ENS 47459
ENS Event | |
|---|---|
15:28 Nov 19, 2011 | |
| Title | the Low Pressure Safety Injection System Was Subjected to High Pressure Resulting in Both Trains Being Declared Inoperable |
| Event Description | On November 19, 2011, Unit 1 was in Mode 3. Boration of the four reactor coolant system (RCS) cold leg injection lines was in progress using High Pressure Safety Injection pump 'A'.
During this activity, 'SI CHK VLV Leak Pressure Hi' alarms were received at 0828 [MST]. The 'A' and 'B' Low Pressure Safety Injection (LPSI) subsystems were declared inoperable because the pressure downstream of the motor operated LPSI injection valves was above 1525 psia. This elevated pressure potentially impacts the ability of the LPSI RCS loop injection valves to open. The high differential pressure may exceed the capability of the motor operator. All four injection line pressures were found above 1525 psia and LCO 3.0.3 was entered due to both trains of LPSI being inoperable. At 0839 [MST], pressure in the 'A' train injection lines was lowered below 1525 psia and 'A' LPSI subsystem was declared operable and LCO 3.0.3 was exited. At 0842 [MST], pressure was reduced below 1525 psia on the 'B' train injection lines and the 'B' LPSI subsystem was declared operable and LCO 3.5.3 condition A was exited. This call is being made to report a condition that could have prevented the fulfillment of a safety function required to mitigate the consequences of an accident and unanalyzed condition that existed for 11 minutes while both LPSI subsystems were inoperable. The NRC Resident Inspector has been notified.
The following event description is based on information currently available. If through subsequent reviews of this event, additional information is identified that is pertinent to this event or alters the information being provided at this time, a follow-up notification will be made via ENS or under the reporting requirements of 10CFR50.73. This notification is a retraction of ENS 47459 which was made by Arizona Public Service to report a condition that could have prevented the fulfillment of a safety function required to mitigate the consequences of an accident and an unanalyzed condition that existed for 11 minutes while both LPSI subsystems were declared inoperable when pressure downstream of the motor operated injection valves for safety injection subsystem were declared inoperable. An engineering review of the motor operated valves thrust and torque calculations determined that the affected valves would have been fully capable of performing their intended safety function at the time of the pressure excursion. The NRC Resident Inspector has been notified of this retraction. |
| Where | |
|---|---|
Palo Verde  Arizona (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+1.33 h0.0554 days <br />0.00792 weeks <br />0.00182 months <br />) | |
| Opened: | Amado Fernandez 16:48 Nov 19, 2011 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Dec 15, 2011 |
| 47459 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Standby (0 %) |
| After | Hot Standby (0 %) |
Palo Verde with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
WEEKMONTHYEARENS 539682019-04-01T03:06:0001 April 2019 03:06:00
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