RS-17-119, Braidwood, Units 1 and 2 - Full Action Request Report AR 789791, Potential Loss of Margin in Ms Tunnel Pressurization Calc., Redacted
Text
Go Back Print l New Search l Home AR Number: 00789791 Linked ARs Aff Fac:BraidwoodAR Type: CRStatus:COMPLETEAff Unit: 01Owed To: A8952CAPDue Date:01/21/2009Aff System:
MSEvent Date:06/20/2008 CR Level/Class:
4/DDisc Date:06/20/2008 How Discovered:H03F Orig Date:06/24/2008 Action Request Details
Subject:
POTENTIAL LOSS OF MARGIN IN MS TUNNEL PRESSURIZATION CALC
Description:
Originator: Supv Contacted: Condition
Description:
Based on Byrons IR#789344, Byron was reviewing calculation 3C8-0282-001,Main Steam Tunnel Pressure Study for Main Steam Line Break, for AF FSOstructural margin issues. This calculation is the basis for UFSAR section C3.6 for HELBs in the MS Tunnel. The concerns arise when considering thevent paths assumed in the calculation for pressurization. The MSIV room personnel access door at elevations 401 and the HVAC blank off plates atelevation 416 are assumed to blowout at a pressure of 1.5 psid. Byronnoted that security bars and screen mesh are located on the outside of theHVAC discharge damper and blowout panel area; if the blank off platesblowout they will be captured by the security grating and screen meshgreatly reducing the assumed venting capability. Also, the assumption thatthe blowout blank-off plates will fail at 1.5 psid such that venting occurs (it appears reasonable that the access door would fail at therequired 1.5 psid). Simple calculations find that a pressure in excess of1.5 psid is required to fail the plate itself.A walkdown was performed at Braidwood and determined that both U-1 and U-2A/D MSIV rooms have an approximate 92 x 46 blank-off plate, 3/16 inchthick with 5/8 diameter bolting (see M-1265 Sht 2). The U-1/U-2 B/C MSIVrooms have an approximate 33 x 45 blank-off plate, 3/16 inch thick with5/8 diameter bolting. Simple calculations find that a pressure in excessof 1.5 psid is required to fail the plate at Braidwood also. SimilarMSIV room security bars and screen mesh are installed at Braidwood, thus,this issue applies to Braidwood also.For an MSIV room containing two MSIVs, the calculation assumes 4 ventpaths; the 2 archways into the tunnel (73 ft2 each), one HVAC blowoutpanel at 51.3 ft2 and the remaining vent path consists of a blowoutpanel/401 access door combination at 75.8 ft2 for a combined vent area of273.1 ft2. Given that the vent paths in question represent approximately 40 pct of the total vent area, a significant increase in MSIV roompressure would be expected if these paths were to fail to function (eitherdue to capture by security grating or failure to detach from thestructure). Exacerbating this is that choked flow conditions exist at one of the archways into the tunnel; this means that an increase in MSIV roompressure due to the obstructed vents will not result in a fully offsetting increase in flow out the remaining vents paths. As room pressure increases, the remaining archway flow would most likely choke.Page 1of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet The failure of the vent paths potentially could result in pressuresgreater than previously analyzed. This in turn could challenge the alreadymarginal AF/FSO structural limits and require increasingly qualitativearguments for AF013 operability.There are 4 mitigating factors to offset the blowout panel concerns:1. A recent change to the UFSAR negates the need to consider breaks in theMSIV room itself (the current limiting location). However regulatorycorrespondence between ComEd and NRC in an SER dated 1/07/85 stillrequires breaks to be postulated in the tunnel. Calculation 3C8-0282-0001does contain results for a break in the MS tunnel and gives a peakpressure of 13 psi in the MSIV room and 16.5 psi in the tunnel justoutside the MSIV room assuming that the blowout panels function. Thisdoes demonstrate that a break outside the room results in lower pressuresin the room.2. The availability of the vent path via the access door at 401 elevationto open at 1.5 psid is not in question. This is supported by review ofcalculation 3C8-0182-0001 for a comparable door.3. A simplified, informal model of the MSIV rooms (without any blowoutpanels/HVAC dampers or door) was constructed by Corporate Engineering using an approved software (GOTHIC). The significant change made was inusing more realistic mass and energy inputs from RELAP. Using this model the highest pressure in the MSIV room (for a break in the room ) is 21.3psig. Note that although this is slightly higher than the 19.7 psigcurrently assumed in the UFSAR the expected value for a break in thetunnel would be a few psi lower (based on paragraph 1 above).4. Because the peak HELB impulse pressure occurs within the first few seconds of the accident, a