Leak is Sellafield's 'biggest environmental issue'
SellafieldA longstanding leak at "Britain's most hazardous building" is a nuclear plant's "single biggest environmental issue", a select committee has heard.
The leak in the Magnox Swarf Storage Silo (MSSS) - built more than 50 years ago at Sellafield in Cumbria - started in 2019 after first occurring in the 1970s.
Labour MP Luke Charters told the Public Accounts Committee (PAC) on Thursday that every three years the silo leaked enough material to fill an "Olympic-sized swimming pool".
Sellafield head Euan Hutton said the leak did not "pose a detriment to the public".
The silo contains Magnox fuel cladding, mostly made up of magnesium, which was removed from nuclear fuel rods.
It was built in the 1960s, with three further extensions built in the 1970s and 1980s.
The leak is being caused by a crack in the underground portion of the silo, Mr Hutton told the committee.
He said the team had "excellent ground modelling and monitoring" which showed the activity was staying in the ground beneath the facility.
The head of the Nuclear Decommissioning Authority (NDA) called the silo "Britain's most hazardous building" and said the best way to the stop the leak was "to empty the silo as efficiently and quickly as we can".
He said it was the "single biggest environmental issue" facing the nuclear plant
Mr Hutton said the team hoped to empty the silo by about 2059.
'Nobody underestimates challenge'
A National Audit Office (NAO) report in October 2024 suggested timelines for emptying the silo were about 6 to 13 years later than previous estimates.
When asked about these delays, Mr Hutton said the team currently only had one machine which could do the work.
"The challenges that we've had this year is the interface between the new equipment which we've installed and the old equipment that was already there," he said.
Mr Hutton said the team were currently commissioning a second machine, adding: "With those two machines in operation that will start to significantly reduce the waste in that old part of the building."
Lee McDonough, a senior official at the Department for Energy Security and Net Zero (DESNZ), said "nobody underestimates the challenge".
"There's a huge knowledge base about what's actually happening to the radiation."