05000395/LER-2011-001, V. C. Summer Regarding Failure to Maintain One Train of Safe Shutdown Systems in Accordance with Appendix R Section III.G.a/III.G.3
| ML11186A972 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 07/01/2011 |
| From: | Gatlin T South Carolina Electric & Gas Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 11-001-00 | |
| Download: ML11186A972 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 21.21(d)(4)(i) |
| 3952011001R00 - NRC Website | |
text
Thomas D. Gatlin Vice President, Nuclear Operations 803.345.4342 A SCANA COMPANY July 1,2011 Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555
Dear Sir / Madam:
Subject:
VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 DOCKET NO. 50/395 OPERATING LICENSE NO. NPF-12 LICENSEE EVENT REPORT (LER 2011-001-00)
UNANALYZED CONDITION DUE TO FAILURE TO MAINTAIN ONE TRAIN OF SYSTEMS FOR SAFE SHUTDOWN IN ACCORDANCE WITH APPENDIX R SECTION III.G.a/III.G.3 Attached is Licensee Event Report (LER) No. 2011-001-00 for the Virgil C. Summer Nuclear Station Unit 1. This report describes an Appendix R violation for postulated fires in the Main Control Room, the Cable Spreading Room or the North Chase, which could have caused isolation of the B-Train essential electrical bus (XSW1 DB). SCE&G is submitting this report in accordance with 10 CFR 21.2(c), "Reporting of Defects and Noncompliance," and 10 CFR 50.73(a)(2)(ii)(B), regarding an unanalyzed condition due to failure to maintain one train of systems for safe shutdown.
Should you have any questions, please call Bruce Thompson at (803) 931-5042.
Very truly yours, JMW/TDG/gr Attachment c:
K. B. Marsh S. A. Byrne J. B. Archie N. S. Cams J. H. Hamilton R. J. White W. M. Cherry V. M. McCree R. E. Martin NRC Resident Inspector M. N. Browne P. Ledbetter Thomas D. Gatlin D. L. Abstance J. C. Mellette K. M. Sutton EPIX Coordinator INPO Records Center Marsh USA, Inc.
Maintenance Rule Engineer NSRC RTS (CR-1 1-02298)
File (818.07)
PRSF (RC-11-0095)
Virgil C. Summer Station, Post Office Box 88 ° Jenkinsville, SC. 29065 - T (803) 345-5209
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)
, the NRC may sfor each block) not conduct or sponsor, and a person is not required to respond to, the digits/characters finformation collection.
- 3. PAGE Virgil C. Summer Nuclear Station Unit 1 05000 395 I
OF
- 4. TITLE Failure to Maintain One Train of Safe Shutdown Systems in Accordance with Appendix R Section I11. G. a/III.G.3.
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NO.
05000 FACILITY NAME DOCKET NUMBER 05 03 2011 2011 1
0 07 01 2011 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
DE-FUELED Q 20.2201(b)
Q 20.2203(a)(3)(i)
Q 50.73(a)(2)(i)(C)
Q 50.73(a)(2)(vii)
O 20.2201(d)
[] 20.2203(a)(3)(ii)
Q 50.73(a)(2)(ii)(A)
[
50.73(a)(2)(viii)(A)
O 20.2203(a)(1)
Q 20.2203(a)(4)
Q 50.73(a)(2)(ii)(B)
Q 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i)
Q 50.36(c)(1)(i)(A) i:
50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL Q 20.2203(a)(2)(ii)
Q 50.36(c)(1)(ii)(A)
[
50.73(a)(2)(iv)(A)
Q 50.73(a)(2)(x) o 20.2203(a)(2)(iii)
Q 50.36(c)(2)
[1 50.73(a)(2)(v)(A)
[73.71(a)(4) 000 Q 20.2203(a)(2)(iv)
Q 50.46(a)(3)(ii)
[
50.73(a)(2)(v)(B)
Q 73.71(a)(5) o 20.2203(a)(2)(v)
Q 50.73(a)(2)(i)(A)
[J 50.73(a)(2)(v)(C)
[I OTHER CI 20.2203(a)(2)(vi) 5 50.73(a)(2)(i)(B)
I] 50.73(a)(2)(v)(D)
Specify in Abstract below or in
CAUSE OF EVENT
A root cause analysis was conducted to identify the reason a fire in either the MCR, CSR or CB412 North Chase could result in a hot short rendering the B-train essential electrical bus (Bus 1DB) inoperable. The result of this analysis has determined the most likely cause to be human error in Appendix R reviews performed by the vendor. The review of Appendix R circuits was in large part a manual process of evaluation that was prone to human error. Failure to consider a possible hot-short-to-ground for circuit ESM301XB during the original Appendix R analysis and the re-analysis in the early 1980s is indicative of human error. Due to the elapsed time since these errors were made, the exact cause could not be determined.
