Atoms for power; Sodium graphite reactor

LAURA. And. I transcribed the program produced by Purdue University under a grant from the Educational Television and Radio Center in cooperation with the National Association of educational broadcasters. On today's program written and produced by Bob McMahon we'll pay a visit to the 30 m reactor experiment located in the center is going to mountains not far from Los Angeles California. This is McMahon speaking during the past weeks on Adams for Paar we visited the sites of four of the five experimental prototype reactors that go to make up the atomic energy Commission's five year program of reactor development. As you may recall from these previous broadcasts these five experimental

reactors are being built so that questions that have never before been answered regarding the construction maintenance and operation of atomic power reactors will be solved. Out of more than 80 suggested designs for nuclear power plants. These five experimental par plants were chosen because it appeared that they would furnish best the much needed information and experience in connection with power reactors. Each of the five experimental reactors facilities represents a different technical approach to the production of electricity from the atom. One of the most promising of these experimental approaches seems to lie along the road of the sodium reactor experiment. The sodium reactor experiment like all other nuclear reactors utilizes the fissioning atoms of the atomic fuel your radio when these atoms split they release some of the energy that is locked up and all matter large amounts of this released energy are given off in the form of heat and the case of the sodium reactor experiment or as are easy as it is called About twenty thousand kilowatts of heat

will be produced. Once this heat has been obtained it can be used to generate steam. The steam under pressure is piped to a turban. This turbo generator and the rest of the electrical generation portion of the nuclear power plant are the same as in a conventional coal fired plant. All this sounds deceptively simple. It is anything but that. It was less than 100 years ago that man learned how to manufacture electric power from the burning of fossil fuels. At that time its manufacture was a complicated business one with a lot of question marks where facts were needed. The only way these questions could be answered was to build and operate power plants. Observe the results. Experiment with what looked like more efficient and safer techniques of operation and make improvements. Today the situation is the same in the new atomic power industry. Pioneering work that will set the stage for future generations of atomic power reactors is going for it. And atomics international division of

North American Aviation Incorporated is one of the places in our country today where this important pioneering effort is taking place to arrive at useful power from a fishing atom we have to do two things. First we have to split the atom. Then we have to put the resultant energy of the splitting atom to work for us. We must have what is known as a chain reaction. We must be able to control that chain reaction started to stop it speeded up or slow it down as we wished. If enough uranium is assembled under the correct conditions to form a so-called critical mass a chain reaction can be maintained. That is there must be a sufficient number of neutrons present in the critical mass of uranium to make their capture by fissionable atoms such as uranium 235 probable for there are many other places for the neutrons to go besides into the nucleus of a fissionable atom. Now we can increase the number of available neutrons in the reactor by enriching the fuel that is by adding extra quantities of fissionable uranium 235. But even if we do

this there is still something else that must be done before a sustained chain reaction will start. These neutrons are traveling at terrific speeds around about the atoms because fission is more likely to occur when the neutrons remain in the vicinity of the uranium 235 nuclei for longer times instead of speeding past them at their tremendous speeds. Most reactors use slow neutrons to keep the chain reaction going. To slow these neutrons down to speed where there capture by fission of all atoms is more likely a material known as a moderator is used. The neutrons are slowed down by bumping into the atoms of the moderator somewhat in the same way that a billiard ball slows down when it collides with the other balls on the billiard table. Moderator material should contain atoms that will not absorb or capture too many neutrons during this slowing down process in the sodium reactor experiment. Graphite is used as a moderator to slow down the neutrons for capture by a fissionable atom. When each of the uranium 235 atoms fission it releases in turn one

two or sometimes as many as three neutrons. Many of these new neutrons are captured by other fissionable atoms releasing more neutrons and from this we get our chain reaction. This chain reaction once started and maintained builds up at a tremendously rapid rate and a mere fraction of a second the resulting heat energy has made the reacting mass so hot that if the heat is not continuously removed in some way the whole reacting mass would melt. For this reason power reactors all require a coolant a means for removing the heat and subsequently using it to produce electricity by means of a turbo generator and a coal fired plant. The heat from the burning fuel is used to turn water into steam and to run the turbo generator. The same thing can be done in an atomic reactor. A few weeks ago we visited the experimental boiling water reactor at the argon laboratory and saw how this is done. Another approach being used today is to cool the reactor with water under high pressure so that

somewhat higher temperatures can be maintained. We witness this technique last week when we visited the pressurized water reactor. Since we have used hot water and steam systems for many years in our fossil fuel plants we have a great deal of technological experience close at hand when we are dealing with these media. This of course is one of the chief reasons why water has been used as a coolant in so many reactors. Another advantage of water cooling and this is peculiar only to the reactor business is that water is one of those substances which can be used simultaneously as a moderator as well as a coolant. But unfortunately there are several drawbacks to the use of water as a coolant in the atomic reactor. One of these is the fact that water captures neutrons fairly readily and to offset this either more fuel or fuel enrich with additional quantities of uranium 235 must be added in the reactor. This makes it more expensive to operate.

