05000266/FIN-2010003-04
Finding | |
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| Title | Potential Degradation of Reactor Protection System P-9 Permissive Operability |
| Description | During the forced outage, the inspectors identified an URI regarding the licensees utilization of the P-9 permissive below 50 percent power with less than full condenser steam dump capacity available. Specifically, the inspectors identified that operation in this condition had the potential to have been in violation of TS 3.3.1, condition S.2, or TS 3.0.3
On Saturday, June 19, 2010, the inspector responded to the plant for a Unit 2 unplanned reactor trip. Prior to the trip, Unit 2 was at 44 percent reactor power for condenser cleaning activities. The plant alignment had one circulating water pump secured and the steam dumps to the related condenser bays tagged out-of-service in anticipation of workers entering the related water-boxes for maintenance. At this power level, the main generator monitoring circuitry incorrectly sensed a fault on the generator, which resulted in a generator trip and a related turbine trip. As a result of the turbine trip, reactor controls sensed a power mismatch and automatically inserted control rods to control reactor coolant temperature. However, with half of the steam dumps out-of-service, operators were unable to stabilize reactor power and inserted a manual reactor trip The inspectors reviewed operator and equipment performance during the transient and noted no significant issues; however, the inspectors noted that the P-9 permissive was in effect at the time of the transient. The P-9 permissive is a TS reactor protection system feature that bypasses the reactor trip on a turbine trip when the reactor power is less than 50 percent. At Point Beach, the plant design was that the condenser steam dump system, when at full functional capacity, was capable of coping, without operator involvement, with a 40 percent load rejection and an additional 10 percent load reduction can be accounted for by the insertion of the control rods. The inspectors were concerned that the designed automatic plant response following the turbine trip was defeated as a result of the the licensee taking half of the steam dumps out-of-service. Had the steam dump system been at full capacity, the transient would have been much smaller, more easily controllable, and would have required little, if any, manual operator intervention The inspectors reviewed generic plant information and found that not all Westinghouse plants utilize the P-9 permissive and that the permissive is a function of steam dump capacity. Subsequently, the inspectors reviewed the licensees current licensing basis and were unable to determine, before the end of the inspection period, if the steam dump capacity was a basis or an input into design assumptions for the P-9 permissive circuit. However, the related TS basis stated that Below the P-9 setpoint, a load rejection can be accommodated by the Steam Dump System, and In MODE 1, a turbine trip could cause a load rejection beyond the capacity of the steam dump system, so the Power Range Neutron Flux interlock must be OPERABLE. The inspectors concluded that with half of the steam dump capacity unavailable, the load rejection could not have been accommodated by the steam dump system as stated. Based on the statements in the TS basis, the licensee is reviewing the acceptability of bypassing steam dumps below 50 percent reactor power and continuing to call the P-9 function operable with less than full steam dump capacity available The inspectors further questioned the licensees statement in AR 01175719, initiated on June 21, 2010, which stated in this alignment with four dumps out-of-service, the condenser steam dumps do not operate as designed in Automatic, therefore, the mode selector switch will be placed in manual....The switch will be left in manual throughout the duration of the condenser water box cleaning. The condition report further stated that in manual/pressure control mode, the steam dump valves no longer have the ability to blow open in less than 3 seconds; instead, the steam dump valves could take as long as 20 seconds to open in this mode This issue is unresolved pending the licensees evaluation of the technical basis for the P-9 permissive reactor protection interlock, and pending the evaluation of the effects of operation below 50 percent power with steam dump valves outof-service or in manual mode (URI 05000266/2010003-04; 05000301/2010003-04, Potential Degradation of Reactor Protection System P-9 Permissive Operability). |
| Site: | Point Beach  |
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| Report | IR 05000266/2010003 Section 1R20 |
| Date counted | Jun 30, 2010 (2010Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.2 |
| Inspectors (proximate) | K Barclay M Kunowski M Thorpe Kavanaugh N Feliz Adomo P Cardona Morales R Ruiz S Burtond Chyud Mcneil K Barclay K Carrington M Garza M Kunowski M Phalen P Cardona Morales R Krsek R Ruiz S Burton |
| INPO aspect | |
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Finding - Point Beach - IR 05000266/2010003 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Point Beach) @ 2010Q2
Self-Identified List (Point Beach)
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