05000458/LER-2018-010, Reactor Scram Due to Turbine Control Valve Failure
| ML19009A412 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 01/09/2019 |
| From: | Vercelli S Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RBG-47926 LER 2018-010-00 | |
| Download: ML19009A412 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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) 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)(v), Loss of Safety Function |
| 4582018010R00 - NRC Website | |
text
-- Entergy_
RBG-47926 January 9, 2019 Attn: Document Control Desk U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738 Entergy Operations, Inc.
River Bend Station 5485 U.S. Highway 61 N St. Francisville, LA 70775 Tel 225-635-5000 Steven Vercelli Site Vice President River Bend Station 10 CFR 50.73
Subject:
Licensee Event Report 50-458 I 2018-010-00, "Reactor Scram due to Turbine Control Valve Failure".
River Bend Station, Unit 1 NRC Docket No. 50-458 Facility Operating License No. NPF-47
Dear Sir or Madam:
In accordance with 1 O CFR 50. 73, enclosed is the subject Licensee Event Report. This document contains no commitments. If you have any questions, please contact Mr. Tim Schenk at 225-381-4177.
Sincerely, SV/twf
Enclosure:
cc:
Licensee Event Report 50-458 I 2018-010-00, "Reactor Scram due to Turbine Control Valve Failure".
NRC Region IV Regional Administrator, w/o Enclosure NRC Senior Resident Inspector-River Bend Station, Unit 1 Ji Young Wiley, Department of Environmental Quality, Office of Environmental Compliance, Radiological Emergency Planning and Response Section Public Utility Commission of Texas, Attn: PUC Filing Clerk NRC Project Manager
NRCFORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
Estimated burtlen per 18Sponse to comply with this mandatory collection request: BO hours.
Reported lessons learned are incorporated into the lcensing process and fed back to
~RREov, LICENSEE EVENT REPORT (LER) industry. Send comments regarding burtlen estimate to the Information Services Branch
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(T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail
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(See Page 2 for required number of digits/characters for each block) to lnfocoUects.Reso..-ce@nrc.gov, and to the Desk Officer, Office of Information and
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(See NUREG-1022, R.3 for instruction and guidance for completing this form Regulatory Affairs, NEOB-10202, (315~104), Office of Management and Budget,
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3.Page River Bend Station -
Unit 1 458 1
OF 4
05000
- 4. Title Reactor Scram due to Turbine Control Valve Failure
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facllltles Involved I
Sequential I Rev Facility Name Docket Number Month Day Year Year Number No.
Month Day Year NA 05000 NA Facility Name Docket Number 11 10 2018 2018 -
010 -
00 01 09 2019 NA 05000 NA
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)
D 20.2201(b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2201(d)
D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(vlii)(B) 1 D
D D
D 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1 )(l)(A) 0 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. Power Level D 20.2203(a)(2)(11)
D 50.36(c)(1 )(il)(A)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(B)
D 73.71(a)(5)
D 20.2203(a)(2)(1v)
D 50.46(a)(3)(11)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1) 100 D 20.2203(a)(2)(v)
D 50. 73(a)(2)(i)(A)
D 50.73(a)(2)(v)(D)
D 73.77(a)(2)(i)
D 20.2203(a)(2)(vl)
D 50. 73(a)(2)(1)(B)
D 50.73(a)(2)(vll)
D 73.77(a)(2)(11)
D 50. 73(a)(2)(i)(C)
D Other (Specify in Abstract below or in Research Council on Structural Connections. There is no documentation that this recommendation was ever satisfied.
CAUSAL ANALYSIS rrurbine Control Valve Number Three Unexpected Closure lfhe unexpected closure of CV3 on November 10, 2018 was determined to be due to failure of all 20 of the push rod spring housing coupling bolts.
lfhe Research Council on Structural Connections recommends the bearing surface of the CV3 push rod spring housing joint
~o be flat with a slope of less than 1 :20. There was no record found of the push rod spring housing joint flatness at the time of assembly in 2012. During the Digital EHC upgrade in March 2017, the switch arm, which is part of the push rod spring housing joint bearing surface, was found to be bent. The 2017 evaluation of this condition assumed that the joint bearing surface was not affected by the bent switch arm and the CV3 repair was scheduled for a planned outage in March of 2019.
Preliminary measurements of the CV3 switch arm after the November 2018 event indicated that the bearing surface was over 0.0625 inches out of flat at some of the bolt locations and therefore did not meet the Research Council on Structural Connections recommendation. The out of flat condition on the joint bearing surface amplified the stress on the push rod spring housing coupling bolts causing them to fail.
lfhe cause of the bent switch arm is not readily apparent. There are no physical interferences that could cause the deformation that was identified on the switch arm.
lfransient Response of Turbine Control Valve Number Four rThe failure of CV4 to respond to the CV3 closure transient as designed was determined to be due to incorrect procedural guidance.
~ review of Ovation parameter settings discovered that the CV4 load limit was set at 100%, rather than the correct value of 103%. The operating procedure used to enter the load limit value called for a load limit value of 100% instead of the correct value of 103%. This error was traced back to procedure revisions performed as part of the Ovation Digital EHC upgrade in March of 2017.
With the load limit incorrectly set, CV4 stroke was limited to between 44% and 70% open. With a load limit set at 103%
CV4 would be able to stroke to the full open position during a single CV closure.
CORRECTIVE ACTION TO PREVENT RECURRENCE The following actions have been completed to prevent recurrence.
Inspect all CV bolting for loose or broken switch arm bolts.
Review Ovation data for all CVs and CIVs to confirm hydraulic functionality.
Inspect all other CV switch arms for flatness and broken switch arm bolts.
.. Review Ovation data for all CVs and CIVs for symptoms of a bent switch arm or broken bolts.
... Review Digital EHC procedures that change load limit for correct values.
.. update operating procedures to include the correct load limit values.
- 3. LER NUMBER lfhe following actions have been assigned to prevent a recurrence of this event and are documented in the station corrective action program.
... visual inspection of CIV bolting shall be performed during the next refueling outage to confirm no bolts are broken.
... visual inspection of CIV switch arm shall be performed during next refueling outage to confirm no deformation.
.. Develop a preventive maintenance strategy for CV and CIV switch arm and bolting inspections. Inspections should include bolt tightness verifications and ensure that the bearing surface is flat with a slope of less than 1 :20.
... Review all Digital EHC procedures and verify that all manually entered Ovation parameters are correct and consistent with
~heir basis.
1-Develop a preventive maintenance strategy for Ovation parameter verification as part of the startup procedure.
SAFETY SIGNIFICANCE
The unexpected closure of CV3 and subsequent reactor scram are bounded by transient analysis contained in the Updated Safety Analysis Report. Following the reactor scram, all major systems performed as designed. No safety injection systems were actuated either manually or automatically as a result of the event. Therefore this event is considered to be of minimal significance to the health and safety of the public.
(NOTE: Energy Industry Identification System component function identifier and system name of each component or system referred to in the LER are annotated as (**XX**) and [XX], respectively.) Page 4
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