By: Tom Tamarkin
December 14, 2014
Abstract
Fusion is the ultimate source of energy for human civilization in all sense of the word. Because fusion transforms mass directly to energy according to Einstein’s theory of special relativity (E=MC²,) a very small amount of fusion fuel creates a very large amount of energy. The cost of fusion fuel (Hydrogen-deuterium and Lithium) per mWh of energy is so close to zero that virtually all the cost of electricity generated from fusion arises from the capital cost of the power plant and its amortization of development, operating and maintenance costs. The profit potential of fusion power is immense. Fusion can be used to create synthetic liquid and gas fuels for the transportation industry, thereby replacing petroleum and natural gas, as well as virtually unlimited electricity. Direct fusion propulsion has long been considered by NASA for the next generation of manned spacecraft for long distance space exploration. Fusion power is environmentally clean, emits no greenhouse gases, and produces no appreciable radioactive waste. The planet’s fossil fuel reserves are severely limited. Whereas current nuclear fission fuel resources such as Uranium and Thorium still remain abundant, nuclear power has safety, radioactive waste, and weapon proliferation issues. Fusion power is the only known hope for mankind’s survival on this planet in the foreseeable future.
In this paper, we describe fusion power and its ability to provide all the energy the world can consume for eternity. Next we summarize the status, politics, and legacy of the United States government funded fusion research program and provide a historical perspective of the development of alternate fusion approaches. Then we explain how fusion energy can be developed by private entrepreneurial enterprises using the innovative approach of Plasma Jet Magneto-Inertial Fusion (PJMIF.)
Table of Contents
1. Background
2. The Government Funded Fusion Program
3. The Truth about the Cost of Fusion Development and the Fusion Alternates
1. Background
1.1. What is fusion?
Fusion is the process that powers the Sun and the stars. It is Nature’s way of creating energy and is the opposite of nuclear fission, the process by which nuclear power is produced today. In fusion, the atomic nuclei of two light atoms fuse to form heavier nuclei. In the process, a large amount of energy is produced due to the conversion of mass directly to energy according to Einstein’s principle of special relativity expressed as E=MC². For commercial production of fusion energy, the fusion reactions considered usually involve the two isotopes of Hydrogen, namely 2H or deuterium (D) and 3H or tritium (T). Deuterium exists naturally in sea water which is a plentiful source of the isotope. It is non-radioactive. Tritium is radioactive, but has a very short half-life of approximately 12 years, and thus is very rare in nature. When deuterium and tritium are chosen as the fuel for a fusion power reactor, tritium is produced as part of a carefully designed fuel cycle involving the very common element Lithium, while deuterium is “mined” from the sea. The nucleus of a deuterium atom contains a proton and a neutron, whereas the nucleus of a tritium contains one proton and two neutrons. When a deuterium nucleus fuses with a tritium nucleus, a Helium nucleus is formed with the release of one neutron. Both the Helium nucleus and the neutron carry the energy produced by the fusion reaction. When one gram of deuterium completely fuses with one and a half grams of tritium, 235,852 kilowatt-hours of energy is produced. At a price of 10 cents per kW-hr, this energy is potentially worth $23,585, less reactor costs. Learn more about fusion from this simple video.
In order to produce fusion reactions, a deuterium-tritium (D-T) mixture is usually heated to a temperature well above 100 million degrees Centigrade in order for the fusion reactions to occur at a significant rate. At such temperatures, the orbiting electrons about the nuclei of the atoms of the D-T mixture are liberated from the electrical attraction of the nuclei which then become positively charged ions, and the mixture of electrons and ions is called a plasma. When a magnetic field is applied to the plasma, the charged particles in the plasma gyrate in circles about the magnetic field lines, preventing their loss from the magnetic field. Thus, in principle, a magnetic field can be used to confine a plasma at very high temperatures keeping them away from any material wall. This is the basic principle of one approach to fusion energy and is called magnetic confinement fusion (MCF). However, in practice, the plasma particles collide and may drift across the field lines and get lost from the magnetic field over a sufficiently long time interval, breaking the magnetic confinement of the plasma.
Another approach to “confining” a hot plasma is to make use of the fact that no matter how hot a gas is, it takes time for the gas to expand and cool because of its own inertia (mass). This is the basic principle of another approach to fusion energy called inertial confinement fusion (ICF). In this approach, a D-T mixture is compressed by some means such as a blast of high power laser beams, which is called the driver, to fusion temperatures and to a very small volume; usually no larger than 0.1 mm in radius, located at some distance from the chamber wall. The fusion reactions occur in this very tiny but very dense ball of plasma for less than a nanosecond. The plasma ball expands and cools and the fusion reactions cease. The process is then repeated like an internal combustion engine in order to produce a continuous stream of energy pulses equivalent to an average continuous power.
The difference between nuclear fusion and conventional nuclear fission is that nuclear fission is accompanied by large amounts of radioactive waste products that have long half-lives (tens of thousands of years), whereas fusion proper produces no radioactive waste products. However, it is anticipated that the very early fusion DT reactors will produce some indirect radioactive products with half-lives of only a few years. Thus, commercial fusion power when realized will not give rise to a nuclear waste problem. Furthermore, in order to maintain the fusion reactions in a reactor, input power is required. In the event of an accident causing malfunction, the input power will be lost and the fusion reactions stop in the reactor. In this sense, a commercial fusion power reactor is fail-safe because it does not have a run-away core melt-down problem as might occur in a commercial fission reactor during an accident or reactor malfunction. And, in fact, fusion is an ideal means to destroy 60 years of accumulated radioactive waste created by over 400 fission power plants worldwide.
In summary, fusion is safe, clean, the fuel cost is near zero and there is enough of it to last the human civilization for millions of years. It is Nature’s own way of producing energy in the Sun and in the stars. We know absolutely for a fact that it works because it has been produced by humans in thermonuclear weapons. What remains to be done is to engineer a solution to generate fusion energy in a commercial power plant at a sufficiently low operating cost in order to produce electricity, as well as liquid synthetic fuels for aircraft and the like, at a lower cost than what is available today. In this white paper, we propose a path to commercial fusion power based on a proprietary fusion concept with a corollary project plan to develop and commercialize the technology.
1.2 The need for fusion:
If all peoples of the world are to live comfortable lives and have the ability to prosper, we must increase total worldwide annual energy production by a factor greater than 5 times current production. That is not possible and if it were it would deplete fossil fuel reserves by the 2050-2060 time frame. “Alternative green and renewable” energy sources can supply less than 4% of projected 2050 total energy requirements. There is only one way to produce this amount of energy to support mankind. That is the conversion of mass into energy through the process of controlled fusion.
The fundamental ingredient required to support mankind is energy. If other nations are to enjoy a decent standard of living, they will require energy resources in amounts approaching those consumed in the United States and west in ratio to their populations. Today the population of the United States is approximately 304,000,000 or 4.4% of the world population, yet the United States consumes 28% of world energy use. Thus, it can be seen that to support our current world population at a standard of living morally acceptable, we would have to increase world energy production by well over 5 times.
Given the fact that energy production from fossil fuels has by most estimates peaked in terms of capacity, and liquid fossil fuels will be depleted within 50 years if developing nations are allowed to become industrialized nations; therefor is only one known and realistic source. That is the direct conversion of mass into energy based on Albert Einstein’s law of special relativity and the equivalency of mass and energy represented by the formula E=MC². This law teaches us that a very small amount of matter, say one gram, has the energy equivalent of a very large amount of energy when converted.
