioning costing. This paper gives an overview of the principles of the unit factor approach and its implementation in costing in relation to dismantling activities. In general, proper evaluation of decommissioning costs is important for following issues and relevant measures for achieving the listed aspects are: · Selection of a decommissioning strategy and activities: several decommissioning options should be evaluated: · Support to a cost-benefit analysis to ensure that the principle of optimization and reasonably practicable measures are applied: the extent of evaluated decommissioning options should cover all possible scenarios for dismantling activities; · Estimate of required financial resources for the selected strategy: the selected option should involve the dismantling activities in a structure and extent relevant to real procedure of dismantling activities; · Preparation of the project schedule, workforce requirements and phased funding needs: dismantling activities should be structured according to the tasks of the decommissioning schedule; · Definition of measures for proper management and maintenance of resources for safe and timely decommissioning: the time distribution and safety related parameters of dismantling activities should be known

[en] This article asks the question of the optimization of the safety in the case of combined risks. Nuclear risk and conventional risks such asbestos, fire, professional illness or accidents. (N.C.)

[en] The challenge of containment is to conciliate the adequate protection of the staff and the environment with industrial constraints like technical feasibility and the control of costs and deadlines. Containments are classified into 4 categories, C1 to C4, C1 for slight levels of contamination and C4 for highly contaminated atmospheres. Usually the containment of an area is achieved with the combination of a static confinement like flexible or stiff air locks with a dynamical confinement obtained with a ventilation system assuring an adequate de-pressurization. 2 research axis are quoted: the impact of incandescent particles in ventilation systems and the air flow through apertures in order to assess the efficiency of dynamical confinements. As each dismantling operation is specific, it is important to make room for new and innovative techniques without putting at risk workers and the environment. With this is in mind, a new standard for containment is being designed. (A.C.)

[en] The following conclusions can be drawn: decommissioning of large commercial nuclear power plants is technical feasible. It can be done within the frame of licensing regulations. Costs for decommissioning will be high; however the overall economic advantages of nuclear power are not considerably influenced. Search for suitable storage facilities and transport methods for large quantities and large dimensions should be started in an early stage. Tools and processes for cutting and conditioning of large radioactive components are still to be developed in detail. (orig.)

No abstract available

[en] The taking into account of dismantling constraints in the design of nuclear facilities allows the reduction of the dosimetry during the dismantling operations, the reduction of the amount of wastes to manage and the saving of time and money by foreseeing an adequate and simple solution for each component. It is to notice that the strategy of life-extension strengthens that of dismantling because life-extension implies the possibility for any component of the reactor except the pressure vessel to be replaced. The feedback experience capitalized on various types of nuclear facilities have enabled IAEA and OECD to publish recommendations to facilitate dismantling. For instance, pipes and ventilation ducts must be designed to minimize the deposit of dust and residues, the natural porosity of concrete must be limited through the use of polishing products or a metal liner, the type and concentrations of impurities present in the structure materials must be controlled to limit radioactivation, the documentation describing the facility must be kept up to date, or the history of contamination events must be recorded all along the life of the facility. The integration of the dismantling constraints in the design stage is illustrated with 3 examples: the Georges Besse 2 enrichment fuel plant, new reactors (EPR, ASTRID and RJH), and ITER. (A.C.)

[en] Many commercial nuclear facilities of the first generation will be taken out of operation in the near future. As of January 2012, total 19 prototype and commercial nuclear reactors have been decommissioned or are under dismantling in Germany. Most of decommissioning projects were successfully performed and a great deal of experience has been accumulated. Selecting a decommissioning strategy is a very important step at the beginning of the decision making process. According to IAEA requirements immediate dismantling is chosen as a preferred option in many countries today. It is associated with less uncertainty, positive political and social effect, and it can make use of existing operational experience and know-how. The availability of funds and final repository is of high importance for a decommissioning strategy selection. The time frame for the dismantling of nuclear facilities depends on the type, size and complexity of the individual project. TUV SUD, which is supervising most of nuclear power plants in Germany, has accumulated lots of experience by taking parts in decommissioning projects. It direct dismantling is chosen, actual light water reactor in Germany decommissioned to green field in approx. 10 years. The activities of TUV SUD cover from establishing the decommissioning concept to the clearance of the sites. This provides an overview of decommissioning projects of nuclear facilities in Europe, including a detail illustration of the German situation. Finally, some recommendations are suggested for the first decommissioning project based on the lessons and experiences derived from many decommissioning works in Europe

[en] High-level radiation of the major components restricts access by human workers, and makes an accident or outage during the dismantling process more difficult to deal with. Since unexpected situations causes waste of budget and an aggravation of safety, the preliminary verification of the dismantling processes and equipment by the tangible remote dismantling simulator is very important. The design optimization of the dismantling processes and equipment is one of the most important objectives of the tangible remote dismantling simulator, as well. This paper proposes a user interface technology to reduce mental transformations for the tangible remote dismantling simulator. At the dismantling process simulation using the tangible remote dismantling simulator, the most difficult work is the remote operation handling the high degrees-of-freedom (DOF) manipulator due to complex mental transformations. The proposed user interface technology reduces mental transformations with constraints using the point projection and direction projection. The test result of the cutting process over the closure head of the RPV demonstrates that the proposed mental transformation reduction technology is operated successfully in the tangible remote dismantling simulator, and lets the operator be easy to control the high DOF manipulator even in the most difficult operation by reducing DOFs to be controlled manually

[en] Today's approach of the dismantling of nuclear facilities is labour intensive and consequently very expensive. NEA's study suggests that research works should be done to find more efficient technologies for decontamination and dismantling. 5 lines of research have been identified by NEA. First, new technologies must be found to get a more accurate spatial distribution of contaminants. Secondly, the different cutting methods must be assessed in terms of efficiency, dosimetry and secondary waste generation. Thirdly, a better understanding of the chemical and physical processes that may be used for the decontamination of metals, concretes, underground water and soil. Fourthly, the management of radioactive waste implies to know the interaction between wastes and packages over a very long period. Fifthly, an accurate characterization of a complex site housing various contaminating sources and different hydro-geological conditions implies the development of 3-dimensional radiation transport codes and the use of innovative means like satellite monitoring. (A.C.)