Harris Plant - Heater Drain System Transients INPO ICES # HNP Root Cause Evaluation

Presentation Outline  System Overview  System History  Atypical System Characteristics  Recent Problems  Cause(s) of Problems  Generic Lessons Learned 2

Heater Drain System Schematic – ‘A’ Train 3

Heater Drain System Schematic – ‘A’ Train (Cont’d) 4

System History  Initial operation experienced significant system instability issues.  Unstable HD and FRV control valve operation due to excessive pressure drops across the valves.  10 plant trips during first five months of power ascension testing and commercial operation, most of which were caused by BOP problems.  A Study recommended seven modifications to the BOP. These included:  Removing an impeller stage from the Heater Drain Pumps.  Replacing the pneumatic controllers on the #4 FWHs, #5 FWHs, and MSR Drain Tanks with electronic level controllers.  Trimming the Main Feedwater Pump impellers.  The result was significantly more stable and reliable plant operation.  The modifications continued to work effectively for the next 25 years of operation. 5

Atypical System Characteristics  No Heater Drain Tank.  Small level transients often result in a Heater Drain Pump trip.  Variable speed Condensate Booster Pumps.  Heater Drain Pump trips have a small impact on overall plant output.  Make and model of electronic controllers are unique to the Heater Drain System.  Knowledge of controllers eventually began to fade.  Knowledgeable personnel (with few exceptions) moved on.  First 20 years - System largely operated and maintained by tribal knowledge and as- needed corrective maintenance. 6

Overall Timeline of NCRs December 1, 2010 – March 5,

Timeline 8

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Root Cause 15 Previous actions taken to address Heater Drain System equipment failures, while appropriate, have not been thorough and intrusive enough to prevent additional failures and associated reactivity management events. Until the most recent series of failures, insufficient attention was given to the source, quality, and age of replacement parts. In addition, considering the number of Heater Drain System components that can cause a reactivity management event and the goal of minimizing the number of reactivity management events, the establishment of preventative maintenance tasks has not been broad and comprehensive enough.

Contributing Causes  Untimely resolution of obsolescence issues and inadequate shelf life controls resulted in defective components being installed.  Components impacting Reactivity Management were not considered in the initial PM basis development work for the Heater Drain System. The resulting lack of PMs resulted in several initial transients and reactivity management events.  Troubleshooting of Heater Drain System events were not managed effectively. 3 of 10 initiating events resulted in a total of 12 additional events before the System was successfully returned to service.  The portion of OP-136 used to set the alternate level controller setpoints for the 4A and 4B FWHs was found to have deficiencies that contributed to the recurrence and severity of Heater Drain System transients and reactivity management events. 16

Generic Lessons Learned  Systematic troubleshooting is vital.  If you don’t have enough data to determine cause, seriously consider restarting equipment to collect more data, rather than replacing all the parts that potentially could have caused the problem.  Clearly define the roles and responsibilities of personnel on your troubleshooting team and insist management respect and follow the organization established.  Divide data collection and other field work from troubleshooting to allow the troubleshooting team to stay focused and function well as a multi-discipline team.  Don’t be so focused on producing a Support/Refute Matrix or Operational Decision Recommendation, that you short change the data collection and analysis. 17

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