Chapter 3 - The Energy Source - Nuclear Fusion Reactors

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57

CHAPTER 3

THE ENERGY SOURCE - NUCLEAR FUSIONRE ACTORS

''Research ca n continue the 20-year trend toward greater plasmaconfinement imes, densities and temperatures, leading to the

full set of ignition param eters by the mid-1990s."

Harold P. Furth,

Physics Today

March 1985, page 53

Potential future energy sources were discussed in Chapter 2. The Fusion Energ y source was shown to

possess the most desirable characteristics for the base load application. This chapter will address the

nature of the fusion reaction and the equipment used for the production of energy. There are several

types of reactors with promise. These will be described to provide insight into the type of reactor

potentially available as the basis for future energy systems.

THE FUSION REACTION

Energy is released by nuclear reactions between light atoms at temperatures of millions of degrees.

This process is called thermonuclear fusion because high temperatures cause light nuclei to fuse

together to produ ce heavier nuclei. For exam ple, in the center of stars four hydrogen atoms (atom icnumber 1) react to produce one atom of helium (atomic number 2). In the nuclear fusion process, the

weight of the hydrogen consum ed is more than the weight of the helium atoms produced. The ma ss

difference is converted to energ y. ^^

Therm onuclear fusion is the source of energy of most stars including the sun. At the center of the sun,

the high temp erature and pressure drive a num ber of thermo nuclear reactio ns. The majority of the

energy is produ ced by reactions of four hydrogen nu clei to form one helium n uclei. In this reaction,

0.711% of the mass of the four hydrogen atoms is converted into energy . This does not seem like a

large percentage change, but the energy equivalent of matter given by Einstein's E = mc^ is extremely

large. The conversion of one gram of hydrogen (a United States nickel weighs about 5 grams) to

helium produces as much energy as the combustion of 15 million grams of oil (112 barrels).

Based on the energy produced per liter, the conversion of hydrogen to helium at the center of the sun

proceeds at a relatively slow rate. The large energy produ ction of the sun is the result of the colossal

volum e of the core where hydrogen is converted to helium. In earth-based laboratories, using current

technology, it is impossible to produce the combination of temperature and pressure existing at the

core of the sun. Even if it were possible to produce solar conditions in an earth based reactor, the

energy output for a reasonable sized reactor would be small. If the solar conversion of hydrogen to

helium were the only fusion reaction known its use would be beyond current technology. Fortunately,

there are several other thermonuclear reactions with the potential for production of fusion energy on

Bromberg, J. L., "Fusion: Science, Politics and the Invention of a New Energy Source", MIT Press, Camb ridge, Massachusetts, 1982



58 An End To Global Warm ing

earth. These reactions use a variety of hydrogen (deu terium) that was consum ed in the core of the sun

in the first milUon years of its Ufe. Today it is only present as a trace constituent of the sun's outer

layers.

Hydrogen is unique among the elements because its isotopes (atoms of identical chemical properties

with different atomic weights) all have separate commo n nam es. The nam e hydrogen is appUed to the

mixture of isotopes found in nature. Hydrogen with an atomic weight of one is accurately called

protium . Hyd rogen with an atomic weight of two is called deuterium (or in the vemac ular "heavy

hydro gen"). Hydro gen with an atomic weight of three is called tritium. The hydrogen on earth is

comp osed of 99.985% protium and 0.015% deuterium. Tritium is unstable with a half-Hfe of 12.5

years and exists only in nearly undetectable quantities as a product of cosmic interactions with atoms

of other materials. The reactions of the heavy isotopes of hydrogen useful in producing energy are

defined in Table 3.1.''«

Most current research is probing the use and control of the D + T reaction because it requires the

lowest ignition energy (tem perature) and produces the highest ratio of energy return. The disadvantage

to this reaction lies in its production of neutrons that cause induced radioactivity in the structure of the

reactor. Other, more challenging, reactions may be used if the proposed developm ent shows that they

are feasible. The following discussion w ill concentrate on the D + T reaction because it can be used in

the near term.

Wa ter is about 11 % hydrog en. A metric ton of water (one cubic meter) contains 111 kilograms of

hydrogen . The hydrogen in water is 0.0157% deu terium, or 0.0174 kilogram s deuterium per metric

ton of water. At first glance, this looks like a small number, but remember a huge amount of energy is

produced by each gram of deuterium . When reacted with tritium the 0.0174 kilograms of deuterium

will produce 1.4 xlO^^ Joules of energy. This is equivalent to about 2500 barrels of oil.

When considered with regard to the amount of water available on earth it is sufficient to provide

energy for many thousand s of years. Mo reover, deuterium can be separated from the water by

electrolysis. Electrolysis is a simple, efficient process. The other fuel, tritium, is a slighdy radioactive,

electron emitting, isotope of hydrogen with a 12.5 year half-life. Tritium is produced from lithium by

reaction with neutrons.

The requirem ent for a successful fusion reactor is the production of the prop er conditions for the D + T

reaction to occur. The reaction rate must be fast enough to make up for the energy required to start and

maintain the reaction and provide net excess for use as the power output. To achieve a fusion reaction,

the nuclei of the atoms must be forced to collide with enough energy to react. This requires a

temperature of millions of degrees. There must be sufficient reactions in a volume to make up for theheat loss and provide net excess energy for use. The reaction must continu e long enough to be self-

sustaining. '^^' '^°

128

129

130

Fowler, T. K. and Post, Richard, "Progress Toward Fusion Pow er", Scientific American, Vol. 215, No . 6, December 1966, Page 23

Chen, Francis F., "The Leakage Problem in Fusion Reactors", Scientific American, Vol. 217, N o. 1, July 1967, Page 76

Gough, William C. and Eastlund, Bernard J., "The Prospect of Fusion Power", Scientific American, Vol. 224, No. 2, February 1971 ,

Page 50



The Energy Source - Nuclear Fusion Reactors 59

Nuclear fusion reaction -- Symbol definition

DT

He^

He^

Pn

B

keV

RATIO

= Deuterium (hydrogen isotope weight 2)= Tritium (hydrogen isotope weight 3)

= Helium isotope, weight 3;

= Helium isotope, weight 4;

= proton

= neutron

= Boron isotope, weight 11

= energy in units of 1000 electron volts per particle

= energy produced/particle divided by the energy required to start the reaction

Reaction

1 D^ + T^

D^ + D^

D^ + D^

D + He'

1 P' + B^

Products

He^ + nHe + nT' + p

He + p

3He'

YIELD

KeV

17,600

3,300

4,000

18,300

8,700

TEMP.

