Monday, February 18, 2008

Reactor safety and dam safety

Reactor safety and dam safety
(Cross posted with updates from bartoncii)

Critics of nuclear power often resort to irrational arguments. For example the words "Three Mile Island," are assumed to have great value in forming their argument, yet defenders of nuclear power point to the Three Mile Island incident, as an example of the safety of nuclear reactor. Infect there were no direct or indirect deaths associated with the "Three Mile Island" incident. A number of court cases, alleging that radiation exposure from the Three Mile Incident caused cancer, but none of the cancer victims could show that they had been exposed to radiation. Numerous research studies conducted in the area of the Three Mile Island reactor incident, showed that no increase in cancer cases developed in the Three Mile Island area after the incident. Thus the Three Mile Island incident demonstrated that even in the event of a major reactor accident, American reactors are designed to protect the public against dangerous exposures to radiation and radioactive materials.

During the 28 years since the Three Mile Island accident there have been important advances in reactor safety. New reactor designs include passive safety features, that would have prevented the TMI accident if they had been included in the Three Mile Island reactors. Critics of Nuclear power steadfastly refuse to recognize advances in nuclear safety. Indeed, most creatics of power, do not appear to understand the difference between reactor designs.

Buy are nuclear critics really concerned about human safety? If they were concerned about safety, then why haven't they looked at dam safety issues. Dams are far more dangerous than reactors.

Am October 2007 news report stated that the US Army Corps of Engineers believes that the Mosul Dam, the largest dam in Iraq is in imminent danger of a collapse that would trigger the biggest flood Iraq has seen since the time of Noah. The report suggest that the flood could kill as many as 500,000 people. In September 2006, the US Army Corps of Engineers discobered that the dam was in danger.

"In terms of internal erosion potential of the foundation, Mosul Dam is the most dangerous dam in the world," the a corps report warned. "If a small problem [at] Mosul Dam occurs, failure is likely." The was built on water-soluble gypsum, and it is leaking like a seive. The corp describe the dam site as "fundamentally flawed".

A collapse of the Mosul dam, would unleash its trillion-gallon lake which would put the nearly 2 million people of the Iraqi city of Mosul under 20 metros (70 feet) of water and parts of Baghdad under 4.5 metros (15 feet) of water, according to Abdulkhalik Thanoon Ayoub, the Musol dam manager. As many as 500,000 people could be killed by the dam failure.

The Wolf Creek Dam:
Most dangerous dam in the United States?

Closer to home, two dams on the Cumberland River Wolf Creek Dam, and Center Hill Dam, are believed to be at high risk for collapse, due to water seepage underneath the dams' foundations. Last year, following the discovery of new leaks, dam engineers announced they were lowering the lake behind Wolf Creek Dam by another ten feet to prevent its collapse. The lake was already 33 feet below its maximum capacity. The dam has been classified as a “high risk” for failure by the US Corp of Engineers. Repair work was underway for 2 years prior to the January 2007 panic. Down the Cumberland river from the Wolf Creek dam are the cities of Nashville, the home of 600.000 people, and Clarksville, home to another 125,000. Low lying areas of those cities would be inundated by any flood unleashed by a Wolf √áreek Dam failure.

In 1983, following unusually heavy rains that filled Powell Reservoir, engineers at the Glen Canyon Dam on the Colorado River, discovered to their horror that water rushing through the dam spillwar was rapidly eroding it, imperiling the huge dam. In order to save the dam, the engineers had to shut the spillway down, and they decided to do that by blocking it with 1"thick, marine grade plywood. That's right folks, all that prevented the collapse of a huge dam, that impounded a 185 mile long lake, was a 1" thick sheet of plywood. Nothing the engineers can do will prevent the situation from happening again. Next time the plywood might not hold. The Glen Canyon spillways were not designed for the discharge of water for prolonged periods of time. High volume use of these spillways for more than a week or two would most likely lead to their catastrophic failure. Once the spillways failed, complete breaching of the dam could occur in a matter of hours. The Bureau of Reclamation did a study of what would happen if the Glen Canyon Dam failed. The study found in the event that the dam was overtopped or breached, a five hundred feet high flood would reached the Grand Canyon. The flood would be 230 feet high when it reached Lake Mead. The study concludes: “ The failure of Glen Canyon Dam due to overtopping would produce catastrophic flooding with unprecedented flood depths and discharges all the way to Lake Mead and Hoover Dam. Even if Hoover Dam did not fail, there would be unprecedented flooding downstream of Lake Mead as well”.

In 1928, the collapse of the St. Francis dam outside Los Angeles unleashed a wall of water 135 feet high that killed 450 people. A 38,000 acre-feet of water was impounded behind the dam. The water weighed almost 52 million tons. The flood destroyed 1,200 homes and demolished 10 bridges. Other American dams have broken with loss of life. For example, the Baldwin Hills Reservoir dam broke in 1963. Five people died. In 1972, coal slurry impoundment dam #3, at Buffalo Creek Hollow in West Virginia broke, killing 125 people, and injuring another 1121. The 1976 collapse of the Teton Dam, on the Teton Riber in Idaho killed 11 people. The Kelly Barnes Dam, located in Stephens County, Georgia, collapsed in 1977 killing 39 people. The most catastrophic flood that occurred as the result of am American dam failure was the Johnstown, Pennsylvania flood, of 1889, which killed over 2,200 people.

Even the imfamous Johnstown flood pales in comparison to the 1975 failure of 62 Huai River dams in China. The Banqiao Dam was designed to withstand a 1000 year flood, which was estimated to be one from a storm that would drop 0.53 meters of rain over a three day period.
In August of 1975 catastrophic 3'+ a day rainfall produced a 1-in-2,000 year flood in the Huai River basin. The Shimantan Dam reservoir filled to twice its capacity and broke on August 8, 1975. A half hour later, the Banqiao Reservoir overtopped the Banqiao Dam, and quickly destroyed that dam's structure. A wall of water 6 miles wide, and 23 feet high rushed down river at a speed of 30 mph. Numerous down stream dams were breached, and an area of 4,600 square miles temporarily turned into a lake. As many as 235,000 people died as a result of the flood and its aftermath.

The Banqiao Dam after its failure

Finally the huge Three Gorges Dam, poses the mother of all flood dangers. The dam is located near a simismic fault. Dam critics have argued that dam designers have underestimated the stresses an earthquake would impose on the dam. The Three Gorges Dam was designed to withstand a "thousand year flood." But then so was the failed Banqiao Dam. Critics of the Three Gorges Dam have pointed to numerous optimistic assumptions, which its designers made. What is so frightening about the Three Gorges Dam is that 75 millions people live down stream from it, and would be threatened by its failure.

'This is a geologically risky area and the dam definitely increases those risks,' said Chen Guojie, a geologist at the Institute of Mountain Hazards in Chengdu. Chinese officials recently admitted that the huge weight of the water behind the dam had started to erode the Yangtze river's banks in many places, which, together with frequent fluctuations in water levels, had triggered a series of landslides. Landslides have caused waves 50 metres high on lake waters.

Officials also said that another four million people in the area would have to be relocated from around the dam because of safety issues. A failure of the dam would unleash a flood 186 meters (600 feet) high. The lake behind the Three Gorges Dam is 600 km (400 miles) long. A flood of that magnitude would be unimaginable.

Despite repeated dam failures and the large loss of human life, and the dangers of further catistrophic failures, nuclear critic like Helen Caldicutt worries only about reactors. Critics of nuclear power catastrophize about its dangers, even though no one has ever died as the result of the operation of a civilian power reactor in the United States. The same critics remain strangely silent about the dangers posed by supposable renewable green energy sources like hydroelectric power dams, despite the deaths of thousands of people, and the danger dams pose to millions of lives.

1 comment:

The North Coast said...

Charles, I came across this older post of yours while searching for more reference material with which to bolster my friendly arguments with "green" neighbors of mine here in Chicago (where God knows we have enough flood risk- thank the Gods there is no potential for a hydro dam here)regarding the desirability of hydro power.

Weird- greens just LOVE hydro until somebody wants to put up a dam anywhere near them. Actually having to deal with such a potential really triggers the NIMBY reflex. Wonder why?

Excellent post, saves me the trouble of running down separate articles on all the dam failures.

Also, I had heard about the danger of Glen Canyon, but had no idea it was so bloody big or impounded so much water.

What "green" advocates don't get is that when you have to factor the weather or climate into your calculations regarding the efficacy and safety of a particular method of power generation, that you are adding a huge UNKNOWN and INCALCULABLE risk. You have to worry about some conditions everywhere- you don't want to position a nuke on top of an active fault, for example- but at least you don't have the things to deal with that you do with a hydro dam, that are impossible to project with accuracy.

Thanks for your great blog. It has provided me with ammunition in my campaign to influence my fellow IL citizens to press for the repeal of the nuclear moratorium here. But most of all it has expanded my knowledge and provided a lot of useful sources for gaining more knowledge of nuclear technology.


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