ANALYSIS OF EVENT
A fire in certain areas of the Control Building could cause a hot-short-to-ground in circuit ESM301XB, which would actuate Relay 51BN-1DB. This relay would subsequently actuate Relay 51BX-1DB to trip all incoming breakers to XSWIDB (offsite power and 'B' EDG breaker when the diesel is in the test start mode), which trips the feeder breaker to the 480VAC XSW1DA1 and XSWIDA2 transformers. Tripping of the feeder breaker also trips the incoming main breakers in 480V busses XSW1DBI and XSWIDB2. This would result in the complete loss of power to the 'B' ESF train until the problem was diagnosed, the relays were reset, and breakers reclosed. Because Fire Emergency Procedures (FEPs) rely on 'B' Train equipment to shut down the plant in the event of a fire in the MCR or CSR, this would have an adverse impact on the ability to safely shut down the plant. The condition is less significant for a postulated fire in the CB412 North Chase because the FEPs rely on 'A' Train equipment.
VCSNS has enforcement discretion for fire issues identified during the transition to NFPA 805 as long as the risk impact of these issues is not 'RED' (Change in Core Damage Frequency (CDF)>I.OE-04/yr) per the guidance in NRC Inspection Manual Chapter 0609, "Significance Determination Process." A PRA Evaluation was conducted to assess the risk significance of both this Appendix R violation and that associated with LER-2011-002-00 to determine if enforcement discretion remains applicable to VCSNS. The results of this evaluation determined that the total CDF increase for both events is below the 'RED' threshold of 1.0E-04/yr, which complies with the requirements for enforcement discretion.
CORRECTIVE ACTIONS
Corrective actions include: 1) roving fire watch patrols were established in the fire zones through which the impacted circuits are routed, and 2) The FEPs were revised to provide guidance for preventing and/or responding to the bus lockout condition. The guidance consists of disabling the XSW1DB Neutral Over-Current relay, confirming that none of the XSWIDB Phase Over-Current Relays have tripped, and resetting and/or verifying the 51BX-IDB relay is not tripped. 3)
Extent of Condition Evaluation was performed and identified no other similar conditions. VCSNS will develop a permanent hardware change as part of NFPA 805 implementation.
PRIOR OCCURRENCES LER-2010-002, "Unanalyzed Condition Due to Wiring Discrepancy in the "B" Emergency Diesel Generator (EDG)
Appendix R Isolation Circuitry," identified a conductor that was not removed during the implementation of a design change in 1983. The cause of this deficiency was a design modification implemented in 1983 that did not contain sufficient information to remove the conductor. The circumstances surrounding this deficiency are not similar to the condition described in this LER.
10 CFR PART 21 REPORTING REQUIREMENTS The following information is provided to meet the requirements of 10 CFR 21.21(d)(4)(i)-(viii). The hot short scenario was not considered during the Appendix R analysis and is considered to be a defect in the circuit design. The lockout of XSWlDB has been determined to be a Significant Safety Hazard (SSH) since it would adversely impact the ability to safely shut down the plant in the event of a fire in any of the three affected areas.
(i) Name and address of the individual or individuals informing the Commission.
Dan Gatlin, V.P. Nuclear Operations SCE&G Co.
Virgil C. Summer Nuclear Station Unit 1 HWY 215 Bradham Blvd.
PO Box 88 Jenkinsville, SC 29065 (ii) Identification of the facility and the activity supplied for such facility or such activity within the United States which fails to comply or contains a defect.
Facility: Virgil C. Summer Nuclear Station Unit 1 Activity which contains a defect:
Appendix R design analysis pertaining to the unanalyzed condition described in this Licensee Event Report.
(iii) Identification of the firm supplying the activity which fails to comply or contains a defect:
Gilbert & Associates, Inc. (now Worley Parsons) supplied the described activity.
(iv) Nature of the defect or failure to comply and the safety hazard which is created or could be created by such defect or failure to comply.
See Description of Event section of this event notification.
(v) The date on which the information of such defect or failure to comply was obtained:
SCE&G completed the Part 21 evaluation on June 27, 2011.
(vi) In the case of a basic component which contains a defect or fails to comply, the number and location of all such components in use at, supplied for, or being supplied for one or more facilities or activities subject to the regulations in this part.
V. C. Summer is a single unit facility. Worley/Parsons is investigating the potential for similar Appendix R analyses performed for other licensees.
(vii) The corrective action which has been, is being, or will be taken; the name of the individual or organization responsible for the action; and the length of time that has been or will be taken to complete the action.
See Corrective Actions section above.
(viii) Any advice related to the defect or failure to comply about the facility, activity, or basic component that has been, is being, or will be given to purchasers or licensees.
Licensees whose Appendix R analyses were performed by Gilbert/Commonwealth are advised to contact WorleyParsons concerning the existence of a similar condition.