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Broken bolts shut
nuclear reactor
By Lee I-chia / Staff Reporter
Taiwan Power Co (Taipower), the operator of the nation’s nuclear power plants,
said yesterday it has finished replacing and repairing six anchor bolts after
local media reported that seven anchor bolts of the first reactor at the
Guosheng Nuclear Power Plant in Wanli District (萬里), New Taipei City (新北市), were
found to be fractured or cracked during annual maintenance last month.
Because the seventh anchor bolt interferes with other devices on site, it will
be necessary to use alternative means to repair it, and its replacement has been
scheduled for inclusion in the next major rehabilitation project, Taipower said.
The first reactor, which began commercial operation in 1981, was temporarily
shut down on March 16 for routine maintenance. Earlier this month local media
revealed that one of the anchor bolts was broken, two fractured, and four
cracked. The report was later confirmed by Taipower
Taipower said there are 120 anchor bolts in the first reactor that secure the
bottom part of the reactor to the steel-reinforced concrete substrate, and that
the weight of all the components in the reactor is supported by the substrate.
It said that according to reactor designer General Electric Co’s (GE) ultrasonic
examination, the other 113 anchor bolts were good enough to ensure the reactor’s
safe operation. GE said the reactor would be able to resume operation once
repairs had been completed, Taipower added.
The fracturing of the anchor bolts could have been caused by defective
materials, the manufacturing process, environmental influences or metal fatigue,
Taipower said, adding that it was difficult to determine what caused the cracks.
However, initial evaluation of the fractured surface appeared to show they were
caused by long-term stress instead of sudden shearing.
Taipower said it would consult other related agencies to analyze and fix the
problem and add vibration sensors near the supporting base of the reactor for
continuous monitoring.
However, at a coordination meeting at the Legislative Yuan on Friday, an
official from the Atomic Energy Council said this was the only case of fractured
anchor bolts in GE BWR-6 boiling water reactors that had ever been recorded
anywhere in the world.
The Chinese-language Liberty Times (the Taipei Times’ sister paper) yesterday
quoted a Taipower official named Lin Te-fu (林德福) as saying GE charged US$3
million for the six newly replaced anchor bolts. The rehabilitation price was
questioned by civil engineer Wang Wei-min (王偉民), who said the bolts were
massively over-priced, and that as the fractures resulted from metal fatigue,
all 120 anchor bolts should have been replaced to ensure safe operation.
In response to the media report, Taipower said the rehabilitation work was
contracted to GE and included emergency treatment by its specialists, the bolt
material, monitoring personnel, structural safety analysis and engineering
design, so the price could not be compared with ordinary mechanical components.
The Green Citizens’ Action Alliance, a civic group, said it was concerned that
ultrasonic examinations might not detect possible metal fatigue in the remaining
113 original anchor bolts until they cracked.
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