ENS 42831
ENS Event | |
|---|---|
02:00 Sep 7, 2006 | |
| Title | Historical Unanalyzed Condition Identified |
| Event Description | On September 6, 2006, an unanalyzed condition was identified during the review of a previous issue discovered on April 18, 2005. The current review was being performed in response to NRC inspection questions regarding the previous issue.
On April 18, 2005, while at 100% power, both trains of standby auxiliary feed water (AFW) flow transmitters were found isolated. The plant had entered Mode 3 on April 8, 2005 for a routine startup after a refueling outage. The transmitters were restored to their normal operational alignment promptly when the condition was identified. These two standby AFW trains are in addition to the typical safety-related AFW motor driven pump trains and turbine driven pump train, for a total of five safety-related AFW pump trains at the site. The two standby AFW trains are designed to address a high energy line break (HELB) event which would disable the other three AFW pump trains. Both of the flow transmitters perform several functions including control room indication of standby AFW discharge flow and valve control functions for the pump discharge valve and pump recirculation valve. With the flow transmitters isolated in both trains of the standby AFW system, an unanalyzed condition existed due to the following: During a postulated HELB, the inoperable flow transmitters would result in the recirculation valve and the pump discharge valve being both full open. Under a steam generator low pressure condition, (as a result of the HELB) with flow through both the open discharge valve and the open recirculation valve, the pump would be in a high flow rate condition until the steam generator level was recovered. The operators would have no indication of flow through the discharge valves and would be operating the system based on steam generator level. During the time assumed for the intact steam generator level recovery, the breaker for the pump motor could be expected to exceed it's time delayed current protection setpoint and trip the motor, preventing delivery of feed water to the steam generator. Both trains of the standby AFW system are allowed by Technical Specifications to be concurrently inoperable for a period of up to 7 days. The actual inoperability occurred over 10 days while the flow transmitters were isolated. Ginna did not report the event at the time the isolated transmitters were discovered because the transmitters' control function was not recognized to interact in an unanalyzed manner with the resulting unavailable control room indication, concurrent with the low pressure steam generator condition associated with the HELB event. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Ginna  New York (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+-2.6 h-0.108 days <br />-0.0155 weeks <br />-0.00356 months <br />) | |
| Opened: | Doug Gomez 23:24 Sep 6, 2006 |
| NRC Officer: | Jason Kozal |
| Last Updated: | Sep 6, 2006 |
| 42831 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 499142014-03-13T20:30:00013 March 2014 20:30:00
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