ML15286A331
| ML15286A331 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 10/30/2015 |
| From: | Mendiola A J Licensing Processes Branch (DPR) |
| To: | Technical Specifications Task Force |
| Honcharik M C | |
| References | |
| TSTF-412 | |
| Download: ML15286A331 (7) | |
Text
October 30, 2015
Technical Specifications Task Force 11921 Rockville Pike, Suite 100 Rockville, MD 20852
SUBJECT:
TRAVELER TSTF-412, "PROVIDE ACTIONS FOR ONE STEAM SUPPLY TO TURBINE DRIVEN AFW/EFW PUMP INOPERABLE" PROVISION FOR 24 HOURS COMPLETION FOR AN INOPERABLE MOTOR-DRIVEN AUXILIARY FEEDWATER PUMP COINCIDENT WITH ONE INOPERABLE STEAM SUPPLY TO THE STEAM-DRIVEN AUXILIARY FEEDWATER PUMP
Dear Members of the Technical Specifications Task Force:
The Technical Specifications (TS) Task Force (TSTF) submitted Revision 3 to Traveler TSTF-412, "Provide Actions for One Steam Supply to Turbine Driven AFW/EFW Pump Inoperable," on January 10, 2007 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML070100363). The NRC staff published a Notice of Availability in the Federal Register on July 17, 2007 (72 FR 13845), for TSTF-412 (ADAMS Accession No. ML071230105).
Subsequently, during plant-specific reviews to adopt TSTF-412, the NRC identified some potential concerns with the provision for a 24-hour completion time when an inoperable motor-driven auxiliary feedwater (AFW) pump is coincident with one inoperable steam supply to the steam-driven AFW pump. Specifically, during the review of TS 3.7.5, Auxiliary Feedwater (AFW) System, for the incorporation of changes based upon TSTF-412, NRC staff found the Traveler allows 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for a plant condition where the remaining plant equipment can no longer meet the minimum design AFW flow to mitigate the accidents described in Final Safety Analysis Report, Chapter 15, Transient and Accident Analysis.
The concerns were discussed during several meetings. The TSTF provided the NRC staff with a white paper in response to those concerns on several occasions, the first of which was on April 27, 2012 (ADAMS Accession No. ML14328A426). As detailed in the enclosure, upon further review of the TSTF white paper and plant-specific submittals, the NRC staff's concerns are resolved. The NRC staff position is that a 24-hour Completion Time is acceptable and the safety evaluation from 2007 is still valid.
TSTF If you have any questions, please contact Michelle C. Honcharik of my staff at (301) 415-1774 or via e-mail to Michelle.Honcharik@nrc.gov.
Sincerely,
/RA/
Anthony J. Mendiola, Chief Licensing Processes Branch Division of Policy and Rulemaking Office of Nuclear Reactor Regulation
Enclosure:
As stated
Project No. 753 cc: See next page
ML15286A331; *concurred via e-mail; **concurred via e-mail internal memo (ML15162A277) NRR-106 OFFICE DPR/PLPB* DPR/PLPB* DSS/SBPB** DSS/STSB DPR/PLPB NAME MHoncharik DHarrison GCasto (MChernoff for) RElliott AMendiola DATE 10/21/2015 10/27/2015 06/15/2015 10/20/2015 10/30/2015 Technical Specifications Task Force Project No. 753 cc:
Technical Specifications Task Force c/o EXCEL Services Corporation 11921 Rockville Pike Suite 100 Rockville, MD 20852 Attention: Brian D. Mann E-mail: brian.mann@excelservices.com James R. Morris Diablo Canyon Power Plant Building 104/5/21A P.O. Box 56 Avila Beach, CA 93424 E-mail: JY1E@pge.com Joseph A. Clark Entergy Nuclear South 5485 Highway 61 St. Francisville, LA. 70775 E-mail: jclark@entergy.com Otto W. Gustafson Entergy Nuclear Operations, Inc.
Palisades Nuclear Power Plant 27780 Blue Star Memorial Highway Covert, MI 49043 E-mail: ogustaf@entergy.com
Henry L. Hegrat FirstEnergy Nuclear Operating Company P. O. Box 97 Perry, OH 44081 Mail Stop A-210 E-mail: hlhegrat@firstenergycorp.com ENCLOSURE OFFICE OF NUCLEAR REACTOR REGULATION TSTF-412, "PROVIDE ACTIONS FOR ONE STEAM SUPPLY TO TURBINE DRIVEN AFW/EFW PUMP INOPERABLE" The NRC staff has reviewed incorporation of changes based upon Technical Specifications Task Force (TSTF) Traveler TSTF-412 into Technical Specification (TS) 3.7.5 Auxiliary Feedwater (AFW) System.
