If no mishaps occur Trawsfynydd nuclear cleanup will take nearly 100 years

The final decommissioning at Trawsfynydd and elsewhere depends on finding a safe long term solution for where to deposit the ILW as well as the High Level Waste (HLW) currently stored at Sellafield. This includes the spent nuclear fuel which was removed when the plant closed.

Trawsfynydd timeline

1959: Construction started

1965 to 1991: Electricity generation
1993 to 1995: Decommissioning starts – fuel removed and sent to Sellafield
1995 to 2016: Recovery of waste and preparations to put the plant into a ‘passively safe’ state
2020-26: Reduction in height of reactor buildings
2040s: Scheduled removal of Intermediate Level Waste to deep geological storage
2074: Final site clearance starts
2083: Site returned to pre-existing state

How do you close a nuclear power station? BBC  By Steven Green 28 Oct 13 As the UK embarks on building what could be a new generation of nuclear power plants, work continues to decommission the first generation of nuclear power stations at sites including Trawsfynydd in Snowdonia which will take an estimated 90 years to complete.

Robotic recovery   Eryl Pritchard is at the controls of a robotic arm engaged in the painstaking process of retrieving radioactive resin from a dark, water-filled vault. “It’s not as simple as it looks,” he says. Nothing about it looks simple. Radioactivity inside the vault means everything has to be done remotely using tools mounted on the robotic arm.

A bank of monitors show the arm from various angles. A control panel shows a mind-boggling array of levers, switches and buttons……..

Some of the decommissioning work is considered too dangerous or uneconomic to carry out in the current phase of decommissioning.

The two steel pressure vessels which contained the nuclear reactors are staying in the reactor buildings until the radioactivity of the steel has decayed to a safer level.

The twin reactor buildings are having their height lowered to reduce the visual impact of the plant on the surrounding Snowdonia countryside.

From 2026 that is how the site will be left with the ILW still stored on site alongside the reactor buildings.

Where does the radioactive waste go?

The final decommissioning at Trawsfynydd and elsewhere depends on finding a safe long term solution for where to deposit the ILW as well as the High Level Waste (HLW) currently stored at Sellafield. This includes the spent nuclear fuel which was removed when the plant closed.

The most likely solution is storage deep underground but a site has yet to be identified. It is hoped that will be established by the 2040s allowing the ILW at Trawsfynydd to be removed. Final site clearance at Trawsfynydd is not projected to start until 2074 with the land returned to its original state by 2083. It is at that stage that the reactor buildings and the steel pressure vessels will be demolished………

Another issue will be what to do with the graphite reactor cores which are still inside the steel pressure vessels at Trawsfynydd.

“One of the problems the UK has with its commercial nuclear power reactors, with the exception of Sizewell B, is that they all have a large graphite core which is used as a moderator, that’s inside the pressure vessel and that’s used to slow the neutrons down.

“There is no real disposal route for the graphite in the UK, the volumes are huge. If you look at the carbon, and the sulphur as well, certain isotopes, the half-lifes are hundreds of thousands of years,” says Belshaw. While the radioactivity will be very persistent, the graphite is only classed as Low Level Waste (LLW), so will probably not be stored deep underground.

Could the decommissioning be done faster?

Twenty years after it closed, many hundreds more people are employed at Trawsfynydd than when it was generating power. And it will be many decades before the site can be fully restored.

Could it be done more quickly? Not economically says its owners, Magnox. Earlier decommissioning would involve more expensive remote operations and still carry the risk of exposing workers to radiation.  http://www.bbc.co.uk/science/0/24642256

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