ENS 50492
ENS Event | |
|---|---|
20:33 Sep 24, 2014 | |
| Title | Unit 1 Train B Rvlis and Iccm Inoperable Due to Data Errors |
| Event Description | At 1533 CDT on September 24, during a Past Operability review for the Unit 1 Train B Inadequate Core Cooling Monitor (ICCM), it was discovered that due to data errors, the as left VDC [voltage DC] value for the Remote Display Power Supply was outside of acceptance criteria during the last performance of SP 1213B 'Inadequate Core Cooling Monitor Calibration,' completed on 8/25/2014. The Reactor Vessel Level Instrumentation System (RVLIS) and the Core Exit Thermocouples (CETs) are subsystems of the ICCM System and were determined to be inoperable during this timeframe. Therefore Tech Spec 3.3.3 Condition A for Train B RVLIS and Tech Spec 3.3.3 Condition B for CETs were not met. Also during this time, Unit 1 Train A ICCM was out of service from 1110 [CDT] on 9/8/2014 to 1530 [CDT] on 9/12/2014 for calibration. Thus, both trains of Core Exit Thermocouples and RVLIS were inoperable during this 4 day, 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> and 20 minute time period.
ICCM System indication is used for Safety Injection Termination and Reinitiation criteria in the Emergency Operating Procedures (EOPs). During the time when both trains of ICCM were inoperable, B Train remained in service and was thought to be operable. This provided the potential for operators to perform an untimely SI Termination or Reinitiation during an accident based on inaccurate information. The Emergency Response Computer System was available to provide accurate backup information to the operators and for timely Emergency Action Limit classification This is reportable under 10 CFR 50.72 (b)(3)(v)(D), Event or Condition that Could Have Prevented Fulfillment of a Safety Function to Mitigate the Consequences of an Accident. Based on new information currently being received from Westinghouse, the ICCM Remote Display Power Supply only functions to communicate data to the display and has no effect on the data values. Thus the ICCM System may have been functioning properly. An update to this information will be provided once it is available The protection of the health and safety of the public was not affected by this issue. The Unit 1 Train B ICCM System was returned to operable status at 2300 [CDT] on 9/24/2014. The license has notified the NRC Senior Resident Inspector.
Based on further analysis and input from Westinghouse, the remote display 12V power supply is operable as long as data is still updating on the display. It was determined that the tolerance acceptance criteria within our procedure was conservative. For this application, the power supply can function at much less than 12V. The acceptance criteria within surveillance procedures were incorrect and procedure changes have been submitted to correct the tolerance. Therefore, there was no loss of safety function. The licensee has notified the NRC Resident Inspector. Notified R3DO (Orlikowski). |
| Where | |
|---|---|
Prairie Island  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.52 h0.147 days <br />0.021 weeks <br />0.00482 months <br />) | |
| Opened: | Steve Ingalls 00:04 Sep 25, 2014 |
| NRC Officer: | Daniel Mills |
| Last Updated: | Oct 6, 2014 |
| 50492 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |