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While. A program produced by Purdue University under a grant from the Educational Television and Radio Center in cooperation with the National Association of educational broadcasters today's program in part adopted from an article by carbon Allardyce and Edward R. tracking all was written and produced by Bob McMahon. It bears the title the first pile the and. The. And. Or. On December 2nd in 1942 a man first initiated and controlled a self-sustaining nuclear chain reaction beneath the West stands of Stagg Field Chicago late in the afternoon of that day a small group of scientists witnessed the advent of a new era in science.
History was made in what had been a squash rackets court precisely at 3:25 p.m. Chicago time scientist George Weil withdrew the cadmium plated control rod which set in motion the first action whereby a man unleashed and controlled the energy of the atom. A few minutes later a telephone rang in the office of Dr. James B called Harvard University. The following code message was sent. Planet in the New World. How were the natives. Very friendly. Are good. The modern Italian explorer of the unknown was in Chicago that cold December day in 1940 to an outsider looking into the
squash court where and Rico fetter me was working would have been greeted by a strange sight and the center of a 30 by 60 foot room crowded on all but one side by a grey balloon cloth. The lope was a pile of black bricks and wooden timbers square at the bottom and a flattened sphere on top. Up to half its height its sides were straight. The top half was domed like a beehive in relation to the fabulous atomic bomb program of which the Chicago Pyle experiment was a key part. The successful result reported on December 2nd formed one more piece for the jigsaw puzzle that was Atomic Energy three years before the December 2nd experiment. It was discovered that one atom of uranium was bombarded by neutrons. The uranium atom sometimes split or fission and later it was found that one atom of uranium fission and additional neutrons were emitted then became available for further
reaction with other you're running them atoms. These facts implied the possibility of a chain reaction similar in certain respects to the reaction which is the source of the sun's energy. The facts further indicated that if a sufficient quantity of uranium could be brought together under the proper conditions a self-sustaining chain reaction would result. This quantity of uranium necessary for a chain reaction under given conditions as known as the critical mass or more commonly the critical size of the particular pile. Original estimates as to the critical size of the pile were pessimistic. It was decided to enclose the pile in a balloon cloth bag which could be evacuated if necessary to remove the neutron capturing air. This balloon cloth bag was constructed by the Goodyear Tire and Rubber Company specialists in the design of gas bags for lighter than air craft. The company's engineers were more than a little puzzled about the aerodynamic qualities of a square balloon. The bag was hung with
one side left open in the center of the floor a circular layer of graphite bricks was placed. This and each succeeding layer of the pile was braced by a wooden frame. Alternate layers contain the uranium by this layer on layer construction a roughly spherical pile of uranium and graphite was formed facilities for the machining of graphite bricks were installed in the West stands week after week. The shop turned out graphite bricks before the structure was half complete. Measurements indicated that the critical size at which the pile would become self-sustaining was somewhat less than had been anticipated in the design. Day after day the pile grew toward its final shape as the size of the pile increased so did the attention of the man working on it logically and scientifically they knew this pile would become self-sustaining. The only question in their minds was when when would it happen behind his man guiding encouraging completely self-assured. Was the
nimble brained fetter me. Those associates describe him as completely self-confident but wholly without conceit. So exact were Fermi's calculations based on the measurements taken from the partially finished pile that days before its completion and demonstration on December 2nd. He was able to predict almost to the exact brick the point at which the reactor would become self-sustaining at Chicago in the early afternoon of December 1st. Tests indicated that critical size was rapidly being approached shortly after 4 p.m. the last layer of graphite and uranium bricks was placed on the pile and further work was postponed until the following day. That night word was passed to the men who had worked on the pile at the trial run was due next morning. About 8:30 on the morning of Wednesday December 2nd the group began to assemble in the squash court at its north end was about going to about 10 feet above the floor. The scientists found me Xin Anderson and Compton were grouped around instruments at the
east end of the balcony on the floor of the squash court just beneath the balcony stood George Wilde whose duty it was to handle the final control rod and the pile were three sets of control rods one set was automatic and could be controlled from the balcony. Another was an emergency safety rod attached to one end of this rod was a rope running through the pile and weighted heavily on the opposite end. The rod was withdrawn from the pile and tied by another rope to the balcony. Hillary was ready to cut this rope with an axe should something unexpected happen. Or in case the safety rods failed the third rod operated by Wyo was the one which actually held the reaction in check until withdrawn the proper distance. Each group rehearsed its part of the experiment. At nine forty five Fermi ordered the electrically operated control rods withdrawn. The man at the controls threw a small switch to withdraw them a small motor wind. All eyes watched the
lights which indicated the rod's position. The balcony group turned to watch the counters who's clicking stepped up after the rods were out the indicators of these counters resembled the face of a clock with hands to indicate a neutron column nearby was a recorder was quivering pen traced the neutron activity within the pile. Shortly after ten o'clock. Jeremy ordered the emergency Rod called Zip pulled out in time. Seven minutes later a family ordered the rod out another foot. Again the counter stepped up there clicking the graph pen edged upwards but the clicking was irregular. It leveled off as did the thin line of the pen. The pile was not self-sustaining yet. I don't have a clock the rod came out another six inches. The result was the same an increase in rate followed by a leveling off. Fifteen minutes later the rod was further withdrawn each time the counter speeded up.
The pen climbed a few points Phemie predicted correctly every movement of the indicators as they knocked off for lunch that day. He knew the time was near. It was a strange between have's rest but there was no pep talk but he seemed supremely confident his team was back in the squash court at 2 p.m.. Twenty minutes later the automatic Rod was reset and while stood ready at the control rod. At 2:50 the control rod came out another foot. The counters nearly jammed the pen headed off the graph paper but this was not it. Counting ratios on the graph scale had to be changed. Fermi ordered the control rod pulled out another six inches at 3:20 p.m. and again the change but again the leveling off. Five minutes later he ordered and pulled out another foot while withdrew the rod. Jeremy said to Compton who was standing at his side. This is going to do it. Now it will become self-sustaining. The trace will climb and continue to climb.
It will not level off from a computed the rate of rise of the neutron counts over a minute period. Decidedly grim faced ran through some calculations on the slide rule. In about a minute he again computed the rate of rise if the rate was constant and remained so he would know the reaction was self-sustaining. His fingers operated the slide rule with lightning speed. Characteristically he turned the rule over and jotted down some figures on its ivory back. Three minutes later he again computed the rate of rise and neutron count the group on the balcony had by now crowded in to get an eye on the instruments. Those behind craning their necks to be sure they would know the very instant history was made. In the background William overbet could be heard calling out the neutron count over an enunciator system. By this time the click of the counters was too fast for the human ear. The clickety click was not a study bur barmy unmoved unruffled continued his computations at last them a closed to slide rule that announced the reaction is self-sustaining. The curve is exponential.
The group tensely watched for twenty eight minutes while the Earth's first nuclear reactor operated the upward movement of the pan was leaving a straight line. There was no change to indicate a leveling off. This was it. We will. Go out. Three fifty three p.m. It was all over. Man had by then initiated a self-sustaining nuclear reaction and then stopped it. He had released the energy from the atoms nucleus and controlled that energy. But this was only the beginning. The investigation of the possibility of the nuclear chain reaction was undertaken for military purposes. Much work remains to
be done before the first atomic bomb was tested at Alma Gordo in New Mexico three and one half years later in July 1945. But that is another story we are interested in. Nuclear reactors. As with all inventions the nuclear chain reaction and be used for good or for evil for constructive purposes or for destructive purposes. Nuclear reactors are constructed devices there are machines for converting the energy of nuclear fission into forms that can be used for useful purposes perhaps by now you began to wonder how this is done. Here is Dr. Donald J Tende a professor of physics at Purdue University to explain the phenomena of nuclear fission. Do you understand what nuclear fission is and why such a large energy release companies fail. Let us review our concepts of the basic structure of matter. You and I the air we breathe the food we eat the clothes we
wear the houses we live in and all the world around us are made up of over seven hundred thousand different materials. And yet all of these hundreds of thousands of materials are combinations of just a relatively few basic substances some 90 odd in number which we call chemical elements. These elements are made up of atoms extremely small units so small that we cannot see them. It takes about 100 million atoms in a line to measure one inch while the atom is the smallest unit into which any chemical element can be divided and still retain its identity. There are still smaller particles that go to make up the atom itself. These particles are found in all out of him so that basically all matter is made up of these elementary particles and chemical elements differ from each other only because of the different numbers and arrangements of these particles
in the material structure. These are elementary particles the basic building blocks of matter are called protons neutrons and electrons. The structure of the atom is much like that of our solar system. Each atom consists of a core of neutrons and protons bound together very tightly with one or more electrons spinning about the core. Much the same concept as the planets of our solar system revolving about the sun compared to the proton or neutron. The weight of an electron is negligible so that over ninety nine point nine percent of the weight of an atom is in the core or nucleus. Actually the fact there which distinguishes one kind of Adam from another and hence one chemical element from another is the difference in the number of protons and neutrons in its core or nucleus. For example in
the case of hydrogen the atomic nucleus contains one proton. The familiar element carbon contains six protons and 6 neutrons in its nucleus. Aluminum has 13 protons and 14 neutrons in its nucleus and so on. In a like manner every chemical element can be identified by the number of neutrons and protons in its nucleus. If it were possible to keep adding protons and neutrons together indefinitely we would find ourselves with an almost infinite number of elements. However when we get up to elements which contain a total of more than two hundred thirty neutrons and protons we find that the course tend to become somewhat unstable indeed with such heavy atoms we find that if we try to add one more neutron to the nucleus the nucleus will sometimes split into two approximately equal
parts forming the lighter atoms. This process of splitting an atomic nucleus is what we call nuclear fission uranium. The heaviest of the elements that occur in nature is made up mostly of atoms that contain 92 protons and 146 neutrons. This is called Uranium 238. But a small fraction of uranium one part out of a hundred forty one or seven tenths of one percent is made up of uranium 235 uranium 235 differs from your opinion 238 only in that it has three less neutrons in its nucleus. The Uranium 235 atom is the atom found in nature that is most prone to undergo fission that is split into the lighter atoms. If we try to add a neutron to it now let's see what occurs during fission. Let's assume
that the nucleus of the uranium 235 atom can be regarded as a cluster of ninety two protons and a hundred forty three neutrons. If one additional neutron is added to this cluster and unstable cluster results This means that the forces which are holding the custard together in the first place are just not strong enough to hold together a cluster containing one additional neutron. The result is that the cluster breaks up into two or in the rare case three smaller plasters the smaller class of neutrons and protons become the cores of lighter atoms called fission fragments for each atom undergoing fission a tremendous amount of energy is released. The source of this energy is matter itself. During the fission process a small amount of matter is destroyed and a large amount of energy has been produced in its place. That mass can be converted into
energy was predicted as long ago as nine thousand nine hundred and five by Albert Einstein. As a result of this release of energy the temperature of the room at reacting mass is race. In addition to the formation of the fission fragments and the release of energy each fission releases one two or three neutrons. These neutrons are important to the continuous production of atomic energy. Since a process of faith is triggered by the addition of a neutron to the uranium 235 nucleus the production of one to three neutrons during each fission means that if additional atoms of uranium 235 are in the vicinity of the fissioning atom it is possible that one or more nearby uranium 235 atoms will capture these neutrons and will them selves undergo fish. These Adams during fish release additional
neutrons thus enabling a Chain Reaction to be set up. For example let us assume that an average of 2 neutrons is released during the fission of each uranium 235 atom. Each of these two neutrons is now capable of producing fission and each of two uranium 235 atoms. When these two uranium 235 atoms undergo fission a total of four neutrons will be produced thus causing four new uranium 235 atoms to fission. This time we will get eight fission is now giving sixteen neutrons each set of physicians increases the number of neutrons and hence new fashions twice as many as in the previous set. It is obvious that after not too many sequences the number of atoms undergoing fission rises into the hundreds then thousands and soon into the millions and billions and even into the billions of billions or more. It is this type of increase infections all of which occur in a small fraction of a second which takes place in an atomic bomb explosion.
However the rate of the chain reaction can be controlled so that the accompanying release of energy can be turned to useful purposes instead of destructive ones. This can be done by seeing to it that after the number of physicians occurring during any period of time reaches a desired level. A means of siphoning off all neutrons over and above one per fission is applied. This can be accomplished by inserting into the mass of uranium. Another material which absorbs neutrons but does not undergo fission. If the right amount of Sorber is used it will absorb 1 out of the two neutrons we previously assumed were produced during fission. So allowing only one neutron from each fission to keep the chain reaction going the rate of the Chain Reaction is prohibited from increasing. And the result is a control chain reaction actually before a
self-sustaining chain reaction can be accomplished. A certain minimum quantity of uranium 235 must be present. This minimum quantity is known as the critical mass. Least amount of mass is required because in quantities smaller than this mass sufficient neutrons escape from the volume of uranium 235 without hitting another uranium 235 nucleus and the chain reaction cannot get started. However if sufficient uranium 235 is present most of the neutrons produced during fission will collide with other uranium 235 nuclei before they have a chance to escape and a chain reaction can be maintained depending on the geometry of the quantity of uranium 235 as well as on the amount of other absorbing materials present. The size of Critical Mass can vary from a few pounds of uranium 235 to well over 50 pounds.
A nuclear reactor is nothing more than a structure which enables a critical mass of fissionable materials such as uranium 235 to be assembled and provides a means of controlling the chain reaction which results from the assembly of the critical mass. Not the least striking feature of reactors is the great variety of possible designs. This is one of the things that make them so different from the power plants that we have been used to. Conventional coal furnace as are all generally recognizable as being called furnaces. And I def are and size and details but essentially they are built and operated on the same fundamental plan less cannot be said of nuclear reactors reactors of many different designs have been built and more new designs are still to come. Some reactors use neutrons moving at the high speeds they have when they are thrown out of the uranium atom when it splits. Some reactors use neutrons which have been slowed down some one but most reactors use neutrons which have been slowed down to as low speeds as possible.
