‘No harm done’: alarm at Daya Bay nuclear plant accidentally deactivated for three months

Committee concludes incident did not constitute safety breach, though it says there is ‘always room for improvement’

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The Daya Bay Nuclear Electricity Plant in Shenzhen. Photo: AP

Published: 12:03pm, 10 Sep 2016Updated: 12:21pm, 10 Sep 2016

An alarm system monitoring the radiation of reactor coolant at a nuclear power plant in Shenzhen was accidentally shut down for three months before the mistake was discovered, although a safety committee insisted the incident did not constitute a safety breach.

Details of the incident were revealed during a biannual briefing of the Guangdong Daya Bay Nuclear Power Station and Ling Ao Nuclear Power Station Nuclear Safety Consultative Committee on Friday.

Three “level zero” incidents were recorded at the Daya Bay Nuclear Power Base in the first half of this year, two of which involved human error. Incidents are categorised into eight levels under the International Nuclear Event Scale, with a level seven alarm being the most serious. A level zero incident denoted “deviation” of normal procedures and had “no safety significance”.

The latest took place on May 24, when a worker at Ling Ao Nuclear Power Station Phase 2 discovered that the alarm system for the radiation of reactor number one was deactivated, with no information displayed.

The alarm was immediately restored. A backup alarm did not detect abnormalities during the shutdown period.

Committee chairman Raymond Ho Chung-tai said they were told by staff members that the system was believed to have been switched off during a scheduled maintenance in late February, but was accidentally left deactivated afterwards.

“There was no harm done,” vice-chairman Tso Wong man-yin added. “But as [we] said, there is always room for improvement for such a large operation.”