George Lawrence

Nuclear energy generation and waste transmutation using an accelerator-driven intense thermal neutron source

We describe a new approach for commercial nuclear energy production without a long-term high-level waste stream and for transmutation of both fission product and higher actinide commercial nuclear waste using a thermal flux of accelerator-produced neutrons in the 1016 n/cm2s range. Continuous neutron fluxes at this intensity, which is approximately 100 times larger than is typically available in a large scale thermal reactor, appear practical, owing to recent advances in proton linear accelerator technology and to the spallation target-moderator design presented here. This large flux of thermal neutrons makes possible a waste inventory in the transmutation system which is smaller by about a factor of 100 than competing concepts. The accelerator allows the system to operate well below criticality so that the possibility for a criticality accident is eliminated. No control rods are required. The successful implementation of this new method for energy generation and waste transmutation would eliminate the need for nuclear waste storage on a geologic time scale. The production of nuclear energy from 232Th or 238U is used to illustrate the general principles of commercial nuclear energy, production without long-term high-level waste. There appears to be sufficient thorium to meet the worlds energy needs for many millenia.

The U.S. accelerator transmutation of waste program

Abstract A national project to develop a future capability to separate actinides and long-lived fission products from spent fuel, to transmute them, and to dispose off the remaining waste in optimal waste forms has begun in the United States. This project is based on the Accelerator-driven Transmutation of Waste (ATW) program developed during the 1990s at Los Alamos National Laboratory, and has its technological roots in several technologies that have been developed by the multi-mission laboratories of the U.S. Department of Energy (DOE). In the Fiscal Year 1999 Energy and Water Appropriation Act, the U.S. Congress directed the DOE to study ATW and by the end of FY99 to prepare a “roadmap” for developing this technology. DOE convened a steering committee, assembled four technical working groups consisting of members from many national laboratories, and consulted with several individual international and national experts. The finished product, “A Roadmap for Developing ATW Technology – A Report to Congress,” recommends a five-year,

Transmutation and energy production with high power accelerators

281 M, science-based, technical-risk-reduction program. This paper provides an overview of the U.S. Roadmap for developing ATW technology, the organization of the national ATW Project, the critical issues in subsystems and technological options, deployment scenarios, institutional challenges, and academic and international collaboration.

LASL High-Current Proton Storage Ring

Accelerator-driven transmutation offers attractive new solutions to complex nuclear problems. This paper outlines the basics of the technology, summarizes the key application areas, and discusses designs of and performance issues for the high-power proton accelerators that are required.

Disposition of Nuclear Waste Using Subcritical Accelerator-Driven Systems: Technology Choices and Implementation Scenarios

The Proton Storage Ring at LAMPF is a high-current accumulator designed to convert long 800-MeV linac pulses into very short high-intensity proton bunches ideally suited to driving a pulsed polyenergetic neutron source. The Ring, authorized for construction at

Los Alamos high‐power proton linac designs

19 million, will operate in a short-bunch high-frequency mode for fast neutron physics and a long-bunch low-frequency mode for thermal neutron-scattering programs. Unique features of the project include charge-changing injection with initial conversion from H− to H0, a high repetition rate fast-risetime extraction kicker, and high-frequency and first-harmonic bunching systems.

High-power proton linac for transmuting the long-lived fission products in nuclear waste

Los Alamos National Laboratory has led the development of accelerator-driven transmutation of waste (ATW) to provide an alternative technological solution to the disposition of nuclear waste. While ATW will not eliminate the need for a high-level waste repository, it offers a new technology option for altering the nature of nuclear waste and enhancing the capability of a repository. The basic concept of ATW focuses on reducing the time horizon for the radiological risk from hundreds of thousands of years to a few hundred years and on reducing the thermal loading. As such, ATW will greatly reduce the amount of transuranic elements that will be disposed of in a high-level waste repository. The goal of the ATW nuclear subsystem is to produce three orders of magnitude reduction in the long-term radiotoxicity of the waste sent to a repository, including losses through processing. If the goal is met, the radiotoxicity of ATW-treated waste after 300 yr would be less than that of untreated waste after 100 000 yr. These objectives can be achieved through the use of high neutron fluxes produced in accelerator-driven subcritical systems. While critical fission reactors can produce high neutron fluxes to destroy actinides and select fission products, the effectiveness of the destruction is limited by the criticality requirement. Furthermore, a substantial amount of excess reactivity would have to be supplied initially and compensated for by control poisons. To overcome these intrinsic limitations, we searched for solutions in subcritical systems freed from the criticality requirement by taking advantage of the recent breakthroughs in accelerator technology and the release of liquid lead/bismuth nuclear coolant technology from Russia. The effort led to the selection of an accelerator-driven subcritical system that results in the destruction of the actinides and fission products of concern as well as permitting easy operational control through the external control of the neutron source.

A High-Performance D-Lithium Neutron Source for Fusion Technology Testing: Accelerator Driver Design

Proton accelerators for driving transmutation applications have beam power requirements in the range 40 MW to 400 MW, which corresponds to energy and current performance requirements in the range 800 MeV to 1600 MeV, and 50 mA to 250 mA. Linear accelerator designs aimed at providing these performance levels have been studied at Los Alamos for the past few years. Appropiate accelerator architectures have been developed, using the existing technology base for water‐cooled‐copper linacs, and key technical issues have been identified and addressed.

A high-flux accelerator-based neutron source for fusion technology and materials testing

A high-power proton linac is being considered at Los Alamos as a driver for a high-flux spallation neutron source capable of transmuting the troublesome long-lived fission products in defense nuclear waste. The transmutation scheme under study provides a high flux (>10/sup 16//cm/sup 2/-s) of thermal neutrons which efficiently converts fission products to stable or short-lived isotopes. A transmuter based on a medium-energy proton linac generating 110 MW of beam power could burn accumulated /sup 99/Tc and /sup 129/I inventory at the US DOEs Hanford site within 30 years. Preliminary concepts for the accelerator are discussed.<<ETX>>

Reliability and availability considerations in the RF systems of ATW‐class accelerators

Recent advances in high-current linear accelerator technology have considerably increased the attractiveness of a deuterium-lithium high-energy neutron source for fusion materials and technology testing. This paper describes a new Los Alamos conceptual design for a deuteron accelerator aimed at meeting near-term flux requirements of an International Fusion Materials Irradiation Facility. The new neutron-source driver concept is based on the idea of multiple accelerator modules, with each module consisting of two 125-mA, 175-MHz radio-frequency quadrupoles funneling 3-MeV cw deuteron beams into a 35-MeV, 250-mA, 350-MHz drift-tube linac.