Challenge; 18; Testing for Tomorrow

This is series number P -76, challenge 2, show number unknown, testing for tomorrow. Recording date, December 17th and 18th, produced by Ross McElroy, directed by Clifford Braun. Video tape by Teletate, this is scene number one, take one. Tiny electric current, search out cracks in stainless steel tubing. An alarm buzzer signals a defect in a piece of uranium. Sound waves pitch so high you can't hear them, bounce back and forth through the uranium, which is immersed in water, searching for those defects. Television screens that show pictures, not of your favorite shows, but of defects in equipment that can't be seen in any other

way. These are part of science today and technology tomorrow. It's called non -destructive testing, important because it will help us all as we face the challenge of tomorrow. Challenge is produced through a grant from the United States Atomic Energy Commission's Argonne National Laboratory. Non -destructive testing, a comparative newcomer as far as engineering techniques go, but one of the most important. What does it mean? To put it most simply, it's a means of examining an object in search of defects, but to do so without destroying it, not like the automobile engineer who runs a car over test runs trying to shake it and beat it to death. Why is it important? The space industry has an example. A rocket engine is made up of hundreds of parts,

each one of which has to be tooled to extraordinary precision. The tiniest defect could bring disaster or take atomic energy. A nuclear reactor looks like a fairly simple instrument from the outside anyway, but it too requires parts that must be as nearly perfect as human engineering can possibly make them. This is where non -destructive testing comes into play. Such testing enables the engineer to detect flaws in hidden areas of a piece of equipment. To relate it to something we all know, it for instance is very similar to the way that a chest x -ray might show your family doctor dangerous shadows that might mean TB. One of the nation's most active groups both in developing and applying new methods of non -destructive testing is here in the metallurgy division at Argonne. It's a group of 15 scientists, engineers and technicians, and its leader is engineer Klaus Rankin. Non -destructive testing certainly is a participant in a space age norm, rockets and reactors are both so expensive that people will go to great

lengths to keep anything from going wrong with them. But the principles we use are really not new at all. For example, did you ever submerge a bicycle in a tube under water to check it for leaks? Sure. Well, this is the basic principle behind non -destructive testing. We choose some physical phenomena which will tell us something about the internal quality of a test object without hurting it in any way. For instance, in these tubes we can x -ray them and the x -rays will show up defects that might occur in here as small dark areas on the film. Isn't this like a medical x -ray? That's right. Perhaps even a better analogy is the x -rays a dentist takes at one's teeth. He can spot cavities with these that he can't see with his eyes alone, and so we can spot defects in this tubing that we can't see otherwise. What sort of equipment do you use? Well this is a conventional medical therapy unit. It's useful for a lot of different purposes.

For thicker sections, however, we use some gamma energy of some kind. Why is that? Well, the gamma radiation in general has a shorter wavelength, so it's more penetrating. You probably remember that they use gamma energy from cobalt 60 to treat tumors, deep tumors inside of people. Well in industrial radiography one can x -ray or radiograph up to six inches of steel using a gamma, and that would take a million volt x -ray machine and that's more powerful than this one is. What does your cobalt equipment look like? Well, Norma Pinsky can show us the various parts of this setup. The coffin here, we call it a coffin, actually it's just a heavy two -wheeled shield enclosure, and it contains the cobalt which is radiating away there night and day. We can't shut it off, but when we're going to use it for an exposure it is moved up into this

projector and it floods the test object with gamma energy and the film here is placed behind the test object. We have a radiograph, a gamma radiograph, made by cobalt 60 of this test object. It's a small chemical reaction vessel and these are its heavy copper walls, which we can see right through with the cobalt. These are the cooling coils, but what we're really interested in is this object running down the middle here, which shows up pretty clearly. A chemical reaction taking place in this vessel at the surface of this fuel here would show some effect on the fuel and whatever effect it had, we could spot using this type of radiography. Since gamma rays are so penetrating, to make sure you're safe, you make exposure by remote control, imagine. That's right, he has to leave the enclosure before he can make an exposure. In a nuclear laboratory like Argonne, scientists, of course, have to do a great deal of work with radioactive

