note: For an excellent summary of the US Drought 2012 and its implications and historical context, please visit WeatherDem’s post here.

A reactor shut down button labelled 'SCRAM!'

Photo: Alan Levine / Flickr

On Wednesday, four giant nuclear reactors shut down, in New York, Pennsylvania, South Carolina, and Maryland, in response to the heat wave. According to a report, Nine Mile Point 1 nuclear reactor in New York, automatically shut down due to high neutron flux, “meaning neutrons are not equally spread around the reactor core.”

In Pennsylvania, Exelon Corporation shut down Unit 1 at Limerick. According to Reuters:

Exelon Corp shut down the
1,130-megawatt (MW) Unit 1 at the Limerick nuclear power plant
in Pennsylvania early Wednesday following an electrical
disturbance on the non-nuclear side of the plant, the company
said in a release.

The outage came at a bad time for the power grid: Homes and
businesses in the U.S. Mid-Atlantic are cranking up their air
conditioners amid a brutal heat wave blanketing the region.

The electrical disturbance caused a loss of power to
generator cooling equipment, the company said. The unit will
remain offline until repairs, inspections and testing are
completed, it said.

In South Carolina, the Charlotte Observer explains that the nuclear plants experienced problems prior to the current heat wave event:

Problems have affected every nuclear plant in Progress Energy’s fleet, eventually spreading to the Shearon Harris plant in southwestern Wake County. The NRC conducted a special inspection at Shearon Harris this summer to understand the failure of safety valves that are designed to prevent high-pressure steam from blasting equipment and scalding plant personnel.

Also, Calvert Cliffs in Maryland shut down, apparently due to a leak in an instrument line.

In summary, when the July 2012 heat wave hit, four major nuclear power plants in the East shut down, for four different reasons, some unconfirmed by the Nuclear Regulatory Commission. This article from McCall News has a nice summary of the four shutdown events:

A unit at Exelon’s Limerick nuclear plant in Pennsylvania shut early Wednesday, according to power traders. Officials at the company and theU.S. Nuclear Regulatory Commissioncould not confirm the Limerick shutdown.

Point 1 nuclear reactor in New York automatically shut on Tuesday due to high neutron flux — meaning neutrons are not equally spread around the reactor core. Power traders guessed it could have been a faulty sensor and the unit could be back soon.

Constellation Nuclear is a venture between French power company Electricite de France SA (EDF) and Chicago power companyExelon Corp.

Constellation Nuclear 855-MW took the Unit 1 at the Calvert Cliffs nuclear plant in Maryland offline by early Wednesday due to a small leak in an instrument line. The company said it had already fixed the plant and was ramping up the unit.

North Carolina-based Duke Energy’s 846-MW Unit 1 at the Oconee nuclear plant in South Carolina also shut by early Wednesday. Details about the Oconee shutdown were not immediately available to comment.

As one who is not an energy expert, I thought that the heat wave would create stress due to increased demand, and that one heat/demand-related problem would lead to a shutdown. I assumed that there would be an in-plain-English explanation of the reactor physics occurrence in a heat wave, leading to automatic shutdown. Apparently, this is not the case. Also, to bring a fifth reactor into the discussion of reactor shutdown reasons, the giant San Onofre Nuclear Generation Station in northern San Diego County has been offline since January, when alarms sounded, and is not expected to return until late August, due to a radioactive leak, that at first was reported as harmless. Voice of San Diego explains:

Highly pressurized, scalding hot, radioactive water was leaking, deep within Southern California’s only nuclear power plant. And one of San Onofre’s thick, concrete containment domes, the infamous twin structures that resemble breasts, wasn’t doing its job. A tiny amount of radioactive particles was escaping into the environment.

This article, titled, Summer Energy Use Could Strain Power Grid, Lead to Outages:
Southern California Edison customers encouraged to conserve energy, take advantage of rebates and incentives. -also mentions the San Onofre power plant.

Elsewhere on the grid, yesterday Con Edison reduced voltage to its Manhattan customers due to the heat wave in New York, placing Manhattan on a brownout, to deal with the heavy demand for energy. During a brownout, incandescent bulbs dim somewhat, and some electric engines run slower. Residents and businesses in Manhattan were still able to continue cooling during the brownout event.

During the current heat wave, where 1000+ records fall in the US within a week, there may be yet another record: power bills to Texas customers and businesses. Texas, which is mostly separated from the rest of the US electricity grid, and owned by huge corporations, is experiencing extreme stress on many levels this season, and power companies such as Austin Energy are cashing in.

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