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THE ROLE OF OAK RIDGE IN THE MANHATTAN PROJECT(FOR A TECHNICAL AUDIENCE)
William J. (Bill) Wilcox Jr., Oak Ridge City Historian
Retired Technical Director for the Oak Ridge Y-12 & K-25 Plants
[During the Manhattan Project (from May 25, 1943) a Jr. Chemist, Tennessee Eastman Corp., Y-12 Plant]
A Lecture for the UT Nuclear Engineering Colloquium, November 9, 2005
I’m honored to have been asked to tell you something of the story of Oak Ridge in WWII,
Knoxville’s then secret neighbor. As one of the thousands of who was privileged to work at Oak
Ridge during those eventful years, I’m always happy to tell that story but I am honored today to tell
it for my first time to a group from “my” university!
Our history starts back in the midst of WWII, in 1942. Back then, 62 years ago, here in Knoxville,
like all other cities in the U.S., people were working hard to support the war that we were dragged
into by Pearl Harbor six months before. TVA was hard at work building more than a dozen dams
to supply power for the nearby Alcoa plants that was producing the aluminum metal crucially
needed for our bombers and fighter planes. Rohm and Haas was manufacturing plastic nose
bubbles and gun turrets for the big bombers. The Coster railroad shops were building rolling stock
and servicing the country’s railroads. Knoxville knitting mills were turning out thousands of
uniforms and other gear. Engineering students here at UT were hard at work studying civil,
mechanical, and electrical, but of course not nuclear engineering.
Then in the fall of 1942, Knoxvillians began to be aware that something new was brewing, with
advertisements appearing in the morning Knoxville Journal and evening News Sentinel wanting
construction workers for some important war work in the farmland out in nearby Anderson County.
And what for was all hush-hush, no one could find out what was going on – the answer to even the
top UT and city officials, was just, “vital war work.”
Army engineers had quietly scoped out an area of 60,000 acres in the farmland of Anderson and
adjoining Roane County, about 12 miles long, 8 to 9 miles wide. It met all 6 of their site criteria. It
was sparsely settled with fewer than 1,000 families that had to be moved out, it had good power
supply from the TVA and good water from the clinch river; it was close to a good labor supply in
Knoxville, was served by two railroads, and the unique ridge and valley typography meant they
could put the several plants and the town in each in their own valley which was good for both
security and safety. The first name Knoxvillians saw it called in the ads was the “Kingston
Demolition Range.” That started lots of rumors so the army quickly changed that to “Clinton
Engineer Works,” and that is what it was called until after the war when it began to be called
simply Oak Ridge – taken from the long time name of the Black Oak Ridge on which the city is
built.
The construction workers came as a flood and the roads out to “the site” were jammed. Then the
next spring, in April 1943, armed guards showed up at all seven gates into the area, and that
stopped any weekend sightseeing. For the next 3½ years, we were a “Secret City.”
So what was going on out there? It had its roots of course back at the beginning of 1939 when the
German chemists Hahn and Strassman reported in Naturwissenschaften the news that bombardment
of uranium by neutrons produced barium, about half its weight, and soon the explanation came that
the uranium nucleus had been split with release of tremendous energy. Physicists around the world
rushed to their laboratories to repeat and confirm this startling news and by mid year 1939 the
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media was speculating about this great new source of energy. One pound of U could drive an ocean
liner across the Atlantic, and so on. Sometimes you hear peace wishers say that if our country had
not developed the bomb, the world would be a better place. No way! Physicists in many countries
like Britain, France, Japan, Russia, as well as the U.S. went to work, and their scientists and
engineers were just as capable as ours in working through the many problems. History has shown
that. The difference in the WWII U.S. was that Albert Einstein and others convinced our President
that if any country might figure out how to do it, we should be the first. Germany had a head start.
We had great respect for German science and technology, and Roosevelt knew if Hitler got an
atomic weapon he would not hesitate to use it. So with the governments’ support, work started in a
half dozen universities to see if a bomb could be made.
Two years later, in the summer of 1942, six months after Pearl Harbor brought us into WWII,
President Roosevelt was told it might be done, but would take a huge effort. He then acted to
combine all the research efforts that had been going on, and ordered the army engineers to head up
the job of building the bomb on a top priority, very secret, all-out effort. Secret so as not to have
others increase their efforts too. The effort was given the code name “Manhattan Project”, simply
because the office of the first District Engineer was in New York City in downtown Manhattan!
So what was Oak Ridge’s mission? It was the extraordinarily difficult challenge of producing more
than a hundred pounds of nearly pure U-235, separating this lighter of the two forms of uranium
that occur in nature from the heavier U-238 that is 139 times more abundant. Difficult because
isotopes behave identically in all chemical reactions so one has to develop a process taking
advantage of their little 1% difference in weight. And, if that isn’t hard enough, U-235 is, as we
hillbillies say, “scarce as hen’s teeth.” In every thousand kilos of uranium you dig out of the
ground, there are only 7 of U-235, all intimately mixed up with 993 of U-238!
By the fall of 1942 the new Commander in chief, the hard-driving and brilliant General Leslie
Groves, had to listen to the university scientists lobby for their favorite candidate process and then
make hard decisions as to what kind of plants to build to produce U-235. The trouble was that none
of the scientists could promise success. Not one had produced more than fractions of a gram of U235. Columbia University researchers championed a process called gaseous diffusion, the
University Of Virginia researchers favored using gas
centrifuges, a US Navy team recommended liquid thermal
diffusion, and the University of California urged using the
electromagnetic approach. Listen and debate with his
advisors the General did, but meantime he knew he would
have to have a city and plants of some kind so he got his
engineers started on the infrastructure.
The very first building they started on was the
Administration building in November 1942. Soon after,
they started to build the city. Soon after that, the
decisions were made and building sizes guessed at –even
without knowing the size of the operating equipment.
Construction contractors were swarming over this valley,
turning farmland into a new city that in two years grew to
75,000 people, the 5th largest in the state, with the 9th
largest bus system in the US, bringing in at the peak some
20,000 commuters every day from as far away as
Chattanooga! But it was secret, not yet shown on any
maps!
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This then was what Oak Ridge was built to do in secret -- build
these two, huge, never-before designed or operated plants in the
midst of a world war with shortages not just of all materials but of
the thousands of technical people who would be needed. It was
driven always by the need to beat the Germans to the bomb. In
1942 the German U-Boats were in command of the Atlantic
Ocean, devastating our merchant freighters, so billboards that
warned “Loose Lips Sink Ships” were effective in reminding
folks not to discuss anything going on at CEW.
Ground breaking for Oak Ridge’s, and the worlds, first U-235
separation plant code named Y-12, took place in February 1943. Some 20,000 construction workers
worked that summer to build the infrastructure and buildings, and install equipment. It seems
incredible today that in just 11 months the first production unit was in operation in January 1944!
The process used for this first isotope separation plant was developed by professor Ernest O.
Lawrence at the University of California. The process used devices they named calutrons, from
“cal” for California, “u” for university, and “tron” from cyclotron.
They operated on the same principle as a mass spectrometer. Y12 eventually had 1,152 calutrons; with 864 big alpha units that
produced about 15% U-235 followed by 288 smaller beta
calutrons that finished the enrichment.
This is a photograph of a group of 96 of the big alpha calutrons,
arranged in an ellipse to conserve the magnetic field, and quickly
code named by the construction folks a “racetrack.” In the left
foreground, notice the d-shaped units that hold the sources and the
receivers. The next slide shows one being inserted in the Calutron
tank.
The alpha calutron electromagnets were huge, about 8 feet tall and
their windings would have required an exorbitant amount of
copper, already in critically short supply because of other wartime
needs. Knowing that silver was an even better conductor, and that
tons were just sitting there in the U.S.Treasury vaults as bullion
reserve, the top official in Oak Ridge went to the Under Secretary
of the Treasury in Washington and explained our top priority need
for silver for a vital war project, and assured him it would be well
guarded and returned right after the war. “Yes, well, Colonel,
how much are you thinking about borrowing? He answered,
“Something between 5 and 10,000 tons. The official was
horrified, “At the treasury we do not speak of tons of silver, our
unit is the troy ounce!” So Y-12 borrowed 408 million of them,
14,000 tons worth more than $300 million. A couple of years
after the war it was all stripped it out and given back to the
treasury!
The next slide shows a beta or second stage track, instead of 96
big calutrons with magnets that are nearly eight feet tall, here
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there are only 36 calutrons in a track and magnets are about half the size. The magnetic field
fringed out from the face of the calutrons so that red line was painted on the floor some six feet
away from the track, and signs warned against approaching closer wearing wrist watches or
carrying steel tools. A janitor one night carrying a mop and bucket had been warned, but could see
no earthly reason for such a rule and since no one else was in sight walked over the red line. His
bucket soon took flight out of his hand and the next morning someone spotted it pasted to the side
of the unit, water and mop on the floor, and the janitor never seen since.
By the end of the war in 1945, Y-12 looked like this,
snuggled in its nice valley, and costing near a half
million, in today’s dollars $5.2 billion. It was built in
less than 3 years. Wartime urgency had ruled out
allowing any time for pilot plant testing, forcing
working out the problems during the production process,
so startup was slow, but eventually very successful. The
start/stop calutron operations were very labor intensive
because of the complex chemical operations required to
recycle everything, and at the peak in May 1945, 22,400
people worked at Y-12. The contractor who operated it,
Tennessee Eastman Corporation of Kingsport, TN was
by far the largest employer of operating people at Oak Ridge during the war.
