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Posts Tagged ‘u-235’

Reid Nixon

S. Reed Nixon, nuclear engineer

On Nov. 30, I had the privilege of interviewing S. Reed Nixon, who lives not far from where I do in Orem, Utah. I met him through my wife, who has known the Nixons for several years. Over the summer, we went to visit them and Reed told me of some of his experiences as a nuclear engineer on Admiral Hyman Rickover’s staff during the 1950s. I couldn’t pass up such an opportunity, so I arranged to bring over my video equipment and interview him on camera.

Reed got into nuclear engineering by chance. He started out by receiving a B.S. in electrical engineering from Caltech in Pasadena (where he had Linus Pauling as a chemistry professor – according to Reed, Dr. Pauling would nervously pace up and down the chemistry lab during his lectures, turning the Bunsen burner gas stopcocks on and off). This was in the late 1940s, after Reed had served two years in the Navy. At the time, Robert Millikan was Chancellor and would have the seniors and their parents over for tea each year. He told how gracious Dr. Millikan was to his mother at the tea party.

Upon graduation, he moved to Provo, Utah where he taught math part-time at Brigham Young University and then started working for Telluride Power Company, which ran the power utilities for southern Utah at that time before it was bought out by Utah Power and Light. Telluride Power Company originated in Telluride, Colorado when the mines there began to have trouble with ground water. The Nunn brothers bought out a number of mines, then contracted with George Westinghouse to design a hydroelectric power system based on alternating current as conceived by Nikola Tesla. This was the world’s first commercial AC system, which supplied power to the mines for pumps that kept the water at bay. Reed had some interesting stories about this original power system, including how it was difficult and dangerous to shut off. When the mines in the Tintic Mining District around Eureka, Utah began to have the same trouble with flooding, the Nunns built a hydroelectric plant in Provo Canyon (now the site of Nunn Park) and transmitted electricity about 40 miles across the valley to Eureka.

USS Nautilus

USS Nautilus, SSN 571

After a few years with Telluride Power, Reed heard of a new laboratory being built in Arco, Idaho to process spent nuclear reactor fuel rods. They needed an electrical engineer. This was about 1951, and nuclear reactors for generating power were a brand new invention. As Uranium-235 splits, it releases free neutrons, which in turn split other atoms. The fission byproducts, such as Barium-141 and Krypton-92 (among other isotopes), are themselves mostly radioactive. Some byproducts, however, are not, and they act as neutron sponges, so that of the three neutrons given off by a single U-235 atom, only about 2.5 are available to continue the reaction. Eventually these products poison the reaction, to where fission will no longer occur spontaneously. The Arco facility (now the Idaho National Laboratory) was built to take the “poisoned” fuel rods and remove the impurities, so that the remaining U-235 could be re-used in reactors. It also was the training facility for the prototype reactor for the USS Nautilus.

After a year or two at INL, Reed applied to receive training in nuclear engineering at Oak Ridge National Laboratory, which was the primary source of U-235 enrichment at the time. It was such a new field that only one textbook had been written, and he could see an opportunity to get in on the ground floor of a whole new technology. Hyman Rickover (later an Admiral) had recently been put in charge of developing nuclear reactors for the navy, and was sending his people to Oak Ridge as well. While there, Reed got to know the navy personnel and also finished as one of the top engineers in his class. His job at INL had meanwhile been eliminated, so he decided to take a chance and apply to be on Rickover’s staff.

Hyman Rickover

Admiral Hyman Rickover, father of the nuclear navy

Rickover was infamous for being a hard-driven workaholic. He was also abusive, profane, and intolerant of anything less than perfection in his subordinates and in the contractors (such as General Dynamics) who were building the first nuclear submarines. He personally selected his staff members and all officers in nuclear vessels until his retirement in 1983. His recruiting interviews were legendary; he was known for being so confrontational during the interviews that several candidates tried to attack him physically, and so he usually had his director of personnel in the room as well for protection. He would push a candidate to the edge – he already knew their technical qualifications or they wouldn’t have been there in the first place. What Rickover wanted to know is how much abuse the person could take.

USS Nautilus

USS Nautilus, SSN 571

Reed Nixon’s interview was probably the easiest one that Rickover ever gave. After Reed was accepted, his job was to act as a liaison with the contractors as they built the USS Nautilus (SSN 571) and USS Seawolf (SSN 575), making sure that all the specifications were followed exactly, even down to inspecting each weld on the reactor vessels with X-rays. Rickover was a demon for quality assurance, and would insist that contractors tear a system apart and start over if there was even the slightest flaw. Reed was a part of Rickover’s staff through the launch of both vessels.

Using nuclear reactors to power naval vessels has many advantages, especially for aircraft carriers and submarines. The power plant can operate for many years without refueling, so there is no need for tankers to follow along and act as targets for enemy torpedoes. Also, the old diesel subs during World War II were noisy and fairly easy to locate, since they had to run close to the surface in order to pull in air and discharge exhaust from the diesel motors. Nuclear reactors run quietly (no moving parts except the propellers) and have no exhaust, so they can run silent and run deep. Our “boomer” subs (those with nuclear weapons) are said to “hide with pride.” Nuclear carriers, such as the USS Enterprise (“nuclear wessels” anyone?) and the USS Nimitz, employ at least four separate reactors. They don’t need to take up a major portion of the ship with diesel tanks, so they can hold more planes and ordnance.

The Nautilus was the world’s first nuclear powered vessel, which used what is now a standard design of saturated water cooling. It was launched in 1954, and was used to test the feasibility of nuclear reactors on ocean vessels. Two of its first accomplishments were to sail under the North Pole (Operation Sunshine) and to sail all the way around the world underwater, thereby living up to its namesake by going more than 20,000 leagues under the sea. It was decommissioned in 1980 and is now a museum in Groton, Connecticut.

USS Seawolf

USS Seawolf, SSN 575

The Seawolf used a more advanced superheated water system with liquid sodium metal as the primary coolant. The sodium, however, was corrosive and difficult to maintain and the pre-heaters for the superheated steam rarely operated at top output. The Seawolf was known as the “Blue Haze” because of a sodium leak that occurred during the original reactor fitting. It was eventually refitted for a standard reactor in 1959. The liquid sodium reactor was sealed in a steal container and towed out to sea on a barge, then sunk 120 miles east of Maryland. The Navy has not been able to relocate the container. Originally launched in 1955, the Seawolf stayed in service until it was decommissioned in 1987 after a long and distinguished career.

Admiral Rickover’s insistence on perfect quality has led to our nuclear navy now having over 5400 reactor years and over 200 million miles sailed without a single accident or even a safety incident related to the nuclear reactors. This perfect operational record should convince the general public just how safe and reliable nuclear power can be, but unfortunately it’s a fact that often goes overlooked.

Reed Nixon worked in Rickover’s office for about two years. One memory he shared of his time there was a memo that Reed wrote to a contractor in which he said that, “we desire that you do the following . . . .“ Rickover wrote a caustic correction in the margin of the memo saying, “We’re the Navy! We don’t desire anything! We demand it!” Reed eventually left Rickover’s staff to work in the private sector as a consultant, promoting the use of nuclear power in industry. Rickover wasn’t at all happy for him to leave.

The Nixons

The Nixons

Our interview ranged over many subjects, from Nikola Tesla to nuclear reactions and the disposal of nuclear waste, such as the radioactive byproducts that had been removed from fuel rods at INL. Reed Nixon was very generous with his time, and it was a pleasure to hear these stories of the dawn of the nuclear age.

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by Eli West

Guest Host

Thorium reactor

Liquid Thorium Reactor

The word “nuclear” means a lot to us today. When we hear it we think of many things: bombs, reactors, uranium, “nuculur,” and radioactive; all of these are connotations of the word nuclear. Let’s explain what each of them means.

We’ll begin with bombs. The common link between nuclear and bombs, is obviously, nuclear bombs; otherwise known as atom bombs. In essence, you have a collection of uranium atoms; specifically Uranium-235, which is very fissile.  In a bomb, a lone neutron is shot at a uranium-235 atom to create uranium-236. Since uranium-236 is too unstable, the isotope breaks apart very violently, shooting neutrons everywhere, and these reactionary neutrons in turn smash into other uranium-235 atoms, and those atoms break apart and smash OTHER atoms. Which is what makes atomic bombs so explosive.

Another think we link to nuclear is uranium. Uranium is a very heavy atom. With a standard atomic weight of 238.03 g/mole, it’s on the heavy side. However, you’re probably used to hearing terms like uranium-238 or uranium-235. What do the numbers mean? Why are they different? What does it change? The number with uranium is indicating the isotope number, which simply means that there are more or less neutrons with the same number of protons. The 238 number gives you the atomic weight of the atom. In order to find out how many neutrons there are, you simply take the atomic number (which is 92, the number of protons in all uranium atoms, regardless of isotope), then take the atomic weight minus the atomic number to find the number of neutrons. In this case it is 238-92=146. So we know that there are 146 neutrons in each atom of uranium 238. Compared to hydrogen, that’s heavy.

Nuculur. I’m not even going to go into that, except to say that the correct pronunciation, by the way, is “new-clear.”

Radioactivity: it’s a word with a history. It’s a word that’s gotten a pretty bad rep over the years, through romanticizing, myths, and fiction. Everyone has heard the stories of people getting hit with gamma radiation and gaining super powers! Or of radiation being like the Black Death, destroying any who get near. The truth is, EVERYTHING is radioactive. Now don’t get scared! That term isn’t quite as bad as believed! Let’s get a few things straight, what exactly does, radiation mean? Well, everything radiates. EVERYTHING. Radiation is just the constant output of energy. We radiate heat, and light, just like the sun; food radiates heat! Some things just radiate such high-energy waves that they become dangerous. THAT is radioactivity.

“Radioactivity refers to the particles which are emitted from nuclei as a result of nuclear instability.”

http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html

Thorium in USA

Thorium concentrations in the USA

Now, where I am going with all this is thorium. What is thorium? It’s an incredibly heavy atom, much like uranium. It has large isotopes, much like uranium. Both of them have a huge half-life, and are highly radioactive; the differences between them are: (1) uranium, when used in nuclear reactors, produces a new isotope of uranium, which can be weaponized in the form of depleted uranium. It can be formed into what are essentially large bullets crafted out of the depleted uranium isotope. The bullet is incredibly dense, and when shot at high enough velocities, can pierce tank armor. It doesn’t explode in a nuclear bomb, but it does spray radioactive uranium all over the inside of the target tank. Thorium, on the other hand, when used in a nuclear reaction will not produce a weaponizable material. Thorium and uranium are both naturally occurring materials.

Thorium is abundant compared to uranium. So as a fuel source it would be cheaper, MUCH cheaper. Thorium is not fissile itself, which means it cannot sustain a low energy chain nuclear reaction, which means that it is not actually usable in nuclear reactors by itself. However, it is fertile, which means slow neutrons can be added to it to change it into U-233 (or uranium-233), which is fissile. That’s why we can’t just start mining thorium and tossing it in nuclear reactors all over the world. First we need to create reactors that can change it into U-233, which would then be fissile.

Thorium deposits in Alaska

Thorium deposits in Alaska

The word thorium has a very simple background. The man who discovered thorium simply decided that Thor was a pretty cool guy, and that maybe he should call this thing thorium!

As of right now there are a few companies around the world that are developing thorium reactors. Their projections for finishing the project are around 2015. That’s five years. Not to mention the actual two or three years it would take to build each reactor. So, the technology is coming, but is a ways off. Some believe that once they get the reactors running, that we could wean the world off oil in as little as five years, or by 2020. However, that’s probably a bit optimistic, and there still is a lot of work before we reach that point.

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