A.L. Aronson

Accelerator-driven subcritical target concept for transmutation of nuclear wastes

A means of transmuting key long-lived nuclear wastes, primarily the minor actinides (neptunium, americium, and curium) and iodine, using a hybrid proton accelerator and subcritical lattice, is proposed. By partitioning the components of the light water reactor (LWR) spent fuel and by transmuting key elements, such as the plutonium, the minor actinides, and a few of the long-lived fission products, some of the most significant challenges in building a waste repository can be substantially reduced. The proposed machine, based on the described PHOENIX Concept, would transmute the minor actinides and the iodine produced by 75 LWRs and would generate usable electricity (beyond that required to run the large accelerator) of 850 MW (electric).

Thorium fuel cycles with externally driven systems

Abstract Externally driven subcritical systems are closely associated with thorium, partially because thorium has no naturally occurring fissile isotopes. Both accelerator-driven systems (ADSs) and fusion-driven systems have been proposed. This paper highlights key literature related to the use of thorium in externally driven systems (EDSs) and builds upon this foundation to identify potential roles for EDSs in thorium fuel cycles. In fuel cycles with natural thorium feed and no enrichment, the potential roles are (1) a once-through breed-and-burn fuel cycle and (2) a fissile breeder (mainly 233U) to support a fleet of critical reactors. If enriched uranium is used in the fuel cycle in addition to thorium, EDSs may be used to burn transuranic material. These fuel cycles were evaluated in the recently completed U.S. Department of Energy Evaluation and Screening of nuclear fuel cycle options relative to the current once-through commercial nuclear fuel cycle in the United States. The evaluation was performed with respect to nine specified high-level criteria, such as waste management and resource utilization. Each of these fuel cycles presents significant potential benefits per unit energy generation compared to the present once-through uranium fuel cycle. A parametric study indicates that fusion-fission–hybrid systems perform better than ADSs in some missions due to a higher neutron source relative to the energy required to produce it. However, both potential externally driven technology choices face significant development and deployment challenges. In addition, there are significant challenges associated with the use of thorium fuel and with the transition from a uranium-based fuel cycle to a thorium-based fuel cycle.

Intercomparison of results for a PWR rod ejection accident

This study is part of an overall program to understand the uncertainty in best-estimate calculations of the local fuel enthalpy during the rod ejection accident. Local fuel enthalpy is used as the acceptance criterion for this design-basis event and can also be used to estimate fuel damage for the purpose of determining radiological consequences. The study used results from neutron kinetics models in PARCS, BARS, and CRONOS2, codes developed in the United States, the Russian Federation, and France, respectively. Since BARS uses a heterogeneous representation of the fuel assembly as opposed to the homogeneous representations in PARCS and CRONOS, the effect of the intercomparison was primarily to compare different intra-assembly models. Quantitative comparisons for core power, reactivity, assembly fuel enthalpy and pin power were carried out. In general, the agreement between methods was very good, providing additional confidence in the codes and providing a starting point for a quantitative assessment of the uncertainty in calculated fuel enthalpy using best-estimate methods.

The PHOENIX Concept

A proposed means of transmuting key long-lived radioactive isotopes, primarily the so-called minor actinides (Np, Am, Cm), using a hybrid proton-accelerator-sub-critical lattice, is described. It is argued that by partitioning the components of the light water reactor (LWR) spent fuel and by transmuting key elements, such as the plutonium, the minor actinides, and a few of the long-lived fission products, that some of the most significant challenges in building a waste repository can be substantially reduced. If spent fuel partitioning and transmutation were fully implemented, the time required to reduce the waste stream toxicity below that of uranium ore would be reduced from more than 10,000 years to approximately 30 years. The proposed machine, based on the described PHOENIX Concept, would transmute the minor actinides and much of the iodine produced by 75 LWRs, and would generate usable electricity (beyond that required to run the large accelerator) of 850 MW{sub e}. 14 refs., 29 figs.

Incineration of Radioactive Fission Products and Transuranics by Muon-Catalyzed Fusion

A system of nuclear transmutation is presented in which fission products and transuranics (TRU) are incinerated using 14-MeV neutrons produced by muon-catalyzed fusion ([mu]CF) and a subcritical core composed of fission products and TRU. The 14-MeV neutrons produced by [mu]CF are used to transmute [sup 90]Sr (fission product) by the (n,2n) reaction. The outcoming neutrons from the [sup 90]Sr cell transmute TRU through fission reactions and [sup 99]Tc through (n,[gamma]) reactions. This fission energy is converted into electric energy to supply 4 GeV-25 mA deuteron beam power, which is used to produce [mu][sup [minus]] mesons. The authors also evaluate the production of tritium that is consumed as a fuel for [mu]CF. The feasibility of the system was analyzed by the MCNP Monte Carlo neutron transport code. The results show that this system can be subcritical and can transmute fission products and TRU with an incineration half-life of [approximately]1 yr and that the deuteron beam energy and tritium fuel required to operate the system can be supplied within the system cycle itself. 16 refs., 7 figs., 3 tabs.

A summary of an inter-directorate C-AD/NSTD Accelerator Driven Subcritical Reactor collaboration

A summary of the activities and of the scientific production o f the “NSTD/C-AD ADS-Reactor Think-Tank” collaboration, o ver the period May 2013 May 2015. Tech. Note NSTD and C-A/AP/568 Brookhaven National Laboratory

Evaluations of 1990 PRISM design revisions

Analyses of the 1990 version of the PRISM Advanced Liquid Metal Reactor (ALMR) design are presented and discussed. Most of the calculations were performed using BNL computer codes, particularly SSC and MINET. In many cases, independent BNL calculations were compared against analyses presented by General Electric when they submitted the PRISM design revisions for evaluation by the Nuclear Regulatory Commission (NRC). The current PRISM design utilizes the metallic fuel developed by Argonne National Laboratory (ANL) which facilitates the passive/``inherent`` shutdown mechanism that acts to shut down reactor power production whenever the system overheats. There are a few vulnerabilities in the passive shutdown, with the most worrisome being the positive feedback from sodium density decreases or sodium voiding. Various postulated unscrammed events were examined by GE and/or BNL, and much of the analysis discussed in this report is focused on this category of events. For the most part, the BNL evaluations confirm the information submitted by General Electric. The principal areas of concern are related to the performance of the ternary metal fuel, and may be resolved as ANL continues with its fuel development and testing program.

HTGR (High Temperature Gas-Cooled Reactor) ingress analysis using MINET

Modeling of water/steam ingress into the primary (helium) cooling circuit of a High Temperature Gas-Cooled Reactor (HTGR) is described. This modeling was implemented in the MINET Code, which is a program for analyzing transients in intricate fluid flow and heat transfer networks. Results from the simulation of a water ingress event postulated for the Modular HTGR are discussed. 27 refs., 6 figs., 6 tabs.