KeV

10

50

50

100

300

RATIO (Y/T)

1760 166

80183

29 1

Table 3.1 Nuclear Fusion Reactions

At ordinary temperatures, the electrons surrounding the nucleus of the atom serve as a buffer and

prevent the nuclei from colliding and reacting. As the temperatu re increases collisions becom e moreviolent and ultimately the electrons are stripped from the atoms leaving bare nuclei. This mixture of

bare positively charged nuclei and negatively charged electrons is called plasma.

In plasma, the positive charged nuclei are strongly repelled from each other by electrostatic forces. At

low temperatures, the repulsion prevents any nuclear reactions. At higher temp eratures, the nuclei

mo ve faster and begin to overcom e the repulsive forces. Wh en the temp erature approaches 100

million Kelvin (at this temperature the average kinetic energy of the particles is about 10 KeV) the

velocity of the nuclei are high enough to overcom e the inter-nuclear electrostatic repulsion. At this,

and higher temperatures, they can react when they collide. Sufficient rea ctions occur, as outUned in

Table 3.1, (above) to keep the mixture hot and provide enough excess energy for external power

generation.

The num ber of positive and negative charges in the plasma is equal. The overall plasm a has no charge

and is termed neutral plasma. The plasma exerts a pressure in the same mann er as any confined ga s.

Unlike most gas, the large number of electrically charged particles present in the plasma makes it an

exceedingly good conducto r of electricity. The high conductivity allows intense electric currents to

flow through the plasma . The electric currents generate strong magn etic fields. The currents and

magnetic fields provide a handle by which the plasma can be manipulated and confined.

To achieve a thermonuclear reaction it is necessary to heat the plasma to the 100 million Kelvin

ignition temperature and contain it for sufficient time that more energy is produced than was used in



60 An End To Global Warming

the heating process. Heatin g, controlling, and maintaining this plasma is the central challenge in the

production of fusion energy.

To produce a fusion reaction the critical factors are the plasma confinement time, the ion density andthe temperature. Wh en a reactor achieves a product of these three variables greater than 10^ , the

reactor is a net producer of energy. ^* These factors can be traded against each other in the design of a

reactor. If the confinement time is long, the temperature and density can be low. If the confinement is

short, the temperature and ion density must be high. There are some practical limitations in this

relationship . If the ion density is low, even with a long confinement time at high temperature, the

reaction may produce net power, but at such a low rate per reactor volume that the reactor would be

too large for use. The various reactor schem es strive to produce a combination of temp erature, density

and confinement time that will result in a practical reactor design.

MAGNETIC CONFINEMENT REACTORS

The electrical conductivity of plasma allows it to be shaped and controlled by magnetic fields. At

reactor start-up the D and T are heated to a temperature hot enough to strip the electrons from the

atoms and create plasma. A temp erature of only 0.015 keV is all that is required to create plasma. This

relatively low temp erature can be produced by simple high voltage discharges. The low temperature

plasma of D and T is captured and held in position by strong magnetic fields. To start the

thermonuclear reaction the D-T plasma is heated by external sources until a temperature equivalent to

10 keV is achieved. At this temperature, and above, with long confinement tim es and adequate

density, the fusion reaction becomes self-sustaining.

The p roduct of the D + T reaction is a helium nucleus, He" , or alpha pa rticle, and a neutron (n). The

average kinetic energy of th e He" is 3,500 keV and the n, 14,100 ke V. The He" has a positive chargeof two. This charge forces it to strongly interact with the plasma. This interaction adds energy to the

plasma. Some helium ions produced by the reaction are lost from the plasma into the surrounding

vacuum and others lose energy by contact with the walls of the reactor. If the losses are not too great,

the interaction of the He" ions with the plasma can provide sufficient energy to keep the plasm a at the

fusion tem perature. The neutron has no charge and passes through the plasma with only shght

interaction. The occasional interactions of the neutrons add a small but valuable bit of heat to the

plasma.

After leaving the plasma, the neutrons interact with the reactor inner wall or the cooUng materials

behind it. The inner wall and the coolant are termed the blanket. When the neutrons react with the

blanket, their energy is deposited as heat. The resulting heat is used in conventional steam generation

to provide process heat for the generation of electricity.

Molten lithium metal is a potential candidate for the coolant to be circulated through the blanket.

Lithium is a light metal with a low melting point (186 degrees C elsius). In the liquid state, it has a

high specific heat and thermal cond uctivity. These properties make it an excellent heat transfer

material and thus, a good choice as a means of remov ing heat from the reactor. When lithium is used

in the blanket for heat transfer it also serves as the primary absorber of the 14,100 keV neutrons from

the D + T reaction.

Soures, John M., McCrory, Robert L. and Craxton, R. Stephen, "Progress in Laser Fusion", Scientific American, Vol. 255, No. 2,

August 1986, Page 68




Lithium is comprised of two isotopes in a ratio of 7.4% lithium 6 to 92.6% lithium 7 . Some of the fast

neutrons from the D + T fusion react with a lithium 7 atom and split it into tritium and helium. The

neutron is slowed down by this collision. Som e of the slow neutrons then react with lithium 6 to

produ ce another tritium and helium atom and 4,800 keV more energy. The tritium is extracted fromthe liquid lithium blanket for use as fuel.

It is feasible to breed more tritium in a lithium cooled reactor than is used in the reaction. The excess

tritium can be used to start other reactors or in a reactor using some coolant other than lithium that

prevents it from b reeding its own tritium. Nature has been kind with the properties of lithium. It is an

excellent choice for transferring heat from the reactor and it is the raw material needed for the

continual production of more fuel. Both these functions can be provided by the use of liquid lithium as

the blanket material. '^^ The isotopic composition of the lithium may be adjusted to provide the proper

balance of lithium 6 and lithium 7 to optimum heat transfer and production of tritium. The lithium can

also be diluted with metallic sodium or potassium to aid in adjusting the tritium production rate.

Achiev ing a fusion reaction requires control of the 10 keV (100 million Kelvin) plasm a. The plasma is

electrically conductive and can be shaped and confined by strong magnetic fields. The ion and

electrons tend to spiral around the magn etic lines of force, but do not move across them. In a linear

machine, magnetic coils around the cylindrical body generate a uniform field parallel to the axis of the

cylinder. The uniform field prevents plasma leakage perpendicular to the axis of the cylinder. With a

uniform axial field, plasm a can still be lost through the ends. The end loss allows a portion of the

plasm a to leak from the reaction zone . If the leakage through the ends is large when com pared to the

total plasma, it has the effect of cooling the plasma below the reaction tempera ture. Two tec hniques

are used to prevent leakag e from the ends.