The reason for this is that the uranium 235 atoms are more likely to capture the slowly moving neutrons which are in their neighborhood for a longer time. In this swiftly moving things. This means that different reactors use different amounts and different kinds of materials. To do this slowing down these materials are called moderators. The neutrons are slowed down by bumping into the atoms of the moderator much like a billiard ball is slowed down when it collides with other balls. Thus the best moderators are materials containing atoms which can collide with but not capture the neutrons. Water heavy water graphite and beryllium appeared to be the best materials for this purpose and these materials are used in many reactors because the uranium 235
atoms are not as likely to capture swiftly moving neutrons which quickly passed by a reactor whose chain reaction depends on fast neutrons much used enriched fuel. That is since uranium is found in nature contains only one part in one hundred forty one of the fissionable material uranium 235. There are not enough uranium 235 atoms in natural uranium to sustain a chain reaction of fast neutrons to make such a reactor work. It is necessary to salt the uranium with greater amounts of uranium 235. This is called enriched fuel. Iranian 235 is the only fissionable material which is found abundantly in nature and even in this case it is mixed with much larger amounts of fissionable uranium 238. However methods have been developed to manufacture two other kinds of fissionable material uranium 233 and
Plutonium 239. Neither of which are found in nature. This is done in nuclear reactors. When uranium 238 atoms and the atoms of normal for him it is store into 30 to capture neutrons. They do not fission but you have products that undergo spontaneous changes leading to the formation of fissionable atoms. Plutonium 239 and uranium 233. You mean in 235 which is found in nature and Plutonium 239 in uranium 233 which can be manufactured in nuclear reactors are the nuclear fuels reactor fuel is can be in solid form and liquid form and conceivably in gaseous form. For the most part nuclear reactors have been designed around the use of fuels in the solid form. However several promising designs have been originated
employing liquid type feel as if solid fuels are used. They may be in the form of rods slugs palettes wire flat plates or other shapes. Liquid fuels may use water solutions of official material salt a melted fissionable salt or a molten form of the fissionable metal or an alloy containing it. Since the nuclear reactor is a constant and continuous source of heat it means must be to find it for withdrawing this heat. If it's to be used to produce useful power. Furthermore if the heat generated in the reactor were not removed the temperatures would continue to rise until the complements of the reactor melted or vaporized. All kinds of coolant have been used in various reactors circulating air. Carbon dioxide or other gases. Water heavy water and various Liquid metals.
Thus we see that reactors can be built in many different ways. Although it is true that reactors must have certain basic components in order to perform their function there are many forms of each major component which can be chosen for a particular reactor as well as many combinations of confidence. Clearly a wide variety of designs is possible. Which of them should be chosen for trial for practical power uses with breeders and non breeders. High low and medium temperatures. Natural slightly enriched and highly enriched fuels homogeneous and lump fuel distributions assorted moderator's coolants and corrosion resistant coatings with all these possible variations. The number of combinations runs high. The problem is not to invent a reactor it is to select one that will yield maximum return. And that's our story of the first pile the one built by Enrico Fermi and how this small beginning has led us to the modern concept of useful power from nuclear
fission. Power McMann radio station at Purdue University grant from the Educational Television and Radio Center scientific advisor to the program Professor Donald J tend to Department of Physics. Well James posted this is Victoria speaking. This program is distributed by the National Association of educational broadcasting. This is the Radio Network.
Atoms for power
The first pile
Producing Organization
Purdue University
WBAA (Radio station : West Lafayette, Ind.)
Contributing Organization
University of Maryland (College Park, Maryland)
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Episode Description
This program features Dr. Donald Tandam, Purdue University and a dramatization of the first nuclear fission experiments.
Series Description
This 15-part series discusses the feasibility of atomic power as an alternate energy source to replace depleted fossil fuels.
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Advisor: Tandam, Donald J.
Guest: Tandam, Donald J.
Narrator: Richter, Walt
Producer: McMahon, Bob
Producing Organization: Purdue University
Producing Organization: WBAA (Radio station : West Lafayette, Ind.)
Writer: McMahon, Bob
AAPB Contributor Holdings
University of Maryland
Identifier: 57-59-5 (National Association of Educational Broadcasters)
Format: 1/4 inch audio tape
Duration: 00:28:55
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Chicago: “Atoms for power; The first pile,” 1957-03-08, University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC, accessed February 29, 2024,
MLA: “Atoms for power; The first pile.” 1957-03-08. University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Web. February 29, 2024. <>.
APA: Atoms for power; The first pile. Boston, MA: University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Retrieved from