We use functional cookies for a number of reasons, such as keeping the Costain website reliable and secure and to analyse how our site is being used.
Will you accept our use of non-essential cookies?

Yes No Privacy Notice

Evaporator D project

Reducing the volume of legacy waste

The largest nuclear decommissioning project in the UK at the time of construction, Evaporator D allowed continued reduction in the volume of highly active legacy waste.

  • Service 1

Sellafield Ltd

  • Service 1

Consultancy & advisory
Complex programme delivery

  • Service 1

Modular design consisting of 11 in-cell modules
396 major plant items
65 nuclear class vessels
Over 21 kilometres of pipework

Key Benefits


Consecutive RoSPA Gold Awards for Occupational Health and Safety

Modular design

reduced schedule risk and construction works on restricted site

Pre-Construction Safety Case

developed and accepted in less than 100 days


of onsite project team recruited in West Cumbria


of project spend with local SMEs

Additional waste processing capacity

As part of the Nuclear Decommissioning Authority’s strategy, Evaporator D was designed to expand Sellafield’s ability to process nuclear waste material and ultimately reduce inventories at the site.

We worked with Sellafield Ltd to design and construct the new evaporator which was required to evaporate highly active raffinate produced during reprocessing of spent nuclear fuel rods. Once concentrated through evaporation, the highly active liquor produced is subsequently vitrified – immobilising the waste in a stable glass form for long term storage and eventual disposal.

Key Challenges

  • Processing of highly radioactive and very corrosive fluids
  • Strictly regulated site
  • Remote site access
  • Located at the heart of an operating nuclear facility
  • Congested site - complex design on a restricted footprint

Innovative construction methods

In order to address the challenges outlined above, our experienced team of engineers drew on expertise from within the oil & gas industry to propose a modular design pre-fabricated and tested off-site, a nuclear first at this scale. 

The project construction comprises 11 in-cell modules

The benefits of this modular approach include:

  • Reduced schedule risk
  • Minimised works adjacent to highly active facilities 
  • Opportunities for early operator training
  • Reduced fault observations at site 
  • Process plant and equipment proven prior to installation

The modules, the largest of which is 27m in height, were delivered by sea, the first time in the history of the Sellafield site that this method has been used. Major temporary works were undertaken to construct a beach landing area, a bridge across the River Ehen and to widen the railway crossing to provide a delivery route onto the Sellafield site.

This first ever delivery of a major component to the beach is the culmination of lots of hard work by a great team of people. We are all very proud of our accomplishment.

Tom McClain, Sellafield Ltd Project Manager, speaking following the delivery of the first module.

Contact and social


Laura Hughes, Sector Director - Energy
01628 842444
[email protected]