2. The Government Funded Fusion Program and the perception that Fusion Development is necessarily a multi-billion-dollar and multi-decade R&D effort
Fusion research has been funded by the United States Government for over 40 years at a total cost in excess of $23 billion dollars. It must be noted that over half of this has been spent in various military programs most recently managed by the NNSA (National Nuclear Safety Administration) under its nuclear weapons stockpile stewardship mandate. The Government funded fusion research has down-selected to two extreme approaches (tokomak-magnetic confinement and laser inertial confinement fusion) very early on, which have proven to have extremely high R&D costs for each incremental step of progress. The official government position today is that it will take another 50 years and approximately $50B more in funding before either of the two approaches could be commercialized. Legend has it that there are more problems in attaining controlled nuclear fusion than scientists anticipated, and that little progress has been made. “Fusion is still fifty years away, and always has been” has become the common refrain of skeptics. But the reason that we do not have commercially available fusion energy is not what is commonly believed.
As a legacy of the government funded fusion research, there is a perception within and without the fusion community that fusion R&D is necessarily a multi-tens-of-billion-dollar and multi-decades R&D program and is thus not suitable for development by the private sector at present. It is a perception that is fostered by the establishment fusion research community (tokomak MCF and laser ICF). It is an argument used by the United States Department of Energy Office of Fusion Energy Sciences (OFES) to justify its long-held policy of early down-select and focusing on the tokomak approach as the path for fusion energy[1]. The argument used by OFES is that there will never be enough Federal resources for developing more than one approach to fusion.
There is also the concern that if the U.S. government is exploring alternative approaches to fusion, it might give rise to a public perception that the scientific foundation for the two mainline approaches of magnetic confinement and inertial confinement, is not sufficiently developed, and thus weaken the argument for continuing the commitment to the multi-billion-dollar investment in the two mainline approaches. Furthermore, since the U.S. has been seen by the rest of the world to be a leader in fusion energy sciences, exploring alternative fusion approaches by the U.S. government might send the “wrong signals” to its international partners in the $20B-plus international ITER project.
Inertial confinement fusion (ICF) research, funded mostly by the National Nuclear Security Administration (NNSA,) has been justified, not for energy application, but for the purpose of scientific nuclear stockpile stewardship in the absence of nuclear weapon testing. Laser ICF is tolerated by the U.S. Department of Energy OFES as a “back-up” (a measure of risk mitigation) to tokomak MCF for fusion energy, because the resources for its development is available from NNSA, and thus the OFES policy of “a focused approach to fusion” (tokomak magnetic confinement) remains whole even though laser ICF is officially pursued by a branch of the U.S. government.
Another result of the long history of fusion research is the perpetuation of another incomplete truth that the government funded research has practically exhausted all possible alternate fusion approaches and has shown that the alternate approaches do not work. In the next section, we will attempt to put the history of the research in alternative fusion approaches in proper perspective and throw some light on the incomplete truth.
3. The Truth about the Cost of Fusion Development and the Fusion Alternates
Recognizing that the facility cost was a large component of the R&D cost which was the principal impediment to the progress of fusion development at the time, around the mid-1990’s, Drs. Irv Lindemuth, Richard Siemon and Kurt Schoenberg of Los Alamos National Laboratory began to examine the cost of developing various fusion concepts in a fundamental way. The fusion parameter space is spanned by two basic plasma parameters, namely the plasma density and the magnetic field embedded in the plasma, which govern the physics of attaining fusion burn. The tokomak attempts to burn a plasma at a density of 1020 ions per m3 in a magnetic field of several teslas (T), while laser ICF attempts to burn a plasma at a density of 1032 ions per m3. In conventional ICF, no external magnetic field is applied to the target, but laser-plasma interaction can self-generate magnetic fields up to about 100 T. Essentially, these two mainline approaches sit at two extreme isolated spots in the fusion parameter space.
The results of the Lindemuth, et al, analysis were presented in various papers, workshops and conferences, since the mid-1990’s and recently collected and published in their paper of 2009 [3]. The principal results of their analysis are:
(ii) For magnetically confined plasma, the amount of plasma energy required to produce fusion ignition is approximately inversely proportional to the square root of the plasma density.
(iii) For fusion approaches that use compression to heat the plasma, the power density of the compression required is proportional to the fuel density and the velocity of implosion.
(iv) The net results of the analysis for the cost of a breakeven fusion facility as a function of the fuel ion density and temperature is shown in Figure 3, which correctly explains the costs of ITER and NIF. ITER corresponds to a point in Figure 3 for a density of 1014 ions per cc and temperature of 104 eV (108 degrees K.) NIF corresponds to a point of 1025 ions per cc and the same temperature.
(v) There appears to be a sweet spot where the burning plasma density is in the range 1019 to 1022 ions per cc. In this sweet spot, the stunning result of their analysis is that fusion approach exists for which breakeven fusion facility might very well cost as low as $51M! (A typical nuclear fission power plant costs in excess of $5.5 billion 2008 USD.)
The tokomak makes use of a fuel density in the range of 1014 ions per cc. In order to ignite the plasma in the tokomak at this low density, at least 2 to 3 Giga Joules of thermal energy must be confined in the plasma by the applied magnetic field. This explains why ITER should cost at least $10B.
Laser ICF attempts to create a plasma with a density in the range of 1025 ions per cc resulting in a pressure of 1017 Pa at ignition. At the same time, because it does not use a magnetic field to suppress heat conduction in the plasma, it is necessary to implode the fusion fuel at a very high velocity of at least 300 km/s for the heating power to outrun the electron thermal conduction losses from the hot spot. The result is that extremely high heating power density in excess of 1018 W cm-2 is required. Very advanced, short-pulse, high-energy lasers are required. This explains why the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory costs about $4B. The plasma densities in tokomak and laser ICF differs by as much as eleven orders of magnitude and represent the two extremes in the fusion parameter space.
During the early years of research in controlled thermonuclear fusion, energy confinement and the efficient heating of the plasma are identified as the two main technical challenges for the attainment of controlled thermonuclear fusion energy. The research in alternative fusion approaches during the 50’s, 60’s and 70’s thus sought in an ad hoc manner various “clever” ways of improving the energy confinement, and/or the heating of the plasma, and many concepts were explored. Generally the search for better confinement or more efficient methods of heating were not very successful, and led to the conclusion that it was very difficult to achieve better energy confinement and heating efficiency than the tokomak configuration. The remaining alternates in this old era (pre-1995 approx.) sought to overcome the engineering problems of the tokomak approach (e.g., disruption, heat extraction, steady-state operation, linked magnetic coils and non-inductive heating, etc.). All the alternates in this pre-1995 era generally aim for a similar spot in the large fusion parameter space as the tokomak or the laser ICF. The alternates in this old era includes stellarator, tandem mirrors, the Astron system, z-pinch, impact fusion, theta pinch, reversed field pinch, field reversed configuration (FRC), spheromak, Polywell, IEC, dense plasma focus, etc.
Another important facet of the history of fusion R&D is that there was a general aversion towards any pulsed fusion approach in the early days of fusion energy research in favor of steady-state approaches. This is mainly because of the nascent nature of the electromagnetic pulsed power technologies in those days and the concern for the high cost of the fabrication of the targets for each pulse. Thus fusion concepts that made use of electromagnetic pulsed power as the driver were seldom taken seriously by OFES (or its predecessor) and thus were never funded at any significant level.
By the early 1990’s, the state of electromagnetic pulsed power technologies had changed dramatically for the better, thanks to a decade or two of defense and SDI related development of the technology. Low-cost, long-lifetime, repetitive pulsed power storage (capacitors,) switching and transmission technologies became conceivable. A small minority of scientists, mainly from the defense and nuclear weapon establishments, began to see the potential for pulsed power to make a contribution to the quest for practical fusion energy.
Intellectually, the exploration of alternate fusion approaches experienced a paradigm shift in the 1990’s. The mid-1990’s represent the watershed in the research of alternate fusion concepts.
The fundamental feature that distinguishes the alternates in the modern era (post-1995 approx.) from those in the old era (pre-1995 approx.) is that modern alternates seek to find the “sweet spot” in the fusion parameter space, taking advantage wherever possible of the plasma physics we have learned to-date. The modern alternates include the various embodiments of magneto-inertial fusion (MIF) which aim for the intermediate parameter space between magnetic and inertial fusion, mirror-based gas dynamic trap, centrifugal confinement, flow-stabilized z-pinch, various embodiments of helicity injection, levitated dipoles, etc.