L I N E A R M A G N E T I C C O N F I N E M E N T R E A C T O R S

One method of reducing the effects of end leakage is to make the plasma confinement cylinder so long

the total volume is large compared to the leakage at the ends. Unfortunately, to confine the plasma in a

simple magnetic cylinder for sufficient time to generate power, the reactor may need to be so long it is

impractical.

Greatly increasing and shaping the magnetic field strength at the ends of the cylinder reduces the

plasma lo ss. If the magnetic field is increased to a high valu e, the ions tend to be reflected from the

high field strength area back toward the relatively lower field strength near the center of the cylindrical

cham ber. Because the ions are reflected from the high field strength regio ns, this type of confinem ent

is called magnetic mirror confinement. Even with extremely strong fields at the ends, some plasm a

still leaks from the reactor.

Part of the leakage from the ends is the result of ions striking the field at an angle too great to be

reflected. Other leakage results from the large difference in mass between the negatively charged

electrons and the positively charged helium, tritium and deuterium ions. The electrons and the ions

have the same thermal temp erature, and thus energy. The velocity of the electrons is much h igher

because they weigh only 0.0027 as much as a deuterium ion . In a mach ine with the ends terminating

in an increased strength magnetic field, with the same cylindrical cross section as the main body of the

reactor, the electrons penetrate much deeper into the pinched portion of the magnetic field. The greater

^ ^ Coppi, Bruno and Rem, Jan, "The Tokamak A pproach in Fusion", Scientific American, Vol. 227, No. 1, July 1972, Page 65



62 An End To Global Wa rming

penetration of the electrons produces a charge separation and the plasma is no longer neutral. A

charged inc rement of plasma at the end plug creates an instability cau sing the mirro r effect to fail. The

charge induced m irror failure allows the remainder of the plasm a to leak from confinement.

Several schemes for improving the simple pinched magnetic field plug at the ends of the reactor

section are under test. These involve the careful shaping of the cross section and linear shape of the

magn etic field at the ends of the cylindrical section. These con cepts have been tested and they show

dramatic impro vemen t in the confinement. Researchers w orking on the linear machines believe it is

possible to build a fusion power reactor today using the cylindrical section with shaped magnetic field

end plugs. The general outline of the mach ine would be as follows.

The central cylindrical section surrounded by magnetic field coils will be long, possibly as long as 100

mete rs. The surface of the cylinder will be fabricated with channels to carry the liquid metal coolant.

Each end of the cylindrical section would be fitted with an electrostatic/ magnetic end cap to prevent

excess leakage of the plasma from the ends. The magn etic field used to confine the plasma would rely

on superconducting coils to minimize the power required to sustain the confinement fields. ^ ^ * ^^

A rudimentary diagram is of a linear machine shown in Figure 3.1. It is shown using superconducting

mag nets to confine the plasma. Supercon ductivity is a property shown by m any metals and alloys.

Among the most useful for the fabrication of powerful magnets are alloys of niobium, titanium,

vanadium and tin. Wh en these alloys are cooled to the tempera ture of liquid helium , 4.2 Kelvin, they

lose all resistance to electrical current flow. If an electric current is started in a super conductive coil,

the coil acts much like a permanen t magnet. The current flow generates a magn etic field. Since there

is no resistance to the current flow, the current continues and sustains the magnetic field indefinitely.

Super conducting coils are used to generate powerful magnetic fields without the continuous

consumption of energy. '^^' '^^

The requirement for exotic alloys and liquid heHum coolant makes superconducting magnets expensive

to build and complex to operate. In applications where strong magnetic fields are required for

sustained times, such as fusion reactors, their cost is low when compared to the cost of continuously

supplying electric power to room temperature ma gnets. There is currently much progress in this area

magn et technology. A class of ceramic supercondu ctors has been discovered that Operate at much

higher temperatures. Som e of these ceramic supercon ductors are making it into the demonstration

market. They are being used in short underground runs to supply power where overhead Unes are not

possible. '^^

New types of permanent magnets are available that produced very strong stable magnetic fields

without expending any pow er. These magnets are an alloy of iron, neodymium and boron. They arecurrently applied to replace the superconducting magnets in nuclear Magnetic Resonance Imaging

mach ine (MRI) used in medical diagnosis. This technology may allow fusion reactors to be developedwithout recourse to liquid helium cooled magnets.

133

134

135

Furth, Harold, "Progress Toward Tokamak Fusion Reactor", Scientific American, Vol. 241 , No. 2, August 1970, Page 50

Conn, Robert W ., "The Engineering of Magnetic Fusion R eactors", Scientific American, Vol. 249, No. 4, October 1983, Page 60

"Magnetic Fusion Development", Proceedings of the Institute of Electrical And Electronic Engineer, Special Issue, 12 articles. Vol.

69, Number 9, August 1981

Bryant, Lynwood, "Advances in Superconducting M agnets", Scientific American, Vol. 216, No. 3, March 1967, Page 114

Wolsky, Alan M., Giese, Robert F., and Daniels, Edward J., "The New Super Conductors: Prospects for Applications", Scientific

American, Vol. 260, No. 2 February 1989, Page 60

Editors, "Superconducting pow er Cables, at last!". Th e Economist, Vol. 360, No. 8230, July 14 2001, Page 75



The Energy Source - Nuclear Fusion R eactors 63

Liquid lithium will be pumped through the reactor walls where it would absorb the thermal energy and

neutrons generated by the plasma. The neutrons from the reaction will react with the lithium to provide

more tritium fuel. After passing through, and cooling the walls of the reactor, the hot lithium will beconducted to heat exchangers to generate steam. The steam will be used to generate electric power by

use of conventional steam turbine gene rators. After it passes through the steam generators, the lithium

will be pum ped back through the reactor. At some point in the heat exchange loop , a portion of the

lithium will be diverted through a tritium separation process where the tritium will be recovered for

- T W O M irrE R M A N . AT SAME SCALE AS REACTOR

I — DEUTRON ACCELERATOR

ELECTRON ACCELERATOR

U T HI U M C OOL A N T C HA N N E L S

later use in the reactor.

Figure 3.1 A Linear Fusion R eactor

Auth or's notional drawing of a linear reactor

The plasma is confined within the reactor by magnetic mirrors at each end of the cylindrical section.