vent path exists through the MSIV room ventilation fans that is not credited in the existing analysis. Although the discharge dampers for the MSIV room fans are failed closed, the fans would be expected to be running prior to the accident, and would continueto run with the discharge damper open for the first few seconds of theaccident until the fans would eventually trip causing the damper to close.Based on the above, Byron and Braidwood engineering believe there isreasonable assurance that structures and components will not be exposed to pressures resulting in excessive degradation or failure. Sargent and Lundyhas been contacted for a more refined analysis on an expedited basis toconfirm existing margin remains acceptable for existing MSIV HELB analysis.Immediate actions taken:Discussed with Corporate Engineering, S&L, Bwd & Byron Engineering.Recommended Actions:
Work Group Eval to Design Engineering to document results of applicableS&L study and create actions for long term resolution of issue in calcsand drawing changes as necessary.List of knowledgeable individuals:Repeat or similar condition?
NoOperable Basis:Based upon current calculations, there is reasonable assurance thePage 2of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet resulting pressure is bounded by current analysis. If reanalysis resultsare less conservative, reroute for further operability evaluation.
Reportable Basis:The EXELON Reportability Reference Manual was reviewed, and no reportability requirements were identified.Based upon current calculations, there is reasonable assurance the resulting pressure is bounded by current analysis. If reanalysis results are less conservative, reroute for further operability evaluation.
Reviewed by: 06/26/2008 05:40:47 CDTReviewer Comments:No additional comments.SOC Reviewed by: 06/26/2008 07:27:17 CDTSOC Comments:(6/26/08 ) ATI created to re-route completed WGE to MRC for review.Department review performed by: 07/10/2008 09:23:45 CDT Evaluation Comments:
Condition/Problem Statement:
There are two AF tunnel covers in each Main Steam Isolation Valve (MSIV) room. The covers provide a flood barrier and a HELB barrier between the MSIV room and AF tunnel. The barrier protects the AF013 valves from theeffects of flooding or a HELB in the MSIV rooms. The AF013 valves aremaintained in the open position. If exposed to a harsh environment, these valves may not be able to close to provide their containment isolation function.The covers are designed to perform a sealing function (leak-tight) betweenthe MSIV rooms and AF tunnel for all design loads including seismic.Based on the design analysis (calcu lation 5.6.3.9), the CEAs for the AFtunnel cover support members do not meet the structural design criteriarequirements with respect to safety factor. The design criteria require afactor of safety of 4 while the design analysis uses a factor of safety of1. The effect of this condition is that the design margin for the CEAs isreduced. Additionally, the design analysis does not address the loadingon the cover and support members due to a high energy line break. Failure of the cover or supporting members could expose the AF013 valves (locatedin the AF tunnel) to a harsh environment, which could adversely impact their containment isolation function.The AF tunnel covers are required to remain intact and in place to ensurethat the AF013 valves are protected against the environments due toflooding and HELB within the MSIV rooms. Additionally, the structuraldesign criteria require a factor of safety of 4 to be maintained for CEAs.The possible failure mechanisms associated with this condition are a catastrophic failure of the plate or supporting member, or the plasticdeformation of the cover or supporting member. Either of these scenarios could expose the AF013 valves to an environment for which the AF013 valveshave not been qualified.The AF tunnel covers and associated support components have been qualifiedindependently for the worst case HELB and the worst case flood in the MSIVroom. Since worst-case conditions are used, the potential failure is nottime-dependant. Additionally the potential consequences will not changeover time since worst-case conditions were used.No other OpEvals at Braidwood are associated with the AF tunnel covers.Thus, this non-conforming condition has no impact on the previouslyPage 3of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet evaluated degraded conditions associated with currently open OpEvals.Statement of Cause:The design analysis (calculation 5.6.3.9) for evaluation of the AuxiliaryFeedwater Tunnel flood seal covers did not include the effects of a HighEnergy Line Break (HELB) on qualification of the covers and supportingelements. Additionally, the design analysis uses a non-standard factor ofsafety for qualification of the concrete expansion anchors (CEAs) used tosupport the covers. This condition was initially identified at Byron (IR's 653093 and 620080) and was found to be applicable to Braidwood (IR 654270). This condition affects the qualification of the followingcovers: 1AFFSO1-6, 1AFFSO1-7, 1AFFSO1-8, 1AFFSO1-9, 2AFFSO1-6, 2AFFSO1-7,2AFFSO1-8 and 2AFFSO1-9. Operability Determination #07-007 was performedto evaluate the degraded condition.Revision 1 of OpEval #07-007 change d the due dates of the items listedunder corrective action 1 and corrective action 2. Note that the date forfull qualification (design change installation date) has not changed.Revision 2 of OpEval #07-007 change d the due dates of the items listedunder corrective action 3 and corrective action 4. This changes theimplementation date of the modification to restore full qualification from 05/30/2008 to 12/31/2008 for both Unit 1 and Unit 2. This change isrequired to accommodate the late receipt of materials required toimplement the modification (Unit 2 materials have arrived; Unit 1 materials have not yet been received). The new due date has been selected to ensure the job can be appropriately planned to minimize installationtime, since the work will not be performed during a refueling outage. Thedegraded condition is not time-dependent; the change in implementationdate is judged acceptable.
Revision 3 of OpEval #07-007 incorporates dynamic loading factors. TheNRC identified a concern related to the justification of operabilitycontained in Revisions 0 through 2 of this OpEval after reviewing Calculation 5.6.3-BRW-08-0045-S, Structural Evaluation of the Flood SealCover Support in the MSIV Rooms, Unit 1 Per EC 369245. This calculationsupports the modification to restore full qualification of the Unit 1 AFTunnel Flood Seals and utilized a dynamic load factor of 2.0 to addressthe peak HELB accident impact load condition of the flood seal cover plateand supporting members. Revisions 0 through 2 of this OpEval did notaddress HELB accident impact load conditions. In addition, Revision 3 ofthis OpEval was completely reformatted to Revision 6 of OP-AA-108-115.Revision 4 of OpEval #07-007 addresses discrepancies identified in IR789791 related to the HELB analysis of record, 3C8-0282-001. The HELBanalysis credited vent paths via blank off plates in the MSIV Rooms.However, the physical construction of the blank off plates prevents themfrom acting as a vent path. In addition, a modified version on the AREVA(Framatone) computer model was used to determine the best estimate resultsto support operability. Further reviews of Calculation 5.6.3.9 identifiedadditional inconsistencies in the determination of factors of safety.Extent of Condition:The original design analysis (Calculation 5.6.3.9) for the AF tunnel coverand supporting members was reviewed to determine the impact of the HELB loading on qualification of the plate, shelf angle CEAs, and the C6 (channel) CEAs. Per this design analysis, the minimum calculated factors of safety are as follows:Plate = 1.34Shelf Angle CEA = 1.08C6 (channel) CEA = 1.47These factors of safety are associated with a loading of 15.83 psig due toPage 4of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet a seismic/flood loading. The AF tunnel covers were not originallydesigned to HELB loading conditions.A re-evaluation of the HELB peak pressures was performed by Sargent &Lundy as a result of the discrepancies identified in IR 789791 for eachunit. Preliminary results from this evaluation indicated that it may be prudent to temporarily modify the blank off plates in the MSIV rooms toprovide additional relief paths in the event of a HELB. ECs 371256 (Unit1) and 371262 (Unit 2) were issued to install foam panels to replace theexisting panels as a Compensatory Measure. These installations arecomplete for both units. Further results from this evaluation indicatedthat it may also be prudent to reinforce the AF tunnel covers to provideadditional margin as a Compensatory Measure. ECs 371281 (Unit 1) and371283 (Unit 2) were issued to install tube steel bracing on the AF tunnelcovers. These TCCs were designed based on a peak pressure of 20 psig witha dynamic load factor of 2.0 (effective peak pressure of 40 psig) toensure all factors of safety are greater than 2. Both compensatorymeasures were initiated to enhance an operable, but degraded condition toensure that the AF tunnel covers will continue to perform their specifiedsafety function.The re-evaluation of the HELB peak pressures utilized new mass-energyvalues as documented in EC 371293. The re-evaluation determined that thepeak pressure for Unit 1 is 21.7 psig and for Unit 2 the peak pressure is19.4 psig. Dynamic load factors consistent with the new peak pressure and load history were determined by Sargent & Lundy to be 1.01 for both units.
