Physical Insights

An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

“Dirty bombs”

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We’ve heard a lot in the media over the last week or so about the radiological “dirty bomb”, following the GAO’s “sting” of the US NRC’s licensing procedures for users of industrial radioactive sources.

The potent, destructive element at the heart of a radiological bomb is not simply a radionuclide.

The potent, destructive force harnessed in the use of a radiological bomb as a weapon of terror is none less than the all-too-familiar Nuclear Boogeyman itself. The fear, ignorance and anxiety which surrounds radioactivity and nuclear technology.

A dirty bomb harnesses pure, concentrated “Nuclear Boogeyman”, and builds it into a weapon of terror, creating one of the most extraordinarily potent weapons of terror conceivable.

For terrorists to create widespread fear and terror, nobody nessecarily needs to be killed or injured at all. The radiological bomb is perhaps, potentially, the exemplar of this idea.

As soon as there’s a hint of terrorism, as soon as there’s a hint of artificial radioactivity, the terror of the Terrorist Boogeyman and the terror of the Nuke Boogeyman will multiply synergistically.

The very idea of terrorism scares the shit out of people, in a way completely out of proportion to any actual quantifiable threat which they may face. This remarkable phenomenon is unique, and is not shared by any known phenomenon you may care to think of. Except for radioactivity.

One millirem, ten millirems, ten Bananas CEDE, it doesn’t matter.

Simply being able to detect and quantify any kind of artificial radioisotope proves, in the public conciousness, that that’s it, there’s deadly radioactivity there, and we’re all going to die.

Consider the Three Mile Island incident. People had the absolute shit scared out of them, over what? 8-10 millirems on average, if I recall correctly.

If we ever see a radiological dispersion device used in an act of terrorism, I think that the result we’ll see will be similar to TMI. Widespread fear and anxiety, with no radiation dose that will actually hurt people.

Here’s an Australian news outlet’s headline: Fake firm sold nuclear bomb material in sting.

Yes, they said nuclear bomb material.

When a Am/Be sealed neutron source used by Halliburton in oil well instrumentation was lost in Nigeria in 2003, here’s what Fox spun it into when they found out:

“The fact that a load of weapons grade plutonium has disappeared from Nigeria should send a signal to all Americans that a nuclear device could be planted here. It is possible. And those with the mindset to do that have to be confronted…But you will not refute. You cannot refute, and neither can anyone else, that we have plutonium missing in Nigeria, we have two rogue governments, North Korea and Iraq, who are certainly capable of aiding and abetting people who will plant an atomic device, a nuclear device in a city in this country.”

Astonishing, isn’t it? The level of ignorance, mistruth and bullshit is simply astonishing.

Now, the radioactive devices in question here are the nuclear moisture/density gauges often employed in civil engineering, made famous by Troxler Laboratories.

Let’s say that our hypothetical terrorist company has just purchased 50 gauges, which they’re licensed for.

These instruments contain two radioactive sealed sources, usually, 8 mCi of Cs-137, and a 40 mCi Am-241/Be neutron source.

Even if 50 of these Cs-137 sources were collected, and dismantled, with the source material (Often Cs-137 Chloride, as far as I’m aware) formed into a dispersible form, that’s 400 mCi of activity, total.

That should be compared to the 1.375 kilocuries of the Cs-137 source involved in the Guiana accident, which is often used as an example of the potential threat of a radiological weapon.

Given a known quantity of a known radioisotope in a known form, with an explosive dispersal charge, the actual degree of dose and the degree of radiological contamination can be quantitatively assessed. Such studies have been performed by various governmental security agencies. I don’t have any examples of those studies in front of me, but perhaps a kind reader will provide a link to remind me?

Rod over at Atomic Insights has got a brilliant post up talking about dirty bombs, what the real risks are, and how people can protect themselves from the real potential risk.

Knowledge is the most effective tool available in the fight against terrorism. That’s absolutely right.


Written by Luke Weston

July 29, 2007 at 3:14 pm

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