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Land ‘delicensed’ at Dorset nuclear site

When a nuclear licensed site, or part of that site, is no longer used for any activity requiring a nuclear site licence the licensee can apply for a variation to their site licence to exclude that part of the site from regulatory control (delicensing).

In general such an application will be made following decommissioning of any facilities contained within the area covered by the application. Decommissioning involves the removal of bulk radioactive material, dismantling and removal of contaminated parts of the facility, dismantling/demolition and clean-up of land to meet an agreed end state for future use.

During July and August ONR has agreed two applications from the site licensee at Winfrith in Dorset, Research Sites Restoration Ltd (RSRL), for a large area of decommissioned land within the nuclear site to be ‘delicensed’. This will allow the land to be re-developed in future. There are no immediate plans for the land but it is anticipated that some of the areas may be used for development of the Dorset Green Technology Park.

The decommissioning work involved demolition of several substantial facilities including the zero energy reactor halls and fissile material store. The total area that has been delicensed in response to these recent applications is equivalent to 10 rugby pitches, in excess of 10% of the site.

Part of ONR’s work in this project was to be satisfied that the delicensed area of land poses ‘no danger’ to the public from ionising radiation arising from previous operations at the site. Consideration of the licensee’s case for demonstrating ‘no danger’ followed the ONR’s published approach to making delicensing regulatory decisions: ONR assesses and inspects on a sample basis, involving specialist expertise, legal advisors, policy functions and liaison with other statutory regulatory bodies, in this case the Environment Agency.

ONR’s response to the recent applications demonstrates our determination to the delivery of commitments as set out in our strategy and the benefits of the continued changes and improvements to our organisation to optimise the targeting of resource to lower hazard/lower risk sites within the UK. In addition the process of making our regulatory decision has been aided by the licensee providing a detailed demonstration of the work undertaken, to assess levels of radioactivity within the areas concerned and demonstrate ‘no danger’.

RSRL has recently submitted proposals to the Nuclear Decommissioning Authority (NDA) to deliver an optimised decommissioning programme that would see the current Winfrith site closure date of 2048 significantly advanced. ONR’s recent experience from these applications increases confidence in the licensee’s ability to meet their aspirations and ONR’s ability to facilitate the delivery of the optimised programme.


The Winfrith site in Dorset was opened in 1957 to offer additional space for theUK’s civil nuclear research programme.

It became a centre for research and development, including the prototype high gas cooled reactor DRAGON and the SGHWR (Steam Generating Heavy Water Reactor), which provided enough electricity to the National Grid to power a small town. Later the site also diversified into other disciplines, such as safety testing and oil exploration.

Winfrith has had at various times, nine research and development reactors, only one of these SGHWR fed into the national grid. The last operational reactor at Winfrith closed in 1995, since then the focus for the site has been on decommissioning.

Of the nine original uniquely designed reactors, seven have been decommissioned and dismantled. The two remaining reactors DRAGON and SGHWR have been defueled and placed in safe care and maintenance.