"Re-racking helped for a while. But you can store the fuel assemblies just so close to one another without risking overheating. If they’re too near each other, there isn’t enough boric acid between them to absorb the flying neutrons.
"A few years after re-racking, the pool was almost full again. At that time, the utility again received permission from the NRC, and the State of Minnesota, to store some of the coolest, least radioactive, fuel assemblies in ‘dry casks’ outside the plant. The dry casks each contain a couple dozen fuel assemblies in a stainless steel container. Every container is encased in tons of concrete.
"The concrete casings of the casks provide nuclear insulation, preventing radioactivity from leaking into the outside world. The older fuel assemblies in the casks are sufficiently inactive that they no longer require water to keep them cool. Simply radiating heat through the concrete shell into the air provides adequate cooling.
"The spent fuel just sits there in these casks on a concrete pad near the plant — waiting for the government to determine a final storage destination."
"Is there any way the casks could blow up?" I didn’t think so — but I wanted to be sure.
"It is impossible for a dry cask to explode. The nuclear reaction inside the cask has slowed to such a degree that it is, to the extent possible, constantly exploding. The neutrons are interacting with fissionable atoms as rapidly as the depleted fuel will allow. Nothing can make these spent fuel assemblies react more violently."
I had already done some dry cask research. I knew the casks were huge and massive — typically about twenty feet tall, ten or eleven feet in diameter and weighed in excess of 150 tons each. They couldn’t be stolen, and it would be very difficult to even break one open.
"What secures the spent fuel pool from sabotage?"
Dana looked at me for a long time without responding. "I’d prefer not to say more about the pool beyond what I’ve already told you."
What she declined to say spoke volumes. I may have found the soft spot I was looking for.
"Just one more question… and you don’t have to answer if you’re uncomfortable."
"Go ahead."
"What would happen if the water in the spent fuel pool stopped circulating?"
"That’s no secret. The water would eventually boil away and bad things would be the result. But there are backup systems in place to prevent the water flow from being interrupted. And there are backup tanks of both distilled water and boric acid, as well."
"What kind of bad things?" I asked.
"No one can say exactly. That precise scenario has never occurred. Some scientists theorize that the fuel assemblies could get so hot that they would ignite their zirconium alloy coatings, creating a zirconium fire. That would be one tough fire to put out. Zirconium burns at about 1000 degrees Celsius."
"Other than fire control, why is burning zirconium a concern? Is it radioactive?"
"It’s not so much the fire that’s the problem — though that would certainly be a localized danger. It’s the lethal elements the fire would release that create the larger concern. Along with the uranium and plutonium, the fuel rods contain at least two other toxic elements in substantial quantities. One is iodine. The second is cesium 137 — a highly radioactive gas.
"Some scientists theorize that, while the fire burns, it would expel large amounts of iodine and cesium 137 into the atmosphere, creating a deadly plume which would expand and travel with the prevailing winds. "
"Exactly how bad would that be?" I asked, fearing that I knew the answer.
"Let me put it this way. In 1986, the Chernobyl Nuclear Plant meltdown resulted in the release of a maximum of 2.4 million curies of cesium 137 into the air. That cesium was still present in the atmosphere at measurable levels over Scandinavia — after circling the globe.
"A typical spent fuel pool in the U.S. today might contain anywhere from 20 million to 40 million curies of cesium 137. The NRC has estimated, in a paper released to the public, that a zirconium fire could release up to 100 % of that cesium. You do the math.
"I’m afraid that’s all I care to say about the pools, Mr. Becker. Are there other questions I can answer?"
"Yes. Just one. How comfortable are you living within six miles of a nuclear power plant?"
"Completely comfortable. Safest, most cost effective and environmentally friendly method of electrical production ever invented."
"Thank you so much for your time, Dana. I’ll make sure to keep this discussion between us."
We both stood.
"I’d appreciate that," Dana said. "Have a nice evening."
Nice evening, indeed.Dana Winston had certainly given me some interesting questions to think about. But just because the consequences of a nuclear plant attack would be horrific, that didn’t mean a plot to assault the plant was in progress. Those same potential consequences had been present for decades — since the inception of the nuclear age. No terrorist had yet successfully attacked a nuke.
Gunner was probably right anyway. There was no reason to suspect terrorism. As gruesome as it was, the murder at the Lab seemed merely a murder. It wasn’t unusual for a killer’s motive to be unknown. And several experts had already counseled me that the professor’s work, and his potassium machine, did not constitute a terrorist threat. Even if an attack on the spent fuel pool might be possible, that did not mean plans for such an attack were underway.
Then again, in the midst of the investigation, the Mongolians had coincidentally reappeared in my life. I have never been a believer in coincidences. And there was still the missing lab device to be considered.
I needed a break. A dinner with my lovely wife.
I was still at the Hog and it was just before five in the afternoon when I called Beth on her cell. She answered the call with exaggerated heavy breathing, stalker style.
"Umm," I said, "I think that’s supposed to be my line."
"With caller ID, it works both ways. Catch up with the times, Babe."
"I am calling to request the pleasure of your presence at a dinner for two this evening at The Norton’s. Fine wine. Gourmet food. Sparkling repartee. And did I mention, fiendishly sinful chocolate dessert?"
"Sounds irresistible. How about 7:30? I’m doing research at the Clothes Horse right now. They’re about to close up shop for the day. Then I need to go home, shower and apply a few breathtaking touches to my appearance before dinner."
"7:30 it is."
This time for eating dinner would have once sounded foolishly early. But in a community where most diners hit the restaurants in time for the ‘early bird special,’ seven-thirty is just about perfect. Any later and you risk being trapped inside the restaurant when they roll up the sidewalks.
I had a little time to kill. It wouldn’t take me quite as long as Beth to morph into my dinner persona. A final Bass seemed a reasonable idea. I caught the bartender’s attention with a raised finger. He brought the ale and a fresh cocktail napkin to my table.
Staring down at the frothy schooner, I resolved to put all thoughts of guerilla warfare, terrorist plots and world domination aside for now. I sealed the resolution with a cool swallow of the Bass, dabbing the foam off my upper lip. A new man.
I nursed the ale in a state of self-hypnosis for the next half-hour, then walked home — six blocks. Small town living has its perks.
When I arrived at the house, Beth was busy trying on various top and bottom combinations, seeking the right je ne sais quoi.