Monday, July 4, 2016

The nuclear debate heats back up

Badge given to Chernobyl 'liquidators' depicts a drop of blood with alpha, gamma, and beta particles
Lamiot, Wikipedia
There were two conflicting news stories this week.

On Monday, President Obama proposed guaranteeing loans for the building of a ‘new generation’ of nuclear power stations. The reason for the government guarantee? Wall Street considers the nuclear power business too risky to invest in. Who’s right, the White House or Wall Street?

It was also reported on Monday that tritium has been found in the groundwater around the Vermont Yankee nuclear power station. This news comes on top of the 27 other nuclear power plants that are likewise known to be leaking. The tritium at the Vermont plant was measured at 70,500 picocuries per liter. That’s bad enough. However, the owners of the plant, Entergy Corp., lied to state regulators and lawmakers by saying the plant did not have the kind of underground pipes that could leak tritium into groundwater. How bad is tritium? 
The government says anything above 20,000 picocuries is dangerous to humans, so the Vermont plant is more than triple that amount. But the medical field questions even the government’s figure. The National Academy of Sciences concluded after an exhaustive study in 2005 that even the tiniest amount of ionizing radiation increases the risk of cancer. According to Dr. Richard Monson, professor of epidemiology at the Harvard School of Public Health, “There is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless.”

In 1973, in the middle of a nationwide oil crisis, then-President Nixon praised nuclear power as the key to making America energy independent, and promised that by the year 2000 there would be 1000 nuclear power plants operating across the country. Today, the total sits at 104.

What happened? A movie called The China Syndrome, first of all, followed within weeks by the accident at Three Mile Island. Quick science lesson:

When I was in Junior High we watched one of those cool Bell Labs movies that explained nuclear power. They showed a room completely carpeted with mousetraps. Each trap was ‘baited’ with a ping pong ball. Then they tossed a ping pong ball into the room. It set off one trap, the two bouncing balls set off two traps, and so on until the room looked like a popcorn cooker.

In a nuclear reactor, the nuclear fuel is in parallel rods, like the fingers on your right hand. Between the fuel rods are control rods, made of a material such as graphite that prevents, or at least slows, the neutrons from one rod flying across to the other rod. (Picture interlacing the fingers of your left hand.) If the control rods are withdrawn, neutrons begin flying like the extra ping pong ball thrown into the mouse trap room. Re-insert the control rods, and the neutrons are restricted.

All this takes place under water. The ping ponging of neutrons creates a lot of heat, heats the water, and the resulting steam spins a turbine attached to a generator. Simple, right? Obviously not. If the water level drops too low, the rods are exposed, and can superheat and melt. If the water turns to steam, same result. So all the complicated stuff in a nuclear power plant is pumps, valves, plumbing and gauges intended to keep the rods at a proper operating temperature.

At Three Mile Island, at about 4:00 a.m. on March 28, 1979, (1) the main feed pumps circulating the hot water to the steam turbines stopped running. The turbines shut down automatically, as did the reactor. However, pressure built up in the primary system (the nuclear portion of the plant). In order to prevent that pressure from becoming excessive, a relief valve opened. (2) The valve should have closed when the pressure decreased by a certain amount, but it did not. (3) Gauges that should have showed the operators the valve was still open failed, and water began pouring out of the stuck valve, and the reactor overheated and partially melted. The amount of radioactive steam that leaked into the atmosphere was relatively small, according to the official reports. Still, “a peer-reviewed study by Steven Wing of the University of North Carolina found that lung cancer and leukemia rates were 2 to 10 times higher downwind of TMI than upwind… In addition, the Radiation and Public Health Project reported a spike in infant mortality in the downwind communities two years after the accident,” according to a Wikipedia article.

Seven years later, it happened again at a place called Chernobyl, with far worse consequences. At Chernobyl, the operators were trying to run a test of how long the turbine would continue to generate electricity if the power from the national grid to the pumps were cut off. They knew it would take about 90 seconds for the diesel generators to come on line, and it was believed that the turbines would continue spinning and generating electricity for at least that long, but it wasn’t known for sure, so they wanted to test it. Three previous attempts to test the theory had failed. The test was believed to be safe. However, when power from the grid to the pumps is cut, the reactor is designed to ‘scram,’ that is, to immediately and completely reinsert the control rods. The day shift was thoroughly prepared for the test, but there was an unexpected need for the reactor to be online, so the test got pushed off to the night shift. While there are differing theories as to what caused the accident, it’s clear that the plant was not designed to have a scram just any old time. As the operators proceeded with trying to meet the requirements for the test, the reactor got more and more out of control, and when they finally decided they had an emergency on their hands and pushed the scram button, the control rods pushed the water away from the fuel rods, and the reactor exploded. It was not a nuclear explosion; rather, an explosion similar to what can happen to a large, overheated boiler. The water in the reactor immediately flashed to steam and the rods, with no water to moderate them, superheated and melted.

This was the classic “china syndrome,” that is, this lump of superhot melted reactor core began to burn through the floor on its way to China, all the while spewing tons of radioactive smoke, steam, and pieces of the reactor into the air and surrounding landscape. A pool under the floor was threatened. If the lump reached that, thousands of gallons of steam would carry the radioactive poison to all points of the compass.

A strange thing happened. Some very selfless people began to step forward, knowing they were gambling with their lives, to try to bring this disaster under control. Later, these folks would be dubbed, “the liquidators.” For example, three men in diving suits went into that pool to open a valve and drain the highly radioactive water out of it. 30 firemen worked to contain the blazes caused by the explosion. Some may have known they were being poisoned, some may not have. All are now dead. Ultimately, a huge concrete box, dubbed “the sarcophagus,” was poured over the remains, even though it was determined – before the work started – that exposure to the site for more than 40 seconds would cause serious health problems or death. Most of the workers who built it have died.

All the trees in a two square mile area around the plant died. Horses on an island four miles from the plant all died. Most of the cattle on the island died. There is a 17 mile ‘exclusion zone’ around Chernobyl where no one is supposed to live, but some elderly people who missed their homes snuck back in and are living there. The exclusion zone will be unsafe for agriculture or continuous human habitation for the next 200 years. The mess inside the sarcophagus will be deadly for about the next 20,000 years.

Does the world need more energy? Absolutely. If a ‘new generation’ of nuclear power plants gets built, will they be able to avoid leaks, health problems, and catastrophes like Three Mile Island and Chernobyl? Time will tell.

Oh, and, by the way, almost 60 years after the first nuclear power plant opened, there is still no solution to the problem of what to do with the spent fuel rods. But that’s another column.


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