materials. I should think that at least some of these materials would tend to expose any photographic film you place next to them, wouldn't they? They certainly would. Well, then how can you possibly perform tests on things that are radioactive? Well, this has been a problem for some years and one solution is to use a product of the fission process, neutrons, to make the exposure and this is best done at a reactor. We're looking now at a research reactor called Juggernaut. A rather dramatic name doesn't mean anything special, I understand. It's just a small atomic furnace used to supply neutrons for research purposes. Neutrons, little particles from the nuclei of atoms. Juggernaut is not used to make atomic power, by the way. In fact, there are research reactors somewhat like this on many college campuses today. Our scientist, Harold Berger, a pioneer in developing a particular technique for non -destructive testing that goes under the name of neutron radiography. He's done his work using this reactor as a tool.

Neutrons, the same particles that contribute to nuclear fission, can also be used for radiography. In fact, our technique is very much like conventional radiography, except we use neutrons instead of x -rays. Do you use the neutron beam as it comes directly out of this opening? With a slight modification in that we deliberately slow down or moderate this neutron beam. Why do you do that? If we were to use fast neutrons, these tend to go through materials quite easily so that we wouldn't get much contrast in our picture. We slow down this beam by inserting graphite into the beam tube. I see. Then once you have your slowed down neutrons, what do you do? The object we want to inspect is placed in front of this rectangular opening with a detecting screen behind it. The screens we normally use are materials that can become radioactive easily. Once we get the radioactive image on the screen, we make it visible

by placing it into a light type box with photographic film and allowing the radioactive screen to expose the film. These screens, as you call them, look almost like ordinary tinfoil to me. I know they're not, but what are they? We use materials such as indium, rhodium, silver, gold, materials which, as I've said, become radioactive easily and which decay rapidly, that is, they have short half -lives. Well, since, as you say, they give off their radioactivity rapidly, this must mean that it takes less time to expose the photographic film. This is true. Harold, can you tell us exactly what you use this equipment for? Our biggest application at the moment is in looking at irradiated reactor fuel material. These are highly radioactive specimens, and we can do this more easily here because the radioactivity won't fog our detectors, as it would with conventional x -radiography. Well, this is pretty much what Claes Rankin was talking to us about just a few moments ago. They're beginning to

set this equipment up now. Perhaps while they're doing that, you might like to see some other applications of neutron radiography. These really look like x -ray pictures, don't they? Yes. It's particularly interesting that neutrons can penetrate material such as uranium or lead very easily, whereas x -rays have a difficult time with these materials. Well, if that's true, then I suppose you could actually use neutrons. Say, I'll take the picture of the water level in a lead pipe, couldn't you? Yes. That's a very good example, Norman, because neutrons are easily transmitted by lead and very highly absorbed by water. I can remember as a schoolboy learning that we were all made mostly of water. We in plants and everything, 80, 90 percent or something like that. Can these radiographs that you make give us a better picture of the tissue of plants and animals than x -rays can? They can give us a picture. It's hard to say whether it's better. For example, this picture of a grasshopper was taken with

neutrons and shows excellent detail, but it does remain a laboratory curiosity. Another illustration of the use of neutrons to detect hydrogen is given by these x -rays and neutron radiographs of a small flashlight battery. These are both shots of a used battery. These are both shots of a new battery. The interesting area is here in the expansion chamber, which in a used battery is filled with a hydrogen -containing material, which is much more easily visible on the neutron radiograph than it is on the x -ray radiograph. That's really fascinating. As I said earlier, these radiographs look like x -ray pictures. But as you've just seen, they were taken with the aid of neutrons. Neutrons that had previously been slowed down, moderated neutrons, as Harold calls them. These neutrons leave fingerprints, radioactive fingerprints. They're left on thin metal sheets, and then they're exposed to photographic film. Are they mere laboratory curiosities? Or might they

someday prove to be valuable tools for research and industry, maybe even for tracing the processes of life itself? Of course, only time will tell. Meantime, here at Argonne, neutron radiography is an invaluable aid in showing exactly what happens to fuel, whether it's uranium or plutonium, the fuel that sustains the chain reaction in an atomic reactor. It's a technique that is very useful for the men designing both today's and tomorrow's atomic power plants. It gives the scientist information he could find in no other way. Well, I think Harold Berger's equipment is about ready now. Let's take a look. Nelson Beck, one of my associates in the division, has irradiated this particular capsule in another reactor here at Argonne. It's highly radioactive now, so it must be contained in this tall cylindrical shielding container. Once we're ready for the exposure, we'll lower it into the exposure position and take a test shot. It's sort of like a portrait

photographer taking a test shot to check his lighting, isn't it? That's essentially true, Norman. We take a test exposure to make sure that it's aligned properly by opening and closing the reactor shutter and exposing a screen behind that capsule itself. We then bring it out and put it in this Polaroid exposure kit and get a quick shot to see how well it's lined up. Harold, how long does it take for the radioactive atoms on the metal sheet to expose the film? Not very long in this case because this is very fast film. Can we see what you've got here? Yes, this is the Polaroid print and we can see the three pins pretty well lined up. In a previous shot or one like this, the finished picture would look something like this, which will show us much more detail. It looks like a pretty good specimen to me anyway. Where do we go from here? Well, that will be up to Nelson Beck, the project engineer, but probably it will

be put back into the reactor for further irradiation. In which case it may serve as one of the reactor fuels of the future. What we've seen Harold Berger demonstrate at the Juggernaut reactor, the technique of neutron radiography, represents just one aspect of non -destructive testing. You might say that these tests are a way to assure a scientist or an engineer that the materials and designs he uses are really good ones. If he didn't test at this early fundamental level, he can never be sure his ideas would result in success. It would sort of be like making a carving knife out of cast iron, only to find that you couldn't sharpen it, or like building a most intricate bridge, only to have the materials snap under the strain and the bridge come tumbling down. Once the design and the materials have been worked out by these methods, non -destructive testing is involved in something else, inspection of the finished product.

This is that other aspect of non -destructive testing I just mentioned. The technician is using these techniques to inspect one of the finished parts for a reactor. These are thin walls, stainless steel tubes, each of them is three -sixteenths of an inch in diameter and seventy -two inches long. They were designed to contain the uranium fuel for an experimental atomic power reactor, which are gone designed for the Atomic Energy Commission. That reactor is on its site at the National Reactor Testing Station out in Idaho. The nuclear heart of this reactor, if we may call it that, is composed of hundreds of tubes cut from the larger ones like the one I have in my hand. Each one of them is filled with fuel and then each of the tubes is sealed. Were there a leak anywhere, some of the radioactive products of the chain reaction would escape. Such an accident would not be dangerous, however. Why? Because detecting instruments

would shut the reactor down instantly, but a long and expensive cleanup operation would be necessary. That's right, Norman. That's why we're so careful about the inspection of these tubes. Any defect which slipped by us at this point would come back to haunt us later on. How do you spot these defects? This is electromagnetic test equipment. Pulsars of current set up induction fields in this area, and as the tube moves through it, any defects in the wall distort the field in such a way that the machine can sense this, and so we get a defect signal. Carlos, can you illustrate that in some way I can relate to? Well, it's perhaps like tapping a baseball bat on a concrete to see if it's sound. And you detect a change in magnetic properties then instead of a change in the transmission of sound, is that right? Right. I heard a bit of a beeper before. What is that? Well, that's the defect alarm signal the instrument produces. What does one of these defects look like? Can you show it to us?

Well, they're usually very difficult or even impossible to see with the unaided eye, but I have some photographs of them here. These, presume, are highly magnified. That's right. This one 250 times, and this one 100 times. The tube is sliced like a piece of sausage, mounted and photographed through a microscope, and these are the kind of pictures we get. This is just actually a segment of the tube cross section, and here's the defect in this one, and here is a crack in the southern one. About how many of these two would you say you rejected? About 15 percent. Isn't that a pretty high percentage? Yes, it is, and it's expensive, too. But the standards in the nuclear industry are quite high, and many commercial processes have trouble meeting these standards. However, the standards in themselves tend to raise the quality of commercial processes. And that's all to the good. That's right. This is one way here at Argonne that we're testing the soundness of actual materials that are slated to be used in reactors. If these probing electromagnetic

waves are distorted by a test specimen, they indicate that something is wrong with that specimen. There are different techniques for testing other products. One of these is ultrasonic testing. Ultrasonic testing is a technique for measuring the transmission of sound waves through a material. Only in this case, in order to get good definition, we use extremely high frequency sound way beyond the audible range. Ultrasonic sound, as we call it. Sort of an ultrasonic stethoscope, isn't it? That's right, and this is the instrument. This is Ron Solner, the physicist in charge of this project. Ron, is that just a tank of ordinary water? Yes, it is, Norm. We generally use water to transmit our ultrasound, even though many other materials have better transmission properties. We use water because it is cheap and relatively easy to handle. The principle involved in this testing

is somewhat like wartime sonar, used to detect enemy submarines by bouncing ultrasonic waves off them. What are you testing here? This is a depleted uranium rod, in which we are looking for cracks or voids located at or near the center of the rod. How do you find those defects, those cracks, those voids? We have many methods of ensuring that we pick up defects. One method is to observe defect signals on the oscilloscope of our ultrasonic instrument. Another method is to have visual or oral alarms, like a buzzer. Another method, commonly employed, is an electrosensitive paper recording, and this is a typical

one here. I presume those little white blanks are the defect. That's right, Norm. You bounce then the ultrasonic waves off the pieces of uranium in the tank. Is that right? The ultrasonic instrument produces electrical oscillations, which are converted into mechanical vibrations by this little device, which we call a transducer. These mechanical vibrations strike the specimen under test and are bounced back to the instrument from the surface of the material and from within the material. Let's see if I've got this right now. What you're looking for then are echoes that don't belong there, aren't you? Echoes that indicate the sound waves are hitting some defect or other, either on or in the uranium specimen you're testing. That's right. There is another ultrasonic technique, which can detect such defects also. Tell me this, can you use these ultrasonic methods to make non -destructive tests on other things or

just on a piece of uranium like that? We can use ultrasonic techniques to inspect such items as plates, tubing, forgings, and so forth. Ultrasonic techniques can also be applied to the inspection of objects which are too big to be moved into a laboratory. Take, for example, a large propeller shaft. At about this point, some of you might be asking how we can be certain that these tests are accurate. After all, we can't actually see the defects unless the specimen is cut up and microphotographed. We have an answer for that. In fact, the equipment in the next laboratory is set up to determine for sure just how accurate these tests are. One of the most important applications of the ultrasonic test method is the detection of voids or empty spaces between fuel and the jacket which surrounds it. You mean like air bubbles? Right. Only much thinner. These non -bondes, as we call them, can't be

seen visually or with an x -ray. But if they occur, there's a possibility of heat buildup behind them due to the fission process and the fuel. If the non -bondes is of sufficient extent, it's possible for the heat buildup to progress to the point where the fuel is damaged or perhaps even melted. That's why this thermal diffusivity experiment, which Ms. Roberta DeNovi supervises and is operating here, is designed to measure the actual heat transfer across a section of a fuel element and then later compare it with the ultrasonic test results from the same piece. Well, if the results of these two kinds of tests are the same, then you must know that ultrasonics gives you a pretty good idea of what you're looking for. That's right. How does this test work? Well, the pulse of heat is generated by the xenon flash tube along with a lot of light, by the way. And it's focused on the specimen right here by the optical system. And we monitor the temperature rise on the back

surface of the specimen. And if this temperature rise is less than normal or slower than normal, then we can deduce the presence of a non -bond. I see. I think before we flash -ish, we should put these goggles on. All right. Well, they sure are dark. Yeah. You ready? Yep. Okay. Now, in a room of subdued lighting, one could see the temperature rise appearing here on the oscilloscope. But once you've measured this heat transfer, then you put the fuel specimen in an ultrasonic tester. That's right. Do the results you get from these two methods of equipment agree with each other? Well, the thermal diffusivity experiment is designed to give us a high degree of confidence in our ultrasonic bond testing. And if it doesn't agree, then we'll have to look for some other method of testing in some cases. I see.

Here we've been seeing the use of one method of non -destructive testing to check another method. Scientists measure the transfer of heat across a sample specimen. The idea is to see if ultrasonic testing reliably indicates the presence of voids of open spaces that impede the transfer of heat. In general, these two methods agree very well. This is just part of the research that goes into perfecting better non -destructive testing methods. We're studying another method of ultrasonic testing, Norman, because it gives us a televised image of a complete flaw. Although we've made a lot of progress with this system, it may be some time before we actually use the technique. The last time I'd familiarized around these, these look just like ordinary television receivers. That's basically what they are, and what you see here is the ultrasonic radiation transmitted through a piece of metal. It looks just like a little round hole, or maybe a pearl in an oyster. That's a flaw in that piece of metal. Can you tell me how you're able to pick up the full image of that flaw? The ultrasonic

radiation is transmitted through the water tank to the detector. We pick up this detected image because there are tiny charges of electricity generated on the surface. Those charges are not all over the surface, though, are they? No, that's the key to getting a television presentation of this picture. I see. Then it's more or less like using sound instead of light to get a TV image. That's essentially it, yes. Perhaps you'd like to see the image of a more familiar object. For example, here's the ultrasonic image of my finger. It looks almost like an x -ray picture of your finger. That's correct. You can see the dense part, for example, the bone quite clearly. Can I guess from this that there are medical applications here? There may be, and there are several organizations interested, Northwestern University, being one of them. Do think someday ultrasonic rays are ever going to replace x -rays in my doctor's office? It's possible. More likely they'll be used as a supplemental technique because ultrasonics can see things that x -rays cannot.

How, for instance, is Northwestern University using this? One of the studies they're making is concerns to heart, the of fluid through the heart. Ultrasonics are particularly sensitive to fluids. I'm beginning now to get some idea of the scope of all this. Someday this technique may not only be used for helping designing tomorrow's nuclear reactors, but even in something like heart disease. It's quite possible, although we still have a long way to go. As you can see, there's a lot of interference in our picture. Fortunately, you can look through this and get a lot of useful information. Thank you very much, Ron. Non -destructive testing. It sounded like a fairly forbidding phrase at first, didn't it? But as we've seen during this half hour, it covers a wide spectrum of man's activities, all the way from medicine to the technology of the atomic and the space age. Though it's as new as tomorrow, really, you might say that some form of non -destructive testing has been going on ever since

man first thumped a watermelon to see if it was right. But the important developments that we have seen are very recent. They've been made necessary by young and exacting sciences. Now, the ideas spun from the brains of young men like Klaus Rankin and Harold Berger. Such testing is necessary at two levels. It's important to the designer, for he must know if the materials he specifies are good enough. And it's important to the user, who must know if he can depend on the finished product. It's the one way to make sure that a product of today's and tomorrow's technology will work. Far more important than ever in this immensely complicated age. That's atomic science is giving us a new and a very practical reason for mankind's eternal search for perfection. An essential part must be excellent, or it won't work at all. It's more true today than ever, as Pinoza 1 said, that all excellent things are as difficult as they are rare. Music

Challenge has been produced through a grant from the United States Atomic Energy Commission's Argonne National Laboratory. Argonne is operated by the University of Chicago. Music This has been a Ross McElroy production Music For National Educational Television. Music This is NET, the National Educational Television Network. Music