05000389/LER-2017-003
| 12-18-2017 | On October 25, 2017, St. Lucie Unit 2 was in Mode 1 operation at 100 percent reactor power when the station discovered that both of the required flow transmitters (indication only) for the 2C steam driven auxiliary feedwater (AFW) pumps had been isolated since October 17, 2017. The transmitters were returned to service and extent of condition walkdowns were completed on the AFW pump flow transmitters for both St. Lucie Units 1 and 2; no other anomalies were noted.
This event was caused by human error because the personnel involved in the AFW flow calibration activities on October 17, 2017 did not adequately perform the system restorative steps in accordance with the governing procedure. Based on the availability of diverse methods to verify AFW flow delivery to the steam generators, this condition had no effect on the health and safety of the public. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. Description On October 25, 2017, St. Lucie Unit 2 was in Mode 1 operation at 100 percent reactor power. Maintenance personnel were troubleshooting indication flow ‘spikes' from FT-09-2C1 [EIIS:BA:FT], the flow transmitter for the 2C steam driven auxiliary feedwater (AFW) pump [EIIS:BA:P] discharge. At 1910 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.26755e-4 months <br />, the operators declared the 2C AFW flow transmitter FT-09-2C1 inoperable as maintenance reported that the transmitter was isolated. FT-09-2C1 was promptly un-isolated, filled and vented, and restored to service at approximately 1915 hours0.0222 days <br />0.532 hours <br />0.00317 weeks <br />7.286575e-4 months <br />. During the extent of condition walkdown, maintenance supervision discovered that flow transmitter FT-09-2C2 was also isolated; it was promptly unisolated, filled and vented, and restored to service at approximately 1925 hours0.0223 days <br />0.535 hours <br />0.00318 weeks <br />7.324625e-4 months <br />. By 2128 hours0.0246 days <br />0.591 hours <br />0.00352 weeks <br />8.09704e-4 months <br /> on October 25, 2017, the extent of condition walkdowns were completed for the remaining electric driven AFW pumps for Unit 2 and all AFW pumps for Unit 1; no anomalies were noted. ContentsCause of the EventInvestigation revealed that the individuals that performed an earlier calibration on October 17, 2017 did not properly perform the restoration lineup in accordance with the governing procedure. Analysis of the EventThis event was reportable under 10 CR 50.73(a)(2)(i)(B) as any operation or condition that was prohibited by the Technical Specifications (TSs). The AFW system consists of two electric driven pumps and one steam driven pump. Each electric AFW pump is normally aligned to its respective steam generator (SG) [EIIS:SB:SG], and the steam driven AFW pump can feed either SG. The 2C steam driven AFW pump is provided with two redundant flow transmitters that are used to provide post- accident AFW flow indication. With both 2C AFW pump flow transmitters isolated, the minimum operable channel requirement of TS Table 3.3-10 was not met. Therefore Unit 2 was in the TS 48-hour completion and 6-hour shutdown action statement per TS 3.3.3.6 (Accident Monitoring Instrumentation) action (b). The 2C AFW pump flow transmitters were isolated on October 17, 2017, when maintenance personnel commenced loop calibrations of the Unit 2 AFW flow loops. When the condition was discovered on October 25, 2017, the 54-hour total completion and shutdown time had already been exceeded. Safety SignificanceThe subject flow transmitters perform no automatic accident mitigation or control functions; they are used to monitor plant parameters during and following a design basis accident. From October 17 to October 25, 2017, the operators would not have the ability to directly monitor flow from the 2C AFW pump. However, the operators have sufficient diverse means to verify that AFW flow is getting to the SGs, such as SG level and condensate storage tank level trends as well as monitoring the effectiveness of decay heat removal via RCS temperature indication. Loss of the primary method to directly monitor the 2C AFW pump flow would not prevent successful mitigation of any design bases accident. Therefore, this condition had no effect on the health and safety of the public. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection. Corrective Actions1. The flow transmitters were immediately returned to service. 2. An extent of condition walkdown identified no other isolated transmitters in the AFW system. 3. The maintenance personnel involved with the earlier calibration that resulted in isolation of the 2C AFW flow transmitters were disqualified pending remediation. Failed ComponentsID: Flow Transmitter for Auxiliary Feedwater Pump 2C Discharge Tag Nos.: FT-09-2C1, FT-09-2C2 Manufacturer: Rosemount Model: 1153DB5 Additional InformationNone. |
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| St. Lucie Unit 2 | |
| Event date: | 10-25-2017 |
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| Report date: | 12-18-2017 |
| 3892017003R00 - NRC Website | |
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