CONCURRENCE PROBABILITY AND DURATION FOR FIRE-INDUCED CABLE 'HOT SHORTS:' ALTERNATING (AC) VS. DIRECT CURRENT (DC)

摘要

In 2008, the author presented the results of a probabilistic/statistical examination of cable "hot shorts" due to nuclear plant fires for alternating current (AC) circuits based on two sets of cable fire tests: (1) the Nuclear Energy Institute (NET) and Electric Power Research Institute (EPRI) series of 18 cable fire tests in 2001; and (2) the U.S. Nuclear Regulatory Commission (NRC) complementary series of electrical performance and fire-induced failure cable tests, consisting of 78 small-scale tests and 18 intermediate-scale open burn tests in 2006 (the CAble Response tO Live FIRE [CAROLFIRE] Program). In 2010, the NRC, in collaboration with the EPRI, as representative of the nuclear industry, completed a follow-up to CAROLFIRE by performing a "series of fire tests ... to assess cable failure modes and effects behavior for DC [direct current]-powered control circuits ... known as the Direct Current Electrical Shorting in Response to Exposure Fire (DESIREE-FIRE) test program." As with the previous NEI/EPRI and CAROLFIRE tests, the DESIREE-FIRE tests similarly produced data on the occurrence and duration of electrical "hot shorts," this time for DC circuits, in terms of the type of cable (thermoplastic [TP] and thermoset [TS]) and equipment supported by the circuits (both motor- and solenoid-operated valves [MOVs and SOVs]). As a follow-up to the 2008 analysis, the author presents a parallel analysis of the probability and duration for concurrence of two and three "hot shorts" for DC circuits, based on the DESIREE-FIRE results, and compares this to the previous analysis for AC "hot shorts."