ENS 42681
ENS Event | |
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02:28 Jul 2, 2006 | |
Title | Manual Reactor Trip Following Large Leak in Condensate System |
Event Description | On July 1, 2006, at approximately 19:28 MST Palo Verde Unit 3 experienced a manual reactor trip from approximately 100% rated thermal power due to a large leak in the condensate system. The sight glass for the 'A' condensate demin vessel blew out of the vessel creating an approximate 6 inch diameter hole. Several thousand gallons of condensate were discharged to the Turbine Building and the environment. Radiation Protection has sampled the condensate water and have verified no activity is present. Unit 3 was at normal operating temperature and pressure prior to the trip. The 'A' Main feedwater pump tripped on low suction pressure and a Reactor Power Cutback Signal was received. Condenser hotwell levels continued to decrease. When the main control board annunciator for the 'B' Main Feedwater Pump Trip Circuit Energized was received the reactor was manually tripped. All CEAs fully inserted into the reactor core. The event was diagnosed as an uncomplicated reactor trip. No ESF actuations occurred and none were required. Safety related buses remained energized during and following the reactor trip. The offsite power grid is stable. No significant LCOs have been entered as a result of this event. There was no loss of normal heat removal capabilities, or loss of any safety functions associated with this event. No major equipment was inoperable prior to the event that contributed to the event. No primary or secondary safety valves lifted during the event. The event did not result in any challenges to fission product barriers and there were no adverse safety consequences as a result of this event. The event did not adversely affect the safe operation of the plant or the health and safety of the public.
Unit 3 is stable at normal operating temperature and pressure in Mode 3. There is no estimated time and date for the Unit 3 restart at the time this call is being made. AFW is being used to feed the steam generators and is discharging steam to the main condenser. The licensee stated that the leak has been secured and that there is no significant standing water in the turbine building lower levels. All the water has drained into sumps or out doors. There does not appear to be any electrical or personnel safety hazards as a result of the water leak. The licensee notified the NRC Resident Inspector.
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 the ENS or under the reporting requirements of 10CFR50.73. This notification is a follow-up to the manually initiated reactor trip event reported on July 1, 2006 (ENS 42681). The notification indicated that the reactor was manually tripped from approximately 100% rated thermal power due to a large leak in the condensate system. Prior to the transient the unit was operating at approximately 100 % rated thermal power, however, the manual trip was actually initiated from approximately 55% rated thermal power following a reactor power cutback caused by the loss of the A train main feedwater pump on low suction pressure. In addition, the ENS report stated that Radiation Protection had sampled the condensate water and verified no activity is present. The condensate actually was found to contain tritium at a concentration of 1.22E-5 uCi/ml. The water from the spill flowed to the onsite storm drains, was captured behind dams, and transferred to the onsite retention basins. Samples of resin from the spill were also collected, analyzed by gamma spectroscopy, and found to not contain licensed radioactive material. The licensee notified the NRC Resident Inspector. Notified R4DO (Shannon) |
Where | |
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Palo Verde Arizona (NRC Region 4) | |
Reporting | |
10 CFR 50.72(b)(2)(iv)(B), RPS Actuation | |
Time - Person (Reporting Time:+-1.08 h-0.045 days <br />-0.00643 weeks <br />-0.00148 months <br />) | |
Opened: | James Blazek 01:23 Jul 2, 2006 |
NRC Officer: | Bill Huffman |
Last Updated: | Jul 2, 2006 |
42681 - NRC Website
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Unit 3 | |
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Reactor critical | Critical |
Scram | Yes, Manual Scram |
Before | Power Operation (100 %) |
After | Hot Standby (0 %) |
WEEKMONTHYEARENS 565512023-06-02T11:05:0002 June 2023 11:05:00
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ENS 419512005-08-27T01:24:00027 August 2005 01:24:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Rps Actuation - Reactor Scram on High Steam Generator Level ENS 408702004-07-14T08:35:00014 July 2004 08:35:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Following a Main Generator Trip ENS 408162004-06-14T14:44:00014 June 2004 14:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event Due to Reactor Trip Due to Loss of Off Site Power ENS 408152004-06-14T14:44:00014 June 2004 14:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unusual Event Declared Due to Reactor Trip Due to Loss of Off Site Power ENS 408142004-06-14T14:44:00014 June 2004 14:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Alert Declared - Reactor Trip Due to Loss of Off Site Power ENS 407952004-06-07T21:58:0007 June 2004 21:58:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Reactor Trip Due to Main Turbine Electro-Hydraulic Control System Failure ENS 407372004-05-09T03:39:0009 May 2004 03:39:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Manual Reactor Trip During Physics Testing Due to Control Element Assembly Slipping 6 Inches. 2023-06-02T11:05:00 | |