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Nuclear reactor heat turned down to stop boilers cracking via The Telegraph

Two nuclear plants shut amid safety fears may be restarted at just 75pc usual power output to prevent more cracks developing, EDF says

Power output at two UK nuclear plants will be curbed for up to two years in order to reduce the heat in their boilers and prevent cracks developing, EDF has announced.

The two twin-reactor plants at Heysham 1 and Hartlepool have been shut down since August amid safety fears following the discovery of cracks in one boiler structure at Heysham.

The ageing reactors are likely to be restarted in coming months at just 75pc-80pc of their usual output in order to prevent high temperatures causing further cracks, EDF said on Friday.

The move will further worsen the risk of power shortages this winter and next.

[…]

EDF said that the reactor where boiler cracks had been found would only return to service at 75pc usual power, “with the affected boilers isolated”.

The other three reactors could also be returned to service – assuming no cracks are found – but with the heat in the boilers turned down.

“As boiler spine defects can only develop into cracks at very high temperatures, two reactors at Hartlepool and one at Heysham 1 could be returned to service at c75pc-80pc power to reduce the temperature to which the boiler spines are exposed,” EDF said in a statement.

The boilers could then be modified over the next two years to enable them to get back up to full power.

EDF is thought to be about three-quarters of the way through checks on the 31 boilers and said that “no further defects have been found”.

[…]

The cracks at Heysham 1 are in a “boiler spine”. The Office for Nuclear Regulation said that the spine “supports the weight of an entire boiler and its failure could lead to water entering the reactor vessel”.

“The potential worst consequences of water entering the reactor vessel is an over-pressurisation of the reactor which could result in lifting of the reactor pressure relief valves. If this was to occur co-incidentally with fuel damage then there could be a direct path to the environment and a release of radiation,” it said.

However, it said the chances of this worst-case scenario emerging were “extremely low”.

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