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December 1, 2007

Deck the Malls With Dirty Nukes


by Gordon Prather

Ho-Ho-Ho. Halloween has now ushered in the year-end shopping season (formerly known as Christmas). We're supposed to deck the malls with boughs of holly. So it's a bit surprising that ABC News has picked-up (uncritically) a Associated Press "report" that Slovakian First Police Vice President Michal Kopcik has thwarted the black-market sale of what Kopcik says is about a pound of almost pure [98.6%] Uranium-235.

According to AP-ABC;

"Experts say roughly 55 pounds of highly enriched uranium or plutonium is needed in most instances to fashion a crude nuclear device. But they say a tiny fraction of that is enough for a dirty bomb a weapon whose main purpose would be to create fear and chaos, not human casualties."

Where do you suppose mainstream-media reporters find their nuclear weapons "experts"?

In order to fashion a U-235 gun-type nuke, like the one we dropped on Hiroshima, with any prospect of getting appreciable fission yield, you need two pieces of almost pure U-235 which – when slammed together – considerably exceed the "bare sphere critical mass" of U-235, which is about 55 kilograms, not 55 pounds. The gun-type nuke we dropped on Hiroshima contained about 120 pounds – inertially "tamped" – of U-235, total.

Furthermore, the "bare sphere critical mass" of almost pure Plutonium-239 is only about 22 pounds, not 55 pounds. But any true nuke expert knows that it is impossible to "fashion a crude nuclear device" – that is, a gun-type nuke – with any prospect of getting appreciable fission yield by slamming together two near-critical mass pieces of Pu-239. The spontaneous fission rate of Pu-239 is too high. You can't slam them together fast enough, or keep them together long enough. Hence all Pu-239 nukes are explosively compressed to super-criticality and held together with inertial "tamping" as long as is physically possible.

As for the ABC-AP expert's assertion that a pound of U-235 can be fashioned into a "dirty bomb," a true nuke expert would know that a pound of ordinary inert non-radioactive lead could be fashioned into a much dirtier bomb.

Scroll back to June 10, 2002, when Attorney General John Ashcroft called a press conference in Moscow to announce that Abdullah Al Muhajir – aka Jose Padilla – had been arrested more than a month earlier at O'Hare International Airport by the FBI on a "material witness" warrant.

Quoth Ashcroft:

"I am pleased to announce today a significant step forward in the war on terrorism. We have captured a known terrorist who was exploring a plan to build and explode a radiological dispersion device, or "dirty bomb," in the United States.

"Let me be clear: We know from multiple independent and corroborating sources that Abdullah Al Muhajir was closely associated with al-Qaida and that as an al-Qaida operative he was involved in planning future terrorist attacks on innocent American civilians in the United States.

"The safety of all Americans and the national security interests of the United States require that Abdullah Al Muhajir be detained by the Defense Department as an enemy combatant."

Two years later, when the legality of Padilla's detainment as an "enemy combatant" became an issue before the Supreme Court, Deputy Attorney General Comey charged that Padilla, while in Afghanistan, had suggested to his al-Qaida "handler," Abu Zubaida, that they construct a real nuke, using "plans" Padilla had found on the Internet.

According to Zubaida, Padilla thought he could produce weapons-grade uranium by rapidly swinging a bucket full of ordinary uranium around his head.

Zubaida didn't think much of Padilla's "P-1" centrifuge. Nor did he think Padilla – or anyone in association with him – could construct a real nuke, even if they had the fissile material. However, Zubaida did think they might be able to construct a "dirty bomb."

According to Comey, the al-Qaida radiological dispersal device would have consisted of "uranium wrapped with explosives."

Now, if uranium is actually the "radiological agent" Zubaida suggested be used, then he didn't know diddley-squat about nukes, dirty or otherwise.

You see, as any nuke expert knows, uranium – enriched or otherwise – is only weakly radioactive, emitting principally alpha particles, which won't even penetrate surgical gloves.

True, uranium is a heavy metal, as is plutonium, but unlike lead, neither are "bone seekers." In fact, if ingested in any form other than as a fine aerosol, they pass right through the system.

So, you can dismiss the AP-ABC "report" about the Slovakian uranium "dirty bomb."

However, two years before Comey revealed what "radiological agent" Padilla intended to use, the dirty bomb experts at the Federation of American Scientists weighed in with a real "dirty bomb" concept.

The FAS dirty bomb was a "coffee jar" containing about a thousand Curies of a true radiological material such as Cobalt-60. (A thousand Curies is about the radiological source-strength of a typical medical radiotherapy unit used to irradiate cancer patients.)

"A successful bomb would have to be designed with great sophistication, first to break open the 'coffee jar,' then to gradually heat the radioactive source so that it vaporized, and finally to scatter it to the winds."

Sophistication?

No explosion?

Gradually heat the radioactive source? Scatter vapor to the winds?

What's terrifying about that?

The only person who would die right away would be the dolt who transported a thousand-Curie gamma-ray source – minus its several hundred pound lead shielding – from the cancer clinic into the mall in a coffee jar.

Actually, the FAS dirty bomb scenario sounds like the 1986 Chernobyl accident.

A graphite-moderated, water-cooled reactor at Chernobyl was being deliberately operated in a zone where the reactor was known to be unstable.

The operators lost control, the reactor ran away, melting the core, setting the graphite moderator on fire and vaporizing the light-water coolant, splitting it into hydrogen and oxygen gases. The fire then ignited the hydrogen-oxygen gas mixture, which exploded, blowing the roof off the reactor building.

About a hundred million Curies of radioactivity were spread over a wide area by invisible gases and thick black smoke.

The fire burned for 10 days.

Downwind, Soviet citizens could see the smoke and the sooty "fallout." But there was no terror, no panic. In fact, one of the other power plants at the Chernobyl site continued to operate throughout the entire ordeal!

Many of those downwind, who were forced to evacuate, didn't want to go. And except for an increase during the first several years after 1986 of thyroid cancer in small children – which is relatively easy to successfully treat – there has been no significant increase in cancer incidence among the downwind population.

But your average would-be terrorist can't transport a 1000MWe Soviet plutonium-producing reactor to your neighborhood mall this post-Halloween shopping season.

However, there are estimated to be more than 10,000 medical radiotherapy units and 12,000 industrial radiographic units in operation worldwide.

Thieves – not terrorists – have stolen several medical radiotherapy units, whose shielding weighs about a ton, to sell as scrap metal.

In the worst incident – in 1987 in Brazil – the thieves removed the highly radioactive source, itself, from the stolen unit. Result? Five persons died within days and others got life-threatening doses of radiation.

Hence, the FAS thousand-Curie dirty-bomb scenario results in a dead dirty-bomber and very little terror.

However, Padilla might have created quite a bit of terror with his uranium (essentially non-radiological) dispersal device if he used enough plastique explosives. Especially if he detonated it in a Chicago mall during the year-end shopping season formerly known as Christmas.


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Physicist James Gordon Prather has served as a policy implementing official for national security-related technical matters in the Federal Energy Agency, the Energy Research and Development Administration, the Department of Energy, the Office of the Secretary of Defense and the Department of the Army. Dr. Prather also served as legislative assistant for national security affairs to U.S. Sen. Henry Bellmon, R-Okla. -- ranking member of the Senate Budget Committee and member of the Senate Energy Committee and Appropriations Committee. Dr. Prather had earlier worked as a nuclear weapons physicist at Lawrence Livermore National Laboratory in California and Sandia National Laboratory in New Mexico.

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