The mirror concept relies on charged particles of the plasma being reflected or turned back on

them selves by magnetic field g radients at the ends of the cylindrical section. In the seventies research

at Lawrence Livermore National Laboratory, in Livermore, California, investigated a variety of mirror

magnetic shapes. One example was the tandem mirror machine. It uses linear cyUndrical plasma,

plugged at the ends by magn etic mirrors to prevent the plasm a leakage. A mirror fusion facility wasbuilt to test this concept. Unfortunately, the facility was mo thballed before testing du e to a shortage offunds. If and/or when these tests are performed, it will establish the laws for scaUng the mirror

confinement concept and provide a basis for comparing mirrors with other types of plasma

confinement sc heme s. Tand em mirror systems were also unde r investigation at the University of

Wisconsin, Madison, Wisconsin and Cornell University, Ithaca, New York.

T O R O I D A L M A G N E T I C C O N F I N E M E N T R E A C T O R ( T O K A M A K )

The second method for the prevention of leakage of ions through the ends of the magnetic confinement

is to eliminate the ends. This is achieved by wrapp ing the confining m agnetic fields up to form a torus



64 An End To Global War ming

(doughnut) shape. This eUminates the ends, but presents a new problem . It is difficult to stabihze a

magnetic field bent into a toroidal shape.

Many of the fusion research machines employ the torus shaped vacuum chamber and magnetic fields.External magnets are used to generate part of the field that confines the plasma, but much of the

confinement is produced by the magnetic fields induced by electric currents in the continuous ring of

plasma. This ring current not only helps generate the confinement magnetic field but it supplies part of

the energy necessary to heat the plasma. These m achines are called Toka mak s, a nam e given to them

by Russian researchers who were the first to use them in fusion e xperim ents. Fusion research

machines of this type are operating in the United States at Princeton University, Oak Ridge National

Laborato ry, Gen eral Atom ics Corporation and the Massachusetts In stitute of Technology . ^^

The toroidal machines have provided a solution for the leakage of the plasma from the ends of the

reaction volume at the cost of greater instability of the fields and complex physical access problems to

the reaction zon e. In the early toroidal mach ines, powerful electric currents flowing in the plasma ring

generated the magnetic field. This generated a uniform field that wraps around the small diameter of

the plasma like hoops around a barrel. The mag netic field lines were closer together (the field was

stronger) on the inside of the torus than on the outside. This resulted in non-uniform heating of the

plasma and allowed it to leak out from the outer surface of the torus at a high rate. With great

difficulty, external coils were added to produce a twist in the magnetic field. The twisted toroidal

fields improved the plasma confinement. Unfortunately, a combination of complex m agnetic field

coils and the piping for heat removal had to be squeezed into the narrow bore in the center of the

toroidal machines. The com plexity and lack of space made construction exceedingly difficult.

In the toroidal machines, significant heating can be achieved by generating a large current flow in the

plasma. This technique is simple and efficient for initial heating. Before the plasma reaches fusion

tempe rature, the electrical resistance becomes so low heating stops. Final ignition temperatures mustbe produced by some other method of heating. ^"^ Figure 3.2 shows the International Toroidal

Experimental Reactor (ITER).

A numb er of metho ds of heating both linear and toroidal plasma are in test. Energy can be pumped

into the plasma by mean s of microw ave or laser beam s. The w avelength of the energy beams must be

carefully selected to achieve good absorption of the energy by the plasma. Additionally, as the plasma

gets hotter the absorption factors change and the beams must be altered to achieve good efficiency.

High intensity sources with the proper wavelength require further development.

Encou raging results have been obtained by a technique called neutral beam heating. This is shown in

the diagram of the linear machine. Figure 3.1 . In this technique, a separate particle acceleratorproduces an intense beam of deuterium ions. The velocity and thus energy of the deuterium ions in the

beam is equivalent to a temp erature much higher than needed for ignition of the D + T reaction. The

beam of charged particles cannot penetrate the magnetic fields confining the plasma because the

charged ions would be scattered by the powerful magnetic fields. To achieve penetration, electrons are

added to the beam to neutralize the charge of the ions. The neutral atoms formed by the combination

of the ion beam and the electrons still have the same effective temperature but can now penetrate the

magn etic field. The neutral beam enters the plasma and its particles collide with the plasma particles.

Furth, Harold P. "Reaching Ignition in the Tokamak", Physics Today, Vol. 38, No. 3, March 1985, Page 52

Davidson, D. C. and 7 others, "Soviet Magnetic Confinement Fusion Research", Science Applications International Corporation,

October 1987




The collision transfers the energy of the beam to the plasma increasing its temperature . The co llision

also ionizes the neutral beam particles that then become part of the plasma. Neutral beam h eating has

been tested in both linear and toroidal machines. This method appears to provide a method of heating

the plasma to the ignition temperature.

With both Unear and toroidal machines, it is necessary to keep the reacting plasma extremely pure.

Electrons in the plasma are moving at high velocities. As they pass through the plasma , they encounter

the positive charged nuclei repeatedly. Each time the electron passes a nucleus its path is changed and

it releases part of its energy as radiation. This radiation travels to the wall of the reactor where it is

adsorbed. This process tends to cool the bulk plasma. The am ount the electron's path is changed is

controlled by the strength of the electric charge on the nuclei. Atom s of high nuclear charge prod uce

far more radiation heat loss than atoms of small nuclear charge. The losses from the interaction of the

electrons with the D, T, and He nuclei are acceptable, but the loss from impurity atoms such as carbon,

nitrogen, and oxygen are unaccep tably high. Atom s of metals used in construction, such as iron, cause

catastrophic radiation heat loss. The initial vacuum in the reaction cham ber must be of extremely highquality. Impurities must be continually remo ved to keep the energy loss from the plasma at an

acceptably low level. This removal process must also remo ve the helium that is produced by the

reaction. Excess helium can lead to excessive radiation losses.

Much progress has been made in developing methods of maintaining the high purity levels in the

plasma . It is now possible to produce plasma with minimu m necessary pu rity and maintain it for the

duration (a few secon ds) of current experimen ts. On Nov em ber 7, 1991 near Oxford in the United

Kingdom, the Joint European Torus experiment generated 2 miUion watts of power in two seconds. ^"^^

The demo nstration used a blend of 14% tritium with 86% deuterium as fuel. This success clearly

demonstrated the scientific feasibility of the generation of energy from fusion reactions. ^"^^ Refinement

and extension of the techniques used in the research machines will lead to the techniques and hardware

suitable for continuous opera tions of a base load power plan t. ^^ ^^ As early as 1976 fusion pow er

plant demonstrations were seriously considered to be feasible. ^"^^

There are a number researchers working to produce or promote magnetically confined fusion reactors.

