Boiler Emergency Depressurisation system

Boiler Emergency Depressurisation system

EDF / Dungeness B Reactor 2

Capula supported EDF with the delivery of a project at Dungeness B Reactor 2 to install an auto Boiler Emergency Depressurisation (BED) system.

From a standing start in February 2020, and after three months and four days’ worth of working smart using advanced design control techniques, the Auto Boiler Emergency Depressurisation (BED) system was successfully tested and handed over to Operations on Thursday 14 May.

This was an incredible cross-functional effort, and the team were acknowledged for successfully delivering this significant project ahead of plan with no safety, quality or commissioning issues.

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"We started investing in the relationship with Capula over a year ago and are now reaping the benefits with a number of successful collaborations. Capula are a fantastic company with a strong nuclear pedigree. The response to everything that we required has been nothing short of astonishing considering the external issues going on at the moment."

Jim Marshall

Lead Architect Engineer
Architect Engineering Branch


During production of Dungeness’ revised boiler tube leak safety case it was recognised that forced and natural gas circulation be affected due to flooding of the gas circulator impeller casings. It was also identified that the assessed probability of 9% chrome tube failure is more likely than originally estimated. The combination of gas circulator flooding and heightened probability of tube failure resulted in a significant increase in the risk posed boiler tube leaks.

To reduce the risk from boiler tube failures, the Boiler Emergency Depressurisation (BED) valves have been modified to open automatically, should the reactor trip due to high coolant gas pressure (435 psig). The system, known as the “Auto BED System”, was successfully tested on R22 after three months and four days’ worth of hard work and was handed over to Operations.

The automation of the BED valves supports the safety case justifications ahead of return to service. The Auto BED system provides a very robust interim solution until boiler lifetime modifications are fitted in 2021.

"This has been an incredible cross-functional effort and recognition needs to be given to NSG, TAG, CTO, Operations and Capula for delivery."

Gavin Lancaster

Plant Manager
Dugeness B Power Station