DIRECT ENERGY CONVERSION (DEC) FISSION REACTORS–A U.S. NERI PROJECT
- Dr. Denis E. Beller, Los Alamos National Laboratory
- Dr. Gary F. Polansky, Sandia National Laboratories
- Dr. Samim Anghaie, University of Florida
- Dr. Gottfried Besenbruch, General Atomics
- Dr. Theodore A. Parish, Texas A&M University
12th Pacific Basin Nuclear Conference (PBNC-2000), Seoul, Republic of Korea, Ott 29-Nov 2, 2000, co–
sponsored by the Korea Atomic Industrial Forum, Inc. (KAIF) and Korean Nuclear Society (KNS, an affiliate of the American Nuclear Society)
The direct conversion of the electrical energy of charged fission fragments was examined early in the nuclear reactor era, and the first theoretical treatment appeared in the literature in 1957. Most of the experiments conducted during the next ten years to investigate fission fragment direct energy conversion (DEC) were for understanding the nature and control of the charged particles. These experiments verified the fundamental physics and identiled a number of specific problem areas, but also demonstrated a number of technical challenges that limited DEC performance. Because DEC was insufficient for practical applications, by the late 1960s, most R&D ceased in the U.S.A.. Sporadic interest in the concept appears in the literature until this day, but there have been no recent programs to develop the technology. This has changed with the Nuclear Energy Research Initiative that was funded by the U.S. Congress in 1999.
Most of the previous concepts were based on a fission electric cell known as a triode, where a central cathode is coated with a thin layer of nuclear fuel. A fission fragment that leaves the cathode with high kinetic energy and a large positive charge is decelerated as it approaches the anode by a charge differential of several million volts, it then deposits its charge in the anode after its kinetic energy is exhausted. Large numbers of low energy electrons leave the cathode with each fission fiagmen~ they are suppressed by negatively biased on grid wires or by magnetic fields. Other concepts include magnetic collimators and quasi-direct magnetohydrodynamic generation (steady flow or pulsed).
We present the basic principles of DEC fission reactors, review the previous research, discuss problem areas in detail and identify technological developments of the last 30 years relevant to overcoming these obstacles. A prognosis for future development of direct energy conversion fission reactors will be presented.
From the earliest days of power reactor development, direct energy conversion was an obvious choice to produce high efficiency electric power generation. Directly capturing the energy of the fission fragments produced during nuclear fission avoids the intermediate conversion of thermal energy and the efficiency limitations of classical thermodynamics. Efficiencies of more than 80% are possible, independent of operating temperature. Direct energy conversion fission reactors could possess a number of unique characteristics that would make them very attractive for commercial power generation. These reactors could be modular in design with integrated power conversion and operate at low pressures and temperatures. They could operate at high efficiency and produce power well suited for long distance transmission. They could feature large safety margins and passively safe designs. Ideally suited to production by advanced manufacturing techniques, direct energy conversion fission reactors could be produced far more economically than conventional reactor designs.
The history of direct energy conversion can be considered as dating back to 1913 when MoseIeyl demonstrated that the charged particle emission could be used to build up a voltage. Soon after the successful operation of a nuclear reactor, E. P. Wigner suggested the use of fission fragments for direct energy conversion. More than a decade after Wigner’s suggestion, the fust theoretical treatment of the conversion of fission fragment kinetic energy into electrical potential appeared in the literature.2 During the ten years that followed, a number of researchers investigated various aspects of fission fragment direct energy conversion. Experiments were performed that validated the basic physics of the concept, but a variety of technical challenges limited the efficiencies that were achieved. Most research in direct energy conversion ceased in the United States in the late 1960s. Sporadic interest in the concept appears in the literature to this day, but there have been no recent significant programs to develop the technology. That remained true until the U.S. Congress passed new legislation to fired nuclear research and development the Department of Energy then initiated the Nuclear Energy Research Initiative (NERI), and researchers at Sandia National Laboratories and several other institutions became interested in once again pursuing this intriguing technology. We report herein the background for this NERI DEC project, recent progress, and Mm-e plans. Technical details of many of the concepts that are being examined in this project, including efficiency calculations, are reported in another recent paper.