05000458/LER-2018-011, For River Bend Station, Unit 1, Condition Prohibited by Technical Specifications Due to Inadequate Design Change of Under Voltage Relay Trip Set Point Range
| ML19023A542 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 01/23/2019 |
| From: | Vercelli S Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RBG-47927 LER 2018-011-00 | |
| Download: ML19023A542 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(ix)(A) 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) 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4582018011R00 - NRC Website | |
text
'-=-" Entergy.
RBG-47927 January 23, 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 P. Vercelli Site Vice President River Bend Station 10 CFR 50.73
Subject:
Licensee Event Report 50-458 I 2018-011-00, "Condition Prohibited by Technical Specifications due to Inadequate Design Change of Under Voltage Relay Trip Set Point Range".
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,
~
. --<'~
~/
SPV/twf
Enclosure:
cc:
Licensee Event Report 50-458 I 2018-011-00, "Condition Prohibited by Technical Specifications due to Inadequate Design Change of Under Voltage Relay Trip Set Point".
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
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018)
, the NRC may not conduct or sponsor, and a
"')
~
person Is not required to respond to, the Information collection.
3.Page River Bend Station - Unit 1 458 1
OF 4
05000
- 4. Title Condition Prohibited by Technical Specifications due to Inadequate Design Change of Under Voltage Relay Trip Set Point Range
- 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 29 2018 2018 -
011 -
00 01 23 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)(viii)(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 )(i)(A)
D 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 )(ll)(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)(ii)
D 50. 73(a)(2)(v)(C)
D 73.77(a)(1) 99 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) 0 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 was found below the TS allowed range with a value of 84.8 VAC. Relays 2784 and 27N2 were found above the TS allowed range with values of 99.0 VAC and 100.4 VAC respectively. The 27N2 relay could not be calibrated and was replaced. The 2782 and 2754 relays were calibrated to within the TS allowable range.
On November 29, 2018, a technical evaluation of the under voltage relays was completed. The evaluation concluded that there was no reasonable assurance that the Division Ill under voltage relay trip values would remain within the TS allowed tolerance for the entirety of the 2 year calibration Preventive Maintenance (PM) interval.
!fhe same surveillance was also performed on October 24, 2016. During this performance, the 2751 and 27N2 relay as found trip set points were found above the TS allowable range with values of 97.6 VAC and 99.5 VAC respectively.
rThere were no other performances of this surveillance at River Bend Station (RBS) in the last three years.
rTherefore, this condition is being reported as a Condition Prohibited by Technical Specifications, 50.73(a)(2)(i)(B).
PREVIOUS OCCURRENCE EVALUATION There have been no recent previous occurrences similar to this condition at RBS.
CAUSAL ANALYSIS In 2011, a drift study calculation was performed on the under voltage relays in question to support extending the SR interval to 2 years for 24 month cycle operation. The calculation concluded that the bounding analyzed drift for these relays is +/-
5.823 VAC for 30 months (24 months+ 25%). Prior to RBS TS Amendment 179, the Division Ill under voltage relay trip set point allowable value range was 80.89 VAC - 93.11 VAC ( 12.22 VAC range). This range would allow the relay to experience the worst case calculated drift and still remain within the TS allowable value range for 24 months, assuming it was calibrated with an as-left value in the middle of the range. RBS TS Amendment 179, issued in March 2013, revised the Division Ill under voltage relay trip set point TS allowable value range to 86.23 VAC - 95.00 VAC (8. 77 VAC range). A relay calibrated in the middle of this range has a +/- 4.385 VAC margin to the limits of the TS allowable range. The bounding analyzed drift of+/- 5.823 VAC is greater than the +/- 4.385 VAC margin to the limits of the TS allowable range of Amendment 179.
An additional contributor was the as-left acceptance values in the SR test procedure. For relays 27N 1 and 27N2, the as-left acceptance criterion was 89.25 VAC - 91.23 VAC (1.98 VAC range). This range ensures that the as-left set point is near the center of the TS allowable range. However, the as-left acceptance criterion for relays 2751, 2782, 2783, and 2784 was the same as the as-found administrative range of 87.63 VAC to 92.85 VAC (5.22 VAC range). This can lead to an as-left set point with only 1.4 VAC margin to the TS allowable limit.
CORRECTIVE ACTION TO PREVENT RECURRENCE The following actions have been completed to prevent recurrence.
Perform the calibration PM on or prior to 12/20/2018. When performing the calibration, the as-left set points shall be between 89.5 VAC and 91.7 VAC to ensure adequate margin to the TS allowable value.
The system monitoring plan has been updated to include monitoring of relay drift.
rThe following actions have been assigned to prevent a recurrence of this event and are documented in the station's corrective action program.
Perform the calibration PM on or prior to 2/17/2019. When performing the calibration, the as-left set points shall be between 89.5 VAC and 91.7 VAC to ensure adequate margin to the TS allowable value.
SAFETY SIGNIFICANCE
The out of tolerance conditions of 27N2 would not have prevented the safety function. The relays are arranged in such a way that actuation of either relay will perform the safety function. Therefore the out-of-tolerance relay would have actuated slightly early on an under voltage condition to separate E22-S004 from its offsite source in both instances. The October 2016 as found trip set point value correlates to an E22-S004 separation from offsite power at 3482.5 VAC. The October 2018 as found trip set point value correlates to 3514.0 VAC.
The out of tolerance conditions of the 27S relays would not have prevented the safety function. Due to the one-out-of-two-twice arrangement, the 27S relays that were found within the TS allowable range would have performed the safety function in both the October 2016 and October 2018 occurrence.
The basis for the bus under voltage TS allowable range is to prevent inadvertent power supply transfer and to ensure power is available to required equipment. In the degraded off-site power scenario, this reported condition would have caused a power supply transfer from offsite power to the on-site safety VAC system slightly sooner than required by TS.
!This condition would not have prevented any safety system function. 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
of 4