Green Blog: A Nuclear Post-Mortem for Sandy

The operators of the Oyster Creek nuclear plant, the reactor that declared an ?alert? during Hurricane Sandy, made several small errors, the Nuclear Regulatory Commission said on Friday. But an inspection team has concluded that ?performance was acceptable and that emergency action level declarations were timely.?

The operators kept control room logs in a way that safety inspectors found hard to decipher later, and at one point, they took a wind level reading off the wrong sensor on their meteorological tower, the Nuclear Regulatory Commission said.

Oyster Creek?s main problem was that the surge, driven by wind and the phase of the moon, allowed water to creep up the structure that the plant uses to take in cooling water. If it had risen high enough, it could have forced a shutdown of the pumps that pull in cooling water.

Oyster Creek is not alone in facing that problem; two reactors on the Missouri River faced the same problem in June 2011. But such incidents are rare, and that is what pushed the Oyster Creek plant to ?alert? status, which the second-lowest of the four-stage ranking of emergencies.

Oyster Creek faced the additional problem of a grid failure, a problem that hits reactors around the country intermittently and requires plants to start up their emergency diesel generators. Nuclear plants ordinarily rely on electricity from the grid for some vital functions.

The reactor was shut down for refueling at the time the hurricane hit, and refueling operations were suspended in preparation for the storm?s arrival. That turned out to be prudent because of the loss of grid power that occurred with the hurricane?s arrival.

The loss interrupted cooling of the reactor and the spent fuel pool. With no operator action, that would eventually have been a problem; the commission?s report said that without cooling, the spent fuel pool would have boiled in 28 hours. Some hours after that, enough water would boil away to create the possibility of fuel damage, meaning a release of radioactive material. But it had no immediate impact because operators re-established cooling after 85 minutes.

(One of the big changes ordered at nuclear plants after the terrorist attacks of Sept. 11, 2001, and reinforced after the Fukushima meltdowns of March 2011, is that reactors have hoses and portable pumps so that if they cannot re-establish cooling, they can simply pump in more water. But Oyster Creek was many hours from requiring that kind of action during Sandy.)

The inspectors said that they had ?encountered challenges with the control room log keeping clarity.? But the station operators notified the state and local authorities promptly as the rising water level triggered the requirement for emergency notifications, the inspectors said, and had filled out some parts of the required forms before the storm arrived.

Reactors? operating licenses require them to shut down if certain wind levels are anticipated. In the case of Sandy, several plants shut down because of rising water or disturbances on the grid. Oyster Creek was the only one to go past ?emergency event,? the lowest level of emergency, to ?alert.?

Source: http://green.blogs.nytimes.com/2013/01/11/a-nuclear-post-mortem-for-sandy/?partner=rss&emc=rss

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