Another drawback is that under the effects of radiation water decomposes into its constituent chemical elements hydrogen and oxygen and for this reason recombine ER's are necessary components of all water cooled reactors. This again contributes to higher operating costs. The third disadvantage we have to consider is the fact that water has a low boiling point at ordinary pressures. As you know it boils at 212 degrees Fahrenheit. Steam from water boarding at ordinary pressures does not constitute an efficient or economical means of heat transfer because it isn't hot enough. The water must be enclosed in a pressurized system in order to get high quality steam at high temperatures. This again contributes to the expense of reactor fabrication and consequent increased cost per kilowatt hour of electric power. An addition to this in order to make reactor operation as safe as possible. It is a firm policy in the United States to require the construction of a containing vessel around the reactor and its components so that if all the water in the reactor flushed

to steam suddenly and an explosion occurred this gas tight pressure vessel would be able to contain the result of pressure of the explosion and the building would not be blown open for example and the case of the experimental boiling water reactor. This gas type building is one hundred and one thousand feet high and eighty feet in diameter. Its wall is a Skin of Steel. Five eighths of an inch thick. Once again we can see that this type of safety measure while it does contribute greatly to making a reactor safe is an expensive means of providing safety. Since water has these important disadvantages as a reactor coolant scientist and engineers are investigating other materials for this operation. Among them the Liquid metals. Here is Dr. Donald J Tende Amar scientific advisor to tell us something about them. Four reactors operating in high temperatures Liquid metals have a number of good qualities as coolants. They have good heat transfer properties

they are stable at high temperatures and they are also stable under intense radiation but they have their disadvantages too in that they are difficult to handle. Also some of these metals are very corrosive at high temperatures and the tanks and pipes through which the coolant flow must be made of materials such as stainless steel which resist corrosion to a large extent up to temperatures of about twelve hundred degrees. The high temperatures at which they can be circulated are one of the important factors that make liquid Meadows show promise as a reactor coolant. A number of metals such as sodium potassium Izmit red tin mercury and gallium have been considered for use as a liquid metal Koons. However most efforts have centered upon the use of sodium bismuth

and a sodium potassium alloy commonly called NAC. The general a prin opinion in present time is that sodium on the whole is the most suitable of these metal Coons and this is the reason why the sodium reactor experiment is being built today. North American Aviation is assisting in financing the development construction and operation of the graphite moderated sodium reactor experiments we've arranged today to talk to some of the key men involved in the project and the first of these is Dr. Sidney Siegel technical director for atomics International at Canoga Park California. Dr. Siegel what are some of the problems that the use of Liquid metals such as sodium gives rise to one of the problems we encounter in working with sodium as the hazard a fire of the sodium comes into contact with air or water. Sodium oxidizes if exposed to either of these substances. However

extensive studies have shown that these hazards can be greatly reduced by the exercise of proper caution. We do this in a number of ways. For example our sodium systems consist entirely of welded construction with very careful inspection of all of the components of the system and all the pipe welds inert gases such as helium and nitrogen are provided in all those regions which will contain sodium vapor in the event of a leak in the sodium system. We sample less gas periodic play during operation. This method of sodium leak detection is especially useful for components on which electrical detectors cannot be conveniently installed. Does the liquid sodium become radioactive in the reactor. Yes it does. And the formation of radioactive sodium by neutron radiation is one of the problems in the operation of a sodium system because of this shielding to protect plant personnel from the dangerous effect of radiation is

needed for coolant tanks pumps pipes and he exchangers. As you can well imagine this makes maintenance problems more difficult and these problems are being investigated in the sodium reactor experiment. Then to avoid the possibility of radioactive hazards which could occur if the water in the steam generator comes into contact with the coolant and intermediate coolant loop is used in the heat exchanger system the first or primary loop contains the radioactive liquid metal coolant that has been circulated through the reactor. This primary loop runs through a heat exchanger word gives its heat to a second loop of liquid sodium which is not radioactive. The secondary lobe of liquid sodium travels to a second heat exchanger where its heat is transferred to water to form steam to drive the turbo generator in the power plant. Another problem in the handling of sodium is the fact that sodium has a fairly

high melting point of two hundred eight degrees Fahrenheit. If the reactor shut down for one reason or another there is some possibility that the sodium might solidify in the reactor cooling system. We get around this problem by jacketing the sodium pipes with electric heaters and thermal insulation in order to preheat the system to 350 degrees Fahrenheit. Of course after the reactor has been in operation at high power for some time the heat which continues to be liberated after shutdown heat will keep the sodium liquid for several days. Can we find ways to pump and pipe the sodium. That are cheaper than the ones we know at present. Yes we are investigating the practicality of less expensive Marit materials of construction cheaper steels more conventional industrial methods of fabrication than we are presently using as experience accumulates in the use of sodium or other heat transfer medium. We expect to find at the extreme