Those currently active are:

CRP P EPFL Lausanne, Switzerland Fusion Power Associates, Maryland USA

http://crppwww.epfl.ch/ http://www.fusionpower.org/

General Atomics, San Diego USA Georgia Tech Fusion Research Center, Georgia USA

http://fusioned.gat.com/ http://fusion.gat.edu/

Jet Joint Undertaking, United Kingdom Max-Planck-Institut fur Plasmaphysik, Garching Ger.

http://www.jet.uk/tour.html http://www.ipp.mpg.de/

141

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143

http://www.fusion.org.uk/

Hamilton, David P, EDITOR "A Fusion First", Science Scope, Science, Vol. 254, No. 5034, November 15, 1991, Page 927

Sweet, William, "Super Powers Promote D esign Effort for Fusion Dem onstration Reactor", Physics Today, January 1988, Page 75

Thomsen, D. E., "Charging Their Way Toward Fusion", Science News, December 21 , 1985, Page 389

"Fusion Power by Magnetic Confinement", Prepared by the Division of Magnetic Fusion Energy of the U. S. Energy Research and

Development administration (ERDA-76/110/1 UC-20)



http://www.ipp.mpg.de/

http://www.jet.uk/tour.html

http://fusion.gat.edu/

http://fusioned.gat.com/

http://www.fusionpower.org/

http://crppwww.epfl.ch/




NIFS, Toki, Japan Princeton Plasma Physics Lab New Jersey USA

http ://nifs. ac j p/ http://www.pppl. gov/

UKA EA Culham Lab. United Kingdom University of Texas, USAhttp://www.fusion.org.uk/ http://w3fusion.ph.utexas.edu/

University of Wisconsin-Madison Los Alamos National Laboratory, New Mexico USA

http://fti.neep.wisc.edu/ http://fusionenergy.lanl.gov/

MIT Plasma Science & Fusion Center Oak Ridge National Laboratory,

Massachusetts, USA Tennessee USA

http://www.psfc.mit.edu

University of California at Berkeley USA

These studies are exam ining various aspects of producing fusion energy. They cover a host of

approach es. One interesting alternative uses magnetic fields that are produced only out side the

reac tors . "^ This reac tor is termed the CFBR and is discus sed below in Other Magnetic Confinement

Techniques.

Ongo ing research is producin g new and useful results. Recently the United States National Fusion

Facility in San Diego (Operated by General Atomics Corporation) announced that they had quadrupled

the rate of fusion in deuterium plasma. '" ^ They attem pted to inc rease the stab ility and lifetime of the

plasma by causing it to spin around the axis of the Tokamak reactor. They found that they could spin

the plasma and that spinning increased stability. They also found that the plasma spin tended to slow

down at an undesirable rate. Further analysis showed that small variations in the smoothness of the

magn etic fields w ere the cause of the slowing. By detecting these small variations and correcting themin real time, the plasma spin did not slow down . The long duration spin stabilized the plasma and

allowed a significantly increase the plasma pressure and temperature. The smo othing of the magnetic

field required very little power because the variations were small. There is good reason to expect this

technique will be useful in all magnetic confinement fusion reactors.

Pow er plant size will be a major factor in the implemen tation of fusion energ y. Very large machines

can function with less intense magn etic fields. Low intensity fields can be operated w ith less stringent

control. Large size provides m ore room for the placement and access of support equipment such as

heat exchangers, magnetic field coils, impurity removal equipment, external heating equipment,

vacuum p ump s and reactor support structures. The workers involved with both the linear and toroidal

machines agree, using today's knowledge it is possible to design a large reactor that will producepower at practical efficiencies. The sizes projected for the operational reactors are in the range of

30,000 to 50,000 Megawatts electrical (MWe), much larger than the 300 to 2,000 MWe of current

powe r stations. The dev elopers of the fusion reactors have seen this large size as a barrier to the near-

term implem entation of fusion pow er. In Chapter 6, we will show this large size is not a barrier, but is

highly advantageous and will allow these large reactors to serve as the backbone of the future power

system.

http://ftision.ps.uci.edu/beam/introb.html

Samuel, Engenie, "Here Comes The Sun", New Scientist, Vol. 171, N o. 2299, July 14, 200 1, Page 4



http://www.psfc.mit.edu/

http://fusionenergy.lanl.gov/

http://fti.neep.wisc.edu/

http://w3fusion.ph.utexas.edu/


http://www.pppl/



The Energy Source - Nuclear Fusion R eactors 67

Figure 3.2 The ITER Tokamak ReactorPicture Down-Lo aded from ITER Web Site

O T H E R M A G N E T I C C O N F I N E M E N T T E C H N I Q U E S

A spherical configuration of a tokomak has shown significant advantages over the design used in

ITER. It is not clear if the advantages w ill remain w hen this type of reactor is scaled to larger sizes.

Another alternate magnetic confinement scheme is under investigation with funding from the Office of

Naval Research. The University of California, Irvine, the University of Florida, Gainesville and the

National High Magnetic Field Laboratory, Tallahassee are members of the team. They hope to

demonstrate a "Reverse Field" confinement that will permit the use of the boron + proton reaction.

They call it the Colliding Beam Fusion Reactor (CBF R). Such a reactor would be a very desirable

break through because the boron-pro ton reaction produces no radioactivity. These reactors also use a




linear configuration. Th ey would superficially be sim ilar to the drawing sho wn in Figure 3.1. During

the initial research phase of the program suggested in Chapter 9, the CBFR should be given much

attention. It would offer a fusion reactor with very low radiation hazard. The presence of side

reactions may produce a small number of neutrons but the promise is a reactor that will be radiationfree and easy and low cost to decommission.

INERTIAL CONFINEMENT REACTORS

Inertial confinement reactors will likely use the same D and T fusion reaction as proposed for the

magn etic confinement ma chines. Magn etic confinement reactors operate at low pressures and

densities and confine the plasma w ith magnetic fields for a relatively long time. Inertial confinement

reactors operate at high densities and attempt to create the reaction in a very short time; a time so short,

that a significant portion of the deuterium and tritium react before expansion cools the mixture enough

to stop the reaction. The reacting plasma is confined by its own inertia. As with the magnetic

confinement reactors there are several different techniques under investigation.

