Edward A. Hoffman

A Fusion Transmutation of Waste Reactor

A design concept and the performance characteristics for a fusion transmutation of waste reactor (FTWR), a subcritical fast reactor driven by a tokamak fusion neutron source, are presented. The present design concept is based on nuclear, processing, and fusion technologies that either exist or are at an advanced stage of development and on the existing tokamak plasma physics database. An FTWR, operating with keff ≤ 0.95 at a thermal power output of ~3 GW and with a fusion neutron source operating at Qp = 1.5 to 2, could fission the transuranic content of ~100 metric tons of spent nuclear fuel per full-power year and would be self-sufficient in both electricity and tritium production. In equilibrium, a nuclear fleet consisting of light water reactors (LWRs) and FTWRs in the electrical power ratio of 3/1 would reduce by 99.4% the actinides discharged into the waste stream from the LWRs in a once-through fuel cycle that must be stored in high-level waste repositories.

Comparative Fuel Cycle Analysis of Critical and Subcritical Fast Reactor Transmutation Systems

Abstract Fuel cycle analyses are performed to evaluate the impacts of further transmutation of spent nuclear fuel on high-level and low-level waste mass flows into repositories, on the composition and toxicity of the high-level waste, on the capacity of high-level waste repositories, and on the proliferation resistance of the high-level waste. Storage intact of light water reactor (LWR) spent nuclear fuel, a single recycle in a LWR of the plutonium as mixed-oxide fuel, and the repeated recycle of the transuranics in critical and subcritical fast reactors are compared with the focus on the waste management performance of these systems. Other considerations such as cost and technological challenges were beyond the scope of this study. The overall conclusion of the studies is that repeated recycling of the transuranics from spent nuclear fuel would significantly increase the capacity of high-level waste repositories per unit of nuclear energy produced, significantly increase the nuclear energy production per unit mass of uranium ore mined, significantly reduce the radiotoxicity of the waste streams per unit of nuclear energy produced, and significantly enhance the proliferation resistance of the material stored in high-level waste repositories.

A Superconducting Tokamak Fusion Transmutation of Waste Reactor

We are developing a Fusion Transmutation of Waste Reactor (FTWR) concept—a subcritical, metal fuel, liquid metal cooled fast reactor driven by a tokamak DT fusion neutron source. An emphasis is placed on using nuclear, separation/processing and fusion technologies that either exist or are at an advanced state of development and on using plasma physics parameters that are supported by the existing database. We have previously discussed the general capabilities of DT tokamak neutron sources for driving transmutation reactors [1] and developed a design concept for a FTWR [2] based on normal conducting magnets. The concept has been further developed in papers dealing with nuclear design and safety [3] and with the evaluation of the potential impact on radioactive waste management [4]. The purpose of this paper is to examine how the FTWR design concept would change if superconducting magnets were used.

A fusion transmutation of waste reactor

Abstract A design concept and the performance characteristics for a fusion transmutation of waste reactor (FTWR)—a sub-critical fast reactor driven by a tokamak fusion neutron source—are presented. The present design concept is based on nuclear, processing and fusion technologies that either exist or are at an advanced stage of development and on the existing tokamak plasma physics database. A FTWR, operating with keff⩽0.95 at a thermal power output of about 3 GW and with a fusion neutron source operating at Qp=1.5–2, could fission the transuranic content of about a hundred metric tons of spent nuclear fuel per full-power-year and would be self-sufficient in both electricity and tritium production. In equilibrium, a nuclear fleet consisting of Light Water Reactors (LWRs) and FTWRs in the electrical power ratio of 3/1 would reduce the actinides discharged from the LWRs in a once-through fuel cycle by 99.4% in the waste stream that must be stored in high-level waste repositories.

Nuclear and fuel cycle analysis for a fusion transmutation of waste reactor

Two metal fuel sub-critical fast reactor concepts, cooled by PbLi and PbBi, respectively, for a fusion transmutation of waste reactor are introduced. Analyses of the nuclear-thermal stability and potential for a criticality event in these reactors are discussed. The results of equilibrium nuclear fuel cycle analyses of these reactors and the impact of transmutation on the characteristics of radioactive waste in repositories are discussed.

Radioactive waste disposal characteristics of candidate tokamak demonstration reactors

Results from the present physics, materials, and blanket research and development programs are combined with physics and engineering design constraints to characterize candidate tokamak demonstration plant (DEMO) designs. Blanket designs based on the principal structural materials, breeding materials, and coolants being developed for the DEMO were adapted from the literature. Neutron flux and activation calculations were performed, and several radioactive waste disposal indexes were evaluated for each design. Of the primary low-activation structural materials under development in the United States, it appears that vanadium and ferritic steel alloys and possibly silicon carbide could lead to DEMO designs that could satisfy realistic low-level waste (LLW) criteria, provided that impurities can be controlled within plausible limits. Allowable LLW concentrations are established for the limiting alloying and impurity elements. All breeding materials and neutron multipliers considered meet the LLW criterion. 34 refs., 9 figs., 5 tabs.

