ENS 43794
ENS Event | |
|---|---|
11:30 Nov 20, 2007 | |
| Title | High Pressure Coolant Inject Inoperable |
| Event Description | On November 20, 2007 at 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />, with the reactor at 100% core thermal power, a power supply failure was discovered in the high pressure coolant injection (HPCI) flow controller circuitry that may have precluded the system from performing its design basis function. Therefore, in accordance with 10 CFR Part 50.72(b)(3)(v) an eight-hour notification is being made.
As background, on November 18, 2007, at 2145 hours0.0248 days <br />0.596 hours <br />0.00355 weeks <br />8.161725e-4 months <br />, the high pressure coolant injection (HPCI) system was removed from service for planned maintenance. The required risk analysis was performed and the appropriate 14 day limiting condition for operation (LCO) was entered in accordance with Technical Specification (TS) 3.5.C. Later on November 19, 2007 at approximately 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> the planned maintenance had been completed and HPCI was restored to the normal standby line-up in preparation for post maintenance testing (PMT). The HPCI valve quarterly operability and HPCI pump and valve quarterly operability tests were performed as the prescribed PMT. Upon initiation, the HPCI turbine was observed to come up to expected rated speed (~4,200 rpm) and expected HPCI pump discharge pressure (~1,300 psig). However HPCI pump indicated discharge flow was observed to be ~2,300 gpm, which is less than the Technical Specification requirement of 4,250 gpm. The HPCI system was secured and remained in the original TS 3.5.C LCO and a troubleshooting plan was initiated. On November 20, 2007, at 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br />, troubleshooting identified a power supply failure in the HPCI flow control circuitry. A replacement flow controller was identified and installed and it is anticipated that appropriate PMT will be initiated by 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br />. The impact of the power supply failure for the design basis operability for HPCl could not be definitively established before the eight-hour notification requirement of 10 CFR Part 50.72(b)(3)(v) was exceeded. The licensee notified the NRC Resident Inspector and the Commonwealth of Massachusetts.
NRC Notification 43794 was conservatively made to ensure that the Eight-Hour Non-Emergency reporting requirements of 10 CFR 50.72 were met pending the evaluation of an atypical condition (low reading) observed with the High Pressure Coolant Injection (HPCI) Flow Controller while performing scheduled surveillance testing for the HPCI System. During surveillance testing on 11/18/07, the HPCI System was started and met or exceeded the Technical Specification minimum requirements designed to demonstrate HPCI System Operability. While testing the specific components of the system, the HPCI Flow Controller was observed to be behaving erratically. Although the HPCI System was still capable of performing its required design safety function, the Shift Manager declared the system inoperable since he did not have definitive indication that the turbine was providing the required flow. Troubleshooting of the flow controller determined that the low flow indication was due to a degraded transmitter power supply located internal to flow controller FIC-2340-1. FIC-2340-1 is located in the main control room and is used to control HPCI system flow rate, and provide power to flow transmitter FT-2358. Although indicated flow rate was only 2300 gpm due to the degraded power supply, actual flow rate was approximately 5400 gpm based on pump hydraulic curves. The power supply in question only supplies power to FT-2358. Normal required supply voltage from this power supply is 28VDC to 36VDC. The degraded power supply could only supply 22.4VDC at the transmitter FT-2358 terminals. The degraded power supply voltage caused transmitter to output a lower than normal current for the actual measured flow rate giving a false low flow rate to FIC-2340-1. An Apparent Cause Evaluation and Past Operability Evaluation were performed in response to this event. These evaluations concluded that HPCI System was capable of performing its intended safety functions with the transmitter power supply degraded. HPCI system was capable of performing its intended safety functions during the time when FIC-2340-1 transmitter power supply exhibited low output voltage. HPCI would have started and supplied design basis flow to reactor vessel under design basis conditions. Thus there would have no impact on nuclear safety. Therefore, this event was not reportable pursuant to 10 CFR 50.72(b)(3)(v)(D). ENS Event Number 43794, made on 11/20/2007, is being retracted. The licensee will notify the NRC Resident Inspector and the Massachusetts Civil Defense Authority. Notified R1DO(Cobey) |
| Where | |
|---|---|
| Pilgrim Massachusetts (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+2.75 h0.115 days <br />0.0164 weeks <br />0.00377 months <br />) | |
| Opened: | John Macdonald 14:15 Nov 20, 2007 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Jan 14, 2008 |
| 43794 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |