05000458/LER-2015-008, Of River Bend Station, Unit 1, Regarding Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller
| ML16050A391 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 01/18/2016 |
| From: | Olson E Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RBF1-16-0002, RBG-47641 LER 15-008-00 | |
| Download: ML16050A391 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(ii)(B), Unanalyzed Condition 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), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| LER closed by | |
| IR 05000458/2017001 (1 May 2017) | |
| 4582015008R00 - NRC Website | |
text
SEn tergy Entergy Operations, Inc.
River Bend Station 5485 U. S. Highway 61 N St. Francisville, LA 70775 Tel 225 381 4374 Fax 225 381 4872 eolson@entergy.com Eric W. Olson Site Vice President RBG-47641I January 18, 2016 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Subject:
Licensee Event Report 50-458 / 2015-008-00 River Bend Station - Unit I Docket No. 50-458 License No. NPF-47 RBFI1-16-0002
Dear Sir or Madam:
In accordance with 10 CER 50.73, enclosed, is the subject Licensee Event Report.
This document contains no commitments. If you have any questions, please contact Mr. Joseph Clark at 225-381-4177.
Sincerely, EWO /dhw Enclosure cc:
U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Blvd.
Arlington, TX 76011-4511 NRC Sr. Resident Inspector P. 0. Box 1050 St. Francisville, LA 70775
Licensee Event Report 50-458 I 2015-008-00 January 18, 2016 RBG-47641 Page 2 of 2 INPO (via ICES reporting)
Central Records Clerk Public Utility Commission of Texas 1701 N. Congress Ave.
Austin, TX 78711-3326 Department of Environmental Quality Office of Environmental Compliance Radiological Emergency Planning and Response Section Ji Young Wiley P.O. Box 4312 Baton Rouge, LA 70821 -4312
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 0113112017 (02-2014)
- ,'-,~
Estimated burden per response to comply with this mandatory collection request: 80 hoomr.
.%,.Reported lessons learned are incorporated into the-licensing process end ted back to industry.
.1Send comments regarding burden estimate to the FOIA, Privacy and Inforniation Collections (LER)
Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by
- .... LICENSEE EVENT REPORT (LR nternet e-mail to Infocollects.Resource~nrc.gov, and to the Desk Officer, Office of Information and (See Page 2 for required number of Regulatory Affairs, NEOn-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. It a means used to impose an information collection does not display a currently valid 0MB digits/characters for each block) control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collecfl on.
- 1. FACILITY NAME 2
OKTNME
.PG River Bend Station - Unit 1 000481O
- 4. TITLE Potential Loss of Safety Function of High Pressure Core Spray Due to Failure of Main Control Building Ventilation Chiller
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MOT A
ER YA EUNIL RVFACILITY NAME DOCKET NUMBER NUMBER NO.
MOT A
YER000 FACILITY NAME DOCKET NUMBER 11 19 2015 2015 008 00 01 18 2016 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[1] 20.2201(b)
[]
20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
[] 50.73(a)(2)(vii) 1 E 20.2201(d)
[]
20.2203(a)(3)(ii)
[] 50.73(a)(2)(ii)(A)
[j] 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
[]
20.2203(a)(4)
[]
50.73(a)(2)(ii)(B)
[]
50.73(a)(2)(viii)(B)
[I] 20.2203(a)(2)(i)
[j] 50.36(c)(1)(i)(A)
[]
50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
.[]
50.36(c)(1)(ii)(A)
[]
50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
[] 20.2203(a)(2)(iii)
[j] 50.36(c)(2)
[j] 50.73(a)(2)(v)(A)
[]
73.71 (a)(4)
El
[
20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(g)
El 73.71 (a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
El OTHER E
20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
[~] 50.73(a)(2)(v)(g)
Seiyi btatblwo nR om36
- 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT TLPOENME IcueAe oe Joseph A. Clark, Manager - Regulatooy Assurance (2)3147l Y
TE FiCMOET MANU-REPORTABLE CAS YTMANU-REPORTABLE CAS YTM CMOET FACTURER TO EPIX I
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH DAY YEAR El YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
[]
NO SUBMISSION j ~
ABSTRACT (Limit to 1400 spaces, iLe., approximately 15 single-spaced typewritten lines)
On November 19, 2015, at 7:24 a.m. CST, with the plant operating at 97 percent power, the high pressure core spray system (HPCS) was declared inoperable following the failure of the operating chiller in the Division 2 control building ventilation system (HVK).
Chiller "D" was in service when the building operator found an oil leak on that machine. The chiller subsequently tripped on low oil pressure. The "A" chiller in the Division 1 subsystem automatically started as designed. The loss of cooling to the various equipment rooms in the control building requires that the supported equipment in those areas be declared inoperable. The Technical Specifications for the Division 3 DC distribution system requires that the H-PCS system be immediately declared inoperable. This condition potentially causes the H-PCS system to be incapable of performing its safety function. Maintenance technicians identified the source of the oil leak as a failed seal on the compressor drive shaft. The apparent cause of the seal failure was the age-related degradation of a setscrew holding one of the rotating elements of the seal, allowing it to get out of position and disrupt the integrity of the seal face. In this event, the "A" chiller automatically started as designed, and it was confirmed to be operating correctly within 10 minutes. The HVK system continued to support the safety function of Division 3 electrical equipment after chiller trip, since the time required to restore an operable chiller is significantly less than the time limit for restoration of equipment room cooling. This event had no actual adverse effect on the ability of the Division 3 HPCS electrical system to perform its design safety function since there was more than sufficient time to align the other chiller in the same division to provide control building switchgear room cooling. This event, thus, did not constitute an actual loss of the ability of the HPCS system to perform its design safety function.
NRC FORM 366 (02-2014)
REPORTED CONDITION On November 19, 2015, at 7:24 a.m. CST, with the plant operating at 97 percent power, the high pressure core spray system (HPCS)
(BG) was declared inoperable following the failure of the operating chiller (**CHU**) in the Division 2 control building ventilation (HVK)(VI) system. HVK chiller "D" was in service when the building operator found an oil leak on that machine. The chiller subsequently tripped on low oil pressure. The "A" chiller in the Division 1 HVK subsystem automatically started as designed.
The HYK system provides cooling to the equipment rooms housing the battery chargers and inverters for the safety-related onsite electrical distribution systems. The loss of redundant cooling to the various equipment rooms in the control building requires that the supported equipment in those areas be declared inoperable. The Technical Specifications for the Division 3 DC distribution system requires that the HPCS system be immediately declared inoperable. This condition potentially causes the HPCS system to be incapable of performing its safety function, and is, thus, reportable in accordance with 10 CFR 50.73 (a)(2)(v)(D).
CAUSAL ANALYSIS Maintenance technicians identified the source of the oil leak as a failed seal on the compressor drive shaft. The apparent cause of the
!seal failure was the age-related degradation of a setscrew holding one of the rotating elements of the seal, allowing it to get out of position and disrupt the integrity of the seal face. A factor contributing to this failure was the lack of specific requirements in both the maintenance instructions and the vendor manual regarding re-use of parts during periodic inspections or seal overhaul.
A review of service history on this chiller, as well as the other three chillers in the system, found that this was the first such failure in the life of the plant.
CORRECTIVE ACTIONS to PREVENT RECURRENCE Maintenance instructions for the chiller seals will be revised to specify which parts must be replaced (vice re-used) during periodic inspections or overhaul.
PRIOR OCCURRENCE EVALUATION No previous similar events have been reported at River Bend Station in the last three years.
SAFETY SIGNIFICANCE
Within the bounds of the site accident analysis, there is a plausible (albeit, highly unlikely) scenario in which a complete loss of offsite power occurs following an unrelated failure of the operating H-KV chiller, concurrent with the assumed failure of the emergency diesel generator in the division opposite that of the failed chiller.
Each of the two divisions of the HVK system has two 100 percent capacity chillers. The chilled water and service water subloops are configured such that manual operator action is required to shift service between the two chillers within a division. In the normal alignment, one chiller is carrying the building heat loads, and one. chiller in the opposite division is in standby, capable of automatically starting in the event that the running chiller fails.