Radioactive waste produced by demonstration and commercial fusion reactors extrapolated from ITER and advanced databases

Abstract The radioactive wastes that would be produced in demonstration and commercial fusion reactors which could be extrapolated from the design database that will be provided by ITER and its supporting R&D and from a design database supplemented by advanced physics and advanced materials R&D programs are identified and characterized in terms of a number of possible criteria for near-surface burial. The results indicate that there is a possibility that all fusion wastes could satisfy a “low level” waste criterion for “near-surface” burial.

Economic Analysis of Complex Nuclear Fuel Cycles with NE-COST

Abstract The purpose of this work is to present a new methodology and the associated computational tools developed within the U.S. Department of Energy Fuel Cycle Options Campaign to quantify the economic performance of complex nuclear fuel cycles. The levelized electricity cost at the busbar is generally chosen to quantify and compare the economic performance of different base load—generating technologies, including nuclear; the levelized electricity cost is the cost that renders the risk-adjusted discounted net present value of the investment cash flow equal to zero. The work presented here is focused on the calculation of the levelized cost of electricity of fuel cycles at mass balance equilibrium, which is termed levelized cost of electricity at equilibrium (LCAE). To alleviate the computational issues associated with the calculation of the LCAE for complex fuel cycles, a novel approach has been developed. This approach has been termed the island approach because of its logical structure, in which a generic complex fuel cycle is subdivided into subsets of fuel cycle facilities called islands, each containing one and only one type of reactor or blanket and an arbitrary number of fuel cycle facilities. A nuclear economic software tool, NE-COST, written in the commercial programming software MATLAB©, has been developed to calculate the LCAE of complex fuel cycles with the island computational approach. NE-COST has also been developed with the capability to handle uncertainty: the input parameters (both unit costs and fuel cycle characteristics) can have uncertainty distributions associated with them, and the output can be computed in terms of probability density functions of the LCAE. In this paper, NE-COST will be used to quantify, as examples, the economic performance of (a) once-through systems of current light water reactors (LWRs), (b) continuous plutonium recycling in fast reactors (FRs) with drivers and blankets, and (c) recycling of plutonium bred in FRs into LWRs. For each fuel cycle, the contributions to the total LCAE of the main cost components will be identified.

Fuel Cycle System Analysis Implications of Sodium-Cooled Metal-Fueled Fast Reactor Transuranic Conversion Ratio

If advanced fuel cycles are to include a large number of fast reactors (FRs), what should be the transuranic (TRU) conversion ratio (CR)? The nuclear energy era started with the assumption that they should be breeder reactors (CR > 1), but the full range of possible CRs eventually received attention. For example, during the recent U.S. Global Nuclear Energy Partnership program, the proposal was burner reactors (CR < 1). Yet, more recently, Massachusetts Institute of Technology’s “Future of the Nuclear Fuel Cycle” proposed CR [approximately] 1. Meanwhile, the French company EDF remains focused on breeders. At least one of the reasons for the differences of approach is different fuel cycle objectives. To clarify matters, this paper analyzes the impact of TRU CR on many parameters relevant to fuel cycle systems and therefore spans a broad range of topic areas. The analyses are based on a FR physics parameter scan of TRU CR from 0 to [approximately]1.8 in a sodium-cooled metal-fueled FR (SMFR), in which the fuel from uranium-oxide-fueled light water reactors (LWRs) is recycled directly to FRs and FRs displace LWRs in the fleet. In this instance, the FRs are sodium cooled and metal fueled. Generally, it is assumed that all TRU elements are recycled, which maximizes uranium ore utilization for a given TRU CR and waste radiotoxicity reduction and is consistent with the assumption of used metal fuel separated by electrochemical means. In these analyses, the fuel burnup was constrained by imposing a neutron fluence limit to fuel cladding to the same constant value. This paper first presents static, time-independent measures of performance for the LWR [right arrow] FR fuel cycle, including mass, heat, gamma emission, radiotoxicity, and the two figures of merit for materials for weapon attractiveness developed by C. Bathke et al. No new fuel cycle will achieve a static equilibrium in the foreseeable future. Therefore, additional analyses are shown with dynamic, time-dependent measures of performance including uranium usage, TRU inventory, and radiotoxicity to evaluate the complex impacts of transition from the current uranium-fueled LWR system, and other more realistic impacts that may not be intuited from the time-independent steady-state conditions of the end-state fuel cycle. These analyses were performed using the Verifiable Fuel Cycle Simulation Model VISION. Compared with static calculations, dynamic results paint a different picture of option space and the urgency of starting a FR fleet. For example, in a static analysis, there is a sharp increase in uranium utilization as CR exceeds 1.0 (burner versus breeder). However, in dynamic analyses that examine uranium use over the next 1 to 2 centuries, behavior as CR crosses the 1.0 threshold is smooth, and other parameters such as the time required outside of reactors to recycle fuel become important. Overall, we find that there is no unambiguously superior value of TRU CR; preferences depend on the relative importance of different fuel cycle system objectives.