The backup for the shutdown system at the Taiwan Power Co's (
The disabled system is designed to flood the reactor with boric acid which would shut down the plant's No. 1 reactor if the conventional cutoff fails. According to Taipower, there was no real risk because the No. 1 unit was off-line for maintenance at the time.
"As the reactor was not operating there was no danger," said an unnamed senior executive at Taipower's nuclear operations department, adding that there were "many other storage tanks holding the boric acid."
The plant, which generates 1,970MW in total and is located just north of Taipei City in Chinshan, has another unit which remains operational and was unaffected by the leak, the executive said.
According to the executive, workers opened and closed a valve during maintenance operations on Sept. 24, but the seal did not maintain its airtight integrity after the maintenance was completed.
Subsequently, six tons of boric acid leaked out of a storage tank and into a water holding pond at the plant, the executive said.
Local reports claimed that Taipower workers didn't know about the mishap until two days after, but executives said it was noticed the next day. Taipower said the boric acid caused no damage to the environment or the plant. The company also said the spilled acid was not radioactive.
When workers tested the valve's pressure, they discovered the seal was not airtight and that one of the boric acid storage tanks was empty.
According to the executive, in times of emergency the boric acid -- listed on the periodic table as 10B -- can be poured into the reactor where its chemical properties would halt the nuclear reaction and bring the unit off-line.
The acid is the essential element used in the backup system for shutting down a nuclear plant where so-called control rods made of boron carbide are inserted into the reactor to stop a nuclear reaction.
Work is under way to replace the boric acid and unit one should be operational around early November, according to the executive.
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