But the General couldn’t be certain Y-12 could do the job in the time he wanted, so he went ahead
with a second, even costlier “backup” isotope separation plant. It came along about a year behind
the Y-12 plant. It was even more costly to build and employed an entirely different technology
called gaseous diffusion. By comparison to the calutrons,
it sounded easy: all one needed to do was to allow some
gaseous form of uranium to seep or diffuse through a
porous membrane code named “barrier”, and a little bit
more of the U-235 will diffuse because their molecules
being a bit lighter move a little faster. But then it starts
getting a little trickier. The holes in this porous
membrane must be smaller in diameter than the mean free
path to minimize collisions with the walls. And they all
need to be the same size, if too large, you have a pin hole
- both isotopes just flow through, if some are too small the
gas condenses and both flow through. And, of course, to
get any decent flow rates, you have to have hundreds of
millions of holes per sq cm. What a set of specs! The secret of how to make that porous barrier
had eluded top scientists in both the U.S. and in Great Britain for over 3 years, both of whom
started trying in 1941.
But that hadn’t stopped the team at Columbia University from selling Gen. Groves on its potential,
and he agreed to build the plant on their assurances that they could solve the barrier problem before
the plant was finished! In addition to the barrier problem, the
engineers faced a long list of new engineering and technical
problems. Right off, very unlike the Y-12 process, the basic
separation factor they could expect was very low. If the barrier
hole size was perfect, they could hope for less than ½ percent
separation in one diffusion operation, so the diffused gas would
have to be collected, repressured and sent through again. They
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came up with a neat design for a diffusion cascade of stages, which is what they called each pass
through the barrier. In this slide three stages are shown, and you see things begin getting less and
less simple. The process required valves to control pressures, gas compressors to restore pressures,
coolers to remove the heat of compression and keep
temperatures constant. And, by the way, Gen. Groves soon
asked, and how many stages do we need with this low
separation factor? Well about 3,000. So how big will this
building be, well not much more than 40 or 45 acres! Wow,
thought General Groves! But they had even more difficulties
to confess!
The good news was that uranium hexafluoride was a nice
stable gas and that fluorine had no isotopes to complicate
separation. The bad news was that it reacted violently with
organics and water and would chew holes in iron pipe, so the
whole 40 acre plant with its thousands of tanks full of barrier
and miles of interconnecting piping would have to be nickel
plated, all pinhole free and yes, some brand new families of materials would have to be invented for
use as lubricants for compressors and gas coolers. Even worse, that exquisite barrier material with
all those holes had to resist either corrosion that would open up the holes or plugging that would
make them smaller. The General had to wonder if it was at all possible to solve all these never
before tackled problems in any reasonable time frame.
Well, the plant the Kellex Corp. engineers finally figured out
how to build required 25,000 construction workers at peak
employment and the first stages were started up in 18 months.
It was truly an awesome accomplishment, built under wartime
conditions. Said to have been the largest building housing a
single process anywhere in the world – it was the largest
building of the entire Manhattan Project. Built in the shape of
a “u”, each leg is a half mile long, 400 feet wide, and 65 feet
high, all of it interconnected. There are four stories: a
basement for ventilating fans and transformers accessed from
the outside, the ground floor for the diffusers and compressors
accessed from inside the “U”, a third floor for all the process
gas piping that interconnects everything, and the top floor
which is the operating floor where operators can do the valving
needed and access the instruments and controls for the process.
If you or Gen. Groves walked into the ground floor where the
compressors were pumping the corrosive gas through the barriers,
this is what you would see: 300 to 400 feet long corridors with
thousands of compressors with their shafts and electric motors
making a lot of noise and heat behind those steel housings. The
compressors are visible together with their shafts and motors.
It was a brilliant engineering effort, and a superb construction effort
– the contractor could hardly believe the Army engineers really
meant it when then said the whole complex 40 acre system had to be
as leak tight as a thermos bottle and clean to the point of not a
fingerprint on the inside of the piping!
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K-25 cost even more than Y-12, $512 million or $5.5 billion in today’s dollars.
In the summer of 1944 just as the first sections of the building were being
finished, the General could finally stop worrying because a workable barrier
was finally developed and the first stages were started up in February 1945,
just 18 months after groundbreaking. It was several months before useful
enrichments of 1% would be reached, so K-25 contributed only in a minor
way to the first atomic bomb, but it proved so much less costly to operate
than the Y-12 calutron plant, that Y-12 was completely shut down in Dec.
1946, a year after the close of the war which it contributed so much to
ending. The layoff of 20,000 had a devastating impact on the city, dropping
from 75,000 to about 30,000 in a few short years.
