ENS 40476
ENS Event | |
|---|---|
17:10 Jan 25, 2004 | |
| Title | Inoperable Refueling Interlock |
| Event Description | This report is being made pursuant to 10CFR50.72(b)(3)(v)(A) and 10CFR50.72(b)(3)(v)(D), Event or Condition that could have prevented fulfillment of a Safety Function needed to Maintain Safe Shutdown and Mitigate the Consequences of an Accident. During Unit 1 refueling operations, it was discovered at 1110 hours0.0128 days <br />0.308 hours <br />0.00184 weeks <br />4.22355e-4 months <br /> 1/25/04 CST that the Refuel Position One-Rod-Out Interlock was inoperable. Because this interlock is credited for mitigating the 'Control Rod Removal Error During Refueling' event evaluated in the UFSAR, this is reportable as an 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> ENS notification.
With the Unit 1 Mode Switch in REFUEL, the one-rod-out interlock function was tested per LaSalle Operating Surveillance LOS-RD-SR4. Since the acceptance criterion of this surveillance was not met, the interlock was declared inoperable and the required actions of Technical Specification 3.9.2 entered. Currently all control rod withdrawals are suspended and all control rods are fully inserted in core cells containing fuel assemblies. The Unit 1 Mode Switch is in Shutdown. Actions are in progress to restore the One-Rod-Out Interlock to an operable status. The licensee notified the NRC Resident Inspector.
During further investigation, it was determined that the system design is such that whenever the Mode Switch is placed in the REFUEL position with a rod withdrawn, no select block is received but a rod withdrawal block is generated. This design feature allows control rods to be inserted should the Mode Switch be placed in REFUEL with any rod out. The LaSalle Operating Surveillance (LOS-RD-SR4) used to demonstrate operability of the Refuel Position One-Rod-Out Block does not currently recognize this design feature and its acceptance criteria is based solely on receipt of the select block. The subject procedure will be revised to ensure all rods are fully inserted prior to performing the surveillance thereby ensuring the logic initial conditions are met to satisfactorily demonstrate the select block function. With these initial conditions satisfied, the Refuel Position One-Rod-Out Interlock was satisfactorily tested on 1/25/04 at 1935 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.362675e-4 months <br /> CST. Therefore, the Refuel Position One-Rod-Out interlock performed as designed and was capable of performing its safety function. Thus, this occurrence was not reportable under 10CFR50.72(b)(3)(v)(A) and 10CFR50.72(b)(3)(v)(D)." The licensee notified the NRC Resident Inspector. Notified R3DO (Louden). |
| Where | |
|---|---|
Lasalle  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-1.73 h-0.0721 days <br />-0.0103 weeks <br />-0.00237 months <br />) | |
| Opened: | John Reymer 15:26 Jan 25, 2004 |
| NRC Officer: | Mike Ripley |
| Last Updated: | Jan 26, 2004 |
| 40476 - NRC Website
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