05000346/LER-2018-001, Borated Water Storage Tank Level Transmitter Out of Tolerance Due to Reaching End of Expected Life
| ML19050A166 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 02/14/2019 |
| From: | Bezilla M FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-19-025 LER 2018-001-00 | |
| Download: ML19050A166 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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)(x) 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 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability |
| 3462018001R00 - NRC Website | |
text
FENOC' RrstEnergy Nuclear Operating Company 5501 North State Route 2 Oak Harbor, Ohio 43449 Mark B. Bezilla Vice President, Nuclear February 14, 2019 L-19-025 ATTN: Document Control Desk United States Nuclear Regulatory Commission Washington, D.C. 20555-0001
Subject:
Davis-Besse Nuclear Power Station, Unit 1 Docket Number 50-346, License Number NPF-3 Licensee Event Report 2018-001 419-321-7676 10 CFR 50.73 Enclosed is Licensee Event Report (LER) 2018-001, "Borated Water Storage Tank Level Transmitter Out of Tolerance Due to Reaching End of Expected Life." This event is being reported pursuant to 10 CFR 50.73(a)(2)(i)(B).
There are no regulatory commitments contained in this letter or its enclosure. The actions described represent intended or planned actions and are described for
- information only. If there are any questions or if additional information is required, please contact Mr. Patrick J. McCloskey, Manager - Site Regulatory Compliance, at (419) 321-7274.
Sincerely,
/1/Ui!J Mark B. Bezilla GMW Enclosure: LER 2018-001 cc: NRC Region Ill Administrator NRC Resident Inspector NRR Project Manager Utility Radiological Safety Board
NRCFORM366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020 (04-2018)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
3.Page Davis-Besse Nuclear Power Station, Unit 1 05000 346 1 OF 5
- 4. Title:
Borated Water Storage Tank Level Transmitter Out of Tolerance Due to Reaching End of Expected Life
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved I
Sequential I Rev Facility Name Docket Number Month Day Year Year Number No.
Month Day Year 05000 FacilityNarrie Docket Number 12 16 2018 2018 -
001 -
00 02 14 2019 05000
- 9. Operating Mode
- 11. This Report is Submitted Pursuanttothe 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) 1 D 20.2201(d)
D 20.2203(a)(3)(ii)
D 50. 73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 50.73(a)(2)(iii)
D 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)(ii)
D 50.36(c)(1)(ii)(A)
D 50)3(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)(iv)
D 50.46(a)(3)(ii)
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)(vi)
~ 50. 73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 73.77(a)(2)(ii)
D 50. 73(a)(2)(i)(C)
D Other (Specify in Abstract below or in The BWST level is monitored by four independent level transmitters. Each of the differential pressure signals generated by these transmitters is monitored by a bistable to provide a trip signal at a low-low level. The BWST allowable value of greater than or equal to 101.6 inches of water and less than or equal to 115.4 inches of water provides the operator with an alarm and a permissive to allow timely alignment of the BWST outlet and containment emergency sump valves to the long term recirculation position. This is to protect the pumps from cavitation for lack of proper net positive *suction head and allow transfer of ECCS suction to the containment emergency sump from the BWST during the recirculation mode of operation before the inventory of the BWST is depleted.
Technical Specification( s ):
Technical Specification (TS) Limiting Condition for Operation (LCO) 3.3.5 requires four channels of SFAS instrumentation for each parameter to be operable in each SFAS train. Failure of any instrument renders the affected channel(s) inoperable and reduces the reliability of the affected parameter and affected systems or components. With one or more parameters with one channel inoperable, Condition A requires that channel be placed in trip in one hour. If the required action of Condition A to place the channel in trip in an hour is not met, or one or more parameters with two or more channels rendered inoperable, Condition B requires the unit to be in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. TS Surveillance Requirement 3.3.5.1 requires a Channel Check be performed on all SFAS parameters once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />.
DESCRIPTION OF EVENT
On December 16, 2018 at 1909 hours0.0221 days <br />0.53 hours <br />0.00316 weeks <br />7.263745e-4 months <br />, with the DBNPS operating in Mode 1 at approximately 100 percent power, a licensed operator performing a scheduled control room panel shift walkdown identified the SFAS Channel 3 BWST Level Indicator displayed approximately 38 feet while the other three indicators displayed greater than 40 feet as expected. The SFAS Channel 3 BWST Level Transmitter was declared inoperable, and at 1935 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.362675e-4 months <br /> the BWST Level Lo Bistable for SFAS Channel 3 was tripped in accordance with Required Action A.1 for LCO 3.3.5.
A review of the analog plant computer points associated with the BWST Level indicators on December 16, 2018, identified the computer points alarmed at approximately 34 feet, which is too low to detect a lowering BWST level value during normal operations. Therefore, a review of the past computer point data for SFAS Channel 3 BWST Level Transmitter was performed, which identified the transmitter output experienced a downward shift of more than two feet at approximately 1154 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.39097e-4 months <br /> on December 16, 2018. The transmitter output value returned to an expected value at approximately 1428 hours0.0165 days <br />0.397 hours <br />0.00236 weeks <br />5.43354e-4 months <br />, and then again shifted downward by approximately two feet at approximately 1901 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.233305e-4 months <br />, with the issue being identified by the licensed operator at 1909 hours0.0221 days <br />0.53 hours <br />0.00316 weeks <br />7.263745e-4 months <br />.
