05000336/LER-2014-005
| Millstone Power Station - Unit 2 | |
| Event date: | 05-17-2014 |
|---|---|
| Report date: | 07-16-2014 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3362014005R00 - NRC Website | |
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1. EVENT DESCRIPTION
At 1933 on May 16, 2014 while in MODE 3, Millstone Power Station Unit 2 (MPS2) exceeded the Limiting Condition for Operation (LCO) of plant Technical Specification (TS) 3.6.2.1 "Containment Spray System" Action a.1 for an inoperable containment spray pump. The 'A' containment spray (CS) pump was declared inoperable at 0018 on May 17, 2014, the date of discovery, following completion of surveillance testing to determine the presence of gas voids. However, the gas found was introduced earlier during the refueling outage. The TS LCO went into effect upon entry into MODE 3 greater than 1750 psia on May 13, 2014, at 1933. TS 3.6.2.1 Action a.1 requires that the pump be restored to OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and reduce pressurizer pressure to less than 1750 psia within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
MPS2 had been in a MODE where the CS system was required to be OPERABLE for approximately 70.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> prior to completion of the testing. The gases were successfully removed by venting and the system was restored to OPERABLE status at 1221 on May 17, 2014, 88 hours0.00102 days <br />0.0244 hours <br />1.455026e-4 weeks <br />3.3484e-5 months <br /> after entering an applicable MODE for TS 3.6.2.1.
This condition is being reported as any operation or condition which was prohibited by the plant's technical specifications in accordance with 10 CFR 50.73 (a)(2)(i)(B).
2. CAUSE
Exceeding the LCO time limit while removing gases was due to not adequately venting the CS system following maintenance performed during the outage and delays in communicating the surveillance results to Operations, combined with a need to schedule performance of the surveillance testing earlier in a refueling outage.
3. ASSESSMENT OF SAFETY CONSEQUENCES
The containment spray (CS) system is composed of two redundant independent trains. The CS system in conjunction with the containment air recirculation and cooling system provides sufficient heat removal capability to limit the post-accident containment pressure and structural temperature below the design values.
The safety consequences of this condition was determined to be low. The "A" Train of the CS system was considered to be unavailable because the amount of gas found during the ultrasonic testing exceeded engineering guidance for system operability. The "B" Train of the CS system was confirmed to be free of voids, and remained available to perform the safety function, if needed. In addition, both trains of containment air recirculation and cooling systems were available during the period to perform the safety function, if necessary. The period of unavailability of the "A" Train of the containment spray system was of short duration, approximately 88 hours0.00102 days <br />0.0244 hours <br />1.455026e-4 weeks <br />3.3484e-5 months <br />, and occurred during MODE 3, while the plant was shutdown.
4. CORRECTIVE ACTION
Corrective actions planned will improve scheduling of system testing for gas voids after outages, and will result in more timely communications of the results from completed testing to Operations.
4. CORRECTIVE ACTION (Continued) Additional corrective actions are being taken in accordance with the station's corrective action program.
5. PREVIOUS OCCURRENCES
There have been no previous occurrences.
6. Energy Industry Identification System (EIIS) codes
- Containment Spray System — BE
- Pump — P