ML20195J741
| ML20195J741 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 11/17/1998 |
| From: | Levis W COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| BYRON-98-0298, BYRON-98-298, NUDOCS 9811250056 | |
| Download: ML20195J741 (5) | |
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Commonwealth Edison Company ll)nm Generating Station 4150 North German Church Road Ilyron. IL 61010-9794 l
Tel H15-2344441 l
November 17,1998 LTR:
BYRON 98-0298 FILE:
3.03.0800 U.S. Nuclear Regulatory Commission
- ATTN: Document Control Desk Washington, D.C. 20555-0001
Subject:
Cancellation of Licensee Event Report 97-011, Revision 0; Docket Number 50-454 The Byron Generating Station is submitting this letter to cancel Licensee Event Report 97-011, Revision 0, Docket Number 50-454. Enclosed for your review is the analysis and justification for this cancellation request.
Sincerely, 7 nn-kkh
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l William Levis Station Manager Byron Nuclear Power Station
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Enclosure:
Licensee Event Report No.97-011 cc:
James E. Dyer, NRC Region III Administrator
~1 NRC Senior Resident Inspector
'j{ l INPO Record Center Comed Distribution List l
1 t' ~ r p ty 9811250056 981117 PDR ADOCK 05000454 S
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A ATTACHMENT JUSTIFICATION FOR THE CANCELLATION OF LER
. NO. 97-011: DOCKET NO. 50-454 i
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BACKGROUND i
On June 26,1997, Byron Station submitted LER report number 97-011; Docket Number 50-454,
.in acco'rdance with the reporting requirements of 10CFR50.73(a)(2)(i) and 10CFR50.73(a)(2)(ii).
The report was submitted due to an identified nonconforming condition related to the Byron Unit 1 Safety Injection (SI) pump lube oil cooler. The identified condition was a missing support bracket on the IB Safety Injection Pump Lube Oil Cooler. The bracket was designed, as an equipment restraint required for seismic qualification of the lube oil cooler and the attached i
piping. The bracket was found missing during an NRC plant walkdown on May 27,1997.
Subsequently, the missing support bracket was documented in the Byron Corrective Action Program's Problem Identification Form (PIF).
DISCUSSION The root cause of the event reported in LER No.97-011 is still unknown as originally reported.
The LER contained information regarding the root cause analysis performed in an attempt to identify the cause of the event. During the root cause analysis investigation, it was determined that several work process deficiencies most probably contributed to the missing 1B SI Pump Lube Oil Cooler Support Bracket. Corrective actions provided in the LER have now been completed and resulted in an improved work control process. The improved work control process has taken lessons learned from this event to improve the criteria and accountability of the inspection and preventive maintenance verification to inspect the equipment worked on for completeness of installation. The improved criteria provides the maintenance supervisors with the direction to inspect completed work for completeness ofinstallation following maintenance activities.
Additionally, the contents and issues contained in the LER were reviewed with the appropriate maintenance personnel to emphasize the human performance deficiencies that were identified as contributors to this event. This review strengthened the supervisor's and worker's levels of comprehension in identifying the human performance deficiencies as the underlying cause for the existence of the process deficiencies that were identified by the Root Cause Investigation.
Furthermore, the LER was assigned for review to the SRO Licensed re qualification training program to emphasize the applicability of related technical specifications when determining equipment operability concerns due to potential structural component deficiencies.
Initially, at the time of discovery, the Byron Station conservatively declared the IB SI pump inoperable. A seismic reanalysis of the afTected piping was not performed at time of discovery during the period of the operability evaluation. Without the reanalysis, it was not known that the pump and piping were operable. A follow up to the LER from discussions with the Byron NRC Resident Inspector, working on closing out the issue, resulted in an additional action item by Byron Station in order to close out the LER. The action was to address the technical aspects of the nonconforming condition by re-evaluating the seismic adequacy of the piping configuration that existed during the time period that the support bracket was missing. The objective was to determine if the nonconforming configuration would have been able to withstand the effects of a design basis seismic event without adversely affecting the safety function of the lube oil cooler and subsequently the safety related design function of the Safety injection (SI) pump.
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- Attachment LER 97-011 Cancellation Page 2 ANALYSIS An engineering analysis was performed (Comed Calculation No. 043824 Addendum C dated October 15,1998) to evaluate the effect of the missing support bracket for the IB SI pump bearing oil cooler subsystem. The analysis was conducted with the understanding that the new analyzed configuration was not representative of the original design basis, but rather, was representative of the as found condition with the bracket missing. Notably, shortly after initial identification of the issue, the system _was restored back to its original design basis.
