05000387/LER-2011-001, For Susquehanna Steam Electric Station, Unit 1 Regarding Single Point Vulnerability with the Potential to Cause Isolations
| ML110620711 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 03/02/2011 |
| From: | Rausch T Susquehanna |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| PLA-6696 LER 11-001-00 | |
| Download: ML110620711 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 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 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) |
| 3872011001R00 - NRC Website | |
text
Timothy S. Rausch Sr. Vice President & Chief Nuclear Officer MAR 0 2 2011 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop OP 1 - 17 Washington, DC 20555 PPL Susquehanna, LLC 769 Salem Boulevard Berwick, PA 18603 Tel. 570.542.3445 Fax 570.542.1504 tsrausch@pplweb.com SUSQUEHANNA STEAM ELECTRIC STATION LICENSEE EVENT REPORT 50-3871201 1-001-00 LICENSE NOS. NPF-14 and NPF-22 PLA-6696 Docket Nos. 50-387 and 50-388 Attached is Licensee Event Report (LER) 50-3 87/20 1 1-00 1-00. This event was determined to be reportable under 10 CFR 50,73(a)(2)(ii)(B) as an unanalyzed condition in 'that a single point vulnerability associated with the steam leak detection system (SLD) might not be able to accommodate a sudden complete failure of the non-safety related Reactor Building (RB)
HVAC heating system temperature controls during cold weather conditions without causing an isolation of HPCI, RCIC, and the main steam lines (MSIVs).
There were no actual consequences to the health and safety of the public as a result of this event.
No regulatory commitments are associated with this LER.
Sincerely,
-- A@
T. S. Rausch Attachment Copy: NRC Region I Mr. R. R. Janati, DEPIBRP Mr. P. W. Finney, NRC Sr. Resident Inspector Mr. B. K. Vaidya, NRC Project Manager
, the NRC ma digitslcharacters for each block) not conduct or sponsor, and a person is not required to respond to, th information collect~on.
- 13. PAGE I
Susquehanna Steam Electric Station Unit 1 05000387 1 of 3
- 4. TITLE lsingle Point Vulnerability with the Potential to Cause Isolations
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR REV MONTH NUMBER NO.
DAY YEAR Susquehanna Steam Electric Station Unit 2 05000388 FACILITY NAME DOCKET NUMBER 01 03 201 1 201 1 - 001 - 00 63 0, a01 \\
05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMllTED PURSUANT TO THE REQUIREMENTS OF 10 CFRS: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 1 20.2201 (d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 20.2203(a)(l) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 20.2203(a)(2)(i)
[7 50.36(c)(l )(i)(A)
[7 50.73(a)(2)(iii) lo. POWER LEVEL
- 20.2203(a)(2)(ii) 50.36(c)(l)(ii)(A)
- 50.73(a)(2)(iv)(A)
[7 20.2203(a)(2)(iii) 50.36(~)(2) 50.73(a)(2)(v)(A) 20.2203(a)(2)(iv)
[7 50.46(a)(3)(ii) 98%
50.73(a)(2)(v)(B) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
- 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
- 12. LICENSEE CONTACT FOR THlS LER 50.73(a)(2)(vii)
[7 50.73(a)(2)(viii)(A) 50.73(a)(2)(viii)(B) 50.73(a)(2)(ix)(A) 50.73(a)(2)(x) 73.71 (a)(4) 73.71 (a)(5)
OTHER Specify in Abstract below or in NRC Form 366A Name Telephone Number (Indude Area Code)
C. E. Manges, Jr., Senior Engineer - Nuclear Regulatory Affairs
((570) 542-3089 MANU-
CAUSE
SYSTEM COMPONENT FACTURER REPORTABLE MANU-
CAUSE
SYSTEM COMPONENT FACTURER REPORTABLE TO EPlX TO EPlX
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR SUBMISSION YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
(XI NO DATE IABSTRACT (Limit to 1400 spaces, i.e.. approximately 15 single-spaced typewritten lines)
On January 3, 201 1, PPL Susquehanna, LLC (PPL) identified a single point vulnerability associated with the steam leak detection system (SLD) for Unit 1 and Unit 2. Specifically, PPL determined that the design and setpoint selection for the SLD Delta Temperature function might not be able to accommodate a sudden complete failure of the non-safety related Reactor Building (RB) HVAC heating system temperature controls during cold weather conditions without causing an isolation of high pressure injection systems (HPCI and RCIC) and main steam lines (MSIVs). This design deficiency had existed since original plant design.
I This event is being reported in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition.
I The cause of the event was a less than adequate single failure analysis that did not provide sufficient detail to identify the vulnerability.
There were no actual adverse consequences. With regard to potential significance, incorporation of the postulated isolation events into the risk model resulted in very small changes to the CDF and LERF. Based on this information, the potential safety impact of the reported event was insignificant.
A corrective action to eliminate the isolation function of the SLD delta T instrumentation has been implemented. In addition, a Failure Modes and Effects Analysis (FMEA) will be performed on all non-Q support systems that could cause an isolation of ECCS systems or all the MSIVs. This proposed action will address the extent of cause.
NRC FORM 366 (9-2007)
I
CAUSE OF THE EVENT
The cause of the event was a less than adequate single failure analysis performed during the original plant design. The original single failure analysis was consistent with the level of detail of other non-Q system single failure analyses performed at that time. Training on Failure Modes and Effects analysis was provided to Engineering staff in 2007. This training provided expectations as to the level of detail of a failure modes and effects analysis for non-Q systems. Using the guidance from this training, the single point vulnerability was discovered during the preparation of 50.59 determinations for the engineering change to remove the isolation function. In the strict sense of the definition, this represents a deficiency of the previous analysis even though it was consistent with PPL and industry expectations for non-Q systems at that time.
ANALYSISISAFETY SIGNIFICANCE Actual Consequences:
There were no actual consequences from this event. The postulated event was that a postulated failure of the RB HVAC heater controller could cause the SLD delta T instrumentation to isolate the MSIVs, HPCI, and RClC if outside air temperatures were low enough (less than approximately 10°F). The heater failure never occurred, therefore the potential isolations did not occur and no transient was experienced. The SLD delta T isolations have been removed from the plant; therefore, the potential issue has bien resolved.
Potential Consequences:
The postulated event was that a failure of the RB HVAC heater controller could cause the SLD delta T instrumentation to isolate the MSIVs, HPCI, and RClC if outside air temperatures were low enough (less than approximately 10°F). For a system isolation to occur, the heater controller had to fail and concurrently the outside air temperature had to be below approximately 10°F. Outside air temperatures of less than approximately 10°F have been reported eleven times in the last two years. Incorporation of these new isolation events into the risk model resulted in very small changes to the CDF and LERF. Based on this information, the potential safety impact of the reported event was insignificant. The SLD delta T isolation functions have been removed from the plant; therefore the potential issue has been resolved.
CORRECTIVE ACTIONS
The following corrective action has been completed:
A modification to eliminate the isolation function of the Steam Leak Detection delta T instrumentation was implemented.
The following corrective action is planned:
Perform a Failure Modes and Effects Analysis (FMEA) on all non-Q support systems that could cause an isolation of ECCS systems or all the MSIVs.
No regulatory commitments are associated with this report.
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