Posts Tagged ‘Jellyfish’

Wednesday, May 16, 2012 @ 02:05 PM gHale

Oversight of Unit 1 at the St. Lucie nuclear power plant in Florida is increasing because of several unplanned shutdowns at the facility.

“Overall, the St. Lucie plant continues to operate safely,” said Victor McCree, the U.S. Nuclear Regulatory Commission’s (NRC) regional administrator for the area that includes Florida. “However, these shutdowns point to performance issues and a trend that needs to be addressed.”

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Florida Power and Light Co. owns and operates the plant, which has two nuclear reactors: Units 1 and 2. The increased oversight applies only to Unit 1, which went online in 1976. Unit 2 began operating in 1983. Each reactor produces 839 megawatts of power.

Three recent outages are on record at Unit 1, said Joey Ledford, a spokesman for the commission.
They are:
Aug. 22: A large influx of jellyfish caused a decrease in circulating water to the main condenser.
Oct. 19: A water pump in the cooling system on the non-nuclear side of the plant failed.
March 31: A steam dump valve opened unexpectedly during testing of the steam bypass control system.

In addition, the August and October outages were “complicated,” meaning the cause was not obvious or involved more than one system at the unit, Ledford said. The March outage is still under review.

“An unplanned outage, what we call ‘scrams’ or ‘trips,’ is not necessarily a bad thing,” Ledford said, “but if they happen too frequently, they can be an indication of trouble that needs to be investigated.”

All three of the shutdowns were manual rather than triggered automatically, said Michael Waldron, FPL’s nuclear communications director.

“Sometimes we make the conservative decision to safely shut down the plant well before an incident can become a potential problem,” Waldron said.

As part of the increased oversight, Ledford said, the commission will conduct an “intensive supplemental inspection” at Unit 1.

“Our people are at the plant every day doing inspections,” he said. “This supplemental inspection will involve sending in additional people from our office. At this point we don’t even know if the scrams are related. Part of the inspection will be to see if there is a common factor.”

Waldron said the outages “were all separate issues” but added that FPL officials “will be prepared to present all out information to the NRC inspectors. We take these issues very seriously.”

Friday, April 27, 2012 @ 03:04 PM gHale

Diablo Canyon nuclear power plant is shut down. Not because of any natural disasters or technical device issues, it is because of jellyfish-like creatures.

Pacific Gas and Electric (PG&E) said large numbers of sea salps entering the plant’s cooling water system caused the shutdown of the one nuclear reactor that was operating at the time. The other reactor shut down early this week for a scheduled refueling outage.

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On Tuesday, the utility lowered the reactor’s output to 15 percent as a result of the salp influx. The unit was later ramped up to 24 percent before being shut down entirely.

The unit will not restart until conditions are favorable to do so, plant officials say.

Salps are small barrel-shaped plankton called tunicates, similar to jellyfish, that can grow to nearly four inches in length. They move by pumping water through their bodies. They often float in the water in string- or rope-like fashion.

Wednesday, March 21, 2012 @ 12:03 PM gHale

A robotic jellyfish, oddly named Robojelly, not only works for underwater search and rescue operations, but could also never run out of energy because it uses hydrogen fuel.

Constructed from a set of smart materials, which have the ability to change shape or size as a result of a stimulus, and carbon nanotubes, Robojelly mimics the natural movements of a jellyfish when placed in a water tank and gets power by chemical reactions taking place on its surface.

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“To our knowledge, this is the first successful powering of an underwater robot using external hydrogen as a fuel source,” said Virginia Tech’s Yonas Tadesse, lead author of a study on the subject.

The jellyfish is an ideal invertebrate to base the vehicle on because of its simple swimming action: It has two prominent mechanisms known as “rowing” and “jetting”.

A jellyfish’s movement is down to circular muscles located on the inside of the bell – the main part of the body shaped like the top of an umbrella. As the muscles contract, the bell closes in on itself and ejects water to propel the jellyfish forward. After contracting, the bell relaxes and regains its original shape.

They were able to replicate the movement in the vehicle using commercially-available shape memory alloys (SMA) – smart materials that “remember” their original shape – wrapped in carbon nanotubes and coated with a platinum black powder.

The robot gets its power by heat-producing chemical reactions between the oxygen and hydrogen in water and the platinum on its surface. The heat given off by these reactions transfers to the artificial muscles of the robot, causing them to transform into different shapes.

This green, renewable element means Robojelly can regenerate fuel from its natural surroundings and therefore doesn’t require an external power source or the constant replacement of batteries.

At the moment, the hydrogen-powered Robojelly has been functioning while clamped down in a water tank. Researchers said the robot still needs development to achieve full functionality and efficiency.

“The current design allows the jellyfish to flex its eight bell segments, each operated by a fuel-powered SMA module. This should be sufficient for the jellyfish to lift itself up if all the bell segments are actuated.

“We are now researching new ways to deliver the fuel into each segment so that each one can be controlled individually. This should allow the robot to be controlled and moved in different directions,” Tadesse said.

Friday, July 1, 2011 @ 11:07 AM gHale

High volumes of jellyfish forced a nuclear power station in Scotland to shut down for two days after they swam into seawater filters.

As a precaution staffers manually switched off both reactors at the Torness plant.

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In an effort to get the nukes back up and running, fishermen in the area helped fish out the jellyfish so it could start generating power again.

EDF Energy said they were unsure when the plant in East Lothian would re-open.

It is the common jellyfish — known as Aurelia aurita – that swam into the filters. The plant uses seawater to cool the reactors.

Although they do not sting, experts said no one should handle them without gloves.

A spokesman said the unit shut down as a precautionary measure after finding the jellyfish. In addition, there was no danger to the public at any time.

The seawater screens filter out debris in cooling water which enters the plant.

“Reduced cooling water flows due to ingress from jellyfish, seaweed and other marine debris are considered as part of the station’s safety case and are not an unknown phenomenon,” an EDF spokesman said.

“This was a precautionary action and the shutdown cooling systems performed in a satisfactory manner and both reactors were safely shut down.”

 
 
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