The Attack of the Jellyfish

An influx of tiny, jellyfish-like creatures last week forced the shutdown of one of the reactors at the Diablo Canyon nuclear power plant in California. The creatures are called “Salp” and they can be held in the palm of a hand, although they can grow up to four inches in length. They maneuver in the water just like squid by pumping water through their gelatinous bodies and ejecting it in a stream.

Because of an influx of the photoplankton they feed off, millions of the little critters were swarming in the waters at Diablo Canyon, which sits on an 85-foot cliff overlooking the Pacific Ocean. Some hapless Salp were getting sucked into the plant’s intake structure and pulled up against screens that protect the condensers and heat exchangers from marine debris.

Some of creatures passed right through the screens within the intake structure and passed right through the plant; but others got caught up against the metal mesh, clogging the screens. The plant’s Unit 1 has been shut down since April 22 for a refueling outage that is expected to last several weeks. On April 23, operators reduced power in the Unit 2 reactor to 15 percent as a protective measure. The Salp don’t pose a danger to any of the plant’s safety systems, but operating at lower power minimizes the impact of a shutdown, if one becomes necessary.

On April 25, it did. The buildup of Salp in the intake prompted operators to manually shutdown the reactor. All systems functioned as designed and no unexpected equipment issues were encountered. Unit 2 restarted last weekend.

Victor Dricks
Public Affairs Officer, Region IV

How the NRC uses Enforcement to Protect People and the Environment

A big part of the NRC’s mission to protect people and the environment depends on the companies and individuals we regulate meeting our requirements. The NRC’s Office of Enforcement has a number of tools that serve as deterrents and emphasize the importance of compliance with NRC requirements. These tools encourage the prompt identification and timely correction of violations by the licensee, certificate holder, or applicant. They include, in part, Notices of Violations, civil penalties, and Orders that modify, suspend or revoke a License.

The NRC’s Enforcement Policy spells out the NRC’s policies and procedures in initiating enforcement actions and the responsibilities of the Commission in reviewing these actions. But it is important to remember that a policy statement is not a regulation and the Commission may decide to deviate from the policy statement to respond appropriately to the circumstances of a particular case.

To identify violations of its regulations, the NRC conducts inspections and investigations. Violations have varying levels of significance. In assessing the significance of a violation, the NRC considers four specific factors:

(1) actual safety or security consequences;

(2) potential safety or security consequences;

(3) impact on the ability of the NRC to perform its regulatory oversight function; and

(4) willfulness.

Willful violations are of particular concern to the NRC because the agency’s regulatory program is based on licensees and their contractors, employees, and agents acting with integrity. For most violations identified at power reactors, the significance of a violation is assessed using the significance determination process of the Reactor Oversight Process.

The Enforcement Policy was last updated on July 12, 2011, after interaction with affected stakeholders. We’re happy to take any questions or comments you have about the policy in the comments below.

John Wray
Sr. Enforcement Specialist
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