CAUSE OF EVENT
The SFAS Channel 3 BWST Level Transmitter issue was determined to be caused by the transmitter reaching the end of its expected service life. The transmitter was determined to have been installed approximately 42 years ago during original plant construction.
ANALYSIS OF EVENT
- 2. DOCKET NUMBER 346 YEAR 2018
- 3. LER NUMBER SEQUENTIAL NUMBER 001 The BWST level transmitters monitor the BWST level and initiate an SFAS Level 5 signal on BWST level low-low. This output signal provides a passive permissive interlock to allow operators the ability to shift REV NO.
00 ECCS suction from the BWST to the Emergency Sump by allowing operators to open the Decay Heat Pump Suction From Emergency Sump Valves and close the associated BWST Isolation Valves. The transfer of suction source from the BWST to the Emergency Sump is a manual transfer. The Probabilistic Risk Analysis.
(PRA) models failure of the SFAS Level 5 permissive signal, as well as failure of the valves to be repositioned (or failure of the human action to manually transfer the suction), which could result in the inability of the plant to shift ECCS suction from the BWST to the Emergency Sump.
The four-channel SFAS is a two-out-of-four logic circuit, such that when any two level instruments sense a BWST level low-low, the permissive interlock will actuate for both trains. With the SFAS Channel 3 BWST Level Transmitter indicating approximately two feet lower than the other three channels, it would have tripped its respective output module sooner than desired on a decreasing BWST level. The remaining three channels, which were reading within expected values during the time period in question, would have ensured the permissive interlock would only have actuated within the required values. By procedure and by training, Operators would monitor, log, and trend BWST level, so they would be aware of the proper time to transfer the suction of the ECCS pumps from the BWST to the Emergency Sump, and there would be minimal increase in the likelihood of failing to perform the required action. Therefore, this condition was of very low
safety significance
Reportability Discussion:
Based on the plant computer data for SFAS Channel 3 BWST level, the transmitter was not reliably capable of performing its required TS function for the entire time starting at December 16, 2018, at 1154 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.39097e-4 months <br />. The instrument was declared inoperable at 1909 hours0.0221 days <br />0.53 hours <br />0.00316 weeks <br />7.263745e-4 months <br /> when the condition was discovered and Required Action A.1 of LCO 3.3.5 was taken at 1935 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.362675e-4 months <br /> when the BWST Level Lo Bistable for SFAS Channel 3 was tripped. 10 CFR 50. 73(a)(2)(i)(B) requires reporting of any operation or condition which is prohibited by the Technical Specifications unless the listed exceptions are met. For this issue, with the transmitter considered inoperable at 1154 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.39097e-4 months <br />, the channel was required to be tripped within one hour, or at 1254 hours0.0145 days <br />0.348 hours <br />0.00207 weeks <br />4.77147e-4 months <br /> per LCO 3.3.5 Condition A This required action was not performed within the associated completion time because the instrument inoperability was unknown until discovered at 1909 hours0.0221 days <br />0.53 hours <br />0.00316 weeks <br />7.263745e-4 months <br /> during the TS Surveillance Requirement 3.3.5.1 Channel Check, which is performed every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. LCO 3.3.5 Condition B required the unit be placed in Mode 3 in the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, or at 1854 hours0.0215 days <br />0.515 hours <br />0.00307 weeks <br />7.05447e-4 months <br />. The bistable was tripped at 1935 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.362675e-4 months <br />, exceeding the TS completion time (total allowed restoration and shutdown outage time) by 41 minutes.
Therefore, this issue is reportable as a Licensee Event Report per 10 CFR 50.73(a)(2)(i)(B). Because only one channel of SFAS BWST level instrumentation was affected by this issue, no loss of safety function occurred.
CORRECTIVE ACTIONS
Completed Actions:
On December 17, 2018, at 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br /> the SFAS Channel 3 BWST Level Transmitter was calibrated and declared Operable.
On January 3, 2019, after SFAS Channel 3 BWST Level Transmitter output began to indicate a degrading trend, the level transmitter was replaced with an equivalent transmitter and returned to service on January 4, 2019.
SFAS Channel 4 BWST Level Transmitter was replaced and returned to service on January 22, 2019, after displaying erratic indication on January 20.
Scheduled Actions:
Maintenance Activities have been scheduled to replace the SFAS Channel 1 and 2 BWST Level Transmitters in June 2019.
PREVIOUS SIMILAR EVENTS
Licensee Event Report (LERs) 2016-001 reported the simultaneous inoperability of two BWST level channels due to the failure to initially recognize that entry conditions for the TS had been met following a loss of power to an SFAS Channel. The corrective actions taken in response to the 2016 event were focused in the area of human performance and would not have prevented this current hardware event.
I 00 Page 5 of5