care we now use in assembling and testing such systems can be reduced with accompanying the economy cheaper methods of pre-heating the sodium system simpler and less expensive instruments are being studied. For example we have already developed pumps for like what sodium uses which are significantly cheaper than the type originally regarded as necessary for this type of service. Well thank you very much Dr. Siegel. And now that we know something of these specific problems connected with the sodium reactor experiment and how they've been solved by the scientists and engineers at Atomic International suppose we asked Dr. W.E. Parkins chief of engineering to describe the interior of the reactor to us. The sodium graphite reactor has been installed below ground with the upper surface of its top she'll let floor level in the reactor room. The primary loops containing the radioactive sodium are also below floor level. And are installed in concrete wall galleries. Motors for the

mechanical sodium pumps and for the control run drivers are located above floor level for easy maintenance. The secondary sodium lines extend from the first set of heat exchangers. To locations above ground level to the second set of heat exchangers where we produce steam. The entire core of the reactor all of which is below ground. Is contained and I want to 1 1/2 inch thick stainless steel vessel. Here we use stainless steel because of its. Resistance to corrosion and also because of its high strength at elevated temperatures. This stainless steel vessel is some 9000 feet deep and 11 feet in diameter. The graphite moderator for the reactor is supported and located on a stainless steel good plate near the bottom of this car tank. The graphite is placed on this grid in the form of hexagonal prisms some 10 feet high

and about 1 foot in diameter. And clad with zirconium sheet. Zirconium is a metal which does not absorb too many neutrons and does not readily corrode. These graphite assemblies are which make up the core region have a zirconium tube installed along their center line. In this are going into the fuel elements of slightly enriched uranium clad in thin stainless steel are suspended. Sodium coolant flows up through the spaces between the fuel elements and there's a cone into. It flows upward from the bottom of the tank. Past the uranium fuel which is undergoing fission in. And out of pipes located near the top of the tank. That's it cools the fuel elements as it travels along. By the time a sodium is passed through the reactor core it has an average temperature of 900 60 degrees Fahrenheit. And it is ready to go to the first of the heat exchangers and begin the

process of making steam for power. The car tank and all its inner components which are highly radioactive. Are surrounded with a steel shield five and one half inches thick. I mediately outside of this shield is an outer tank designed as an emergency means of containing the sodium in the event a leak should occur in the course of. This hour to either surrounded by approximately a foot of thermal insulation. And this in term is contained in another tank called the cavity liner. This liner serves as a form for the concrete foundation in which the entire reactor is located. At floor level in the reactor building. There is a special type of concrete which constitutes the top shield for the reactor. The part of the shield just above the reactor core can be rotated. This rotatable

shale contains a total of 81 small plugs and three large plugs. If it should prove necessary by rotating the shield to the proper position and removing one of the large plugs. Any particular one of the graphite assemblies can be removed. This rotatable shield by the way it weighs a total of about 75 times when all of its internal plugs are in place. It uses 6 feet of thickness of this dense concrete. Control rod mechanisms which are used either to limit or to increase their rate of chain reaction. Also extend down through this top shield. Well how do you will manage to get the fuel elements into are out of the reactor without being exposed to a high degree of radioactivity since you have to take the plugs out to put the uranium in. We use a special led shield apparatus called a fuel cask. This cast can move across the reactor room when suspended from a crane. It is some

thirty five feet in overall height and itself weighs about 50 times. It is placed over one of the small plugs containing a fuel element. If then this and gauges the plug and lifts it with the appended fuel element. Up out of the reactor core and into the cask. It then rotates this element around the inside of the cask and at the same time brings a new fuel element into position over the open plug hole. This new fuel element is then lowered into the reactor. This is all done by mechanical means and the radioactivity level in the reactor room is not appreciably raised during the process. What happens then to the spent fuel element. It is carried in the cask over to the cleaning or storage facilities in another part of the reactor room. After any residual sodium is removed the spent elements are stored in storage tubes until they are removed for chemical processing.

Well I think with that description of yours we should have a very good mind's eye picture of the sodium reactor experiment. Oh thank you very much Dr. Park. Next we'd like to talk to Dr. John C. star vice president of North American Aviation and general manager of atomics international not to star What can we hope to learn from building an operating a reactor such as the sodium reactor experiment. Well we know that the reactor design is certainly feasible and that the sodium reactor experiment will produce power but there are still numerous features of such a plant which affect the economics of a complete system that have not been tested in actual practice. Before electricity from the atom can become a satisfactory economic reality that engineers must find ways to lower the construction costs and improve the performance of nuclear reactor systems.

