H. M. HASHEMIAN, Analysis and Measurement Services Corp., USA

DOI: 10.1533/9780857097453.2.284

Abstract: This chapter will address the ageing of nuclear power plant cables and test methods for these cables to manage ageing and verify reliability. The focus will be on instrumentation and control (I&C) cables, low-voltage cables and medium-voltage cables. Ageing due to long-term exposure to temperature, radiation, humidity, and other environments can cause the cable insulation material to deteriorate, allowing moisture into the cable. This can in turn cause cable failure and jeopardize plant safety. Various techniques are available to assess cable condition and health, including electrical and mechanical measurements, and chemical tests. Of these, electrical measurements are preferred as they allow in-situ cable testing in operating plants. Prognostic techniques estimate residual life of cables using data from periodic tests. To guard against ageing, nuclear power plants are implementing ageing management programs and regulators are writing new requirements for acceptable programs and techniques for cable ageing management.

Key words: insulation resistance, high-potential (Hi-Pot), partial discharge, quality factor, dissipation factor, AgeAlert™, LCR (inductance, capacitance, and resistance) tests, time domain reflectometry, frequency domain reflectometry, reverse time domain reflectometry.

6.1 Introduction

The thousands of miles of electrical cable and wire in light water reactors deliver the power and the signals enabling safety — and non-safety-related equipment to operate in normal and in post-accident conditions (U. S. NRC, 2010a; Hashemian, 2010; AMS Corp., 2011). All plant instrumentation and control (I&C) systems depend on reliable plant wiring (AMS Corp., 2010). They bring the necessary signals to the operators, control equipment, and safety systems, as well as delivering commands to activate relays, pumps, valves and motors. Reliable instrumentation signals are often essential to maintaining redundancy or containing an accident, and the loss of a cable can result in the loss of crucial performance and operational data. Similarly,

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