Sad to say, scaring the pants off you soccer moms and mall-rats has become a growth industry in this country, gainfully employing thousands of people, in and out of government. The scare-monger battle cry is that terrorists are planning to use various weapons of mass destruction on each and every one of you.
Today we will discuss "dirty" nukes.
What is a "dirty" nuke? Well, it’s not a nuke at all. The proper name is a radiological dispersal device. An RDD delivered by your hypothetical terrorist would consist of a few pounds of powdered radioactive material packed around a few pounds of high-explosive. The terrorist would carry the RDD into your mall and detonate the explosive, dispersing into the air the radioactive material, which would soon "fall-out" to the floor.
Contrary to what the scare-mongers have told you, an RDD is in no sense a weapon of mass destruction. A few people including the terrorist might be killed by the high explosive. But essentially no one would be killed on the spot or die later from radiation.
An RDD is not a nuke. It does not contain a critical mass of fissile material such as uranium-235 or plutonium-239. Hence, no uncontrolled chain reaction no nuclear explosion is possible. The total amount of radiation emitted per unit time in the mall is the same before, during and after the RDD detonation. Before, however, the radiation-emitting material is concentrated. Afterward, the radiation-emitting material is spread all over the place.
So, suppose some terrorist comes into your mall this weekend and detonates a few pounds of high-explosive. How can you mall-rats tell whether he has detonated an RDD or not? You can’t, unless you happen to be carrying and know how to operate both a gamma-ray radiation detector and an alpha-particle detector. You can’t see radiological contamination. You have to trust your radiation detectors to tell you where the radiation emitters are.
Now, an alpha-emitter is no threat to you unless you ingest it. Alpha-radiation won’t even penetrate your outer skin. The range of a typical alpha-particle in air is only an inch or so. That means that if you want to find out whether the terrorist has just contaminated your mall with long-lived alpha-particle emitters, you’re going to have to get down on your hands and knees and crawl around, holding your alpha-particle detector about an inch above the floor.
Alpha-emissions per unit time tend to diminish very slowly, so once you’ve found an area that is contaminated, it’s going to stay that way for a thousand years or so. If you want to continue working in that area, be sure you wash your hands and feet every time you come out. It might be simpler to just install wall-to-wall carpet over the contaminated area.
On the other hand, gamma-rays are highly penetrating, so you won’t have to get down on your hands and knees to find their emitters. Intense gamma-ray sources are used to treat cancer, but continuous whole-body exposure to gamma-ray radiation levels several orders of magnitude above normal is not good for you.
Fortunately, gamma-ray emissions per unit time of man-made radiological materials tend to diminish fairly rapidly with time. So, if you detect unhealthy gamma-ray levels in some part of your mall, put a rope around the area, and don’t spend much time inside the rope for the next 100 years or so. If you absolutely need to use that area, putting down carpet won’t help, but you can just hose the area down with about a ton of water, further dispersing that radiological material right down the drain.
But, think about it. Scaremongers to the contrary, why would a terrorist employ an RDD to strike terror into the hearts of you soccer moms and mall-rats if none of you had any way of knowing what he had done? How would you know to be terror-stricken unless you had your handy-dandy gamma-ray detector on you?
That brings us back to the post-Sept. 11 growth industry. Congress is in the process of spending billions and billions of your tax dollars to train and equip hundreds of thousands of policemen, firemen, doctors, nurses, school teachers and crossing-guards to rush to the scene of a suspected terrorist event and start looking for evidence of every imaginable chemical, biological and radiological contamination.
The ones down on their hands and knees will be looking for alpha-emitters.