For those of you interested in the various scales that quantify major disasters, we have a new entry for you: The International Nuclear Events Scale. The INES is an eight-point (0 to 7) numeric scale developed by the International Atomic Energy Agency for communicating the level of danger represented by a nuclear accident, designed so international authorities can comprehend and respond to the threat quickly, appropriately, and effectively.

Before we go any further, this is not the oft-misquoted list of buzzwords such as Bent Spear and Broken Arrow that show up in oh-so-many Hollywood movies, though such terms do have some basis in reality. Those are code phrases used by the U.S. military to describe incidents involving nuclear weaponry, while the INES is a civilian system used to describe events involving non-weaponized nuclear systems and materials.

Put another way, Broken Arrow refers to a missing nuclear bomb. INES Level 7 refers to a nuclear reactor meltdown.

An INES Level 0 event represents absolutely no danger to anyone or anything, but it was at least enough of a hiccup that the incident observer felt it worth reporting to international authorities. Think of it as the nuclear equivalent of the Check Engine light in your car.

In contrast, the poster child for an INES Level 7 event — and the only example of the worst possible INES rating — is the Chernobyl disaster, rated by most authorities as the most lethal and dangerous nuclear event in human history, short of those that actually involved nuclear weapons.

This is not to say that the Chernobyl disaster released the greatest volume or intensity of radiation ever to result from a nuclear accident. The lethality of the Chernobyl accident is largely attributable to the fact that it released radioactive fallout into open air.

Winds then carried that fallout over a devastatingly large area. This wind-borne fallout exposed millions of innocent bystanders to increased cancer risks, and it rendered an entire city uninhabitable for the next few thousand years.

Still, the highest dose any single individual received from the Chernobyl disaster was an estimated 1,600 rems — definitively lethal but far from the record dose suffered by a human accident victim.


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What was the highest dosage of radiation ever suffered by a human being from a conventional nuclear accident — the highest lethal rem count ever inflicted outside the detonation of a nuclear weapon?

On Dec. 30, 1958, technician Cecil Kelley was hard at work at the Los Alamos National Laboratory in New Mexico using chemical reagents to purify plutonium isotopes. In a tragic sequence of events, Kelley inadvertently created a brief nuclear criticality in one of the purification vats, leading to a radiation burst that dosed him with a staggering 12,000 rems — more than seven times the highest dose suffered by any victim of the Chernobyl disaster.

The cause of the accident was deceptively simple: There was more Plutonium-239 isotope in the reagent vat than anyone suspected. When Kelley activated the vat’s automated stirring mechanism, it brought sufficient amounts of Pu-239 together to create a short-lived nuclear reaction.

The vat went up like a flashbulb, blasting Kelley with an intense burst of nuclear radiation — an estimated 900 rad from fast neutrons and 2,700 rad from gamma rays — the highest recorded accidental human exposure in history.

(As a measure of scale, the 1945 nuclear bombings of Hiroshima and Nagasaki exposed some victims to monumentally higher dosages than Kelley, with some estimates placing dosages in the range of 200,000 rems. The explosive effects of the bombs, however, make accurate assessments of the dosages almost impossible.)

Kelley began suffering classic symptoms of acute radiation poisoning instantly, and he died 35 hours after exposure. Without resorting to graphic details, it’s sufficient to say that Kelley’s body exhibited some of the most extreme examples of these symptoms ever witnessed by physicians.

Dozens of scientists around the country received samples of Kelley’s tissue. Those samples became some of the most infamous specimens in a controversial human tissue analysis project that examined the effects of radiation on more than 1,500 subjects over the course of several years.

Kelley’s case remains one of the landmark medical examples of the effects of radiation exposure — something to keep in the annals of nuclear research, medical science, and Geek Trivia.

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