Reaktorhodet

Reaktorhodet is the upper closure plate of a nuclear reactor vessel, sealing the reactor core region from the containment space. In English terminology it is usually called the reactor pressure vessel head (RPV head). The head provides access to the interior of the vessel for installation and maintenance of components such as the control rod drive mechanisms (CRDMs) and reactor instrumentation penetrations.

Structure and functions: The head is a heavy steel plate bolted to the top of the reactor vessel. It contains penetrations through which the control rods are driven into the core and through which sensors and cooling lines pass. The head and its penetrations form part of the reactor's primary pressure boundary and must withstand high pressure, temperature, and neutron irradiation.

Materials and design: Heads are typically forged steel designed for high strength and corrosion resistance. Seals or gaskets and flange connections are used to prevent leakage. Design must accommodate thermal transients during start-up and shutdown.

Maintenance and safety: The reactor head is subject to regular inspection and non-destructive testing to detect cracking or corrosion around penetrations. Issues such as leakage or cracks at penetrations may require repair or replacement of the head during a planned outage; complete head replacement is a major operation in affected plants.

Terminology and usage: The Norwegian term reaktorhodet is used in technical documentation and textbooks as a direct translation of the English concept. The term denotes a critical pressure boundary component of the reactor system.