Nuclear power plants – Instrumentation systems important to safety – Electrical penetration assemblies in containment structures
|Publication Date:||1 May 2018|
|ICS Code (Nuclear power plants. Safety):||27.120.20|
This document applies to electrical penetration assemblies (EPAs) in containment structures of nuclear power plants. It covers the engineering safety requirements to be met in the design, calculation, qualification, fabrication, assembly, testing, and installation of EPAs.
EPAs provide gas-tight and pressure-resistant penetrations through the containment for one or more electrical circuits. EPA requirements are divided into mechanical (e.g. containment integrity), and electrical or optical aspects regarding safety. The mechanical requirements are valid for all EPAs. The electrical or optical requirements are derived from the functional requirements of the connected systems, applied for monitoring and mitigating postulated events such as design basis events (DBE; e.g. loss of coolant accidents) and/or design extension conditions (DEC; e.g. severe accidents).
EPAs are distinguished by the type of electrical or optical circuit in which they are used. The derived types of EPAs are identified as follows:
• medium voltage power,
• low voltage power,
• instrumentation, and
• fibre optic.
For the purpose of this document, EPAs include:
• electrical conductors up to the connection interface inside and outside the containment (penetration conductors);
• the electrical insulation systems of penetration conductors including the electrical insulation of the connection interface;
• components for the resistance to environmental conditions, such as pressure resistance, gas tightness, temperature resistance, radiations resistance, seismic resistance enclosure of this EPA, and for connection with the containment wall;
• if required, permanently connected equipment for leak tightness monitoring;
• standard electrical connection interfaces such as cable lugs, terminals, and connectors;
• terminals and/or junction boxes (if necessary).
The components, which are not part of an EPA, include:
• components of the containment wall for the attachment of the EPA, such as sealing surfaces for bolting, or pipe connections, or nozzles requiring welding;
• cables and wires connected to the EPA conductors or connectors;
• terminal elements such as cable lugs, terminals, connectors or soldering sleeves attached to the cables and lines connected;
• leak test or evacuation devices connected temporarily to penetrations;
• the requirements for external circuits, connected to the EPA or the containment structure.
This document does not cover requirements for EPAs regarding operation and maintenance.