11 Aug (NucNet): EDF Energy has shut down two reactors at the Heysham A nuclear power station and two reactors at the Hartlepool nuclear station after a possible defect was detected on the spine of one boiler at Heysham A unit 1 (Heysham A-1), EDF Energy has said in a statement.
The defect was first detected as an “unexpected result” during a routine ultrasonic inspection of a boiler spine at Heysham A-1 in 2013, EDF Energy says.
EDF Energy conducted equivalent inspections of the remaining seven boiler spines of Heysham A-1, as well as on unit A-2 and the two units at Hartlepool. The results from these inspections were normal.
A subsequent inspection at Heysham A-1 during a refuelling and maintenance outage in 2014 confirmed a defect, described as “unexpected cracking” of the boiler spine, as indicated in the previous tests. The reactor remains shut down while in-depth investigation of the defect goes on.
EDF Energy estimates the full investigations will take about eight weeks.
Unit Heysham A-2 and the two units at Hartlepool were shut down today as a precaution in order to carry out further inspections and to ensure the safe operation of the reactors.
EDF Energy says the inspection and installation of monitoring devices will take several days before the Office for Nuclear Regulation (ONR) can allow the units to return to operation.
The ONR said it was satisfied with EDF Energy’s decision and that the operating company was taking “appropriate and conservative action”.
The boiler spine and the possible defect are inherent to the design of the two units at Heysham A and the two units at Hartlepool.
Each reactor has eight boiler units and the boiler spine supports the weight of the tubes assembled in a coil formation around the spine and located inside each boiler.
The four reactors at Heysham A and Hartlepool are advanced gas-cooled reactors. Heysham A-1 and Hartlepool-1 began operation in 1983, followed by Heysham A-2 and Hartlepool-2 in 1984.
