When A Plant Changes Hands

Neil Sheehan
Public Affairs Officer
Region I

FitzPatrickTowerViewIn February, Entergy announced plans to permanently shut down the James A. FitzPatrick nuclear power plant on Jan. 27, 2017. However, there are indications – based on recent negotiations between Entergy and Exelon – that the facility may not cease operations after all.

On Aug. 9, Exelon announced it had reached a deal to purchase the Scriba (Oswego County), N.Y., boiling-water reactor from Entergy for $110 million. This agreement occurred after the New York State Public Service Commission approved Zero Emission Credits, or subsidies, which will help upstate N.Y. nuclear plants stay online amid historically low energy prices.

Challenging market conditions had earlier prompted Entergy to announce the plant’s closure. The NRC in 2008 had approved a renewal of FitzPatrick’s initial 40-year operating license, extending it until October 2034.

Before the sale of the plant can be completed, the transaction will undergo reviews by the NRC, as well as other regulatory agencies. NRC staff will evaluate Exelon’s technical and financial capabilities to ensure the plant’s safe operation and to provide reasonable assurance that adequate funding is available to safely decommission the unit after the final shutdown has occurred.

Exelon currently owns and operates 22 reactors at 13 plant sites in the U.S. The company also runs Fort Calhoun under a contract with the Omaha Public Power District.

We will publish on our website and in the Federal Register a notice of having received the license transfer application, dated August. 18, and the opportunity to request a hearing on the proposal. As for the process itself, such reviews generally take from six months to a year. For example, when the FitzPatrick operating license was transferred from the New York Power Authority to Entergy in 2000, the review was completed in about half a year.

As a footnote, Exelon already owns the Nine Mile Point nuclear power plant, which is located next-door to FitzPatrick.

Part II: How the NRC Uses a Defense-in-Depth Approach Today to Protect the Public

Mary Drouin
Senior Program Manager
Division of Risk Assessment, Performance and Reliability Branch

Defense-in-depth is a central theme in the NRC’s regulatory oversight of the nuclear power industry. As our agency historian, Tom Wellock, discussed in Monday’s post, the concept of defense-in-depth emerged during the trench warfare of World War I. The idea of multiple lines of defense was applied to nuclear safety in the 1950s as the leading concept for protecting the public from the consequences of a nuclear reactor accident.

The NRC’s predecessor agency, the U.S. Atomic Energy Commission, spelled out defense-in-depth in a 1957 report called WASH-740, Possibilities and Consequences of Major Accidents in Large Nuclear Power Plants. “Should some unfortunate sequence of failures lead to destruction of the reactor core … no hazard to the safety of the public would occur unless two additional lines of defense were also breached,” the report said.

These words are at the heart of defense-in-depth as it has been practiced for six decades: multiple layers of defense to protect against accidents and their effects to ensure the risk to the public is acceptably low.

In a recent report issued this spring, Historical Review and Observations of Defense-in-Depth (NUREG/KM-0009), the NRC looks at how the concept has evolved in practice over the years. It also includes views from other government agencies and the international community.

As the report explains, defense-in-depth recognizes that our knowledge is imperfect. Although we plan for all conceivable accidents, the unexpected may still occur. Even if we have anticipated an event, its characteristics and impacts may be unpredictable. Our design and operation of nuclear plants need to be robust enough to compensate for this lack of knowledge. Defense-in-depth offers multiple layers of protection in case one or more layers fail.

So we don’t just rely on preventing an accident; we also need strong defenses to mitigate the effects of any accident that does occur. This applies to nuclear power plants, waste management and security as well.

In practice, defense-in-depth addresses three principles that should be factored into the design and operation of systems and components to provide additional confidence that an accident would not compromise the defensive layers:

  • Redundancy means more than one component performs the same function – for example, having multiple pumps instead of a single one;
  • Independence means these multiple components rely on separate and distinct attributes to function – the multiple pumps have separate piping from the water tank to where they discharge, and are housed in separate compartments; and
  • Diversity means the multiple components performing the same function rely on different design features to operate – motor-driven pumps versus steam-powered pumps.

dindgraphicIn reactor safety, the layers of defense might be:

  • Maintain reactor stability by limiting the ability of events to disrupt operation (with protective measures such as fire-safe or flood-tight doors, seismically designed buildings)
  • Protect the reactor should operation be disrupted (emergency reactor core cooling with redundant pumps)
  • Barrier integrity to guard against a release of radioactivity to the environment (leak-tight containment structures, filtered vents, containment sprays) and
  • Protect the public if a release does occur (emergency preparedness plans)

This versatile framework can apply whether the risk to the public comes from the reactor, spent fuel pool, nuclear waste or security threats.

%d bloggers like this: