It's not a nuclear bomb, but it is a normal bomb laced with as much highly radioactive material as can be packed with it. The media and others who feed off the publicity bonanza, are well aware that its real value is hysterical paranoia. After the initial blast it is doubtful that anyone would be seriously injured either now or in the future. Except for the terrorist who tried to build it.

The dynamite or other explosive material is no problem. It's all over the map and readily available. The radioactive material is a bit more of a difficulty.

Low radioactive materials like uranium or even plutonium, don't make it. They are not radioactive enough. If you can get enough uranium to be as radioactive as you would theoretically like for a small effect - say a couple of thousand curies, it becomes a device weighing no more than about 6,000 tonnes. And even smaller quantities are not at all effective, as it is self shielding - the small amount of radiation anyone could be exposed to is from the surface few millimetres. It is an even better radiation shield than lead. It would also be easily cleaned up. Uranium is out.

Bomb-grade Plutonium is a little better, but with a half-life of 24,000 years it is also of low radioactivity, and you would need about 33 kilograms. It is also self shielding. It is also very expensive and - oops! - too much in one place. Goodbye terrorist. No, it would not be a nuclear explosion, as it is not being confined in exactly the right way, which is very hard to do. But if you can get enough of it together in one place - say about 10 kilograms - you can get to see that wonderfully warm Cerenkov glow first hand as you get a fatal radiation dose that will see you off in a few hours, and your little device gets spread a few feet, but no further. The authorities would love to clean that one up, as it is quite simple to do with the right tools. Of course you might try to build it into a real bomb, but that would take time, and the kind of money and facilities that only governments and very large industrial organizations have. You would also have to escape detection while you are doing it. Another caution is about the purity. If you are not sure how pure the plutonium is you might have a more serious problem with shorter half-lives and spontaneous fission, as only the purest plutonium is predictable. Anything else is very dodgy. Plutonium is out.

Spent nuclear fuel would be ideal. It is highly radioactive - at least for the first few months - and it would be a major embarrassment to everyone if you could steal some. You might have a bit of difficulty getting it moved though as they are all in very high security areas and they need about a metre of high density concrete shielding or a few tons of lead if you expect to survive. Better re-think that one too.

Oh, one more problem. You really need to change the physical state of nearly all of these items. They are mostly pellets or ceramic solids of some kind, and if you expect to disperse them for greatest effect you are going to have to grind them up. Now there's a challenge for some terminally minded individual.

Hospital and industrial devices are the way to go, or so the pundits believe. They are usually short half-life, so they are highly radioactive, but they will usually hang around long enough to create a lot of panic. A hospital cesium-137 source (about 30 year half-lie), or an industrial cobalt-60 device (about 5 year half-life) of about 2,000 curies would make a small start, and the nice thing is that even very big ones weigh only a few grams. But don't think you could pop it into your pocket and walk out. It would be a very short trip. The difficulty is, that they are shielded by a massive amount of either lead or uranium, or are sitting below a pool of water. If you try to steal it without a few tons of shielding you are talking a fatal dose in seconds to minutes. Take the shielding along while you work on your device, and you might survive a bit longer. But then you face quite a problem delivering this bomb. If you remove the shielding you die quickly. If you keep the shielding, you'll have difficulty moving it. Darn! There is this ONE other problem again. If the material is not in a powder form, you will have to grind it up so that it will disperse more effectively in the blast. If you don't grind it up, then as with the uranium, plutonium or spent fuel, you will just spread a few pieces around that could be easily found and safely picked up. You'd better think about this one as it will create quite a headache deciding how to grind it up without getting fried.

Much shorter half-life materials - like iodine-131 - are even more radioactive, but they don't come in large quantities and they still need a lot of shielding. It would be a real bummer if you spent all your ingenuity and time building a bomb with this stuff only to realize that by the time your device is ready, you are dying, but the nuclide is dead because it decayed while you were working. Tough tamales.

So let's assume you built your device and managed to survive, and you detonated it somewhere. Oh dear. All that awkward radiation is now either contained within a small space - and can be cleaned up by the right people who know what they are doing, and who do it all the time. Or it is widely dispersed, on the ground and decaying. If it is dispersed even a block or two it would be more of a curiosity to people who collect luminous radium watches, and uranium glazes and minerals (I do), but it would be unlikely to kill anyone. Of course the spin doctors talk about future cancers without realizing that radiation is one hell of a weak carcinogen and do not want you to know that good old nature herself is a few thousand times more potent than even a moderate dose of radiation. If it were not so, we would long ago have stopped using it in hospital treatments to save thousands of lives a year and natural background radiation would have killed us off shortly after birth. Why would you believe someone who knows even less about it than you do (the media and special interest groups) and who is interested only in frightening you? Think about it.

There are lots of nice things about radiation, which is why I love to work with it professionally. It is SO easily detectable. We have devices all over this country that we use to prospect for uranium from a couple of thousand feet or more in the air. We are not looking for large amounts either, just a faint signal above background so you may not be able to hide for very long.

A two thousand curie device anywhere - especially with little or no shielding around it - would be like sending up a flare announcing your location to all the SWAT teams in the land. We use the same devices to see what is moving along highways and across borders and to and from scrapyards. There are a lot of radioactive materials moving around the world, about 18 millions shipments a year, and a lot of devices to measure them. The big ones tend to stand out very well, especially without shielding. I remember that the alarms would go off quite often at the nuclear plant at which I worked. On one occasion it was because of the camera lenses of the media types who were after some scary story. It sure surprised the hell out of them. They were bringing radiation INTO a nuclear plant and setting off the alarms! It gave them quite a dose of perspective, but not enough.

Others are when radiographers are doing their inspections somewhere within a few hundred yards, or when a welder accidentally leaves a welding rod in his pocket. At times it occurs when someone comes from working in his radon-rich basement without changing or showering. Sometimes it was because a worker had just come from hospital after receiving some internal diagnostic procedure or treatment. The alarms would start to go off shortly after he arrived in the parking lot. He was always rather easily found and was told to let certain people know when he would be coming and going over the next week or so, so that they could reset the alarms when he was far enough away. No one panicked, as it was not unusual, and it was certainly not life threatening. Major hospitals treat and discharge many such people each day, especially after radio-iodine treatment of the thyroid and they are easily detected if you have the equipment. I do, and have come across several of them in other workplaces. They are all over the place. The strange thing is, that these people would be an even bigger local source of radiation in society than any widespread contamination from any terrorist dirty bomb. No-one panics now, mostly because they neither know nor care. Not until the media and other spin artists get into the act.

Forget the dirty bombs. Stick to the petty crime - it's a lot safer. If you haven't had several years of high quality radiation training, and do not have a reasonable understanding of what can go wrong, you'll send up enough signals about what you are doing where you are, and go out of this world with the wrong rosy glow - a semi-permanent one. There are too many other typical terrorist things to do, that won't kill them first. And terrorists hate to die before they achieve their objective. But it is a made for media issue that will be milked as hard as it can be.

John K. Sutherland, New Brunswick,, Canada

Dr. Sutherland, a member of the Scientific Committee of EFN, has worked with radiation for the last 40 years and in the energy and nuclear industries for the last 22 years. He writes extensively, and has published numerous articles in many newspapers for public education, and many peer reviewed scientific articles. He has taught High School teachers about radiation, risks and energy. He is an adjunct professor at UNB where he teaches a course to undergraduate and graduate engineers on Nuclear Safety and Reliability. He has contributed to many licensing and nuclear training documents and has written extensively on radioactive wastes, the nuclear fuel cycles and energy.