An unanticipated trip of an operating chiller automatically initiates the start sequence of the standby chiller. If the start of that standby chiller is closely followed by the loss of offsite power, the assumed subsequent failure of the diesel generator then leaves the HVK system with no chillers aligned for service. These circumstances result in the failure of the cooling function of the H{VK system until the operators take the manual actions. The maximum time needed to perform the realignment has been conservatively estimated to be 76 minutes. Calculations have determined temperatures in the Division 3 equipment rooms will remain below the 122 F limit of the equipment for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
In the event on November 19, the "A" chiller automatically started as designed, and it was confirmed to be operating correctly within 10 minutes. The HVK system continued to support the safety function of Division 3 electrical equipment after chiller trip, since the time required to restore an operable chiller is significantly less than the time limit for restoration of equipment room cooling. This event had no adverse effect on the ability of the Division 3 HIPCS electrical system to perform its design safety function following the trip of a HYK chiller since there is more than sufficient time to align the other chiller in the same division to provide control building switchgear room cooling. This event, thus, did not constitute an actual loss of the ability of the HPCS system to perform its design safety function.
(NOTE: Energy Industry Component Identification codes are annotated as (**XX**))
REPORTED CONDITION On November 19, 2015, at 7:24 a.m. CST, with the plant operating at 97 percent power, the high pressure core spray system (HPCS)
(BG) was declared inoperable following the failure of the operating chiller (**CHU**) in the Division 2 control building ventilation (HVK)(VI) system. HVK chiller "D" was in service when the building operator found an oil leak on that machine. The chiller subsequently tripped on low oil pressure. The "A" chiller in the Division 1 HVK subsystem automatically started as designed.
The HYK system provides cooling to the equipment rooms housing the battery chargers and inverters for the safety-related onsite electrical distribution systems. The loss of redundant cooling to the various equipment rooms in the control building requires that the supported equipment in those areas be declared inoperable. The Technical Specifications for the Division 3 DC distribution system requires that the HPCS system be immediately declared inoperable. This condition potentially causes the HPCS system to be incapable of performing its safety function, and is, thus, reportable in accordance with 10 CFR 50.73 (a)(2)(v)(D).
CAUSAL ANALYSIS Maintenance technicians identified the source of the oil leak as a failed seal on the compressor drive shaft. The apparent cause of the
!seal failure was the age-related degradation of a setscrew holding one of the rotating elements of the seal, allowing it to get out of position and disrupt the integrity of the seal face. A factor contributing to this failure was the lack of specific requirements in both the maintenance instructions and the vendor manual regarding re-use of parts during periodic inspections or seal overhaul.
A review of service history on this chiller, as well as the other three chillers in the system, found that this was the first such failure in the life of the plant.
CORRECTIVE ACTIONS to PREVENT RECURRENCE Maintenance instructions for the chiller seals will be revised to specify which parts must be replaced (vice re-used) during periodic inspections or overhaul.
PRIOR OCCURRENCE EVALUATION No previous similar events have been reported at River Bend Station in the last three years.
SAFETY SIGNIFICANCE
Within the bounds of the site accident analysis, there is a plausible (albeit, highly unlikely) scenario in which a complete loss of offsite power occurs following an unrelated failure of the operating H-KV chiller, concurrent with the assumed failure of the emergency diesel generator in the division opposite that of the failed chiller.
Each of the two divisions of the HVK system has two 100 percent capacity chillers. The chilled water and service water subloops are configured such that manual operator action is required to shift service between the two chillers within a division. In the normal alignment, one chiller is carrying the building heat loads, and one. chiller in the opposite division is in standby, capable of automatically starting in the event that the running chiller fails.
An unanticipated trip of an operating chiller automatically initiates the start sequence of the standby chiller. If the start of that standby chiller is closely followed by the loss of offsite power, the assumed subsequent failure of the diesel generator then leaves the HVK system with no chillers aligned for service. These circumstances result in the failure of the cooling function of the H{VK system until the operators take the manual actions. The maximum time needed to perform the realignment has been conservatively estimated to be 76 minutes. Calculations have determined temperatures in the Division 3 equipment rooms will remain below the 122 F limit of the equipment for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
In the event on November 19, the "A" chiller automatically started as designed, and it was confirmed to be operating correctly within 10 minutes. The HVK system continued to support the safety function of Division 3 electrical equipment after chiller trip, since the time required to restore an operable chiller is significantly less than the time limit for restoration of equipment room cooling. This event had no adverse effect on the ability of the Division 3 HIPCS electrical system to perform its design safety function following the trip of a HYK chiller since there is more than sufficient time to align the other chiller in the same division to provide control building switchgear room cooling. This event, thus, did not constitute an actual loss of the ability of the HPCS system to perform its design safety function.
(NOTE: Energy Industry Component Identification codes are annotated as (**XX**))