The subsystem in question consists of a small portion of the Essential Service Water (SX) system supply and return lines to the oil cooler. A review of the original design basis analysis concluded that the lube oil cooler configuration (with both support brackets installed) was modeled as the anchor point for the subsystem piping seismic analysis. Anchor points are modeled in piping l
dynamic analysis as rigid attachment points where no torsional, translational, and axial displacements are assumed to occur under the design basis accident loading conditions. In other words, the anchor point is assumed to not be affected by the induced forces and reactions, and remains rigid without any deflection occurring in all six degrees of freedom.
The method used to perform the analysis was to model the portion of the supply and return piping to the bearing oil cooler using the Integrated Piping Analysis System (PIPSYS) computer program. The model, with all its dimensions used to perform the analysis, was developed from As-Built piping isometries in the Comed controlled drawing system. Also, the pipe support drawings were reviewed for accuracy against the installed plant configuration. Pipe stresses due to internal pressure, deadweight, operating basis earthquake (OBE), and safe shutdown
- earthquake (SSE) were determined using equations 8 and 9 of the ASME Section III Code i
Sections ND-3652.1 and 3652.2 respectively. The stress allowables for the various service levels are provided in section ND-3611.2 of the ASME Section III code. The design basis loading combinations for the service levels are defined and provided in Comed Piping Design
. Specification document 01-10-52, Revision 1, Table CL2-3.5.2.1-1. Flanges in the piping system were also evaluated using the PIPSYS program. The method used by the PIPSYS program is consistent with the method contained in Section ND-3658 of the ASME code.
i The SX piping system does not meet the criteria for high energy line systems and therefore does not need to be evaluated for high energy line break analysis Due to the moderate energy lines that comprise the system, it is also not required to postulate pipe breaks in the analysis of these l
lines: Section CL2-3.5.3.7 of the Comed Piping Design Specification contains the guidance to establish SX piping system functional capability by comparing the analyzed stresses with the corresponding allowables. This is done conservatively by comparing the analyzed SSE stresses against the OBE allowable.
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- Attachment LER 97-011 Cancellation Page 3 j
The only valves modeled into the analysis of this subsystem were 1-1/2" manually operated ball valves procured to Comed specification F-2918. Per the Piping Design Specification, end load check for valves are only required for valves procured to specification F/L-2702. There are rm valve nozzle end limits specified for these valves, as the valve body is stronger than the pipe. The analyzed acceleration values for these valves were reviewed and compared to the allowable contained in the Piping Design Specification and found to be acceptable.
The pipe support loads for the supports adjacent to the cooler nozzles were compared to the design basis qualified loads. All analyzed support loads were found to be acceptable with significant margin to the allowable loads. The loads on the supports further from the cooler were not checked since these supports were included for modeling purpose only and those loads were i
less accurate due to the presence of the fictitious anchors modeled. Additionally, the supports farther from the cooler were less likely to be affected by loads resulting from the missing bracket.
CONCLUSION In conclusion, the PIPSYS analysis of the portion of the SX piping that was included in the model j
documented in Comed calculation 043824 Addendum C, for the condition of the missing support bracket on the IB SI pump bearing oil cooler, was found to be within the allowable pipe stresses, with significant margin. No moderate energy leakage cracks were postulated, as it was not required for this system. It was also determined that the analyzed portion of the modeled piping met the functionality capability criteria as required by Comed Piping Design Specification Document # 01-10-52, Revision 1. Furthermore, the pipe support loads were acceptable and the remaining cooler support bracket was determined to be capable of sustaining the loads applied to it from a design basis event without loss of function to the bearing tube oil cooler. Therefore, the subsystem remained fully qualified even with the missing support bracket and reasonable assurance has been demonstrated to show that the missing bracket would not have affected the function of the bearing lube oil cooler. Thus, the safety function of the SI pump would have not been affected during an emergency during the time period that the bracket was missing.
Therefore, reasonable assurance has been demonstrated and documented to show that LER report number 97-011; Docket No. 50-454 may be cancelled due to the component not being in a inoperable or degraded condition during the period of time that the support bracket was missing.
Furthermore, Comed has now concluded that the SI pump operability was never degraded or challenged and that the reportable event may be retracted. Comed conservatively declared the Si inoperable at the time of discovery.
Additionally, Comed once again concludes that the health and safety of the public were never challenged or compromised during the time that the Si pump bearing lube oil cooler bracket was missing as previously reported.
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