Trawsfynydd environmental permit variation application

Closes 6 Aug 2024

Opened 9 Jul 2024


Nuclear Restoration Services Limited (NRS) (formerly Magnox) has submitted an application to Natural Resources Wales (NRW) to change its Environmental Permit for the former Trawsfynydd Nuclear Power Station site.

This change, termed a ‘variation’, is a legal requirement under the Environmental Permitting Regulations (England and Wales) 2016.

NRS is a wholly owned subsidiary of the Nuclear Decommissioning Authority, which owns the site. Trawsfynydd Nuclear Power Station closed in 1991 and its decommissioning is the responsibility of NRS.

The Environmental Permit relates only to the disposal, and receipt for disposal, of radioactive waste on the site. It does not relate to the operation of the nuclear reactors during their time in active service.

As part of the variation application, NRS is proposing the demolition, infilling, and capping of the Trawsfynydd Ponds Complex, a set of relatively low-profile buildings that run alongside the two reactor buildings.

Documents relating to the application are linked at the bottom of this page.

You can see the full number of application documents by phoning our Customer Service Centre on 0300 065 3000 or emailing to arrange access to view them online.

We have launched a four-week public consultation while we start the determination (technical assessment) phase of the application process.

You can provide comments on the application by taking part in our consultation, linked at the bottom of this page.

Application details

Application number: EPR/GB3835DE/V006

Address: Trawsfynydd Decommissioning Site, Blaenau Ffestiniog, Gwynedd, LL41 4DT

Operator: Nuclear Restoration Services Limited

The central structures of the ponds complex are the concrete cooling ponds formerly used for cooling and interim storage of used nuclear fuel before it was sent to Sellafield in Cumbria for reprocessing.

The cooling ponds and adjoining storage vaults have box-like below-ground structures with void spaces up to six metres deep with a total volume of around 5,000 cubic metres.

The proposed demolition of the above-ground concrete structures of the ponds complex will result in slightly radioactive, mainly broken concrete, filling the void space. The material will then be closed in - a process known as capping.   

If approved, the proposed infilling will be regulated by NRW as a type of on-site disposal of solid radioactive waste, known as disposal for a purpose. 

In addition, leaving the radioactively contaminated structures in the ground will also be a type of on-site radioactive waste disposal - termed in situ disposal. 

The joint environmental regulator’s guidance states the objective is to ensure a nuclear site is brought to a condition at which it can be released from future radioactive substances regulation.

Therefore, to approve the application we must be satisfied the proposed demolition, disposal and capping is done in ways that are safe and meet our standards for the protection of people and the environment, now and into the future, while allowing the site to be released from radioactive substances regulation in the future.

As part of the application NRS has submitted an initial site-wide environmental safety case, supported by over 30 technical reports. 

This includes current estimates of the amounts of radioactivity in the proposed disposals, the rationale behind the design of the proposals, and assessments of potential impacts on people and the environment, extending from the near term into the far future. 

The site-wide environmental safety case seeks to demonstrate to NRW that the application will allow the site to be released from radioactive substances regulation in the future, and that NRW’s quantitative guidance levels for impacts from radioactivity will not be exceeded.

Estimates of the amounts of radioactivity in the proposed disposals are expected to decrease in the next few years. As decommissioning work within the ponds complex progresses, it will become possible to measure the actual remaining levels of radioactivity on the surfaces of structures currently inaccessible or awaiting decontamination.

We are anticipating a lengthy determination phase for this application, and we will be keeping the public informed throughout.

During this period, it is expected the site-wide environmental safety case will be updated, as more information becomes available.

Why your views matter

We understand this permit variation is of particular interest to the public and local community.

We are required legally to consult with the public on applications such as these.

This is your chance to view the application supporting documents and respond to our consultation with your comments. You can view the application supporting documents and take part in the consultation below.

Take part in our consultation


  • Trawsfynydd


  • Fly-fishing
  • Cockles
  • Newport Green and Safe Spaces
  • Rivers
  • Flooding
  • Llifogydd
  • Community Volunteers
  • Gwirfoddolwyr Cymunedol
  • Management
  • Woodland Opportunity Map users
  • marine developers
  • marine planners
  • Network Completion Project Task and Finish Group
  • South West Stakeholder group
  • Citizens
  • National Access Forum
  • Gwent
  • citizens
  • water companies
  • NFU
  • DCWW
  • Anglers
  • Coal Authority
  • Educators
  • SoNaRR2020
  • Mine recovery specialists
  • Arbenigwyr adfer mwyngloddiau
  • Metal mines
  • Mwyngloddiau metel
  • Coastal Group Members
  • Wales Biodiversity Partnership
  • Equality, Diversity and Inclusion


  • Permits