Situation update #1 Ill. nuke plant

[ensho]

http://hisz.rsoe.hu/alertmap/index.php?smp=&lang=eng


Situation Update No. 1
On 16.08.2010 at 18:40 GMT+2

Exelon Corp. is investigating the cause of shutdowns this morning of two nuclear reactors at Braidwood Generating Station. The Unit 2 turbine tripped off line at 2:06 a.m., followed 13 minutes later by a shutdown of the Unit 1 reactor. Nuclear Regulatory Commission spokeswoman Prema Chandrathil said in the case of Unit 2, there was a problem with the path of the electrical current, which tripped the turbine and, in turn, the reactor. In the case of Unit 1, she said, a secondary cooling system malfunctioned, which led steam to be released from the main release valve for cooling purposes. The unit was then manually shut down, she said. “All of these steps went forward as designed, as engineered and as planned,” she said. “The utility and the NRC are investigating. We have to go ahead and try to determine what exactly happened there, and if (the two incidents) are connected.” Chicago-based Exelon said environmental experts are testing condensate and water in the system for tritium – a radioactive form of hydrogen – which would have been released into the air with the steam. According to the NRC, tritium levels are likely to fall well below regulatory limits. The company said the shutdowns pose no threat to plant personnel or the public. “As this happened overnight, we understand our neighbors may have heard the venting steam and we want to make sure they know there is no cause for concern. We appreciate their patience,” Braidwood Station Site Vice President Amir Shahkarami said in a statement.

Tritium occurs naturally but is produced in greater concentration in nuclear reactors. The isotope can increase the risk of cancer but is considered one of the least dangerous radioactive substances because it leaves the body quickly, according to the EPA. This March, Exelon agreed to pay more than $1 million to settle lawsuits filed by Atty. Gen. Lisa Madigan after the company allowed radioactive tritium to leak outside three nuclear power plants. Leaks of tritium-contaminated water seeped into the ground around the company’s Braidwood, Byron and Dresden plants and, under orders from the state, the company cleaned up contaminated groundwater, improved monitoring and ensured that wastewater was diluted enough to meet federal standards. After the Braidwood contamination was revealed in 2006, the Nuclear Regulatory Commission cited Exelon for failing to respond properly to 22 leaks dating to 1996. The nuclear plant is about 60 miles southwest of Chicago. At full power, its two reactors produce enough electricity to power 2 million homes. The NRC said the reactors will stay offline until the causes of the malfunctions are determined and fixed.
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[Pavulon]

1. Great support for safe design. Fault detected,

system taken offline. This is how the navy maintains thousands of reactor years of operations in a safe manner.

[SidDithers]

2. Another post highlighting the multiply redundant levels of safety features...

installed on America's electricity generating reactors.

+1

Sid

[ThomWV]

3. Just goes to show how safe they have become.

[Statistical]

4. Amazingly safe and redundant systems.

The entire system using laws of physics errs of the side of caution.

If something abnormal happens the system shuts down reliably, safely, and predictably.

It doesn't require some human to even spot the problem and go running to hit magic red shutdown button.

Western Pressurized Water Reactors (PWR) operate in a very narrow range.

Too little pressure = shutdown
Too much pressure = shutdown
Too little heat = shutdown
Too much heat = shutdown
Too little neutron flux = shutdown
Too much nuetron flux = shutdown
Too little steam = shutdown
Too much steam = shutdown
Too little load = shutdown
too much load = shutdown

When something abnormal happens usually the plant CAN still run however to always ere on the side of caution it shuts down as a precaution.

If cars were as safe they would shutdown if they are going to slow, too fast, too far, not far enough, getting too low gas mileage, getting too high gas mileage, under too much weight, not carrying enough weight, tire pressure too high, tire pressure too low. All doors not shut, all doors not reporting shut, all doors reporting shut but never reported opening before shut, operating a time not expected, operating in a place not expected, weight of driver more or less than expected, coolant level to high, coolant level too low, coolant too hot, coolant not getting hot enough, engine friction too high, engine friction not high enough, unburnt gas ratio too high, unburnt gas ratio too low, velocity vs fuel consumed too high, velocity vs fuel consumed not high enough, etc.