Nuclear reactor

The invention: 



The first nuclear reactor to produce substantial

quantities of plutonium, making it practical to produce usable

amounts of energy from a chain reaction.



The people behind the invention:



Enrico Fermi (1901-1954), an American physicist

Martin D. Whitaker (1902-1960), the first director of Oak Ridge

National Laboratory

Eugene Paul Wigner (1902-1995), the director of research and

development at Oak Ridge









The Technology to End a War



The construction of the nuclear reactor at Oak Ridge National

Laboratory in 1943 was a vital part of the Manhattan Project, the effort

by the United States during World War II (1939-1945) to develop

an atomic bomb. The successful operation of that reactor

was a major achievement not only for the project itself but also for

the general development and application of nuclear technology.

The first director of the Oak Ridge National Laboratory was Martin

D. Whitaker; the director of research and development was Eugene

Paul Wigner.

The nucleus of an atom is made up of protons and neutrons. “Fission”

is the process by which the nucleus of certain elements is split

in two by a neutron from some material that emits an occasional

neutron naturally. When an atom splits, two things happen: A tremendous

amount of thermal energy is released, and two or three

neutrons, on the average, escape from the nucleus. If all the atoms in

a kilogram of “uranium 235” were to fission, they would produce as

much heat energy as the burning of 3 million kilograms of coal. The

neutrons that are released are important, because if at least one of

them hits another atom and causes it to fission (and thus to release

more energy and more neutrons), the process will continue. It will

become a self-sustaining chain reaction that will produce a continuing

supply of heat.

Inside a reactor, a nuclear chain reaction is controlled so that it

proceeds relatively slowly. The most familiar use for the heat thus

released is to boil water and make steam to turn the turbine generators

that produce electricity to serve industrial, commercial, and

residential needs. The fissioning process in a weapon, however, proceeds

very rapidly, so that all the energy in the atoms is produced

and released virtually at once. The first application of nuclear technology,

which used a rapid chain reaction, was to produce the two

atomic bombs that ended World War II.





Breeding Bomb Fuel



The work that began at Oak Ridge in 1943 was made possible by a

major event that took place in 1942. At the University of Chicago,

Enrico Fermi had demonstrated for the first time that it was possible to

achieve a self-sustaining atomic chain reaction. More important, the reaction

could be controlled: It could be started up, it could generate heat

and sufficient neutrons to keep itself going, and it could be turned off.

That first chain reaction was very slow, and it generated very little heat;

but it demonstrated that controlled fission was possible.

Any heat-producing nuclear reaction is an energy conversion

process that requires fuel. There is only one readily fissionable element

that occurs naturally and can be used as fuel. It is a form of

uranium called uranium 235. It makes up less than 1 percent of all

naturally occurring uranium. The remainder is uranium 238, which

does not fission readily. Even uranium 235, however, must be enriched

before it can be used as fuel.

The process of enrichment increases the concentration of uranium

235 sufficiently for a chain reaction to occur. Enriched uranium is used

to fuel the reactors used by electric utilities. Also, the much more plentiful

uranium 238 can be converted into plutonium 239, a form of the

human-made element plutonium, which does fission readily. That

conversion process is the way fuel is produced for a nuclear weapon.

Therefore, the major objective of the Oak Ridge effort was to develop a

pilot operation for separating plutonium from the uranium in which it

was produced. Large-scale plutonium production, which had never

been attempted before, eventually would be done at the Hanford Engineer

Works in Washington. First, however, plutonium had to be pro-

duced successfully on a small scale at Oak Ridge.

The reactor was started up on November 4, 1943. By March 1,

1944, the Oak Ridge laboratory had produced several grams of plutonium.

The material was sent to the Los Alamos laboratory in New

Mexico for testing. By July, 1944, the reactor operated at four times

its original power level. By the end of that year, however, plutonium

production at Oak Ridge had ceased, and the reactor thereafter was

used principally to produce radioisotopes for physical and biological

research and for medical treatment. Ultimately, the Hanford Engineer

Works’ reactors produced the plutonium for the bomb that

was dropped on Nagasaki, Japan, on August 9, 1945.

The original objectives for which Oak Ridge had been built had

been achieved, and subsequent activity at the facility was directed

toward peacetime missions that included basic studies of the structure

of matter.



Impact



The most immediate impact of the work done at Oak Ridge was

its contribution to ending World War II. When the atomic bombs

were dropped, the war ended, and the United States emerged intact.

The immediate and long-range devastation to the people of Japan,

however, opened the public’s eyes to the almost unimaginable

death and destruction that could be caused by a nuclear war. Fears

of such a war remain to this day, especially as more and more nations

develop the technology to build nuclear weapons.

On the other hand, great contributions to human civilization

have resulted from the development of nuclear energy. Electric

power generation, nuclear medicine, spacecraft power, and ship

propulsion have all profited from the pioneering efforts at the Oak

Ridge National Laboratory. Currently, the primary use of nuclear

energy is to produce electric power. Handled properly, nuclear energy

may help to solve the pollution problems caused by the burning

of fossil fuels.



See also Breeder reactor; Compressed-air-accumulating powerplant; Fuel cell;

Geothermal power; Heat pump; Nuclear power plant; Solar thermal engine; Nuclear reactor