R. Pampin

THE BACK END OF THE FUSION MATERIALS CYCLE

Abstract Within the framework of the International Energy Agency, an international collaborative study on fusion radioactive waste has been initiated to examine the back end of the materials cycle as an important stage in maximizing the environmental benefits of fusion as an energy provider. The study addresses the management procedures for radioactive materials following the changeout of replaceable components and decommissioning of fusion facilities. We define this as “the back end” of the fusion materials cycle. It includes all the procedures necessary to manage spent radioactive materials from fusion facilities, from the removal of the components from the device to the reuse of these components through recycling/clearance, or to the disposal of the waste in geological repositories. Fusion devices have certain characteristics that make them environmentally friendly devices; minimization of long-lived waste that could be a burden for future generations is one of these characteristics. Recycling and clearance procedures and regulations have been recently revised, and the effects of these revisions on back-end fusion materials are examined in the paper. Finally, an integrated approach to the management of back-end fusion materials is proposed, and its application to three fusion reactor designs is discussed.

Revision of the inventory and recycling scenario of active material in near-term PPCS models

A sound approach to the recycling of fusion irradiated material is being developed. Study of industry experience, and consideration of realistic processing routes and techniques, provide a more sensible estimation of recycling feasibility than earlier studies based on purely radiological criteria. Under this approach, the analysis of active material in two models of the power plant conceptual study (PPCS) has been revised in more detail and accounting for the latest design features, nuclear data and international guidelines. A careful inventory of the materials has been performed, and estimation made of the radiological characteristics of all PPCS tokamak components, for the first time studying individual constituents and materials. Evaluation has been made of time scales for the radioactivity to decay to predetermined levels, which represent the spectrum of technological difficulties posed by the nature of the irradiated material. Three main mechanisms for the optimization of the materials management strategy have been identified during the assessments: segregation of components into individual materials, in situ refurbishment and stringent impurity control.

ANALYSES AND PRELIMINARY RESULTS OF AN UPDATED ITER RADIOACTIVE WASTE ASSESSMENT

Abstract The scope, methodology, and preliminary results are presented of a series of neutron transport and activation analyses aimed at updating the ITER radioactive inventory assessment and assisting the waste management planning. Calculations are performed using state-of-the-art three-dimensional models, codes, and data libraries and thereby overcoming earlier conservative one-dimensional evaluations. The latest information on component design, maintenance, materials, and French regulatory framework is used. Results include categorization snapshots at different decay times, time histories of activation, IRAS index and other radiological quantities throughout the machine, and guidelines on interim decay times for different components. The aim is to provide information for the design and development of ITER systems, maintenance operations, and waste management processes and services.

The Back-End of Fusion Materials Cycle: Recycling, Clearance and Disposal

Abstract In order to maximize the environmental benefits of fusion power generation, it is important to clearly define the parameters governing the back-end of the materials cycle. A fusion-specific approach is necessary and needs to be developed. Recycling of materials and clearance (i.e. declassification to non-radioactive material) are the two recommended options for reducing the amount of fusion waste, while the disposal as low-level waste could be an alternative route for specific materials and components. Both recycling and clearance criteria have been recently revised by national and international institutions. These revisions and their consequences for fusion material management are examined in this paper. It is also important to define the various processes and routes to avoid generating active waste from fusion as much as possible. Two ways are explored within the fusion community: first, the development of materials leading to low activation levels, avoiding the generation of long lived radionuclides through a strict control of the impurity content in materials; second, the development of suitable and reliable processes allowing either clearance of as much material as possible (potentially after adequate treatment) or recycling most of the remaining materials within the nuclear industry.

Management of fusion activated materials

This study addresses an integrated approach to the management procedures for active mate-rials following the changeout of replaceable components and decommissioning of fusion facilities. The attractive environmental features of fusion are put into evidence, and the question of nuclear weapon proliferation relevance of fusion power plants is briefly discussed. Reference is made to previous U.S. and European assessments of the back-end for fusion power plant studies, stressing that most materi-als can be cleared or recycled, and/or disposed of as low-level waste. Just recently, both clearance and recycling concepts and limits have been revised by national and international organizations. These revisions and their consequences have been examined in this paper and the references therein. A new radioactive materials management strategy has been proposed for the clearance, recycling, and disposal approaches