*, History of the

GRAPHITE REACTOR

at Oak Ridge National Laboratory

What Is Nuclear Fission?

Nuclear fission occurs when the atomic nucleus of a heavy element, such as uranium or plutonium, absorbs
a neutron and then splits apart into lighter atomic nuclei, releasing free neutrons and tremendous amounts of
energy. The free neutrons can be absorbed by other heavy nuclei, triggering further fission events and creating

a self-sustaining nuclear chain reaction.

The Graphite Reactor was fueled with natural uranium, with an isotopic composition of 99.3% ***U and 0.7%
238). The reactor was designed to use the neutrons produced by *5U to convert *°U, which cannot support

a chain reaction, to Pu, an isotope of plutonium.

Technology Innovations —

The Graphite Reactor was designed with the controls, radiation
shielding, and cooling systems needed for a production reactor.
Its natural uranium fuel was created in the form of 1x4-inch
slugs, encapsulated in gas-tight cylindrical aluminum jackets.
These were inserted by hand into horizontal channels in the
graphite moderator and pushed into position using long rods.
Only 800 of the available 1,248 channels contained fuel slugs.
The graphite moderator, a 24-foot cube made of stacked
blocks, slowed the neutrons emitted by the fuel to a speed at
which the uranium nuclei could readily absorb them.

With 24 to 54 slugs per channel, the reactor usually contained
about 54 tons of fuel. Irradiated fuel slugs were pushed through
the fuel channels to the back of the reactor, where they fell into
a canal filled with water 20 feet deep. Here they were loaded
into buckets using long poles and transported underwater to a
cell in the adjacent chemical processing plant. The water and 7
feet of concrete surrounding the reactor prevented the escape
of radiation.

During reactor operations, the nuclear chain reaction was
controlled using a system of seven 8-foot-long control
rods—three steel and cadmium rods that dropped vertically,
and four steel and boron rods positioned horizontally—that
could soak up neutrons, To start the reactor, the three vertical
rods were raised from the core, and two horizontal rods were
partially or completely withdrawn to adjust the power level.

The reactor had a maximum power of 4,000 kW and was
cooled by air moved by huge fans. After passing through the
reactor core, the cooling air was filtered, removing 99% of its
radioactive particles, and exhausted through a 200-foot stack.

‘HI Bridge tubes

Bi Safety rod

7 ft. thick concrete shield
Graphite thermal column
Channel scanning device
BJ Airfiow batfie

| Loading elevator

1) Fuel loading channels
through shield

| Uranium-graphite lattice
{0 Air inlet

‘iil Air exhaust

{B| Control rod location

iB] Experimental hole



History of the

- GRAPHITE REACTOR

at Oak Ridge National Laboratory

The Graphite Reactor,
1943-1963

GRAPHITE aS
=
Tins
The ORNL Graphite Reactor was the
first reactor to:

e Produce microgram quantities of
plutonium used in developing a
nuclear weapon

© Produce radioisotopes for science

© Produce electricity from nuclear
energy and provide a test bed for
the light water reactors used today

° Enable studies of the health
hazards of reactor radiation

¢ Prove the feasibility of reprocessing
nuclear fuel

¢ Produce a radioisotope, carbon-14,
which was used to treat cancer

e Enable the discovery of a new
element

© Enable studies of radiation damage
to metals and the structure of
matter using neutron scattering

A Vital Tool for Big Science

The birthplace of Oak Ridge National Laboratory, the X-10 Graphite
Reactor was the world’s first continuously operated nuclear reactor.
Built during the World War II Manhattan Project, the Graphite Reactor
successfully produced plutonium (Pu) and enabled the demonstration
of the chemical separation processes used to produce plutonium for
the second atomic bomb.

After World War Il, the reactor was the nation’s principal source
of radioisotopes for academic, scientific, medical and industrial
use, and supported research in many fields of physics, chemistry,
biology and engineering.

Ernest Wollan and Clifford Shull

Neutron Science, 1946; Future Nobel Laureate Clifford Shull and Ernest
Wollan pioneer neutron scattering studies, demonstrating that neutrons can
be used to probe the nature and structure of matter.

A Place in Histo

“From its secret birth to its reluctant retirement, the Graphite Reactor
contributed immeasurably to the defense of this nation’s liberty, and to
the betterment of man’s everyday life.”

Glenn Seaborg,
Chairman of the U.S. Atomic Energy Commission from 1961 to 1971

U.S. DEPARTMENT OF

National Laboratory



1939

THE ATOMIC
AGE OPENS :

I Nobel Laureate Albert
| Einstein signs a letter
| to President Franklin
| D. Roosevelt asking
| the U.S. government
| to develop the fission
| bomb before
| Germany does.

Robert Oppenheimer and Albert Einstein

Tue UNITED STATES
I 9 4 | ENTERS WorRLD Wak II

Plutonium is discovered by — ERS
= On December 7,

Glenn Seaborg at the University

of California—Berkeley. 5 ;
Seaborg and his team oe 4 magoces Panes.
develop a multistage au scS US NeW ey
ehenical proseesto | ships at Pearl Harbor. |
separate plutonium
from uranium and
concentrate and
purify Pu.

GRAPHITE REACTOR
1S BorN

The new laboratory is called Clinton Laboratories. From February to
November, 150 buildings are erected, employing 3,000 construction
workers and costing $12 million.

1943

| At5 a.m. on November 4,

#1 spontaneous nuclear chain |
reactions begin at the
Graphite Reactor.

1944

AMERICAN
DISCOVERIES

1940

Multiple separation processes for enriching uranium are
conceived. The electromagnetic separation process would
later be used at Oak Ridge's Y-12 plant to supply uranium for
the first atomic bomb.

The Manhattan Project is born.

Col. Leslie Groves is charged with

the military aspects of the project,
and Robert Oppenheimer is tapped to lead the technical
development. The goal of the project is production of
uranium and plutonium and development of an atomic
bomb.

USHERING IN
THE ATOMIC AGE

In December the first sustained,
controlled nuclear chain
reaction is demonstrated

at Chicago Pile 1 at the
University of Chicago.

Il Enrico Fermi is chosen as manager of the
Graphite Reactor project, and his team

THE RACE
TO THE BoMB

The first gram quantities of purified plutonium are shipped from
Clinton Laboratories to Site Y in Los Alamos, New Mexico.



IB Plutonium production reactors at |
94 ) Hanford Engineer Works in Richland, | THE Boss Drop,
Washington, produce usable quantities W lV iT
of “°Pu for a plutonium bomb. | I ENDS

August 6: ae
The United States drops a “y
uranium-fueled atomic bomb on s
Hiroshima, Japan. The uranium came

from the Y-12 plant in Oak Ridge.

August 9:
The United States drops a
plutonium-fueled atomic bomb on
Nagasaki, Japan. The plutonium
came from the Hanford Engineer
Works in Washington state.

RADIOISOTOPE PRODUCTION New AGE
AND NEUTRON SCIENCE OF DISCOVERY
The Graphite Reactor produces the first radioisotopes from a reactor, carbon-14. The discovery of the element promethium is

‘Anew era of nuclear medicine begins. announced. It was isolated from by-products of
. uranium fission at the Graphite Reactor in 1945.

20 years after first going critical.
Logan Emlet uses electricity produced by the Graphite Reactor

to operate a small engine. This is the first demonstration that A N. ATIONAL
heat from a reactor can be used to produce electricity. L

The Graphite Reactor
| is designated a
Registered National
Historic Landmark
by the National Park

tL. Doan, Alvin Weinberg,
"and Glenn Seaborg