Document: NUREG-0800
Document ID: b75d082b-2493-4543-981a-2ee136d737cf
Document Type: srp
Title: BTP 8-9-1
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1405/ML14057A433.pdf
Revision Date: 2023-06
Chapter: 8
Section ID: 8
CFR Part: 
CFR Title: 

Content:
n event that occurred on December 22, 2012, where one of the 3-phases of 230 kV overhead line connections was broken. Second, the Forsmark, Unit 3 in Sweden reported that protective relaying scheme is vulnerable to open phase events based on an event that occurred on May 30, 2013 (circuit breaker to the 400 kV grid was disconnected in two phases, when power source to the safety buses were in the process of realigning to an alternate 70 KV source). In both events, EDGs did not automatically connect to the safety buses because the plant design did not have features to address open phase conditions. Based on the Byron Station operating event, the staff issued U.S. Nuclear Regulatory Commission (NRC), Information Notice 2012-03, “Design Vulnerability in Electric Power System,” dated March 1, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML120480170). On July 27, 2012, the staff issued NRC Bulletin 2012-01, “Design Vulnerability in Electric Power System,” to confirm that licensees comply with Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(h)(2), 10 CFR 50.55a(h)(3), and Appendix A to 10 CFR Part 50, General Design Criteria (GDC) 17, or principal design criteria specified in the updated final safety analysis report. Specifically, the NRC requested licensees to provide information by October 25, 2012, (1) regarding the protection scheme to detect and automatically respond to a single phase open circuit condition or high impedance ground fault condition on GDC 17 power circuits, and (2) operating configuration of engineered safety features buses at power. The Electrical Engineering Branch staff has reviewed the information that NRC licensees provided and the detail of this review is documented in a Summary Report dated February 26, 2013 (ADAMS Accession No. ML13052A711). Safety Significance of open phase condition: At Byron, both offsite and onsite electric power systems were not able to perform their intended safety