U.S. NRC Blog

Transparent, Participate, and Collaborate

Nuclear Power Plants Ready For Major Winter Storm

Neil Sheehan
Public Affairs Officer
Region I

winterstorm

Update: The Pilgrim nuclear power plant experienced an automatic shutdown, or scram, early Tuesday amid Winter Storm Juno (as dubbed by the Weather Channel). Here is additional information:

Entergy had sequestered staff on-site prior to the storm. The NRC also had an inspector stationed on-site overnight. Reactor power was reduced to 75 percent overnight, per procedures, as the grid experienced voltage fluctuations. Operators started the plant’s two emergency diesel generators and transferred electrical loads for safety systems to those on-site power supplies due to concerns with off-site power.

One of two 345-kilovolt offsite lines was deenergized due to weather concerns. At about 52 percent power, the second 345-kilovolt line that provides off-site power to the plant tripped, resulting in a reactor shutdown, or scram, at about 4 a.m. (Nuclear power plants not only generate power and send it to the grid, they also receive a certain amount of power from the grid for operational purposes.)

A third off-site power line, a 23-kilovolt line, remains available. However, the emergency diesel generators for now remain the primary source of power for safety systems. The reactor was safely shut down, with plant safety systems performing as expected. The exact cause of the loss of the 345-KV power lines is still being investigated.

Entergy intends to take the reactor to “cold” shutdown. NRC inspectors will continue to monitor plant activities and efforts to restore off-site power, as well as any troubleshooting and repair work.

 

The atmospheric stars have aligned once again to produce a powerful mid-winter storm aimed squarely at coastal areas in the Northeastern United States. Officials in a broad swath stretching from New Jersey to Maine have been warning residents to prepare for a blizzard that could produce prodigious amounts of snow, hurricane-force winds and dangerous travel conditions.

There are several nuclear power plants in the storm’s path and the personnel at those facilities will not be sitting back and simply awaiting its arrival. Plant procedures call for multiple checks and preparations in advance of such a winter blast.

Among other things, plant personnel will ensure that doors designed to prevent flooding are ready to perform their task; fuel oil tanks for emergency generators are appropriately filled; and the site grounds do not have loose objects which could become airborne amid strong winds and cause damage.

On a related note, the NRC will be monitoring those preparations and stationing inspectors to keep watch on the plants as they weather the storm. An inspection procedure and checklist dealing with adverse weather protections will guide the inspectors as they conduct those assessments.

It’s important to note that all nuclear power plants have technical specifications that dictate how they have to respond to a significant storm. As an example, if wind speeds are in excess of specified limits, a plant would have to shut down.

Safety at nuclear power plants is never taken for granted, and that is certainly true when storms can present additional challenges for operators. The NRC will be keeping watch until the most potent storm of the winter of 2014-15 to hit the Northeast thus far has headed out to sea.

 

16 responses to “Nuclear Power Plants Ready For Major Winter Storm

  1. Public Pit Bull February 1, 2015 at 9:31 am

    An update on the status of Pilgrim is long overdue. You have left us hanging here! When I checked the daily status report on Pilgrim 1/30 it still showed it was out of service. In this case is no news is good news?! This plant has a terrible safety track record, you remind us of it, and then you give us the mushroom treatment when the plant has a significant operational event.

  2. mjd January 29, 2015 at 10:33 am

    Neil, I take issue with your headline use of the word “ready.” The operational event evidence says otherwise. And this is the same type of “blah, blah” you posted for hurricane Sandy. Has nobody noticed we are in a cycle of severe Mother Nature events? It seems obvious to me that the plant strategy for dealing with these severe weather events is at least worthy of a new look. If both the frequency and intensity of severe weather is increasing it has clearly changed the paradigm. My point is simple, the coping strategies remain entirely reactive and based on the time period of less frequent and less severe weather events. With Pilgrim the strategy seemed to be hang on connected to the grid and hope for luck that a grid disturbance doesn’t take us down. This storm was highly forecast. Grid disturbances in severe weather are the number one risk causing loss of plants during severe weather, yet the coping strategy remains entirely reactive to the event. They even had a red flag pre-trip during the event, they lost one off site power interconnect and sat with one generator output breaker open. At that point they are one single failure away from a LOOP and a trip, during the exact event most likely to cause the single failure LOOP. Gimme a break, it’s way past the time to rethink the strategy!
    When they lost their first interconnect they should have gone to “stable low load limit power”, kept the generator on-line supplying their own house power, but opened the other generator breaker to the grid, thus removing the possibility of a single failure LOOP during the storm induced grid disturbances.
    There is not a more stable machine than a nuke plant running supplying its own electrical power while unconnected from the external grid. It’s the way all navy plants run, all the time. But yet is apparently not considered a coping strategy. It is also a plant configuration all operators understand, as it is exactly where they are during start-up, before they connect the generator to the grid.
    Hurricane Sandy took two plants down due to grid disturbances (I believe), one was inexcusable as they choose to keep the plant connected to the grid as the forecast remnant eye track passed directly over the plant in New York.
    A similar (forecast) severe weather induced event recently caused the loss of two units at DC Cook and damaged their intake trash removal system. Because their coping strategy was entirely reactive, not pro-active. In that event a pro-active coping strategy might have prevented sucking a non-recoverable amount of suspended debris into the intake. Both plants might have survived on low load limit (at reduced Circ Water flow) until the severe weather passed and the intake trash removal system caught up. A cheaper and quicker recovery.
    It isn’t necessarily the NRC’s job to formulate these coping strategies, but you can at least stimulate the discussion by asking utilities if they are doing the best thing for the right reasons in light of the current weather trends. IMO, in the current severe weather strategy is not the best strategy, as it leads to plant trips, which always challenge the plant systems (Pilgrim HPI).
    With events that are going to challenge the grid and off-site power sources the least risky approach is to go to low load reactor limit supplying your own power, unhook from the grid, and ride it out. It allows the quickest recovery and least risk of plant challenges and damage. You will have a part to play, granting discretionary enforcement on TS required Off Site Power sources in some cases.
    But no, I don’t think everybody is “ready” for the current severe weather paradigm.

%d bloggers like this: