05000373/LER-2015-002
| Lasalle County Station Units 1 And 2 | |
| Event date: | 12-12-2014 |
|---|---|
| Report date: | 02-10-2015 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition |
| Initial Reporting | |
| 3732015002R00 - NRC Website | |
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CONTINUATION SHEET
2. DOCKET 6. LER NUMBER 3. PAGE 2015 LaSalle County Station, Units 1 and 2 002 - 00 LaSalle County Station Units 1 and 2 are General Electric Company Boiling Water Reactors with 3546 Megawatts Rated Core Thermal Power.
A. CONDITION PRIOR TO EVENT:
Unit(s): 1/2 Reactor Mode(s): 1/1 Event Date: December 12, 2014 Event Time: 1500 CST Mode(s) Name: Power Operation Power Level: 100%/100%
B. DESCRIPTION OF EVENT:
On December 12, 2014, both Units 1 and 2 were in Mode 1 at 100% power with an NRC Triennial Fire Protection Inspection in progress. During the inspection, it was identified that there were no documented breaker-fuse coordination analyses for the 250 VDC control power supplies to Reactor Core Isolation Cooling (RCIC)[BN] valves that are required to be operated from the Remote Shutdown Panel (RSP)[JL] in the event of a fire in the Main Control Room (MCR). Breaker-fuse coordination evaluations were conducted, and found that the power supply breakers to two RCIC valves might trip before the fuses, requiring the breakers to be reset before they could be operated from the RSP. The plant current licensing basis does not identify the contingency actions required to reset the breakers prior to operation from the RSP. RCIC operation from the RSP is the method credited for reactor vessel inventory makeup in the event of a fire in the MCR. This condition is common to both Units.
The affected valves are 1(2) E51-F031, the RCIC suppression pool suction valves, and 1(2) E51-F046, which supply lubricating oil cooling for the RCIC turbine. If the control power supply breakers for these valves tripped, they could not be operated from the RSP without locally resetting the breakers.
This occurrence is reportable under 10 CFR 50.73(b)(2)(ii)(B) as an event or condition that resulted in the plant being in an unanalyzed condition that significantly degraded plant safety. An ENS report was made to the NRC (EN 50675) at 2115 ET on December 12, 2014, pursuant to 10 CFR 50.72(b)(3)(ii)(B).
C. CAUSE OF EVENT:
This condition has existed since original construction. Documented breaker-fuse analyses were not required by engineering standards in place at that time.
D. SAFETY ANALYSIS:
The safety significance of this event was minimal. The Technical Specification 3.5.3 operability of RCIC was not affected by this condition.
In the event of a fire in the MCR, RCIC would be available from the RSP to maintain vessel inventory for sufficient time for the valve failure(s) to be identified and diagnosed, and for operators to reset the breakers and open the valves. The normally closed 1(2) E51-F031 valve is not required to establish suction from the suppression pool until low water level in the Condensate Storage Tank is reached, which takes approximately four hours based on station blackout coping studies. Additionally, evaluation has shown that the RCIC turbine can run for approximately three hours without lube oil cooling in the event that the 1(2)E51-046 valve does not open.
E. CORRECTIVE ACTIONS:
- Information Notice 97-48, "Inadequate or Inappropriate Interim Fire Protection Compensatory Measures," was reviewed and compensatory measures implemented, including the issuance of a Standing Order communicating the issue to the operating crews and directing the Safe Shutdown Equipment Operator to report to the respective 250 VDC switchgear to reset any tripped breakers in the event of a fire in the MCR.
- Contingency measures to reset the breakers as needed in the event of a fire in the MCR once control has been transferred to the RSP will be added to the appropriate procedures.
- The breakers and/or trip settings will be modified for the affected RCIC valves as required.
F. PREVIOUS OCCURRENCES:
A search of LaSalle LERs over the last 10 years did not identify any previous events related to breaker-fuse coordination issues.
G. COMPONENT FAILURE DATA:
No component failures occurred during this event.