Our Fleet RM Team would like to know how other sites would classify/grade the following event: 

 

During the initial power escalation following a refueling outage, QPTR alarms required a flux map to verify quadrant power tilt and allow for new currents to be installed to clear the alarm. Originally, the hot channel factors surveillance was to be performed at 73% (the next scheduled flux map) but was performed at ~50%.  If the 50% map had passed all acceptance criteria, the 73% map would not have been required and all restrictions based on hot channel factors would have been removed all the way to full power; other hold points would have still been required.  The power ascension procedure states that the acceptance criteria for the Intermediate Power (40% to 75%) map to be the technical specification on hot channel factors, which references the COLR limit: “Once after each refueling prior to exceeding 75% RATED POWER and every 31 effective full power days thereafter” the FQN transient needs to be confirmed within limits.   

 

During the power ascension, it was decided to confirm the FQN transient using the 50% map to allow for power to be increased >75%. FQN transient was determined to be outside the COLR limits,  which caused the entry into the TS action statement.  The calculated margin was -1.701% based on a measured value with uncertainties of 5.085 compared to the limit of 5.00.

 

As a result, the following actions were required:

-Reduce the AFD limits greater than or equal to 1% for each 1% that the FqN transient exceeds its limits within 4 hours after this determination has been made.
-Similarly reduce the Power Range Neutron Flux-High Trip Setpoints and Overpower delta-T Trip Setpoints within 72 hours by greater than or equal to 1% that maximum allowable power of the axial flux difference limits is reduced.

A WO was made for I&C to make adjustments to the Power Range Neutron Flux-High Trip Setpoints and OPDT Trip Setpoints as specified above. 
Prior to completing the WO, the flux map at 73% power determined that there was no need to Reduce Overpower Delta T trip setpoints and the WO was canceled.  It was noted that the ~50% map was not originally planned and would not have been performed except for the QPTR alarms-instead the 73% would have been performed. 

 

1)      How would your site classify the above event in reactivity management space (precursor, incident, event…)?

2)      What is the justification for the grading (the example or statement from your procedure with your grading requirements)?

Thank you in advance. 

 

Adina LaFrance

 

The significant problems we face cannot be solved at the same level of thinking we were at when we created them.  -Albert Einstein

 

Nuclear Analysis & Fuel

Reactor Engineer

Surry Power Station

Email: Adina.K.LaFrance@Dom.com

Phone: 757-365-2658

Pager #: 4290