Bad time for nuke shutdown

Group says outages show safety problem

When the alarms went off and the emergency lights started flashing Tuesday morning, operators and engineers at the Shearon Harris nuclear plant went into a well-rehearsed mode: the forced outage plan.

Progress Energy's reactor, about 25 miles southwest of Raleigh, shut down automatically, an event triggered by a mechanical malfunction. Nuclear reactors are designed to shut themselves off under a variety of conditions, most of them never drawing notice by the public.

Shutdowns are often short-lived interruptions: In Progress Energy's case, Shearon Harris was restarted late Thursday and the 900-megawatt reactor is expected to be fully operational sometime today.

But to nuclear opponents, an abnormal occurrence of shutdowns indicates reliability and safety problems downplayed by the nuclear industry.

The N.C. Waste Awareness and Reduction Network, a Durham group that has opposed the Shearon Harris plant for 15 years, claims Shearon Harris is one of the most dangerous nuclear plants in the country, in part because the plant led the nation in unplanned shutdowns from 2002 through 2005, according to N.C. WARN's assessment.

Tuesday's unplanned shutdown was the ninth at Shearon Harris since 2002. By comparison, Progress Energy's Brunswick nuclear plant, near Southport, had six unplanned shutdowns at each of its two reactors during a similar time period, according to the company's records.

Officials at Progress and the Nuclear Regulatory Commission, the federal agency that regulates reactor safety, have repeatedly maintained that the Shearon Harris plant is operating safely.

"Shutdowns are the result of safety systems working properly," said Julie Hans of Progress Energy.

Shearon Harris tripped offline at an especially sensitive time, when N.C. WARN and other nuclear critics are intensifying their criticism of the plant's nuclear performance. The aggressive scrutiny is timed with the Raleigh-based utility's plans to seek federal licenses for up to four new reactors, two at Shearon Harris and two in Florida. The shutdowns don't inspire confidence, said Jim Warren, director of N.C. WARN.

"It means that their safety systems have been challenged more frequently," Warren said.

An unplanned shutdown is one of the most common training scenarios for nuclear plant operators, who prepare for shutdowns and other unusual occurrences about 100 hours a year in a control room simulator situated at the complex.

One of the unplanned shutdowns at Shearon Harris in recent years was caused by a lightning strike. Most of the others were caused by problems with pumps.

Tuesday's shutdown was the result of a failed monitor on the main generator, shutting off the turbine that produces electricity, in turn tripping the nuclear reactor that drives the turbine. The generators at all Progress Energy power plants -- including those fueled by coal and natural gas -- have such a monitor, called a "relay," to ensure that the power is not grounded but rather flowing out to the transmission system.

"If you lose your source of generation, you don't want your reactor to run," said Ed Wills, manager of operations at Shearon Harris. "Basically, you don't want your reactor running ... without a place to send your electricity."

The crews at Shearon Harris had isolated the malfunction to the relay monitor 15 minutes after the midmorning shutdown. The crew spent the next 48 hours trying to determine whether the system tripped because the monitor was defective, or whether indeed the monitor worked and detected a problem with the generator. To make that determination, crews of six electricians, working 12-hour shifts, disconnected the generator, a 300-foot transmission conduit and five transformers to test them all individually to see if any were improperly grounded. The tests showed that the system was working correctly, Wills said.

An inspection of the monitor showed that it was charred. It's still unclear why it failed. The company replaced two monitors Thursday, Wills said. Even though the reactor shuts off instantaneously, it will take up to 20 hours to rev up the reactor to full power.