DIRECT CONVERSION OF NUCLEAR ENERGY TO ELECTRICITY
Mark A. Prelas
Nuclear Science and Engineering Institute E2433 Lafferre Hall, University of Missouri-Columbia, Columbia, MO 65211 USA
E-mal: PrelasM@missouri.edu
Mark A. Prelas
Professor Prelas has been involved in nuclear energy conversion research since 1975. He has published over 300 articles and has numerous books to his credit. Some, such as the Handbook of Industrial Diamond and Diamond Films (1997), are viewed as the most influential text in their respective fields. He holds 13 US and international patents and has 6 patents pending.
Early in his career he developed a keen interest in energy conversion. As part of his undergraduate thesis he worked on the design and development of underwater turbines for extracting energy from ocean currents. As a graduate student at the University of Illinois from 1975-79, Professor Prelas worked with Professor George H. Miley on nuclear pumped lasers which use radiation from nuclear processes as the energy source for driving a laser. Professor Prelas' pioneering work in the field of nuclear-pumped lasers led the discovery of an atomic carbon laser driven directly by ions from nuclear reactions.
In 1979, Professor Prelas joined the faculty at the University of Missouri-Columbia. His early years at Missouri, he received grants to study the direct production of hydrogen from nuclear reactions and published several influential papers. In 1981 he was awarded a Gas Research Institute (GRI) fellowship where he participated in an advisory group mapping out future research directions in the production of fuels from inorganic resources. As part of his work as a GRI fellow he focused on a concept which he had developed earlier in his career using a two step process in which nuclear reactions first produce photons efficiently using an excimer transition, then transport the photons to a transducer. He articulated three potential transducers. The first was to produce hydrogen through direct or indirect chemical processes. The second was to produce electricity using UV photovoltaic cells made with advanced materials. The third was to drive a laser with photolytic excitation. In 1981 he published the concept of a Nuclear Light Bulb, describing a new energy conversion method based on excimer fluorescence sources driven directly with ions and the conversion of the fluorescence to electricity by wide bandgap photovoltaic cells. During this time period he developed several reactor concepts for the nuclear light bulb including an aerosol core reactor which utilized aerosol particles to produce the nuclear reaction and a surrounding gas for producing a weak plasma and fluorescence.
In 1981 the McDonnell Douglas Foundation awarded Professor Prelas a one million dollar gift in support of a superconducting magnetic fusion center. Professor Prelas raised $1,000,000 in matching monies including a gift of $100,000 from Union Electric Corp., a gift of $100,000 from ARMCO, $500,000 from the National Science Foundation. Professor Prelas and his students, pursuing his interest in direct conversion of fusion energy, built a superconducting magnetic test facility and tested four solenoid superconducting coils (39 inches major diameter, 17 inch inner diameter with a peak field at center of 8 Tesla) for the purpose advancing Nuclear Light Bulb research in the area of fusion. Professor Prelas and his students then built a supporting experiment called the Missouri Magnetic Mirror Machine (with peak fields of 1.0 Tesla at center) to model the physics of electron ring production.
In 1984 Professor Prelas was among the first group of the National Science Foundation's Presidential Award winners.
He continued his work on light production from nuclear reactions through funding from the National Science Foundation and produced significant work in UV emissions from nuclear driven fluorescence sources, and continued his work on transducers for the nuclear light bulb for the production of hydrogen, the development of ultraviolet photovoltaic cells and on photolytic lasers. He received a patent on a remotely driven solid state laser with fluorescence generated by nuclear reactions.
He received department of energy funding to develop a laser system using a microwave driven excimer fluorescence source to drive solid state lasers. He was able to demonstrate high efficiency UV excimer sources driven by microwaves. His pioneering work on the development of excimer fluorescence sources continues to draw interest.
Лекция профессора Университета Миссури-Коламбия, доктора М. А. Преласа будет представлена во время торжественной церемонии награждения в Государственной Думе РФ 29 ноября 2008 г. в 1500.
Lecture of professor of the University of Missouri-Columbia, Dr. M. A. Prelas will be presented during rewarding ceremony in the RF State Duma November 29, 2008 at 1500.
In 1985, Professor Prelas initiated a research effort aimed at the development of diamond and aluminum nitride photovoltaic cells, the second part of his nuclear light bulb concept. He expanded the nuclear light bulb concept to use radioisotopes in advanced nuclear battery concepts. In 1989, DOE supported the development of diamond and aluminum nitride photovoltaic cells. Professor Prelas undertook the challenge of making n-type and p-type diamond and aluminum nitride as building blocks for a UV photovoltaic cell. In this program he, his post doctors, collaborators and students were able to solve some fundamental problems in doping wide band-gap materials. .J They developed several unique doping methods such as Field Enhanced Diffusion with Optical Activation (FEDOA) <t which was able to produce n-type diamond and p and n type aluminum nitride and contact diffusion which has been used for impurity addition to crystalline materials in particulate form. They utilized FEDOA to produce a diamond ! p-n junction in 1996. Wide band-gap materials have properties that are electronically favorable and have broader _ applications than UV photovoltaic cells. Diamond for example would make a transistor that is more than 30 times Jj faster than a silicon transistor; operate at higher temperatures and at higher radiation levels. Professor Prelas has £ been an important contributor to the development of wide band-gap materials for electronics, tooling, ±= electrochemistry, radiation resistant coatings, hydrogen storage, chemical sensors, biological sensors and energy g conversion. His work continues on all of these applications.
g In 1992, Professor Prelas was selected as a Senior Fulbright Fellow and was a visiting Professor at the
™ University of New South Wales, Australia. There he worked with Professor Heinrich Hora and developed several 0 patents on direct energy conversion, solid-state lasers and wide band-gap electronics.
In early 1990's, Professor Prelas and his colleagues began to look at diamond films for a variety of applications in fuel cell technology. Some of this initial work demonstrated that diamond was capable of storing enormous amounts of hydrogen. Additional work was focused on diamond as a suitable electrode material and a potential high temperature replacement material for the proton exchange membrane. This research received funding from Honda Corporation, Daimler Benz, Norton Diamond Film and Rhombic Corporation and continues to show promise.
A conceptual energy conversion technology, which converts the particulate radiation emitted from nuclear reactions (e. g., fission, fusion and radioisotope decay) to electrical energy without intermediate thermalization of the high-grade ion energy, is the topic of this paper. The potential efficiency for this process, alone, is 40 %, nuclear energy to electrical energy. And, if combined with high-temperature thermionic conversion the nuclear to electrical energy conversion efficiency can approach 45 % while the overall size of the system will remain small. The key to the process is to first convert the high-grade ion energy to photon energy, which can then be directly converted to electrical energy. This process is called Photon-Intermediate Direct Energy Conversion (PIDEC). PIDEC is usable with radioisotopes, ion-producing plasma (hot) fusion reactions, as well as fission. In addition to improved efficiency, the PIDEC process also promises advantages in volume, mass, and cost.
This paper will focus on applications using radioisotopes for the PIDEC process. The radioisotope can be introduced as a gas or a solid. Solid radioisotope can take the form of an aerosol (microspheres) or thin films with scale lengths significantly shorter than the range of the alpha or beta particles, dispersed in a fluorescer. In the first step of the process, the ion energy is transported to the fluorescer, and produces photons. Then, in the second step of the process, the photons are transported out of the flourescer to photovoltaic cells, which efficiently convert the photon energy to electricity. This mobile power concept is called the Radioisotope Energy Conversion System (RECS).
Even though there are many possible solid, liquid or gaseous fluorescers that can be used, this paper will focus on a particular gaseous fluorescer called excimers. Efficient production of excimer (non self-absorbing) photons by ions has been demonstrated. Photovoltaics using wide band-gap materials — such as SiC, C (diamond), and AlN — have band-gaps that are acceptable matches for the energy of the photons emitted by excimer fluorescers.
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, 1. Technical Discussion
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¥ Nuclear technology has been in search of a
| technologically/economically feasible method of ° converting the energy of nuclear reaction prod-& ucts directly into electricity for many years [1]. g NASA has successfully used thermionics with the ° Radioisotope Thermal Generator (RTG) systems 0 in a number of missions (e. g., Apollo-SNAP-27 generators, Voyager, and Cassini). The energy resulting from the de
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