Response of Nuclear Power Plant Instrumentation Cables Exposed to Fire Conditions (NUREG/CR-7244, SAND2017-10346R)

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Publication Information

Manuscript Completed: November 2017
Date Published: January 2019

Prepared by:
A. Muna
C. LaFleur
D. Brooks

Sandia National Laboratories
Risk and Reliability Analysis, Department 8851
P.O. Box 5800
Albuquerque, NM 87185-0748

Gabriel Taylor, NRC Project Manager

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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Abstract

This report presents the results of instrumentation cable tests sponsored by the US Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research and performed at Sandia National Laboratories (SNL). The goal of the tests was to assess thermal and electrical response behavior under fire-exposure conditions for instrumentation cables and circuits. The test objective was to assess how severe radiant heating conditions surrounding an instrumentation cable affect current or voltage signals in an instrumentation circuit.

A total of thirty-nine small-scale tests were conducted. Ten different instrumentation cables were tested, ranging from one conductor to eight-twisted pairs. Based on a previous study, the focus of the tests was thermoset (TS) cables. As such, only two of the ten cables had thermoplastic (TP) insulation and jacket material and the remaining eight cables were one of three different TS insulation and jacket material. Two instrumentation cables from previous cable fire testing were included, one TS and one TP. Three test circuits were used to simulate instrumentation circuits present in nuclear power plants: a 4–20 mA current loop, a ¹0–50 mA current loop and a 1–5 VDC voltage loop. A regression analysis was conducted to determine key variables affecting signal leakage time.