Design of Nitrogen Diverse Hold Down Systems

The Background.

Booth Welsh were selected to design and build turnkey instrumentation, control and diagnostic systems for thereplacement N2 DHD plants. The systems monitor and control Nitrogen Storage, Vaporisation Plant (NSVP) andBlowdown and Injection (BDI).

The replacement systems are a key part of lifetime extension at both plants.

Nuclear Power Plants

years client relationship

MW supplied to the National Grid across both sites

EDF supplies 1/5th of the UK's electricity

The Client: BOC

BOC, a subsidiary of Linde, are the UK’s largest provider of special gases, producing atmospheric gases such as oxygen, nitrogen and argon for over 120 years. BOC, a member of the Linde group were contracted by EDF to design and build replacement Nitrogen Diverse Hold Down (N2 DHD) systems at their Hunterston B (HNB) and Hinkley Point B (HPB) sites.

HNB located on the west coast of Scotland and HPB located in Somerset are licensed nuclear sites. Each operating two Advanced Gas-cooled Reactors, known as Reactors 3 and 4, the plants supply the national grid with 965MW and 955Mw respectively. Their operating licenses extended until 2023. The reactors are cooled by CO2 gas.

The Solution.

Working to a challenging program, Booth Welsh took the project’s instrumentation requirements from concept through design and build to a tested installed solution atboth sites.

Design activities included development and design and construction lifecycle of:• Process control logic diagrams• Functional Design Specifications• Detailed Design Specifications• Control Panel Design (power distribution, schematic wiring diagrams, Generalarrangements in adherence of the client’s Human Factors Engineering teamrequirements.)• Cabling and infrastructure specification and design• Instrument specification, installation, configuration and testing.• Alarm panel specification, design, build, installation and testing.• Central Control Room (CCR) control fascia design and build.• Alarm panel design and build.Additional activities included design and build of a sacrificial control panel for seismic qualification testing at a leading test facility.