Of these techniques laser driven implosions have received the most attention. In this technique, a

small sphere of deuterium and tritium is frozen solid at about 10-15 Kelvin. A group of powerful

lasers capable of short pulses is focused sym metrically on the sphere. With the sphere at the proper

location, the lasers are pulsed. The laser energy converges on the sphere from all directions

com pressing and heating it to fusion ignition tem peratures. The ignition of the fusion reaction causes

the sphere to explode. The energy from the explosion of the deuterium and tritium sphere is captured

as the useful o utput of the reactor.

To achieve a net output of energy the laser pulse must be exceedingly powerful, carefully shaped and

aimed with great precision. The high pulse power is required to compress the deuterium and tritiumsphere from its normal density of 0.1 gram per cubic centimeter to 10 or more grams per cubic

centimeter. The com pression and heating from the laser energy heats the sphere to a temperature far

higher than the minim um necessary to achieve fusion. The enormous compression and extreme

temperature is necessary to achieve the highest possible percentage of energy released in the short time

available. The sphere is small and will explode, expand , and cool in nanosec onds.

To achieve substantial energy release a large fraction of the potential fusion energy reactions must take

place . ^ ^ ^^ The la ser pulse m ust perform the compression and heating in a time so short the hot

expand ing deuterium reacts with the tritium before the gas can expand and cool. The laser pulse

compressing and heating the sphere must be symmetrically applied and accurately aimed or it will

drive the sphere from the focus point of the lasers before it is fully heated.

Progress has been made in understanding the requirements of laser energy, pulse shape and duration.

Neutrons have been detected from spheres ignited in laser fusion experim ents. The neutrons indicate

some fusion reactions have occurred. Unfortunately, the amount of energy released is many times

smaller than was used to ignite the reaction. The current goal is "break even". This is defined as

equality of energy input for ignition and energy produced by fusion reaction s. There is still much work

to be performed to achieve break even. Achieving a net excess of energy, required if laser fusion is to

be used as an energy source, will be even more difficult.

Emmett, John L., Nuckolls, John and Wood, Lx)well, "Fusion Power by Laser Implosion", Scientific American, Vol. 230, No. 6, June

1974, Page 24

Lubin, Moshe J. and Fraas, Arthur P., "Fusion by Laser", Scientific American, Vol. 224, No. 6, June 1971, Page 21




One of the topics receiving m uch attention is the efficiency of the lasers. The largest laser is at the

Nov a facility located at the Lawrence Liverm ore Laboratory in California. The Nova test facility u ses

neody mium glass lasers having an efficiency of between one and two percent. This means for every100 watts of input power only one to two watts of laser radiation are produ ced. The w avelength of this

type of laser is 1090 nanom eters (nm ). This radiation is just bey ond the red end of the visible spectrum

at 700 nm and is termed the near infrared. This wavelength ha s been shown to be longer than d esirable

for optimum heating and compression of the deuterium and tritium fuel pellet. By the use of non

linear optical effects, it is possible to double the frequency, and thus halve the wavelength of this

radiation, to provide 545 nm radiation. The doubling process does not convert all the energy in the

laser beam to the shorter wavelength. Conversion efficiencies of 30 to 60 percent may be possible.

This frequency doubling process can be applied a second time to provide radiation with a wavelength

of 272 nm. The shorter wavelength radiation m ay be more useful in igniting the fusion reaction, but its

production further low ers the efficiency of the laser system.

The consequence of the low laser efficiency is low overall power generation efficiency and a large

amount of circulating power within the plant. The low overall efficiency is of little consequen ce from

the standpoint of the utilization of fuel, but it creates a major prob lem of w aste heat rejection. If much

of the input laser energy is converted to waste heat, the heat rejection b y the plant will be extreme. For

example, if the laser system delivers 2% efficiency, 50 units of energy must be supplied to the laser to

place one unit of energy on the target. The electrical generators used to convert the energy from the

target reactions to electricity will be no more than 40% efficient. To obtain the 50 units of laser drive

energy the target must release 125 units. At this break even point the reactor is producing no usab le

output but is only sustaining its own operation. It is producing 125 units of energy, one used to ignite

the reaction and 124 expend ed as waste heat. To achieve a useful energy output the reactor must

produce far more than 125 units of energy for every one unit used to ignite the reaction.

The low energy efficiency laser presents a near insurmountable challenge. With a 1% efficiency laser

at least 14% of the total available energy from the deuterium tritium reaction must be recovered just to

break even; that is, to produce enough energ y just to keep the plant operating. This leaves no output

energy, or zero plant efficiency. If it is possible to achieve 25 % energy release, the plant will have an

overall efficiency of 17%, with 56.8% of the total energy released by the fusion reaction being used

just to run the laser system. In the research performed thu s far, the amount of fusion energy released

has been less than 0.01%. It is not clear if it will ever be possible to achieve the large fraction of

energy release necessary to design a system producing net power.

Current research is investigating two approaches to achieve inertial confinement fusion. In the direct

approach a short wavelength, high intensity laser pulse is focused directly on the pellet containing thefusion fuel. The outer layers of the pellet are violently vaporized and heated to a high tem perature.

This process is termed ablation. The expansion of the hot outer layer compresses the inner core of the

pellet causing it to implode . Energy from the hot outer layers and the laser continue to heat the inner

core until it reaches fusion tempe ratures.

In the indirect approach, an outer layer surrounding the deuterium tritium pellet absorbs the driver

beam energy . This outer layer is made of elements that generate X-ray when heated by the laser

beams. This outer layer converts the driver beam energy into X-rays. The X-rays implode and heat

the core of the target. To achieve a net energy gains the driver must achieve energy coup ling to the




target with high ablation pressure (greater than 50 miUion atmospheres) with low fuel preheat and

highly compressed fuel (density greater than 200 grams per centimeter).

Several facilities are performing experim ents. The NOVA at Law rence Liverm ore in California is themost powerful neo dym ium laser system in the world. It has the capability of delivering a burst of

50,000 to 70,000 joules (a 100 watt electric light uses energy at a rate of 100 joules per second) of

infrared energy at a wavelength of 1,054 n anom eters (one nanom eter is one billionth of a meter, that is,

10'^ meters). With frequency conversion, it can deliver about half this energy at 527 (visible green)

and a third at 264 (ultraviolet) nano meters. Using the ultraviolet radiation the NOV A facility has

achieved target compression to 24 grams per centimeter.

