Document: NUREG-0800
Document ID: 61198d64-419c-45ea-aebb-cf34c3b171fe
Document Type: srp
Title: Revision 0 – July 2015
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1505/ML15057A085.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8
CFR Part: 
CFR Title: 

Content:
(See LER 50-334/2007-002, ADAMS Accession No. ML080280592); and a single event that affected Nine Mile Point, Unit 1 (See LER 50-220/2005-04, ADAMS Accession No. ML060620519) and the neighboring James A. Fitzpatrick Power Plant (See LER 50-333/2005-06, ADAMS Accession No. ML060610079.) These events involved offsite power circuits that were rendered inoperable due to an open circuit in one phase. In each instance (except South Texas, Unit 2), the condition went undetected for several weeks because offsite power was not aligned to the ESF buses during normal operation and the surveillance procedures, which recorded phase-to-phase voltage, did not identify the loss of the single phase. At South Texas, Unit 2, offsite power was normally aligned to ESF and nonsafety plant buses and the reactor was manually tripped by the operator when the three Circulating Water Pumps were tripped by the open phase condition. Operating experience has identified three similar international events: 1. On December 22, 2012, Unit 1 at Bruce Power Plant in Canada was in shutdown condition when a maintenance cooling system pump (P1) tripped. Operators tried to manually start pumps P1 and P2 but both failed to start due to the electrical protection schemes. Field operators identified a loss-of-phase condition caused by a break in one of the 3 phases of the 230 kV overhead line connection. 2. On May 30, 2013, Forsmark Unit 3 in Sweden reported an event resulting from human error. The plant was in a refueling outage with one of the two 400-kV offsite power circuit breakers and a 70-kV back-up power supply breaker open due to maintenance work. While testing the protective relaying for the main generator, an erroneous trip BTP 8-9-3 Revision 0 – July 2015 signal was sent to the remaining 400-kV offsite power source circuit breaker. One of the three phases in the circuit breaker failed to open, resulting in a double open phase condition in the power circuit (i.e., two open phases). Some of the