Waterford Plant: Are NRC Component Design Bases Inspections Sufficient (CDBI)

The fundamental question is... why didn't Entergy pick this up on their own years ago and why didn't the NRC pick it up on their CDBI inspections.

I count two CDBI inspections at Waterford for a total of 13 violations. Should't violations be going down at time goes on?

IR 2007-007 violations 8

IR 2011007 violations 5 

Palisades issues with the CDBI:

Are your “nads” safe: Seeing the Big Picture with the NRC and Palisades in One Design Inspection Report?

 

Basically they couldn't see if the fan was working. Waterford's response to NRC. TMI came about because, they monitored if the valve was energized or not, not if  the actual position of the valve. The valve indication said it was close, while the valve actually was open. This is a very similar event as TMI.

A root cause analysis was completed under CR-WF3-2013-2530 that identified the root cause as "the importance of monitoring EDG Exhaust fan differential pressure was not previously recognized."

Basically the problem with risk perspectives, these complex calculations are littered with assumptions deep within complex technical talk that outsiders can't understand. Most NRC officials can't explain risk perspectives to the public. These assumption most times are not carefully vetted and their is very little independence verification of this.  

Reference Documents:

LER 2013-005-00

December 30, 2014: WATERFORD SUPPLEMENTAL INSPECTION REPORT 05000382/2014011

January 30, 2014: WATERFORD INSPECTION  REPORT 05000382/2013008; PRELIMINARY WHITE FINDING

At this time, the licensee noticed that the malfunction of the exhaust fan was due to a separation of the fan hub assembly from the hub sleeve, which effectively separated the fan from the fan motor.

The licensee conducted an apparent cause evaluation and determined that the most likely cause of the failure was due to a failure mode that was inadvertently introduced when maintenance personnel reworked the fan hub to sleeve connection in 1999. Specifically, on March 17, 1999, during a train B emergency diesel generator fan operational surveillance run, the fan motor tripped on overcurrent. The licensee investigated the condition and determined that the motor windings failed to operate. The licensee removed the fan hub assembly and installed a new motor to the fan. During the subsequent electrical bump test for the new motor, the technicians noted that the fan operated in the reverse direction because the licensee wired the leads for the motor in the opposite direction. The licensee determined that the reverse torque on the fan hub was sufficient to cause the fan hub spanner nut to back off its threads and allow the hub to drop down off the hub sleeve. This damaged the hub sleeve threads and spanner nuts. At that time, the licensee reworked the hub sleeve threads and developed Engineering Evaluation, ER-W3-1999-0301-00, Revision 0, to add four more set screws  to reduce the likelihood of future events with the spanner nut backing off the sleeve. These design field changes reduced the allowable stress of the fan hub to sleeve connection and increased the loading on the hub sleeve threads, respectively.

4:  SUBJECT: WATERFORD STEAM ELECTRIC STATION, UNIT 3 - NRC INSPECTION REPORT 05000382/2013008; PRELIMINARY WHITE FINDING

Nothing wrong with the blades

The licensee’s operability evaluation determined that the most likely cause for the elevated room temperature was due to a change in the minimum setting of the variable pitch blade controller that may have occurred during previous maintenance activities. The variable pitch blade controller is actually a Hydramotor. The Hydramotor uses an internal positive displacement pump to provide hydraulic pressure that operates a piston that in turn changes the pitch of the fan blade. The Hydramotor controller adjusts the blade pitch to a minimum position when the emergency diesel generator starts to allow air flow through the room. The licensee indicated that the controller probably did not move to its minimum position. The licensee generated a work request to perform more troubleshooting on the variable pitch settings for the fan.

Additionally, the inspectors noted that the Final Safety Analysis Report stated, in part, that the control room operator was provided with safety-related indication on the operation of each exhaust fan. The inspectors concluded that the licensee did not provide this safety-related indication for the operation of the exhaust fan. Specifically, the inspectors noticed that the computer records on April 25 and May 20, 2013, showed that the train B emergency diesel generator exhaust fan LO FLOW computer point indicated abnormal flow for the duration of both operational runs. This low flow indicator is available for the exhaust fans on the plant monitoring computer in the control room. However, this indication is not routinely monitored during emergency diesel operational tests. The low flow indicator is a non-safety-related pressure switch that measures a differential pressure across the exhaust fan. The set point for the switch is 1 inch water gage (inwg) that reads “LO” in response to the fan blade not rotating at the same speed as the fan motor and reads “NT LO” when operating properly. Local indication for this pressure switch is available near the exhaust fan actuator outside the train B emergency diesel generator room on a different elevation. A review of the surveillance procedures identified that each contained acceptance criteria that must be satisfied to constitute satisfactory performance of the surveillance. However, the procedures did not include the exhaust fan differential pressure local indication nor refer to the plant monitoring computer point as an acceptance criterion to demonstrate the operability of the emergency diesel generator ventilation exhaust fan assembly. The inspectors determined that the licensee performed the same operational surveillance on the train B emergency diesel generator using Procedure OP-903-068 on May 20, 2103. The train B emergency diesel generator surveillance results were found to be acceptable and the exhaust fan was considered to be operable. However, a review of the low flow indicator computer point showed the same LO FLOW condition as indicated during the operational surveillance run on April 25, 2103. As a result, the inspectors concluded that the train B emergency diesel generator exhaust fan failed sometime after the start of train B emergency diesel generator operational run on April 25, 2013.

The t/2 exposure period between April 22 and April 25, 2013, was 1.5 days.

The analyst assumed that, even if the severe accident guidelines were not yet entered, operators would take the action to promptly start and load the temporary diesels if Manually Start Temporary Diesel Generators needed. The emergency diesel generators would auto-start and load. Conversely, operators would need to manually start and load the temporary diesel generators. Operators believed that they could successfully start, parallel and load the temporary diesels in 30 minutes. The licensee determined that core damage would take at least 60 minutes assuming a station blackout with the concurrent failure of the turbine driven auxiliary feedwater pump. Operators therefore would have sufficient time, but not extra time. The task did not appear overly complex and operators had adequate procedures to guide their actions. Operators receive just-in-time training prior to staging the temporary diesels, but not all operators receive hands-on training with the units.

Two 1500 kW emergency diesel generators were installed in parallel to support the train B emergency loads. Procedures limited the temporary diesel generator power load to 1750 kW (approximately 875 kW per emergency diesel generator). The safety-related emergency diesel generator provides over 4400 kW of power.