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National Museum of Nuclear Science & History

Ray Smith’s Interview

Manhattan Project Locations:

Ray Smith is the historian at the Y-12 National Security Complex. He provides an overview of the history of Oak Ridge, the uranium enrichment processes undertaken at the Y-12, K-25, and S-50 plants during the Manhattan Project, and how the Fat Man and Little Boy bombs worked. Smith talks about efforts to preserve Oak Ridge’s unique history.

Date of Interview:
September 6, 2013
Location of the Interview:


Cindy Kelly: Okay, let us get started. Cindy Kelly with Atomic Heritage Foundation, September 6, 2013. I am here with Smith. The first question is please say your name and spell it. 

Ray Smith: My name is Smith. That is R-A-Y S-M-I-T-H. I am the historian at the Y-12 National Security Complex.

Kelly: That is terrific. This is going to help us put together a little vignette. What is Oak Ridge? This is especially for people who are visiting the Hanford site. Could you give us a brief explanation? What is Oak Ridge? 

Smith: Oak Ridge came about because of the Manhattan Project. Prior to 1942, about November of 1942, this was a small rural community of ridges and valleys here in East Tennessee. There were small communities. When the Manhattan Project started, there were about 3,000 people that had to leave to make room for the 60,000 acres that the government needed for the Manhattan Project. In November of 1942, there were notices tacked up on their doors. Those people had to leave in a matter of weeks. Construction began almost immediately. The reason for the construction was that General Groves wanted a plant site. He needed some place to say this is where we are starting the Manhattan Project. Oak Ridge was that choice. Oak Ridge was intended to separate the uranium-235 for the first atomic bomb. It was used to first put in place the electromagnetic separation process, which turned out to be the Y-12 site. 

Also at the same time, construction was being planned and started on the graphite reactor, which is at what is now the Oak Ridge National Laboratory. The reason for that was to prove that you could produce plutonium in a uranium reactor. Once that was done, then Hanford came into play. That is where they built the reactors to produce that plutonium. Oak Ridge continued to be the focus of the uranium-235. 

The other process that they started was the gaseous diffusion process at the K-25 site. It was being developed alongside the electromagnetic process. It was first to come on. But by March of 1945, the gaseous diffusion process was coming on. A third process, the thermal diffusion process, also fed a little bit of enriched material into the Y-12 K neutrons. In a nutshell, the reason for Oak Ridge is to produce enough [00:03:00] uranium-235 for the Little Boy – the first atomic bomb ever used in warfare. That is why we came into being. 

The Y-12 site was unique in that it had never been tried before. Ernest Lawrence had developed this concept of a cyclotron that would separate – or a big mass spectrometer that would separate this uranium. They designed something called a calutron. California University Cyclotron is what it stands for. It was an apparatus that used magnets to separate the two isotopes of uranium – the 238 and the 235. A very simple way to think about that is if I had two rubber bands hanging down from my hand. I put a golf ball on one and a ping-pong ball on the other. I swung it for half a turn. That golf ball would stretch that rubber band further than the ping-pong ball. So you get two arcs. That is what happens with uranium-235 and 238. The centrifugal force causes the 238 to make a larger arc than the 235. You can catch that 235. That is what they were looking for. The only problem is with 1,000 pounds of uranium ore, you only have seven pounds of uranium 235. It is a very difficult process. It is a simple process, but very difficult to get enough of that material. 

They used 1,152 calutrons. They had 22,000 people working on those calutrons for almost a year to get enough material for Little Boy U-235 and have a little bit left over. It was a very special process that had never been tried before. Of course, the one interesting note is that Great Britain knew. In the late 30s, the scientists were aware that you could release a lot of energy if you could get enough uranium 235 together. They did not have the resources. Great Britain did not have the resources to do that. So they came to the United States and said we need you. You have those resources. In fact, the Manhattan Project was a tremendous use of a lot of resources across the nation. The three main sites of Los Alamos, Hanford, Washington, and Oak Ridge were not all that were involved in it. There were many other people that were doing lots of things in support of them. Those were the three main sites for the Manhattan Project. 

Kelly: That is great. Can you do the same thing you did [00:06:00] for Y-12 for K-25? 

Smith: I can. The other process that came to be used at Oak Ridge and in fact after the war ended, was the process that has been used all through the Cold War to generate the uranium 235. It is gaseous diffusion. The gaseous diffusion process is different from the calutrons and Y-12. That was a batch process. It took 22,000 people and 1152 calutrons. In the gaseous diffusion process, it is a continuous operation. It takes fewer people. In fact, you can operate K-25 on a tenth of what it costs to operate Y-12. That is one of the reasons that they shifted to that process. 

How it works is you have a barrier material that is inside some stages where the gaseous process material is pumped through. As it comes through, this barrier material that it passes through has lots of holes. They are very small holes. In a space the size of my thumbnail, you will have 200 to 300 million holes. They will all be the same size. They will all be equally spaced. As you push this material through in any one-process step, that 235 will go through just a little faster than the 238. In each of those 3,000 stages, you will begin to accumulate a little bit more and a little higher percentage of the uranium 235. This is a continuous operation process. It pumps the material in gaseous form through a barrier material that has small holes. It accumulates a higher percentage of 235. 

Kelly: That is very good. Is there somebody up there? 

Smith: I do not know whom.

Kelly: Yes there is. 

Smith: S-50, let us talk about that. The calutrons at Y-12, they first thought that they would only need a few. Then when they realized how slow the process was, they doubled the capacity at Y-12. Even then, they were frustrated at the slow pace. [00:09:00] Remember, they thought they were in a race with Germany. They were afraid they were going to get the bomb first. 

Oppenheimer and Groves were thinking about how they could speed up this process. They learned that the Navy was experimenting with something called thermal diffusion. Just by chance, they had built the world’s largest steam plant to produce electricity for the K-25 gaseous diffusion process. However, the barrier material was not hardly ready yet so they could not put that process in place. They had this huge steam plant. So Oppenheimer says to Groves, “Why don’t we build a thermal diffusion plant here by this steam plant? Use that steam and put a slightly enriched feed material into the Y-12 calutrons. That should speed up the process.” 

Groves agreed and that is what they did. Groves went to the contractor, M.H. Ferguson at the time, said, “I need a thermal diffusion plant built. I need it built by this steam plant. I need it in 90 days.” The contractor said, “It cannot be done.” Groves looked him in the eye and said “you have 80 days.” They built it in 76 days. They operated it for three months. By feeding the slightly enriched material into those calutrons at Y-12, they calculated that they shortened the war by three weeks. That thermal diffusion process was a boost to help the calutrons at Y-12 get to that material sooner. 

Also in March of 1945, the gaseous diffusion process did come online and began to feed material into the calutrons at Y-12. By May or June of 1945, they were cleaning out all of those 1152 calutrons. They were getting that material out and getting out to Los Alamos so they could actually build the needed materials to build Little Boy. 

Kelly: How much material did they have? 

Smith: Y-12 worked on those 1,152 calutrons, 22,000 people for almost a year as they built those calutrons and worked the process. Ultimately, they shipped about 60 kilograms. It was about 140 pounds. That is less than a gallon in volume. The way they would do that is kind of interesting. As they took the material out of those calutrons, they would put it in small gold-lined coffee cup sized containers. They put two of them in a briefcase, strap it to an Army Lieutenant’s arm, dress him up to look like a salesman, put him on a passenger train up through Chicago and out to Los Alamos. That is the way all the uranium for Little Boy got transported from Y-12 out to [00:12:00] Los Alamos. 

An interesting thing about that is just a side note from a security standpoint. When they shipped that material out with two people, they would ride that train up to Chicago. Then they would transfer it to two other people. They would ride the train out to Los Alamos. The two that went to Los Alamos knew that they got something in Chicago and took it to Los Alamos. The two that came from Oak Ridge knew they got something in Oak Ridge and took it to Chicago. Neither one of them knew where the other endpoint was. That was something that Groves insisted on. There was that kind of separation to keep the security. 

Kelly: That is good. Do you know how much material they produced during World War II? Were they ready? 

Smith: That is an interesting note about the amount of material for atomic bombs at the time. Of course, the plutonium being produced at Hanford, Washington was used in the Gadget and was used in Fat Man. The uranium bomb, Little Boy, was the one that Y-12 produced, K-25 provided some, and S-50 is the thermal diffusion. They provided feed materials into Y-12. After having produced all that Y-12 could produce, they sent enough for Little Boy and a little left over. It was not enough for another bomb. The same thing was true with Fat Man and the Gadget. They were very low on the amount of materials for a third explosion, if you might. When President Truman threatened Japan with a rain of ruin if you do not surrender, it was somewhat of an empty threat. He did not have another nuclear weapon or atomic bomb at the time. It would have taken some period of time to build another one. The plutonium would have been the fastest because it would have taken a good long while for Y-12 to produce enough uranium for another Little Boy. 

Kelly: Maybe you can just explain Fat Man and Little Boy, for people who do not know the terms. 

Smith: I can. Little Boy is the one that was the uranium bomb that used uranium 235. The way it was designed is they called it a gun barrel design. You have a little bit of uranium here and a little bit of uranium here with a barrel between them. There was a little dynamite behind this one to blow them together. When this one comes down, it kind of seats itself inside the other half or piece of the material. That gets enough of it together that the neutrons start splitting the atoms. You have an enormous explosion. 

The Fat Man bomb, on the other hand, is an implosion type of bomb. [00:15:00] It was designed with a plutonium core in the middle with 32 implosion devices on the outside that had to implode all at once so that you would compress that plutonium to make it go into a critical state. The problem that they had and the reason for using the Gadget on the Trinity explosion is if they only had one of those 32 that did not go off, then you would not have that compression that you needed. It would have a blowout. They needed to test that. They did not need to test Little Boy. They knew that if you got enough of that material together, it was going to explode. Just pushing it together was all you needed. In the Fat Man configuration, you needed to compress that plutonium. They needed to test that to be sure it would happen. That is the difference between the plutonium-based bomb, the Fat Man, and the uranium-based bomb of Little Boy. 

Kelly: That is good. He is doing okay. What are some other questions you get on a usual basis? 

Smith: Why “Y-12” is always a question. The response is that “Y-12” does not stand for anything. There was Y-12, X-10, which is now the Oak Ridge National Laboratory, K-25 the gaseous diffusion plant, and S-50 the thermal diffusion plant. 

The only one of those four that might have any significance to the name is K-25. The K might stand for the Kellex Company that built the gaseous diffusion equipment. The 25 is a shortcut name for uranium 235. The two is off of the right hand side of 92 – the atomic number for uranium. The five is off of the right hand side of 235. They called it 25. They did the same thing with plutonium. They took the four off the right hand side of 94, and the nine off the right hand side of 239. They called it 49.  

There is a fellow that has written a book—Jeremy Bernstein. The name of his book is Plutonium, the World’s Most Dangerous Material. On the cover of his book, he has a huge watermark of a four and a nine. He knows the story. But Y-12 does not stand for anything. Interestingly enough, Y-12 National Security Complex still retains that original Manhattan Project name of Y-12. Most of the other sites have changed their names to other things over the years. But Y-12 proudly holds on to that code name of Y-12. 

Kelly: That is good. What is Oak Ridge doing to preserve its history? 

Smith: Well, [00:18:00] we are hopeful that the Senate will pass that Manhattan Project National Historical Park bill. It will be a part of those three locations – Hanford, Los Alamos, and Oak Ridge. 

Here in Oak Ridge, we are hoping that we will be able to put together a hub in a spoke concept. You will have the American Museum of Science and Energy to be the place where the National Park Service would have a central location here in town. The visitors would learn about Oak Ridge and its history. Then they would also have the opportunity to go visit the K-25 site, which will be preserved with the original footprint of the U. There will be a history center there, a viewing tower there, and also there will be a replica of the building itself. It is just a small piece of it. But it will have some of the original equipment in it, so that you will be able to see that gaseous diffusion process equipment in a setting that would replicate what the original building looked like. You can see the size of the U, so you will have an impression of how large it was. 

At Y-12, there will be an opportunity to visit Building 9731, which is the first building completed on the site. It has the world’s only alpha calutron magnet still intact inside that building. Then Beta-3 – building 9204-3 – is the building that still has beta calutrons in it. Those calutrons continued to operate here at Y-12 for a number of years by the Oak Ridge National Laboratory to separate isotopes that were used to feed over to the graphite reactor. They would make those medical isotopes. Dr. Alvin Weinberg, who was the director of the laboratory for many years, says it is the most important contribution Oak Ridge has made to the world – those medical isotopes. The same equipment and same science that produced the uranium for Little Boy also produced the stable isotopes that are used as targets to produce medical isotopes. 

The third part of those spokes, if you will, will be that graphite reactor. It is over at the Oak Ridge National Laboratory. It is a national historical landmark on the register of historical places. It has been since 1964. It still has the features of the operating reactor. In other words, you would see the face. You can go into the control room. You can see the places where they actually loaded the stable isotopes to produce those medical isotopes. It would be an outstanding exhibit for people to see. Those three spokes off of the main hub are what we are hoping to develop as a part of the Manhattan Project [00:21:00] National Historical Park here in Oak Ridge. 

Kelly: What I might do is splice on a little bit about the town site and houses. That is so unique. 

Smith: Let me talk about that a little bit. Another aspect of the Oak Ridge history would be a part of the Manhattan Project National Historical Park. It is the city itself and the town site – the Jackson Square area. It was the original Townsite. We are renovating the [Alexander Inn] guesthouse, which is where all of the people stayed that came here during the Manhattan Project. It is going to be a senior living center. But the lobby and the exterior of the building are going to look just like it did in 1945. A part of the national park tour will also include the city. 

Kelly: Maybe you can talk just a little bit about the Alphabet Houses. It is interesting there that they have sister Alphabet Houses. Can you talk about that? 

Smith: One aspect of Oak Ridge’s history that is still visible today is those Alphabet Houses. If you go up from Jackson Square and just start driving up the ridge on any of the avenues that go up the hill, you will go by the different Alphabet Houses. You will go by the As, the Bs, and the Cs. You will see the larger houses up near the top of the ridge. There is a road up there called Olney Lane. They called it Snob Knob back during the Manhattan Project. That is where Colonel Nickels lived. His home is still up there. It has been maintained over these years. There are others who have lived up there as well in the larger houses in the city. 

Kelly: Okay, thanks. How about the Castle on the Hill? Tell us about that. 

Smith: Okay. Just across the street – the main street of the Oak Ridge turnpike from the Jackson Square town site area is where what is called the Castle on the Hill is. The reason it was called a Castle on the Hill is because it was such a large office building. By the way, it is located between Pyatt’s Place and Tadlocks Farm. 

To get that into perspective, I have to tell you that John Hendricks is the one who predicted that that is where that building would be placed. He is known as a local legend here in Oak Ridge as the prophet of Oak Ridge. He died in 1915. 

In about 1900, he said that there would be a large factory built in Bear Creek Valley that would help win the greatest war there will ever be. He said there would be a city built on Black Oak Ridge. He said there would be a railroad spur go down by his property line. He said the seed of power would be between Pyatt’s Place and Tadlocks Farm. [00:24:00] As I said, he died in 1915. 

In 1942, November when they came in to start the Manhattan Project, the first shovelful of dirt they dug was right between Pyatt’s Place and Tadlocks Farm. That is where they put the administration building. That was called the Castle on the Hill. That is where the federal office building is today. That city on Black Oak Ridge is Oak Ridge. That railroad spur runs right down by his property line in Hendricks Creek subdivision named for John Hendricks. Of course, Y-12 is in Bear Creek Valley, where the uranium for Little Boy was obtained that did help win World War II. I do not know what you think about prophecy. But the legend is that John knew it was coming. 

Kelly: That is great. 

Smith: Let me tell you the Senator [Kenneth] McKellar story. You might not use it, but it is a good story. If you read in the history books about how Oak Ridge was chosen, they will say that it is because of these ridges and valleys. All of East Tennessee is laid out this way with ridges and valleys lying across the terrain. They are running from northeast to southwest. They thought that if they placed the plants down in the valleys, if one of them exploded, those ridges would protect the city, which is just on the other side of Pine Ridge, from Y-12. I am not sure about that, but that is what the history books say. 

However, what may be closer to the truth is that when Albert Einstein wrote that letter to President Roosevelt saying Germany is buying up all this uranium ore. He thought they were going to be building a bomb. Roosevelt knew it would be an expensive undertaking, so he put General Groves in charge of the Manhattan Project. Groves had just finished building the Pentagon. He knew how to put a large construction project together. He knew how to get private industry involved. He knew how to spend money. President Roosevelt also called in Senator McKellar. He said, “Senator I need to put a large amount of money against the war effort. I cannot let the press or anyone know how much it is or what it is being used for. Can you help me with that?” 

Senator McKellar said, “Yes, Mr. President. I can do that for you. Just where in Tennessee are you going to put that thing?” That might have more to do with us getting selected than any ridges and valley or lay of the land. 

I will tell you one more Senator McKellar story. I know this one is true because the man that it happened to is still alive today. His name is Lester Fox. He is the patriarch of the Fox Automobile Dealerships in this area. In 1942, he was a sophomore in high school in Oliver Springs. It is a little community just north of here. He and his buddy were skipping school. They were playing a pinball machine. When they got through, they were walking down the main street of the little town. [00:27:00] They walked by the telephone office. The telephone operator leaned her head out and said, “Lester go get the principal. He has an important phone call.” 

Lester is skipping school, but he does. He goes and gets the principal. The principal comes and takes the phone call. He comes back to the school, calls all the students together in an assembly, and says, “I have just gotten a phone call from Senator McKellar. He wants me to tell you to go home and tell your parents you are going to have to find another place to live. The government is going to take your property for the war effort.” 

Lester swears that is the way these 3,000 people first learned they were going to have to get off of 60,000 acres in order to make room for the Manhattan Project. In a matter of days, they were getting notices tacked up on their door that said they had just weeks to get off their property. Many of them did not have automobiles. They did not have trucks to move their belongings. If they had an automobile, they might not be able to buy gas for it or tires. Those things were rationed. What they did have were young men in the military getting killed in that war. They wanted to do anything they could to help stop the killing. They got off their property in a matter of weeks in order to make room for the Manhattan Project. 

Let me say something about the designators for the sites. Oak Ridge, being the first site that was started, was designated the X-site. Of course, we had the Y-12, X-10, and what turned out to be the Oak Ridge National Laboratory. The K-25 and S-50 – K-25 being gaseous diffusion and S-50 being thermal diffusion – those were located at the X site here in Oak Ridge. The Los Alamos site was the Y site. Then Hanford was designated the W site. Now of course, Los Alamos was where the material was being shipped to. Fat Man, Little Boy, and the Gadget were assembled there. But the process materials coming from the X site to the Y site and from the W site to the Y site is the way that you have to look at the Manhattan Project. It is the three sites and how they were complementary. Plutonium was coming from the Hanford site. Uranium was coming from the X site here in Oak Ridge. Then the assembly [00:30:00] work was done at Los Alamos. 

Kelly: Once again, XYZ. 

Smith: That is right, XYW. 

Kelly: That is cool. Now there were check-in stations built. 

Smith: Oh okay, let us talk about that very quickly. Oak Ridge started in 1942 and was a secret city, a closed city, until March of 1949. During that period of time, there were seven gates around Oak Ridge that you could come through. When you came through the gates, you had to have a reason for being here, someone that you were coming to see, or have a badge to get in. Everyone age 12 or above wore a badge. 

In March of 1949, the decision was made to open up the city of Oak Ridge to let the public in. Not all Oak Ridgers thought that was a good idea. They had grown to like the security, if you will, of being in what might have been one of the first gated communities. The government decided to open it up. When they did, they decided to build these check-in stations. There are three of them still here today. There is one on Bethel Valley Road, which was to isolate the Oak Ridge National Laboratory. There is one on Scarborough Road that was to isolate the Y-12 plant. There is on one the Oak Ridge turnpike out to the west that was to isolate the K-25 site. They were used to let the public come into the main part of the city, but to keep them away from the three government sites unless they were authorized to go there. They used those check-in stations from 1949 until 1953. 

In 1953, they decided to move the fences back to the actual sites. They did. When they did that, they no longer needed the check-in stations. The check-in stations have continued to be here. They were included in the historic district of Oak Ridge back in the middle nineties when they were looking at that. Two of them have been renovated and are used as small meeting places. They are decorated with many of Ed Westcott’s photographs. We use them just to have meetings for people coming into town that cannot get to the sites. We can meet with them in those little check-in stations – two of them. The one over on Bethel Valley Road has not been renovated. It has been painted to keep it from deteriorating, but the inside of it had not been renovated. 

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