Halcrow is providing multidisciplinary engineering services for the design of the D1209 replacement ventilation system. The design services being provided by Halcrow include: active ventilation; structural engineering; electrical control and instrumentation (including power supplies and back-up generation); design of a new stack and the modelling of the dispersion of the stack discharges; preparation of nuclear safety case documentation and installing care and maintenance provisions for the existing D1209 ducts, which incorporate active and inactive elements.

The 300m long D1209 spine duct provides safety critical ventilation to the Fuel Cycle Area (FCA) and must be maintained in an operational state whilst the replacement system is installed and commissioned prior to changeover. The replacement system must then operate continuously for a design lifetime of 40 years and accommodate progressive shut down of the facilities served by the duct. Mechanical and electrical systems covered by Halcrow’s commission also include fan selection, acoustic assessment, discharge monitoring and sampling systems.

Halcrow is providing assessment and justification for design decisions to provide an auditable trail demonstrating best practicable means, whole life costs and substantiated safety case. The systems proposed are designed by Halcrow to meet demanding availability, reliability and maintainability (ARM) targets.