Federal inspectors, plant operators discuss nuke plant leak
By Michael Graczyk
Associated Press Writer
The Associated Press
Federal regulators told operators of the South Texas Project
nuclear plant on Monday they would notify them by the end of the week whether a
generating unit idled by a pair of leaks in a reactor can be restarted now that
the repairs have been completed.
"I think you can tell from our presentation we're very
satisfied with the actions you have taken," Dwight Chamberlain, acting deputy
regional administrator for the Arlington-based Region IV Nuclear Regulatory
Commission, said after hearing an explanation of the inspections, repairs and
future monitoring by operators of the power plant near Bay City.
"We believe we have developed a very strong safety culture
at South Texas Project," said Joe Sheppard, president and CEO of the STNP
Nuclear Operating Co. "We believe we
have done it right and we believe we are ready to restart Unit 1 to service in
a safe and reliable manner."
Unit of the twin reactor South Texas Project about 90 miles
southwest of Houston already was shut in March for routine refueling and
maintenance when an inspection April 12 detected a tiny deposit containing
boric acid described as about half the size of an aspirin on the bottom of the
containment area of the reactor vessel.
Small vertical cracks known as "axial" cracks,
were found in two of the 58 instrumentation tubes inside the reactor vessel, a
6-inch-thick steel container 46 feet high and more than 14 feet wide. Instruments within the tubes measure the
operations of the reactor.
"We believe the cause of this condition was a fabrication
flaw in the original construction that created and overstressed condition that
caused the initiation of the cracks," Sheppard said.
"This theory has merit," Russ Bywater,
a senior reactor analyst and head of the NRC inspection team, said. "The repair is acceptable no matter what the
cause of the cracks in the weld."
Experts from as far away as France
and Japan were
brought in to help devise a repair plan that involved cutting out the cracked
part of the vessel and replacing it by welding in a more corrosion-resistant
alloy for the tubes, which were described as having the circumference of a
person's little finger.
Sheppard noted that since the specific problem had never
occurred before, "We deployed technology in May that did not exist in April."
"We have properly addressed the ...condition in a safe and
comprehensive manner," plant manager Ed Halpin
said. "The engineering analysis
supporting the repair has been very thorough.
We understand the cause and actions for future monitoring have been put
"We have confidence in the repair and the quality of the
work that has been done. Unit 1 is ready
for a safe reliable startup and return to power operations."
"We're confident the repair is fine." Bywater
He also said inspectors were confident of the commitment of
the plant managers to monitor the reactor and its twin Unit 2.
Another possible cause of the leak was a phenomenon known as
primary water stress corrosion cracking, a slow corrosion for certain alloys
that can occur at high temperatures and stress levels.
That problem has been found at other nuclear plants but in
tubes at the top of the reactor and not the bottom, like at South
Bywater said samples of the metal
taken from the cracked area of the vessel were being tested but results would
not be known until later in the year.
All 58 of the instrumentation tubes on Unit 1 were examined
and no other cracks were found. The
repairs were completed earlier this month.
The plant's second reactor, which remains up and running, is set for maintenance in 2005, when it will
undergo similar inspection.
"We just have to wait and see," Halpin said about prospects for a green light from the NRC to restart Unit 1. "We're ready.
We want to do it safely. We're not in a rush."
The two reactors produce 2,500 megawatts of electricity and serve more than 1 million homes in south central Texas. Unit 1 went into service on August 1988. Unit 2 joined it 10 months later.
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