Polar Vortex Vs. Nuclear Plant

Exelon Nuclear's Limerick Generating Station

Blogger's Note: It's not often we get guest bloggers on The Digital Notebook, although your submissions are always welcome.

In fact, we've never had one.

And this is only kind of one.

You see, the Nuclear Regulatory Commission has its own blog, which I read, and they had a post Monday which seemed relevant given today's weather. Further, it's written by Neil Sheehan, a fellow with whom I have regular contact for stories about the Limerick Generating Station and I have always found him to be well-informed.

So, I figured, what the hell? This is what he has to say on a subject I thought you might find interesting. You can click the link above and read it there, or read it here.

When the temperatures plunge into Arctic territory, there are few parts of the infrastructure not impacted in one way or another. Pipes can freeze, roads and bridges can quickly ice over and car batteries can go dormant.

Now, with what meteorologists are calling a “polar vortex” flooding much of the country with a blast of frigid air, precautions are being taken to guard against potential effects. Count U.S. nuclear power plants among those facilities gearing up for the 2014 version of the Big Chill.

As of Monday afternoon, no plants were reporting any problems of note related to the frigid extremes, but ongoing checks will be in order to ensure that remains the case.

The NRC’s regional offices in the Midwest and Northeast are keeping an eye on plant owners’ responses to the unusually low temperatures. Plants in the affected areas have entered off-normal procedures that entail minimizing regular surveillance activities and increasing the frequency of checks and walkdowns (visual evaluations) of equipment that could be impacted by the temperatures.

Beaver Valley Nuclear Power Plant

NRC Resident Inspectors, who are assigned to specific sites, will continue to monitor the situation. The inspectors use an “Adverse Weather Protection” inspection procedure to guide their assessments of whether plants are ready for extreme temperatures, including the bitter cold. Those reviews are typically done at the start of the season.

“As applicable, verify cold weather protection features, such as heat tracing, space heaters, and weatherized enclosures are monitored sufficiently to ensure they support operability of the system, structure or component (SSC) they protect,” the procedure states in part.

It also instructs inspectors to perform walkdowns to verify the physical condition of weather-protection features.

The NRC has long recognized the need for nuclear plant owners to be on guard for extreme cold-related issues. Along those lines, the agency in January 1998 issued anInformation Notice on “Nuclear Power Plant Cold Weather Problems and Protective Measures.” Although such notices do not require a specific action or written response, they do serve to make plant owners aware of possible concerns.

For example, the Information Notice discussed an ice plug that formed on Jan. 8, 1996, at the Millstone Unit 2 nuclear power plant in a service water strainer backwash drain line. Service water refers to water taken from a nearby source of water -- be it the ocean, a lake or river -- used for cooling purposes in the plant and then returned.

To prevent a recurrence of the problem, the plant owner changed an operating procedure to ensure closer monitoring when service water intake structure temperatures drop below 40 degrees Fahrenheit and to make use of portable heaters or go to manual operation of the strainers.

Nuclear power plants are designed to withstand weather extremes. Nevertheless, NRC inspectors will be on hand to keep a close watch on plant conditions during the “vortex” and beyond.

Open House on Limerick Nuke Performance Set

Exelon Nuclear's Limerick Generating Station

If you have ever wondered how safe the Limerick Nuclear Generating Station is, Wednesday, April 18 is the time to find out.

That is the date that the U.S. Nuclear Regulatory Commission will conduct its annual "open house" to discuss the plant's performance over the prior year.

The meeting will take place at the Limerick Township Building, 646 West Ridge Pike, from 6 to 8 p.m. and is open to the public.

NRC staff members, including the on-site inspectors, will be on hand to discuss the plant's safety record over the year.

NRC oversight will be increased in 2012 as the result of a finding of "low to moderate safety significance," regarding the operation of Limerick's Unit 2 generator.

The finding was the result of "inadequate procedures" related to the operation of two main feedwater system valves, which would have been inoperable in the case of an accident  as a result of the problem.

As The Mercury reported in December, for a month last spring, two safety systems needed in case of a nuclear accident at Exelon Nuclear's Limerick Generating station were not working properly due to an error by plant personnel.

Exelon operates two boiling water reactors at the Limerick plant.

One, designed to get enough water to one of the nuclear reactors at the Limerick Generating Station during an accident; and another, designed to isolate radiation in the plant's containment building during an accident, would both have failed if called upon to perform during a nuclear accident, the NRC found.

An NRC team inspection is planned for the week of June 11 "to review the company's root cause and contributing cause evaluation for the problems; its assessment of potential similar issues; and its corrective actions to prevent a recurrence," according to an NRC release.

"Our expectation is that Exelon will thoroughly address the issues that contributed to the 'white' inspection finding finalized for Limerick late last year," NRC Region 1 Administrator Bill Dean said in the release.

"Ensuring that occurs will be a focus for the NRC in 2012," he said.

In 2011, "our inspectors spent time checking on whether there were any immediate safety concerns at U.S. nuclear power plants following the March events at the Fukushima Daiichi facility in Japan," Dean said. "Those reviews indicated the plants remained safe for continued operation."

Below is a timeline I put together that allows you to follow along with the developments after the earthquake and how they affected Limerick.

Earthquakes and Nuclear Plants on Dipity.

(If the timeline doesn't appear or work right, don't blame me. Every since I started paying for the Dipity service, it was gone straight down hill. If all else fails, in theory, you should be able to see the timeline by clicking on this link.)

The hydrogen explosion at Fukushima.

But one of the more significant outcomes of the NRC's review of the Fukushima disaster is an order for Limerick to install an upgraded venting system designed to correct the problem at the Japanese plant that allowed hydrogen to build up and cause an explosion that blew apart Japan’s Fukushima Dai-ichi nuclear reactor buildings last March, spreading radiation in a 40-mile radius and forcing the evacuation of 90,000 homes. .

As The Mercury reported here last month, Exelon Nuclear has until the end of 2016 to install a new ventilation system.

You can read the annual assessment for the Limerick plant for yourself on the NRC web site or by clicking here.