Two U.S. nuclear reactors that have long been idled—one for roughly two years and the other for three—may see even longer periods of shutdown, new reports suggest. Federal regulators said significant work remains before the Fort Calhoun nuclear power plant in Nebraska can be restarted, while Progress Energy Florida on Monday told the Florida Public Service Commission (PSC) that it was a week away from submitting a draft report evaluating repair options for its Crystal River reactor.

Fort Calhoun, a 478-MW reactor located north of Omaha, Neb., has been offline since April 9, 2011, when it was shut down for a scheduled refueling. Rising flood water from the Missouri River from June to September that year extended the outage. On June 7, 2011, meanwhile, the plant suffered an electrical fire that was later found to have started in a replacement electrical breaker where poor alignment between components increased electrical resistance on some parts, causing them to heat up and fail. The fire knocked out power to the redundant electrical system, resulting in the loss of spent fuel pool cooling for about 90 minutes. Last year it was discovered that structural supports inside the containment building aren’t sturdy enough to support the building under extreme events.

At a meeting last week with the Nuclear Regulatory Commission (NRC), the reactor’s owner, Omaha Public Power District (OPPD), pointed out that Exelon (hired about four months ago to manage the reactor’s operations until its license expires in August 2033) was overseeing repairs and improving the plant’s safety culture. NRC regulators said, however, that "significant" work remains and stressed that there is no timetable for restarting the reactor.

At Progress Energy’s Crystal River reactor in Florida, initial damage to the plant’s containment building occurred in late 2009 while workers were creating an opening in the structure to facilitate replacement of the steam generators inside. The work to create the opening caused a delamination (or separation) in the concrete at the periphery of the containment building. The unit was already shut down for refueling and maintenance at the time the damage was found.

Then in mid-March of 2011, during the final stages of returning the unit to service, work was suspended while engineers investigated and subsequently determined that a second delamination had occurred in another area of the structure. Similar to the initial delamination, the second separation occurred about 9 inches from the outer surface of the concrete. The Crystal River Nuclear Plant containment structure is about 42 inches thick, contains both horizontal and vertical tensioned steel tendons, and is lined with a 3/8-inch-thick steel plate. The plant had originally been slated to restart in April 2011, following the uprate, but in June 2011, the company said restart would not occur until at least 2014.

Last October, a review commissioned by Duke Energy after its recent merger with Progress Energy estimated repairs could escalate to as much as $3.5 billion and take eight years to complete in the worst-case scenario.

Progress Energy Florida on Monday told state regulators that it was close to submitting a draft report evaluating repair options for the beleaguered reactor to the company’s chief nuclear officer. The decision to proceed with repairs could be made as soon as this summer.

The delay has been complicated by a dispute between Progress Energy and an insurance company over who will cover costs for the repairs. A prior settlement between the utility and consumer advocates calls for the utility to begin refunding customers $100 million in 2015 and 2016 if repairs were not begun by 2012. The NRC is also slated to decide, within three years, whether to approve an extension to the plant’s federal license when it expires in three years.

Sources: POWERnews, NRC, OPPD, Florida PSC
—Sonal Patel, Senior Writer (@POWERmagazine)