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Monday, March 21, 2011

Nuclear safety

I know I've posted about this before, but in light of the recent tragic problems with nuclear power plants in Japan, it occurred to me that it might be worth revisiting events of long ago that converted me from a supporter of nuclear power to a skeptic.

Roughly thirty years ago, I was working as an economic expert on an anti-trust case involving pipe snubbers for nuclear reactors (Barry-Wright v. ITT-Grinnell et al). Pipe snubbers are essentially shock absorbers, designed to protect the miles and miles of piping in nuclear plants from earthquake damage. The snubbers need to allow the pipes to expand and contract as they heat and cool but still prevent them from swinging back and forth too wildly when earthquake tremors shake them.

Design engineers specify the exact position and placement of each snubber in the plant so as to maximize their effectiveness in protecting the pipes from damage, and it is essential that the snubbers are located exactly as specified in the plant designs.

At the time I was working on this case, there were two types of pipe snubbers; a) hydraulic snubbers, and b) mechanical snubbers, made principally by Pacific-Scientific. Hydraulic snubbers were much like the hydraulic shock absorbers found in your car, with a piston and a hydraulic cylinder to resist and cushion sudden shocks. Mechanical snubbers were more like the springs in your car.

Hydraulic snubbers were used in the earliest plants, but as the years went by, it became clear that the high radiation caused the hydraulic seals to break down, resulting in leakage of the hydraulic fluid and consequent failure of the snubber. In fact, in some plants, more than half of the hydraulic snubbers had been found to have failed. Because of this, many older plants were being retro-fitted with mechanical snubbers, and designs for newer plants called for mechanical snubbers in favor of hydraulic snubbers.

In the course of trying to define the size and nature of the market for these devices, I was conducting a survey of every existing and proposed nuclear plant in the country to determine the number and type of pipe snubbers used in or proposed for each plant.

Early in my investigation, I interviewed a construction supervisor at one of the plants then under construction in the South. As I was discussing the supposed superiority of mechanical snubbers over hydraulic snubbers with this gentleman, he asked me skeptically if I had ever spent any time at a nuclear plant construction site. I said I hadn't.

“Well,” he said, looking at me as if I were still wet behind the ears, “the first thing you have to know is the reality of what goes on in the field as opposed to the theory dreamed up by the plant designers in their ivory towers. Frequently, the engineers will specify a location for a snubber where there is no convenient place to affix it to the wall or ceiling of the building. So, the workers either move it 15 or 20 feet to a more convenient place or, in some cases, they'll drill a hole in the containment wall (a huge no-no) to attach a jig to hold the snubber.”

“But,” I said, “I'm told it's critical that the snubbers be located exactly where the designers specified. The whole design is based on putting the snubbers exactly between the nodes of the standing waves the pipes would experience.”

“Maybe,” the fellow retorted, “but I've worked on five plant sites and I've yet to see an inspector catch a misplaced snubber. But, it gets worse than that. When they are hanging other fixtures in the plants, often the easiest thing for the guys to do is walk on the pipes they've already hung, instead of getting a ladder. In other cases, the guys sit on the pipes while they break for lunch. Many of the mechanical snubbers are not designed to carry a man's weight, and when people walk or sit on the pipes, it bends the springs freezing them in place.”

In other words, many of the mechanical snubbers were broken before the plant was even finished. And, worse than that, the mechanical snubbers break in a locked position, so they can't even accommodate normal expansion and contraction, much less do any effective snubbing in an earthquake. When the hydraulic snubbers break, they usually break in an unlocked position, so the pipes can still move when they expand and contract.

All that seemed bad enough until I called the general counsel for Pacific Gas and Electric (PG&E) to inquire about the snubbers used in the two reactor units at the Diablo Canyon plant. The general counsel put me on a conference call with the site engineer at the construction site, and I explained that I needed to know the number and type of pipe snubbers in each unit.

The site engineeer said, “That's easy. Just I sec, I'll pull the blueprints for the two units, and we'll count them.”

A few minutes elapsed, and he returned to the phone. “Okay, let's see here. Hmmm. Let me see. Hmmm. Something seems odd here. Hmmm. There's something odd here that I'm going to have to check out, so I'm going to have to fax you the information. It might be several days.”

I waited patiently for about a week. Then, one morning in late September or early October, 1981, I picked up my New York Times and read that the pipe snubber design plans for the two Diablo Canyon units had been inadvertently switched. In other words the designs for Unit 2 had been used to build Unit 1 and vice versa. As the Times wrote:

The mix-up that caused the improper placement of supports designed to protect the cooling systems of the two Diablo Canyon nuclear reactors from earthquakes occurred because a single, transparent blueprint was prepared for both, and someone failed to attach instructions to flip it over. The Pacific Gas and Electric Company disclosed today that the plans for installation of mandatory seismic safety supports in its twin reactors were depicted on a single transparency that was supposed to have carried instructions to read one side for one reactor and the other side for the second. The investigation of the construction blunder is part of an inquiry by the Federal Nuclear Regulatory Commission into design errors in the earthquake-safeguard systems at the plant. The plant has been the subject of demonstrations concerning its safety because it is near an undersea fault at San Luis Obispo, Calif. The company alerted the authorities about the errors last Monday.

A couple of days later, the general counsel called me back to apologize for the delay, saying that the snafu with the blueprints being switched would prevent them from giving me the snubber information right away.

I have no way of knowing for sure, but I have always suspected that if I hadn't called PG&E, the Diablo Canyon units might have eventually gone online without anyone knowing that the design plans had been switched. Indeed, less than a month before my original phone call to PG&E, the Times reported that licensing of the plant was imminent and one unit was expected to go on-line in a low power configuration within a month.

All of this has given me a healthy degree of skepticism when the scientists and engineers who design these plants in their ivory towers quote vanishingly small odds of plant failure from various causes. If the Diablo Canyon plant could get as far along as it was without anyone noticing the wrong blueprints had been used, just think how many other smaller errors could have been overlooked.

I'm not necessarily saying that we should refrain from using nuclear power. After all, I'm sure that so far, many more people have been killed by pollution from coal fired electric plants and gasoline propelled automobile engines than from radiation leaks from nuclear plants. Nevertheless, I am convinced that there's no such thing as a fail-safe nuclear design – if it's not the reactor itself, it's the cooling tanks for the spent fuel rods (as we've seen so tragically in Japan). No matter how well designed the protective devices may be, the construction crews building the plants may inadvertently alter them and weaken their effectiveness. For every eventuality anticipated by the designers, there's likely one that they didn't anticipate. For every safety check and maintenance task mandated by regulators, sooner or later some will be missed.

As low as those risks may be, if nuclear plants are sited near major population centers in the United States, sooner or later there is going to be a tragedy of epic proportions, possibly involving millions of people. I'm not sure whether nuclear power is worth that risk. I am sure that we should do many other obvious things first (e.g., using low wattage lighting, fuel efficient appliances, solar and wind power generation, etc.).


Blogger KISSWeb said...

Good story -- and warning!!

2:23 AM  
Blogger KISSWeb said...

Antitrust? What the hell is that?

6:32 PM  
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