In addition, further margin was recovered from conservatisms inCalculation 5.6.3.9. EC 371345 was a pproved which captures all thechanges related to the HELB loading and determined the following factorsof safety for the CEAs:Unit 1 Unit 2 Shelf Angle CEA = 1.25 Shelf Angle CEA = 1.39C6 (channel) CEA = 1.28 C6 (channel) CEA = 1.43The above factors of safety are applicable with the blank off platesmodified and prior to the installation of the tube steel bracing on the AF tunnel covers. As of the date of this OpEval revision, the tube steelbracing of the Unit 1 AF tunnel covers has been installed under EC 371281.With this EC installed all factors of safety are nearly 4 and designmargin is restored.As indicated above, the factors of safety for the Unit 2 CEAs are lessthan 2 and the installation of the tube steel bracing of the Unit 2 AFtunnel covers is pending.Load capacities for CEAs are determined by testing numerous anchors undercontrolled conditions. Ultimate loads are based on a mean average ofthese test results and are normally reduced for design applications to account for any differences from the controlled conditions that may exist in the field. Safety factors for concrete expansion anchors are introduced to account for three key issues; 1) loose bolts/undertorque; 2)inaccurate load distribution/modeling; and 3) cyclic loading. None ofthese issues are applicable to the CEAs installed in the support detailsfor the AF tunnel covers as discussed below:Loose Bolts/Undertorque:The anchors used in this installation were installed to the requirements of Byron/Braidwood Specification F/L-2722, Form 1778 and SpecificationBY/BR/CEA, the installation specifications in place at that time ofinstallation. Conformance to the requirements of these specificationswere ensured by an approved Quality Assurance program, which included inspections to ensure each anchor was installed to required specificationsPage 5of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet including minimum embedment depth, angularity, minimum spacing, andminimum installation torque. Each of these parameters provide additionalassurance that the conditions present in field are consistent with the tested conditions. Therefore, loose anchor bolts are not expected andvisual inspections verified that the installed anchors show no indicationof localized degradation or cracking that could adversely impact the CEAperformance.Inaccurate Load Distribution/Modeling:The shelf angle configuration at one edge of the plate consists of asingle row of bolts resisting the vertical load from the plate. The calculations contained in Calculation 5.6.3.9 account for the verticalload and resulting moment causing both shear and tensile force on theanchors. The single row of bolts is not conducive to load distributiondue to plate flexibility that is normally considered in a typical multiple bolt base plate arrangement. Similarly, the CEAs for the channel support member are loaded in direct shear and are not subject to additional forcescaused by base plate flexibility.
Cyclic Loading:
The CEAs used in this application (closure plate support) experiencesignificantly different conditions than those used in a typical pipingsystem or equipment support applications. For example, piping supportsare typically subject to cyclic loading due to changing operating conditions experienced during heat-up or cool-down, or due to flow inducedvibration. For the closure plate, there are no significant loads appliedduring normal operation. Therefore, the installed condition of the CEAsat the time of the postulated HELB event would not be appreciably different than when they were originally installed.A HELB load is not a normal working load or sustained load. When takinginto account the higher loading conditions due to a one-time, non-recurring and short duration accident load such as a HELB event, aminimum factor of safety of 1.25 for Unit 1 and 1.39 for Unit 2 is adequate to provide reasonable assurance that the CEAs will perform asrequired on the AF tunnel covers. Thus, although the CEAs do not conformto the administrative limit for safety factors applicable to CEAs (safetyfactor of 4), operability is supported.From Calculation 5.6.3.9, the original FOS for the plate (1.34) was basedon the collapse load determined from the Formulas for Stress and Strain.