It is in this sweet spot of the fusion parameter space that our proposed fusion approach PJMIF sits. Because a lower implosion velocity is planned, a magnetic field is required to suppress the heat loss during the compression. Because it uses a magnetic field as well as plasma implosion, it is essentially a hybrid of MCF and ICF, and is an approach in the class of fusion approaches called magneto-inertial fusion (MIF) or magnetized target fusion (MTF)[4, 5].
Though there were sporadic MIF-related efforts before the 1990’s, significant research effort to develop the scientific knowledge base of MIF or MTF did not begin until the mid and late 1990’s. An issue central to all plasma implosion schemes is the Rayleigh-Taylor (RT) instability. By the early 1990’s, after decades of defense-funded work on the implosion of thin cylindrical metallic shells called solid liners, the science and technology of imploding these thin metallic shells have matured to the point that they are ready for application. The RT instabilities in these liners during the implosion are well characterized and their control is well in hand. Equally mature at the time was the science and technology of producing field reversed configuration (FRC) plasma as the magnetized target plasma to be imploded. The small, fledgling MIF community, led by the Los Alamos National Laboratory group, thus selected the solid-liner technology as the implosion scheme combining with an FRC as the magnetized target to provide the first experimental “existence proof” of MIF[6] (Figure 4). In terms of seeking OFES funding support for the experiment, the choice of FRC has the added political advantage of making connection with the broader magnetic confinement scientific program of OFES. The solid-liner experiment (FRCHX) has been funded by OFES over the last nine years with a cumulative funding total of about $20M.
The implosion of the liner is accomplished by passing megamperes (MA) of current through the liner, which is electrically connected to a set of electrodes and transmission plates. During each shot, a large amount (10s of kg) of electrode and transmission line materials are destroyed as well as the solid liner. Though reactor embodiment of the solid-liner MTF has been suggested in the past, the main criticisms of the approach by critics of the solid-liner MTF are:
b) The cost of the recycling of the destroyed hardware after each shot.
c) The clearance of solid material debris from the reactor chamber after each shot.
References
[1] S. C. Hsu, T. J. Awe, S. Brockington, A. Case, J. T. Cassibry, G. Kagan, S. J. Messer, M. Stanic, X. Tang, D. R. Welch, and F. D. Withespoon, “Spercially Imploding Plasma Liners as a Standoff Driver for Magneto-Inertial Fusion,” IEEE Trans. Plasma Science.
[2] Tony Feder, “US narrows fusion research focus, joins German stellarator,” Physcis Today, p. 30, September, 2011.
[3] I. R. Lindemuth and R. E. Siemon, “The fundamental parameter space of controlled thermonuclear fusion,” Amer. J. Phys., vol. 77, p. 407, 2009.
[4] I. R. Lindemuth and R. C. Kirkpatrick, “Parameter space for magnetized fuel targets in inertial confinement fusion,” Nucl. Fusion, vol. 23, p. 263, 1983.
[5] R. C. Kirkpatrick, I. R. Lindemuth, and M. S. Ward, “Magnetized target fusion: An overview,” Fusion Tech., vol. 27, p. 201, 1995.
[6] T. Intrator et al., “A high density field reversed configuration (FRC) target for magnetized target fusion: first internal profile measurements of a high density FRC,” Phys. Plasmas, vol. 11, p. 2580, 2004.
Click here for “Development of Practical Fusion Power Plasma Jet Driven Magneto-Inertial Fusion”
The scientific and technical description is adapted from the following paper with permission, and is hereby acknowledged:
S. C. Hsu, T. J. Awe, S. Brockington, A. Case, J. T. Cassibry, G. Kagan, S. J. Messer, M. Stanic, X. Tang, D. R. Welch, and F. D. Witherspoon, “Spherically Imploding Plasma Liners as a Standoff Driver for Magneto-Inertial Fusion,” published in IEEE Trans. Plasma Sci. @ 2011