Three Mile Island

Used as the example of dumping borated water to poison a reactor. Single-sentence reference. ## Figures referenced

Titanium, zirconium, and hafnium. Titanium we already know about. Zirconium is a structural material in a very special application. Anybody know what? [Tom holds up a sample.] This is crystal bar zirconium. You can tell it's fairly heavy. It's made by reducing zirconium tetrachloride on a hot wire of zirconium, and it just grows from the vapor phase. This is a Zircaloy alloy tube — nuclear reactor fuel cladding. Very low nuclear cross-section. Those little neutrons go right through it. So it won't poison the reaction. If you know anything about nuclear reactors, one of the ways you poison the reactor is you put boron in there — you have borated water. Boron absorbs neutrons like gangbusters, and so you can poison the reaction and shut it down. If you have something like Three Mile Island and you want to shut it down, you dump borated water on top of the reaction to poison it and stop it. Zirconium has very low nuclear cross-section, which means it's transparent to neutrons. It has to be very pure, because a little bit of hafnium impurity poisons it — hafnium starts absorbing neutrons at very low concentrations.

Used to introduce the stress-corrosion-cracking vs. stress-assisted-cracking distinction as an insurance-policy issue. GPU's attorney reads the policy, finds corrosion is excluded, and the terminology gets rewritten — a "day and a half" later — to remove "corrosion" from the press releases.

They'll appreciate a replaceable piece. They have to go in there for some changes. And eventually you're going to replace water, so you just put a patch in. I remember what happened at TMI [Three Mile Island] — on the first day and a half they called it stress corrosion cracking. And it was stress corrosion cracking. But then some attorney for GPU [General Public Utilities] read their insurance contract, which excluded corrosion. So after a day and a half they called it SAC, stress-assisted cracking. What type of cracking is not stress-assisted? You don't get a crack unless you have stress. But they needed to get that "corrosion" word out of the press releases. And then we got into the debate of, corrosion is a slow gradual process — if something occurs in thirty minutes, is it a slow process? You'd say no.

The *sister* reactor (reactor 2) to the famous accident. Restart attempt produced polythionic acid attack on a nickel-based superalloy heat exchanger; stress corrosion cracking in thirty minutes; $30 million repair. Used as the worked example of the legal distinction between "stress corrosion cracking" (insurance-excluded) and "stress-assisted cracking" (insurance-covered) — and as a case study in how attorneys rename phenomena to fit contract language.

Then you get into questions like Three Mile Island — the sister reactor at Three Mile Island, where they wanted to restart that nuclear reactor. They started up the steam generator. There's a type of acid that you can't produce regularly in the laboratory, but under the high pressures and the startup temperatures, with some sulfur contamination, you get polythionic acid. It's a polymerized sulfur compound. This nickel-based superalloy heat exchanger on reactor 2 — not the one that had all the problems, but they were trying to restart it so it could generate electricity a couple years after Three Mile Island — they started it up, and within a half an hour they had stress corrosion cracks, and it cost them thirty million dollars to repair.