The OMEGA laser at the University of Rochester, Rochester, New York, uses a glass laser and can

deliver 2,400 joule s at a wavelength of 350 nanom eters. OM EGA has generated 2 xlO^^ fusion

neutrons for a reaction efficiency of about 0.001%. This efficiency is far below the 25% to 75%

needed for a fusion reactor.

The current research into laser based inertial confinement fusion energy is conducted at:

University of Rochester, New York. http://www.lle.Rochester.edu.exterual_index.html and

Lawrence Livermore National Laboratory, California http://www-lasers.llnl.gov/

Los Alam os Laboratory in New Mex ico has terminated its work with the ANT AR ES system operating

at 10.6 micrometers because it was shown it would not be possible to generate sufficient heating or

comp ression with the 10.6 microm eter wave length radiation. They have turned their efforts to the

developm ent of krypton-fluorine lasers. They have generated 10,000 joules pulses at 250 nanometers

at efficiency of 1.5%. In 1989, this laser system had not yet been incorp orated into a fusion testapparatus and little recent data is available.

Sandia Laboratory has been working with a compression heating system using beams of charged

particles to irradiate the targets. The charged ions tend to repel each other. The more powerful the

beam the mo re the charged p articles interact. This produces great difficulties in focusing the beam to

strike the tiny fusion target. Progress is being made, but this system is well behind the laser systems. ^^^

Production of the laser or particle beam capable of igniting the fusion reaction is only part of the

challenge in the developm ent of the inertial confinement fusion reactor. The beam s must have targets

upon w hich to act. The targets must be small spheres fabricated from solid mixtures of deuterium andtritium. To provide a solid target the spheres must be encapsulated in a strong material that will not

interfere with the fusion reaction, or they must be held at temperatures well under the solidification

temperature of hydrogen (14 Kelvin). Solid particle targets are necessary so they can be handled and

placed at the exact focus of the ignition beams.

The amount of energy release from the reaction of a single target pellet is not large. To achieve a high

rate of energy production, to provide a continuous power output, the reactor must sequentially ignite a

Yonas, Ceroid, "Fusion Power with Particle Beams", Scientific American, Vol. 239, No. 5, November 1978, Page 50

VanDever

Page 831

VanDevender, J. Pace and Cook, Donald, "Inertial Confinement Fusion with Light Ion Beams", Science, Vol. 232, May 16, 1986,

http://www-lasers.llnl.gov/

http://www.lle.rochester.edu.exterual_index.html/



rhe hinergy Sourc e - Nuc lear l*usion Reac tors 71

continuous stream of target pellets at a high rate. The target particles must be placed at the target point

with great accuracy so that the energy beams can cause uniform ignition. These are difficult problem s

and, thus far, little progress has been made at providing solutions useful for an operational power plant.

Some of these schemes may ultimately be developed to a level where it is possible to use them to build

a practical fusion power plant, but for the near term, planning should be based on magnetic

confinement concepts.

The linear or toroidal magnetic confinement machines are the fusion reactor system most nearly ready

for implem entation. Researche rs from the primary developers of these machines have written that a

mach ine of appropriate size can be designed that would produce useful pow er. With current

understanding, engineering skill and materials they estimate the power output of a full-scale

operational plant will be in the range of 30,000 to 50,000 Megawatts electric (100,000 to 150,000

Meg awatts therma l). A simplified schem atic diagram of such a reactor was shown in Figure 3.1 . This

output level is 15 to 25 times larger than the current largest pow er plants. The deve lopers see this largepower output as a barrier to the use of fusion energy and are directing their efforts at achieving fusion

reactions in smaller reacto rs. Chapter 6 will show large size is not a barrier, but will be an advantage

in the construction of the energy systems needed for the future.

There are other approaches to fusion un der discussion or investigation. Cold fusion g enerated mu ch

interest several years ago but no one has been successful at reproducing consistent experimental

results. ^^ Investigators of sonoluminescen ce have mea sured som e very high temperatures at the

center of collapsing gas bubb les. Som e have speculated that a tempe rature high enough to product

fusion migh t be possible. * ^ At the time of this writing, neither of them seems to offer much prom ise.

However, it would be foolish not monitor these efforts to ensure we use the best methods.

FUSION REACTOR SAFETY

Fusion power generators are inherently safe. The magnetic confinement of the plasma must be

carefully co ntrolled and balance d to sustain the nuclear reaction. Any disturban ce of the operating

conditions will result in termination of the reaction. No comb ination of system failure, operator error,

natural disaster or sabotage can cause the fusion reaction to run awa y. A nuclear explosion , melt down

or similar catastrophic accident is not possible. A violent event, one of sufficient mag nitude to disrupt

the total reactor, could cause a chemical or electrical fire similar to any indu strial fire.

Fission reactors produce of kilograms quantities of highly radioactive cesium 137, iodine 131, and

strontium 90. Tons of uranium and plutonium are also present in a fission reactor. If released in anaccident these radioactive isotopes can be absorbed by the body and retained for some length of time.

The fusion reactions do not use or produce any of these toxic elements.

Tritium is the only radioactive m aterial used in the fusion reaction. Tritium h as a half-Ufe of abou t

12.5 years and gives off relatively low energy electrons. It is one of the least hazardous radio active

elem ents. If released, the tritium would com bine with oxygen to form water. Ingested tritium wo uld

tend to be eliminated within a few days. Consu mption of large quantities of tritium free water w ould

be a major element in the treatment for tritium exposure.

Rafelski, Johann and Jones, Steven E., "Cold Nuclear Fusion", Scientific American, Vol. 257 , No. 1, July 1987, Page 84

^ ^ Crum, Lawrence A., and Matula, Thomas J., "Shocking Revelations", Science, Vol. 276 30 May 1997, Page 1348




Contamination from a fission reaction can last for thousands of years because of the long half-life of

the fission-produced radioactive isotop es. If, by an unusual set of circumstances a plot of ground

becomes contaminated with a hazardous amount of tritium the area would be safe within a few decadesbecause of the short half-life of the tritium.

Using the design postulated above the hazard of a fusion reactor can be estimated. Fusion reactors will

present only a tiny fraction of the radiation hazard potential of a uranium fission reactor. There is only

a small quantity of radioactive tritium present in the reactor. Based on the tritium usage in research

reactors it would seem likely a power reactor would have less than a few kilograms of tritium at the

pow er plant at any given time. This would probably be distributed 10% to 20% in the plasma, 20% to

40% ready for future insertion in the plasma and the un-recovered tritium present in the lithium

coolant.

