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Allying with CNSL to deliver excellence in nuclear decommissioning

The Sellafield plant in Cumbria

Nuclear plants have long lifespans, but when the time comes to shut down, it’s an immensely complicated process.

As part of Cumbria Nuclear Solutions Limited, Tetra Tech’s engineers, project and asset managers have allied with six other consultancies for well over a decade to deliver safe, cost-effective, and environmentally friendly decommissioning programmes.

With our combined skills and knowledge, the CNSL consortium has worked throughout the entire nuclear cycle to deliver excellence in front-end engineering, design, integration, and implementation of projects to dismantle nuclear reactors.


CNSL represents one of the longest standing collaborations at Sellafield, offering an unrivalled breadth and depth of decommissioning experience.

This collaboration has joined together companies with a proven track record in the nuclear sector, including Tetra Tech, James Fisher Nuclear, REACT Engineering, Shepley Engineers, Jacobs Stobbarts, and Westinghouse Electric Company.

To reach our clients’ project mandates, our team has confronted the many uncertainties that any decommissioning strategy must address, including hazards, constraints, risks, and issues. At the same time, we have had to identify viable decommissioning strategies at a very early stage and overcome tight timescales.

Collaborative working

Technical experience might be an important prerequisite to success, but what Sellafield valued more than that was an alignment of shared cultural values that would foster better collaborative ways of working.

A large component of what has made CNSL’s work a success is the commitment to good relationship management and an ‘idea meritocracy system’ where each organisation is treated as an equal part of a joint team. The benefits of this has trickled down to everything from day-to-day communications to more efficient delivery and quicker problem-solving.

The CNSL Approach

CNSL has developed a logical phased approach on many of its projects to address three principal elements of nuclear decommissioning:

Understanding the start point for decommissioning

To ensure viable solutions were found, we have produced specifically tailored reports to define the likely status of plant facilities at the start of future decommissioning, as well as the key factors affecting operations. Plant mock-ups and proof of principle trials have played a major role in helping to define viability.

Understanding the end point for decommissioning

CNSL has carried out detailed waste and radiological activity calculations to give a complete understanding of the volume and radiological condition of the waste to be dealt with in decommissioning the plants.

Developing the decommissioning scheme

By clearly defining current plant status, waste volumes and final product form, CNSL set in place the optimal conditions to develop a robust decommissioning work breakdown structure and viable scheme.

In addition to taking a proactive approach to stakeholder engagement, our design and engineering capabilities have proven instrumental to ensuring mandates have been completed to cost and programme estimates.


CNSL’s wide experience has allowed us to not only meet mandates in a way that withstands detailed scrutiny by the Nuclear Decommissioning Authority and other stakeholders, but to exceed expectations. This much has been clear from the strong positive feedback from our client and members of senior panels in groups such as the British Nuclear Group.

The many innovative bespoke designs and extensive trialling implemented by our team have made the otherwise daunting task of dismantling nuclear plants and removing waste viable.

As a testament to the consortium’s success, we reached a momentous milestone in 2019 of one million hours without a lost time accident.

A good safety record does not happen by accident. It’s about teams collaborating and staying motivated around health and safety…The effort the individuals put in to ensure we go home safely is often tireless. It’s a massive achievement for the operatives, supervisors, and all support teams across the board.

Jack Tomlinson, Safety Hub Lead, CNSL

The experience undertaking this complex work has given us unique insight into the requirements of all project stakeholders. This has ultimately given us a more informed approach to meeting the needs of our client and the programme at hand with rapid and cost-effective modification of solutions that have minimal impact.

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