Often overlooked in Oak Ridge histories is the fact that we also
used a third brand new isotope separation process here, namely
liquid thermal diffusion. In this slide it is that long black
building along side the K-25 powerhouse with the smoking
chimneys. Called S-50, it was a small $16 million dollar
effort using technology developed and sponsored by the U.S.
Navy. It ran only for one year, but it supplied LEU at about
1% to Y-12 as feed and somewhat increased their productivity.
It proved very difficult to operate, using superheated steam at
very high pressures on the inside and cold water on the outside
to provide the thermal gradient across a thin liquid UF6
annulus. This is the isotope separation process that both the Germans and the Japanese tried
unsuccessfully to develop in WWII.
Although 97% of Oak Ridge’s WWII effort was spent
on U-235 isotope separation, we did have a tie with the
plutonium project through our graphite reactor-- the
world’s first production nuclear reactor. Shown here
under construction, the dark building in the center, it was
built in 1943 in a remarkable 10 months, achieving
criticality on November 4, 1943. Its purpose was to
make gram quantities of the element plutonium so that
chemists could develop the large-scale processes for
separating it from uranium and the fission products
when they got the big production reactors running at
Hanford. By contrast to the 36,000 people involved in isotope separation, there were only 1,500
working on this vital task, but out of those small roots grew the Oak Ridge’s research centerpiece
today, the world-renowned Oak Ridge National Laboratory, operated by UT in partnership with
Battelle.
That’s what we did at the plants during WWII. What
about the city? Back in WWII Oak Ridge looked
entirely different than it does now. Today our tree-lined
city of 27,000 is a sleepy little town compared to the
hectic wartime camp of 75,000. The town then looked
just like what it was – a big, brand new army base, built
super-fast on cleared farmland to do a particular job,
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never intended to last much past the war. The army
engineers in two years built miles of fences, nearly
10,000 homes for families; 90 two story dormitories for
13,000 single folks like me; 16,000 temporary hutments
for construction workers and soldiers, 5,000 trailers, 9
neighborhood schools, a dozen shopping centers; every
thing we wanted but liquor stores because our two
counties (and your Knox county, too) had local laws
prohibiting the sale of liquor! Yes, we had to use
ingenuity to find booze and then get it in past our wellaware guards at the gates!
But by early spring of 1945 Y-12 was finally operating smoothly like everyone had hoped it would,
finally sending nearly pure U-235 to Los Alamos. Folks in Knoxville, and Oak Ridge, too, would
have been astounded to learn that the product of all that brilliant
and costly effort by so many thousands was being carried out of
the CEW in a briefcase chained to the wrist of a lieutenant in
military security each week, sometimes twice a week! Los
Alamos technicians converted our uranium tetrafluoride to metal
and then made the metal parts for the gun-type atomic bomb, in
which a uranium-235 bullet was fired down a gun barrel into a U235 target, very rapidly creating a supercritical mass that resulted
in the chain reaction and atomic explosion. The last parts were
finished in July and shipped out to Tinian Island in the Pacific, where the first ever atomic bomb
was assembled and ready by August 1st, meeting the Manhattan Project’s near impossible target,
just 2.5 years from ground breaking. No, we did not build the bomb here, but Oak Ridge played a
major role in bringing peace to a world that had been torn by six years of an awful war that saw 54
million humans killed by other humans. When I am asked about our role in the Manhattan Project,
that is my answer. If we could have ended the war any sooner, we should have and would have.
Oak Ridge’s role was a long and uphill struggle over 2.5 years to create new designs, build them,
and work out the bugs and do it just a fast as we could. We scraped the bottom of every barrel
trying to save every milligram of enriched U. It surprises some people to learn that Oak Ridge
spent about 60 cents of every dollar - the blue sector, the plutonium production at Hanford, WA
cost 21 cents - the red sector; and the Los Alamos work 4 cents – the dark purple sector.
Very shortly after the war, Oak Ridge went to work on peaceful applications of nuclear science;
using our Y-12 calutrons and ORNL’s graphite reactor to produce radioactive and stable isotopes
that have been brought great benefits in medicine, agriculture, and industry to peoples all over the
world. Then in the 1950s and ‘60s Oak Ridge put our know-how to work developing nuclear
reactors for power plants and our diffusion plants learned how to sharply cut the costs of 3 to 5%
enriched fuels that made them competitive today. Their clean electric power, though not yet widely
accepted by the public in our own country, has been welcomed and beneficial to so many countries
all over the world.
Y-12 during the past half century has played a continuing vital role in our national nuclear defense
system, and our Oak Ridge National Lab today is building the Spallation neutron source, a $1.4
billion, 800 research tool that researchers from all around the world will use in advancing the
frontiers of bio and materials sciences. These many peaceful benefits of nuclear energy are rich
legacies of the Manhattan Project in which Oak Ridge played such a vital and successful role.
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