A violent event, such as the breaking of the vacuum chamber, would result in exposure of the plasma

to the surrounding air. The tritium and deuterium from the plasma would react with the atmosphere to

form water. The helium would mix with the atmosphere without reaction. The reaction products

would be tritium and deuterium containing w ater. The deuterium containing w ater and the helium are

both entirely non-toxic and could be ignored. Water containing weakly radioactive tritium is a mild

hazard. The total amount of water resulting from the reaction would be in the range of 10 grams to 5

kilograms depen ding on the size of the reactor and its operating condition s. This small amount could

easily be adsorbed by an atmosphere d rier protection system. If the atmosphere d rier system were to

fail at the same time as the reactor, or be damaged by the same event that broke the vacuum chamber,

little hazard would result. On escape from the system, the tritium w ould be diluted by the water in the

atmosph ere. It would present only a slight hazard to the environme nt. This w ould dissipate in a few

years.

When the reactor is operating normally, the tritium is removed from the lithium continuously and the

amoun t present at any given time is small. If an event breached the hthium cooling system, a Hthium

fire w ould be possible. In a Hthium fire, any residual tritium remaining would be burned to water and

released. The violence of the lithium fire will increase the mechanical difficulty of trapping the water

containing the tritium. Fortunately, when lithium bum s at high temperature the product is hthium

oxide. As lithium oxide cools it becomes an excellent absorber of water. The oxide reacts strongly

with water to form lithium hydroxide, a solid. To whatever deg ree this reaction occurred, the tritium

would be tied up as a solid within the confines of the reactor complex. The amo unt of tritium released

would be highly dependent on the details of the accident, condition of the reactor, weather and other

similar variables. In general, should a lithium fire occur, the probability of som e tritium escaping the

reactor would be increased.

Durin g its lifetime, a fusion reactor presents litde radiation hazard. The internal structure, particularly

the vacuum containment vessel and the heat exchanger, will be subject to intense neutron

bombardment. The neutrons will convert some of the elements of the structure into long-lived

radioactive isotopes. Selecting construction m aterials that do not easily become activated can

minim ize radioisotope production. No material is entirely resistant to neutron activation, thus the

decommissioning of a fusion reactor will require the handling and disposal of potentially hazardous

radioactive isotopes. Because of the lack of uranium, plutonium , and fission products, the total

radiation exposure hazard from the decommissioned fusion reactor is 10,000 to 1,000,000 less than

from a decommissioned fission reactor.




If the initial development effort is successful at implementing a CBFR using the boron-proton reaction,

virtually all the hazard arising from rad ioactivity is eliminated. Table 3.1 shows that the boron proton

reaction produces only helium and energy.

DECOMMISSIONING FUSION POWER PLANTS

One of the major problems for the fission power industry is the disposal of the highly radioactive waste

remain ing when an old reactor is decom missioned. When the fission industry started, reactor

decom missioning w as largely ignored. Little effort was made to develop the necessary technology to

protect the environment from exposure to used fuel elements, containment vessels and other

radioactive materials resulting from the disassembly of a worn out reactor. Toda y the fission po wer

industry is confronted with an enormous task of waste disposal with no clearly satisfactory method of

performing the job .

It will be wise to draw detailed plans for decommissioning fusion reactors at the beginning of theirdevelopm ent. This will avoid the wretched waste disposal problems that plague the fission reactor

industry. The fusion reactors will contain far less radioactive material than a fission reactor. Wh atever

the amount, one hundredth to one millionth, proper disposal will be required.

Unlike the waste from fission reactors, none of the radioactive materials present in the

decom missioned fusion reactor can be used to make bom bs. The expended fusion reactor parts will

hold no interest for terrorist groups. The materials are only radioactive isotopes formed in the

structural elements of the reactor caused by the neutrons from the fusion reaction . There are no fertile

elemen ts or isotopes. No dangerous fission products are produced by the fusion reaction. Disposal of

worn out fusion reactors will be safe and simple as compared to the disposal of waste and structures of

decommissioned fission reactors.

Even though the challenge posed by decommissioning and disposal of fusion reactors is small, none of

the current schemes for the disposal of radioactive materials is satisfying. The current schemes

provid e short-term protection and storage, but the waste can pose a hazard for 25,000 y ears. It is

difficult to imagine a place on earth where it can be stored with total assurance no future problem can

occur. Wh ether buried in stable rock formations on land or buried unde r the floor of the ocean, one

can always postulate a natural disaster capable of causing the release of some of the radioactive waste

produ cts. There is always a potential for recovery by terrorists. Non e of the current earth based

schemes can provide the level of protection desired.

At this time, only space disposal can provide absolute protection for humanity, its descendants and theplanet earth. New m ethods may be discovered in the future, but current planning should include the

accounting for disposal of decomm issioned reactor materials in space. W hatever metho d is selected,

good initial planning will make the disposal of the old fusion reactors a safe, relatively easy, and cost

effective process.

The potential for the CBFR reactor is for a reactor that has no radioactivity associated with its use or

decom missioning . If feasible, this type of reactor should be given first priority in the developmen t

effort d escribed in Chapter 6.




S U M M A R Y

This chapter covered the production of heat by fusion reactors and from heat electricity. It showed that

the raw materials used in the production of energy with fusion, deuterium and lithium, weresufficiently abundant to serve hum anity for centuries. These materials have little competing uses. It

described the several paths available for the development of a fusion reactor, linear or toroidal

magn etic confinement and laser or particle beam particle beam co mpression. Each type has its

particular merits and challenges, but the magnetic confined plasma reactor appears nearest to

implem entation in a form most suitable for a future energy system . It evaluated the potential

environmental impact of the use of fusion reactors and showed that, while there are potential hazards,

proper reactor design and planning should reduce the hazards to an acceptable level. This chapter

attempts to show that fusion reactors will be a satisfactory source of energy to provide an energy

system that will supply human needs without harm to the environment. ^^"^

Many current energy needs cannot be easily satisfied by heat and electricity produced by fusionreactors. For credible use of a fusion energ y system it will be necessary to produce a m anufactured

chemical fuel to serve as the medium for the storage and transport of fusion d erived energy. Chapter 4

will show there is only one choice for the manufactured chemical fuel, hydrogen.

^^'^ Holdren, John P., "Fusion Energy in Context: Its Fitness for the Long Term", Science, Vol. 200, April 14, 1978, Page 168

Documents

Chapter 3 - The Energy Source - Nuclear Fusion Reactors