Junk Plant Polo Verde Has A Special Way To Discover Maintenence Problems.

Basically setting up for maintenance issue then uncovering two additional maintenance problems not detected by the plant.

1) Seems something is wrong the breakers during the bus transfer. There are a lot of breaker problems in the industry. Was the busses in synch upon the transfer? Big chance of a electrical explosion.

2) The stuck open relief valve. The is what caused TMI. 

Power Reactor	Event Number: 52226
Facility: PALO VERDE Region: 4 State: AZ Unit: [1] [ ] [ ] RX Type: [1] CE,[2] CE,[3] CE NRC Notified By: MIKE JONES HQ OPS Officer: DANIEL MILLS	Notification Date: 09/08/2016 Notification Time: 04:27 [ET] Event Date: 09/07/2016 Event Time: 21:31 [MST] Last Update Date: 09/08/2016
Emergency Class: NON EMERGENCY 10 CFR Section: 50.72(b)(2)(iv)(B) - RPS ACTUATION - CRITICAL	Person (Organization): THOMAS HIPSCHMAN (R4DO)

Unit	SCRAM Code	RX CRIT	Initial PWR	Initial RX Mode	Current PWR	Current RX Mode
1	M/R	Y	100	Power Operation	0	Hot Standby

Event Text

MANUAL REACTOR TRIP DUE TO STUCK OPEN PRESSURIZER MAIN SPRAY VALVE "On September 7th, 2016 at approximately 2131 Mountain Standard Time (MST), Palo Verde Unit 1 was manually tripped due to a stuck open main spray valve. Unit 1 was operating at 100 percent power at normal operating temperature and pressure prior to the event. A 120 VAC non-class instrument distribution panel was being transferred to its alternate power supply to establish maintenance conditions. The distribution panel failed to transfer. The panel remained energized from its normal power supply; however, multiple components powered from the distribution panel began to exhibit uncharacteristic behavior. At this time, it was noted that a reactor coolant system main spray valve was open. The alarm response procedure was followed; however, the actions taken were unsuccessful at closing the main spray valve. The plant was then manually tripped due to pressurizer pressure continuing to lower. The reactor coolant pumps were turned off to terminate main pressurizer spray flow to control pressurizer pressure due to the inability to close the main spray valve. No ESF [Engineered Safety Features] actuations occurred and none were required. No emergency classification was required per the emergency plan. Safety related buses remained energized during and following the reactor trip. The emergency diesel generators did not start and were not required. The offsite power grid is stable. Limiting condition for operation 3.4.1 was entered due to low pressurizer pressure. No major equipment was inoperable prior to the event that contributed to the event. "Unit 1 is stable at normal operating temperature and pressure in Mode 3. Reactor coolant pumps are secured and natural circulation has been verified. Primary pressure is being maintained at its normal operating pressure manually with pressurizer heaters and auxiliary spray, from the charging system. 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 minimum RCS pressure was approximately 2070 psia (normal 2250). The event did not adversely affect the safe operation of the plant or the health and safety of the public." All rods inserted and the trip was uncomplicated. Units 2 and 3 were not affected and continue to run at full power. The NRC Resident Inspector has been notified.