TSTF-412 recommends two different completion times (48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> or 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) for a condition when one steam supply to the steam-driven AFW pump is inoperable in coincident with one inoperable motor-driven AFW pump. The basis for which completion time is appropriate is whether the capacity of the remaining motor-driven AFW pump can supply 100 percent of the required feedwater flow to the Steam Generators (SG) based upon the requirements to mitigate transients and accident analyses identified in the licensee's Final Safety Analysis Report, typically Chapter 15.
If the remaining motor-driven AFW pump can supply 100 percent of the design flow requirement, then Traveler recommends a 48-hour completion time. If the remaining motor-driven AFW pump cannot meet the design required flow, the Traveler recommends a 24-hour completion time. TSTF-412 evaluation provides the following basis for recommending the 24-hour completion time:
However, for some plant designs there are scenarios in which the combination of an inoperable motor driven AFW train and the turbine driven AFW train inoperable due to an inoperable steam supply can lead to less than 100% AFW flow to the SGs.
Consider, for example, a four loop plant where the steam supplies for the turbine driven AFW train come from two of the SGs. The turbine driven train feeds all four SGs, and each motor driven train feeds two SGs. If one steam supply is inoperable, and the SG with the remaining steam supply becomes faulted due to a Feedline Break (FLB) or Main Steamline Break (MSLB) (whichever is limiting from the standpoint of AFW flow requirements and assuming no single failures), the turbine driven AFW train may not be able to perform its function. If the motor driven AFW train that feeds the two intact SGs is also inoperable, the remaining motor driven AFW train will be feeding only one intact SG. This may not meet safety analysis requirements. Similar scenarios are possible for three loop plants that require two motor driven AFW trains to mitigate a FLB or MSLB. For plants with this design, a Completion Time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is proposed for new Required Actions C.1 and C.2.
TSTF-412 technical evaluation states the following:
Condition A is modified to indicate that the turbine driven AFW train is inoperable due to one steam supply inoperable. With one steam supply inoperable, the turbine driven AFW train is considered inoperable but is still capable of performing its specified function. A new Condition C is proposed that will require restoring an AFW train to OPERABLE status in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if one motor driven AFW train is inoperable and the turbine driven AFW train is inoperable due to one steam supply inoperable. This Completion Time is applicable when the condition could result in the inability of the AFW system to provide 100% of the flow required by the safety analysis for the FLB or the MSLB, whichever is most limiting, assuming no additional single failure.
This Completion Time is reasonably based on the remaining OPERABLE motor driven AFW train, the remaining OPERABLE steam supply to the turbine driven AFW pump, the turbine driven AFW pump still being capable of performing its specified function, and the low probability of an event that would result in the inability of the AFW system to provide 100% of the required flow.
The proposed new Condition C addresses the ability of the AFW system to mitigate the most limiting design basis events (e.g., a FLB or MSLB), excluding a single failure, with one inoperable steam supply to the turbine driven train and an inoperable motor driven train. For example, a typical Westinghouse three-loop design feeds all three steam generators with two motor driven AFW trains and a turbine driven train. The turbine driven AFW steam supplies are taken from two of the steam generators. If the turbine driven AFW train is inoperable due to one steam supply inoperable and a motor driven AFW train is inoperable, and the steam generator with the remaining steam supply is faulted, the remaining motor driven train will be able to feed two intact steam generators. Therefore, the design basis may be met, and the Completion Time of 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> is appropriate.
However, if due to plant design, there are scenarios where 2 out of 3 AFW trains are required for a three loop plant, the more limiting Completion Time of new Condition C (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) is appropriate. For the two loop design, there must be a remaining motor driven train capable of feeding the remaining intact steam generator. TSTF-412 recommendation for a 24-hour completion is based upon the low probability of a particular event occurring during that time and results in the steam-driven AFW pump being unavailable to supplement the remaining motor-driven AFW pump.
The NRC staff supports this approach that the Completion Time is further justified based on the low probability of an event occurring during this interval that would challenge the capability of the AFW system to perform its function. This is consistent with Standard Technical Specification bases philosophy for similar 24-hour Completion Times. The NRC staff position that a 24-hour Completion Time is acceptable is further documented in safety evaluations of the following plant-specific license amendments: Beaver Valley, dated February 21, 2007 (ADAMS Accession No. ML070160593), Waterford, dated October 4, 2001 (ADAMS Accession No. ML012840538), and Point Beach, dated March 25, 2011 (ADAMS Accession No. ML110230016).