05000341/LER-2018-004, Re Inoperability of Reactor Water Cleanup System Isolation Differential Flow-High Function
| ML18323A214 | |
| Person / Time | |
|---|---|
| Site: | Fermi  |
| Issue date: | 07/25/2018 |
| From: | DTE Energy |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML18323A213 | List: |
| References | |
| NRC-18-0042 LER 2018-004-00 | |
| Download: ML18323A214 (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)(i)(B), Prohibited by Technical Specifications 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)(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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 3412018004R00 - NRC Website | |
text
Enclosure 2 to NRC-18-0042 Fermi 2 NRC Docket No. 50-341 Operating License No. NPF-43 Licensee Event Report (LER) No. 2018-004 Inoperability of Reactor Water Cleanup System Isolation Differential Flow-High Function
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- 3. Page Fermi 2 05000 341 1
OF 4
- 4. Title Inoperability of Reactor Water Cleanup System Isolation Differential Flow-High Function
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Number No.
Month Day Year N/A 05000 05 31 2018 2018 -
004 00 07 25 2018 FacityName
- 9. Operating Mode
- 11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply) 20.2201(b)
El 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2201(d)
El 20.2203(a)(3)(ii) 50.73(a)(2)(i)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(1)
El 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(i)
E 50.36(c)(1)(1)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)
- 10. Power Level 20.2203(a)(2)(li)
[jJ50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(lii) i 50.36(c)(2) 50.73(a)(2)(v)(B)
El 73.71(a)(5) 20.2203(a)(2)(Iv)
Fl 50.46(a)(3)(ii)
[/
50.73(a)(2)(v)(C) 73.77(a)(1) 100 20.2203(a)(2)(v)
E] 50.73(a)(2)(i)(A)
/
50.73(a)(2)(v)(D) 73.77(a)(2)(i) 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 73.77(a)(2)(ii)
El 50.73(a)(2)(i)(C)
Other (Specify in Abstract below or in Technical Specification 3.3.6.1, Primary Containment Isolation requires the RWCU Differential Flow-High to be operable in Modes 1, 2, and 3. The high differential flow signal is provided to detect a break in the RWCU System. This will detect leaks in the RWCU System when area or differential temperature would not provide detection (i.e., a cold leg break). This Function is not assumed in any UFSAR transient or accident analysis, since bounding analyses are performed for large breaks such as Main Steam Line Breaks. However, UFSAR Section 6.2.4.2.6, Leak Detection, states "For systems penetrating the primary containment, major leaks in the pipe are located by increased temperature, radiation, sump level, changes in pressure, differential pressure, process line flow, etc. These indications are monitored in the control room to alert the operator when remote manual valves should be closed. In addition, certain indications of leakage will cause automatic valves to close in response to a system accident."
A review was performed for the time the RWCU differential flow high function was previously restored (May 28 at 0046) until this failure (May 31 at 1420). Based on the review it was determined that this function was operable until failure on May 31, 2018 at 1420.
SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS
Within the RWCU, system leakage is generally detected by high temperature sensing instrumentation which senses a leak before a line break by monitoring the temperature rise in the equipment compartment for a system. This is based upon having the leak within the hot portion of the system. However, temperature sensing does not detect leakage from the cold-water part of the RWCU System. In the Differential Flow Leak Detection System, leakage is detected by means of a flow comparison between RWCU system inlet and outlet. If the inlet flow exceeds outlet flow by approximately 55 gpm an alarm is actuated and the RWCU system is isolated automatically.
The RWCU isolation function (low reactor water level) and all other RWCU isolation functions remained operable throughout this event. In addition, the associated RWCU system primary containment isolation valves were capable of being remotely closed by the control room operators throughout this event. Based on this discussion, the safety significance of this event is very low. There were no radiological releases associated with this event.
CAUSE OF THE EVENT
The cause of this event was due to a lost signal from a flow input due to a failed capacitor within the square root converter.
This failure occurrence has been attributed to the replacement C5 capacitor that was taken from the spare parts inventory, and was beyond the usable shelf life causing failure after the square root converter was placed in-service.
As described in LER 2018-003, the capacitor in the square root converter had been replaced on May 28, 2018 with one that was beyond its usable shelf life and functioned until May 31, 2018 when it was observed that flow indication had been lost.
Upon further review of the May 31, 2018 event, it was identified that the square root converter had been replaced following the December 11, 2017 performance of a surveillance procedure where the RWCU Inlet Flow square root converter was found to be out of tolerance and could not be recalibrated.
Cause
Capacitor System: G33 - Reactor Water Cleanup Component: G33K602 Manufacturer: Generic Component
CORRECTIVE ACTIONS
Immediate corrective actions were taken to replace the capacitor within the square root converter and return the RWCU System Isolation Differential Flow - High function to operable on June 1, 2018 at 0947 EDT. Before replacement, the replacement capacitor was verified to be within its usable shelf life to eliminate the potential for recurrence.
In addition, the plant verified the shelf life of the current inventory of capacitors and a 10-year preventative maintenance activity to replace the capacitor due to the 10-year service life was developed following the May 31, 2018 event.
PREVIOUS OCCURRENCES
LER 2018-003 documented a similar failure on May 27, 2018 at 0630 EDT. As described above, the corrective actions taken in response to LER 2018-003 (i.e. to replace the capacitor) did not prevent this LER since the replacement capacitor was beyond its useful life.Page 4
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