What is the cost per kilowatt hour expected to be from a central station part plant using a sodium graphite reactor. This is a very difficult question to answer accurately until such a plant has actually been built. However Present estimates put the power cost in the range of 10 to 12 miles per kilowatt hour which is somewhat high for competitive power in the United States. There are several development possibilities however which if successful may ultimately lower the cost to six or seven miles. And this is a competitive cost for power in most areas. The Using the development possibilities include such things as simplification of the plumbing systems that carry the liquid sodium and the possible operation of the reactor as a breeder or a near breeder with authorial blanket. The advantage of this breeding process of course is that the reactor

manufactures its own fuel as it operates essentially by the utilization of the story I'm originally. And therefore operates on a much more economical basis. Another way we can make the reactor operate more efficiently and economically of course is through improvements to the fuel elements to allow a greater percentage of the fissionable material to be used in each cycle of operation before the fuel elements must be taken out of the reactor and reprocessed. Well I can see from what you've told us that there is a great deal of information to be gained from the construction and operation of this prototype our reactor and its information that we can only obtain by experience. I understand too that the sodium reactor experiment will be the first nonmilitary Atomic Energy reactor to produce power for a private utility is that correct. Yes for the Southern California Edison company has installed electrical generating equipment with a capacity of seventy five hundred electrical

kilowatt adjacent to our nuclear plant. This equipment will then utilize the twenty thousand kilowatts of heat which come out of the reactor experiment. I understand also that atomics International is already in the process of designing a second sodium graphite reactor the sodium graphite reactor is the type of reactor in which the consumer's public power district of Nebraska has expressed an interest. This reactor would be a full sized Central Station plant producing 75000 kilowatts of electrical power. Well this is really quite a jump forward in the art production aspects of the reactor field. What will my relation be between your work on the sodium reactor experiment. And the design and construction of a full scale sodium graphite reactor such as the I planned for the $75000 what plant. We made several significant developments during the construction phase of the sodium reactor experiment and we expect to obtain important operating experience with the

reactor. All phases of work with the sort of reactor experiment including the design development fabrication and installation of Count ponens give us information helpful and directly applicable to the design and construction of a full scale plant. The operating experience we will obtain with the Saudi reactor experiment provides important information applicable to the operation of a full scale plant. The very name of the sodium reactor experiment indicates a project is one of development an experiment to increase our knowledge of the sodium graphite reactor approach which we hope will lead to the development of economical power from nuclear energy. Dr. Starr there are so many and I asked real firms at the present time that want to build reactors and I sometimes wonder if there is going to be a man par problem in the atomic power industry. Just just what is the situation on availability of trained personnel.

There is a problem in this regard. Less than 10 years ago approximately 50 technical people were at work in United States atomic power. Today this figure has increased to approximately 5000. And this is still a relatively small number of technical people working in a field which has so much future promise. The most serious aspect of the manpower question however is for the future in atomic power. It has been estimated that in 20 years we will need at least 23000 engineers and scientists working in the atomic power field are almost five times the present number. Fewer than 500 people are being trained for the nuclear field per year at present. Our schools and colleges are rapidly adding courses in the nuclear sciences. The Atomic Energy Commission and other government agencies are busy with Barry's training programs. And finally private industry is making distinct contributions

by way of on the job training special courses and support of university work. But all concerned with this field will have to greatly increase their activity in this regard. But you do think that within a few short years atomic power are not amik power reactors will be rather commonplace elements in our society. In a general sense my answer would be yes. It appears reasonable to believe that competitive power from nuclear energy will be achieved by about 965 and that by 1980 there will be from 50 to 100 million kilowatts of nuclear power plant capacity in the United States. Well thank you very much Dr. Starr. Ladies and gentlemen today's program on the sodium reactor experiment marks the final program in the series on the five experimental par reactors in the atomic energy Commission's five year program for reactor part of element. Our thanks go to the management and

personnel of atomics international pioneers in the creative use of the atom and the San Francisco office of the Atomic Energy Commission. It was all out cooperation has made this program on an important phase of reactor development in our nation a reality. This week's program of atoms for power was transcribed at the site of the sodium reactor experiment under construction by Atomic International a division of North American Aviation incorporated located Canoga Park California next week. Atoms for power will provide information on problems of disposal and handling of atomic waste in a program dealing with health and safety and the atom atom for power was written and produced by Bob McMahon for radio station WABE at Purdue University under a grant from the Educational Television and Radio Center scientific advisor to the program. Professor Donald J tandem of the produce department of physics who are now writers where Walt Richter and John glade. And this is Jon Bon Jovi's crew speaking. This program is

distributed by the National Association of educational broadcaster. This is the Radio Network.