LOS ANGELES (AP) — The operator of California's ailing San Onofre
nuclear power plant proposed Thursday to restart one of its shuttered
reactors after concluding it could be run safely despite damage to
scores of tubes that carry radioactive water.
A plan to return
even one reactor to service is a milestone for Southern California
Edison, which has spent months unraveling what caused excessive tube
vibration and friction inside the plant's nearly new steam generators,
then determining how it might be fixed.
But the plant is far from returning to robust operation.
Edison's
plan, which must be approved by federal regulators, calls for operating
Unit 2 at reduced power for five months, then shutting it down for
inspections. The outlook for the more heavily damaged Unit 3 is bleaker —
no decision is expected on its future until at least next summer.
Meanwhile,
the company is facing a state review of costs related to the
long-running outage that could leave customers or shareholders with a
huge bill for repairs and replacement power — a figure that had reached
$165 million at midyear. The company did not update those figures
Thursday.
Edison, a subsidiary of Edison International, filed its
proposal with the Nuclear Regulatory Commission, which is expected to
take months to review the details. The NRC has said there is no
timetable to restart the plant.
"The agency will not permit a
restart unless and until we can conclude the reactor can be operated
safely," NRC Chairman Allison Macfarlane said. "Our inspections and
review will be painstaking, thorough and will not be rushed."
The
proposal was immediately denounced by environmentalists and anti-nuclear
activists who have argued for months that restarting the plant between San Diego and Los Angeles would set the stage for a catastrophe. About 7.4 million Californians live within 50 miles of San Onofre, which can power 1.4 million homes.
"Both
these reactors are alike and neither is safe to operate," said S. David
Freeman, a former head of the Los Angeles Department of Water and Power
who advises Friends of the Earth. "While Edison may be under financial
pressure to get one up and running, operating this badly damaged reactor
at reduced power without fixing or replacing these leaky generators is
like driving a car with worn-out brakes."
Edison wants to operate
Unit 2 at 70 percent power, which company officials predicted would
prevent vibration that has caused excessive wear to tubing. Company
officials expressed confidence in the proposal, which followed more than
170,000 tube inspections over more than eight months.
"This is
not an experiment," Pete Dietrich, senior vice president and chief
nuclear officer at SCE, told reporters in a conference call.
The problems center on four steam generators that were installed at San Onofre
during a $670 million overhaul in 2009 and 2010. Tests found some tubes
were so badly corroded that they could fail and possibly release
radiation, a stunning finding inside the nearly new equipment.
The
trouble began Jan. 31, when the Unit 3 reactor was shut down as a
precaution after a tube break. Traces of radiation escaped at the time,
but officials said there was no danger to workers or neighbors. Unit 2
had been taken offline earlier that month for maintenance, but
investigators later found unexpected wear on hundreds of tubes inside
both units.
In a March letter, federal regulators outlined a
series of benchmarks Edison must reach to restart the plant, including
determining the cause of vibration and friction that damaged tubes, and
how it would be fixed and then monitored during operation.
In
June, a team of federal investigators announced that a botched computer
analysis resulted in design flaws that are largely to blame for
unprecedented wear in the tubes.
Overall, investigators found wear
from friction and vibration in 15,000 places, in varying degrees, in
3,401 tubes inside the four generators. And in about 280 spots —
virtually all in the Unit 3 reactor — more than 50 percent of the tube
wall was worn away.
In Unit 2, investigators found that the wall
thickness had been worn away by at least 20 percent in 147 tubes. When
about a third of the wall thickness wears away, a tube is deemed too
risky to keep in service. Edison has retired, or plugged, more than 500
tubes in Unit 2 because of damage or as a precaution, a number within
the margin to continue operating the plant.
Dietrich said Unit 2
was susceptible to the same problems that ravaged Unit 3, but engineers
believe that the extent of damage was different because of manufacturing
and assembly differences that resulted in looser tubes in Unit 3.
Running at lower power should correct the trouble, at least in Unit 2,
he said.
The generators, which resemble massive steel fire
hydrants, control heat in the reactors and operate something like a car
radiator. At San Onofre,
each one stands 65 feet high, weighs 1.3 million pounds, with 9,727
U-shaped tubes inside, each three-quarters of an inch in diameter.
If
a tube breaks there is the potential that radioactivity could escape
into the atmosphere, and serious leaks also can drain cooling water from
a reactor.
Company executives have left open the possibility that the heavily damaged generators in Unit 3 might be scrapped.
The
steam generators were manufactured by Japan-based Mitsubishi Heavy
Industries. The design of the generators also is under congressional
scrutiny.
Cracked and corroded generator tubing has vexed the nation's nuclear industry for years.
Decaying generator tubes helped push San Onofre's
Unit 1 reactor into retirement in 1992, even though it was designed to
run until 2004. The following year, the Trojan nuclear plant, near
Portland, Ore., was shuttered because of microscopic cracks in steam
generator tubes, cutting years off its expected lifespan.
San Onofre is owned by SCE, San
Diego Gas & Electric and the city of Riverside. The Unit 1 reactor
operated from 1968 to 1992, when it was shut down and dismantled.
Copyright 2012 The Associated Press.
