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The International Energy Agency (IEA) has been promoting the IEA Environment, Safety and Economic Aspects of Fusion Power program for many years. Among the tasks of this program, one task in particular deals with radioactive waste management in order to analyze the issue of the final destination of fusion activated and tritiated materials after their use in a fusion power reactor. A collaborative study on these aspects has been carried out in recent years. An optimized waste management strategy is proposed, with the goals of avoiding underground disposal as much as possible, maximizing recycling of activated materials within the nuclear industry, and/or clearance and release to commercial markets if materials contain only slight traces of radioactivity. Some technological problems and recent research advances in this field are summarized.

Designers of heavy ion (HI) and Z-pinch inertial fusion power plants have explored the potential of recycling the target and recyclable transmission line (RTL) materials as an alternate option to disposal in a geological repository. This work represents the first time a comprehensive recycling assessment was performed on both machines with an exact pulse history. Our results offer two divergent conclusions on the recycling issue. For the HI concept, target recycling is not a “must” requirement and the preferred option is the one-shot use scenario as target materials represent a small waste stream, less than 1% of the total nuclear island waste. We recommend using low-cost hohlraum materials once-through and then disposing of them instead of recycling expensive materials such as Au and Gd. On the contrary, RTL recycling is a “must” requirement for the Z-pinch concept in order to minimize the RTL inventory and enhance the economics. The RTLs meet the low level waste and recycling dose requirements with a wide margin when recycled for the entire plant life even without a cooling period. While recycling offers advantages to the Z-pinch system, it adds complexity and cost to the HI designs.

The chamber wall armor is subject to demanding conditions in inertial fusion energy (IFE) chambers. IFE operation is cyclic in nature, and key issues are (a) chamber evacuation to ensure that after each shot the chamber returns to a quiescent state in preparation for the target injection and the firing of the driver for the subsequent shot and (b) armor lifetime that requires that the armor accommodate the cyclic energy deposition while providing the required lifetime. Armor erosion would impact both of these requirements. Tungsten and carbon are considered as armor for IFE dry-wall chambers based on their high-temperature and high-heat-flux accommodation capabilities. This paper assesses the requirements on armor imposed by the operating conditions in IFE, including energy deposition density, time of deposition, and frequencies; describes their impact on the performance of the candidate armor materials; and discusses the major issues.

The issue of waste management has been studied simultaneously along with the development of the ARIES heavy-ion-driven inertial fusion energy (IFE) concept. Options for waste management include disposal in repositories, recycling, or clearance from regulatory control, following a reasonable cooling period. This paper concerns the feasibility of recycling the heavy-ion-beam targets, in particular the hohlraum wall materials that include, for example, Au/Gd, Au, W, Pb, Hg, Ta, Pb/Ta/Cs, Hg/W/Cs, Pb/Hf, Hf, solid Kr, and solid Xe. The choice between target material disposal and recycling depends on the amount of waste generated relative to the nuclear island, the strategy to solve the recycling problem, and the impact of the additional cost and complexity of the recycling process on the overall machine. A detailed flow diagram for the elements of the recycling process was developed to analyze two extreme activation cases: (a) one-shot use and then disposal in a repository and (b) recycling continuously during plant life without removal of transmutation products. Metrics for comparing the two scenarios included waste level, dose to recycling equipment, additional cost, and design complexity. Comparing the two approaches indicated a preference for the one-shot scenario as it generates 1 m{sup 3}/yr of extremely low-level waste (Classmore » A) and offers attractive design and economics features. Recycling reduces the target waste stream by a factor of 10 or more but introduces additional issues. It may produce high-level waste, requires remote handling, adds radioactive storage facilities, and increases the cost and complexity of the plant. The inventory analysis indicated that the heavy-ion-beam (HIB) target materials represent a very small waste stream compared to that of the nuclear island (

The ARIES-IFE study was an integrated study of inertial fusion energy (IFE) chambers and chamber interfaces with the driver and target systems. Detailed analysis of various subsystems was performed parametrically to uncover key physics/technology uncertainties and to identify constraints imposed by each subsystem. In this paper, these constraints (e.g., target injection and tracking, thermal response of the first wall, and driver propagation and focusing) were combined to understand the trade-offs, to develop operational windows for chamber concepts, and to identify high-leverage research and development directions for IFE research. Some conclusions drawn in this paper are (a) the detailed characterization of the target yield and spectrum has a major impact on the chamber; (b) it is prudent to use a thin armor instead of a monolithic first wall for dry-wall concepts; (c) for dry-wall concepts with direct-drive targets, the most stringent constraint is imposed by target survival during the injection process; (d) for relatively low yield targets (

ARIES-AT is a 1000 MWe conceptual fusion power plant design with a very low projected cost of electricity. The design contains many innovative features to improve both the physics and engineering performance of the system. From the safety and environmental perspective, there is greater depth to the overall analysis than in past ARIES studies. For ARIES-AT, the overall spectrum of off-normal events to be examined has been broadened. They include conventional loss of coolant and loss of flow events, an ex-vessel loss of coolant, and in-vessel off-normal events that mobilize in-vessel inventories (e.g., tritium and tokamak dust) and bypass primary confinement such as a loss of vacuum and an in-vessel loss of coolant with bypass. This broader examination of accidents improves the robustness of the design from the safety perspective and gives additional confidence that the facility can meet the no-evacuation requirement under average weather conditions. We also provide a systematic assessment of the design to address key safety functions such as confinement, decay heat removal, and chemical energy control. In the area of waste management, both the volume of the component and its hazard are used to classify the waste. In comparison to previous ARIES designs, the overall waste volume is less because of the compact design.

The choice of target coating and hohlraum wall materials is among the most critical decisions to be made for inertial fusion energy (IFE) designs. Gold and gold/gadolinium have long been considered to be the coating and hohlraum wall materials of choice for direct drive (DD) and indirect drive (ID) targets, respectively, offering high target performance and low beam energy losses. More recently, a variety of other materials have been considered, including W, Pb, Pt, Pd, and Ag for the DD target coating and Au, W, Pb, Hg, Ta, Cs, and Hf for the hohlraum wall of the ID target. The choice of the coating/hohlraum material is a tradeoff between the target design elements such as safety, target physics, economics, etc. We identified the key safety issues and have investigated the neutron-induced irradiation effects of the candidate coating/hohlraum materials using the radiation chamber conditions of the ARIES-IFE dry wall concept. The safety requirements have specific impacts in terms of the coating/hohlraum materials choice.

A critical assessment of the feasibility of IFE chambers has been initiated. This work seeks to define design windows and explore in detail the tradeoffs for various chamber concepts. The work is p...