As cited in the reference, the equation used to determine the collapse load used is subject to a 30% error. Therefore, based on the low FOS, further analyses is required to justify the continued acceptability of the
-inch plate for the revised HELB pressure load.
Preliminary Elastic Plastic Large Displacement Time History Finite ElementAnalyses were performed using the pressure time histories for both Byronand Braidwood Units 1 and 2. The results of this analytical work showthat there is reasonable assurance that the steam tunnel cover plates will withstand the applicable pressure loading without failure. The results ofthis work also show that the stress in the central section of the plate is at yield value of 36 ksi (i.e, the stress in the rest of the plate isunder the material yield value of 36 ksi and additional margin exists).
The maximum displacement anywhere in the plate is 0.4". Therefore, operability is supported for the -inch plate.Operability for both the plate and the CEAs is supported. Fullqualification will be restored by the installation of permanent designchanges EC 369245 for Unit 1 and EC 369246 for Unit 2.There are no followup actions required for this WGE. Any identifiedcorrective and compensatory actions are being tracke d per operabilityevaluation #07-007.Evaluation of any SOC Comments:Page 6of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet MRC Reviewed by: 07/21/2008 11:56:38 CDTMRC Comments:
++++++++++++(7/21/08 ) Per MRC (Engineering Director), Engineering to track anddocument past operability in CAP.
+++++++++++++Page 7of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet Assign #: 01 AR #: 00789791 Aff Fac:BraidwoodAssign Type:TRKG Status:COMPLETEPriority:Assigned To:Due Date:07/14/2008Schedule Ref:Prim Grp:ACAPALLOrig Due Date:07/14/2008Unit Condition:Sec Grp:
Assignment DetailsSubject/Description:POTENTIAL LOSS OF MARGIN IN MS TUNNEL PRESSURIZATION CALC Assignment CompletionIn Progress Notes:Completion Notes:Page 8of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet Assign #: 02 AR #: 00789791 Aff Fac:BraidwoodAssign Type:ACIT Status:COMPLETE Priority:Assigned To:
Due Date:07/15/2008Schedule Ref:
Prim Grp:A8901RAOrig Due Date:07/14/2008Unit Condition:Sec Grp: Assignment DetailsSubject/Description:Re-route completed WGE to MRC for review Assignment CompletionIn Progress Notes:Completion Notes:The WGE has been routed to the MRC. This ATI is complete. 7/15/08 Page 9of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet Assign #: 03 AR #: 00789791 Aff Fac:BraidwoodAssign Type:OPDB Status:COMPLETE Priority:Assigned To:
Due Date:07/01/2008Schedule Ref:
Prim Grp:A8952DEROrig Due Date:07/01/2008Unit Condition:Sec Grp: Assignment DetailsSubject/Description:Revise OpEval 07-007 (Rev. 4)
Assignment CompletionIn Progress Notes:1.0 ISSUE IDENTIFICATION:Title: AF Tunnel Cover Bolt Evaluation Uses Non-standard Safety Factor1.1 IR #: 654270 (Rev. 0,1,2), 783849 (Rev. 3), 789791 (Rev. 4)1.2 OpEval #: 07-007 Revision: 41.3 EC Number: N/A Revision: N/AGeneral Information:1.4 Affected Station(s): Braidwood1.5 Unit(s): 1 and 2 1.6 System: AF 1.7 Component(s) Affected: Unit 1 and 2 Aux. Feed Tunnel Flood Seals1.8 Detailed description of what SSC is degraded or the nonconformingcondition, by what means and when first discovered, and extent ofcondition for all similarly affected SSCs:The design analysis (calculation 5.6.3.9) for evaluation of theAuxiliary Feedwater Tunnel flood seal covers did not include the effectsof a High Energy Line Break (HELB) on qualification of the covers andsupporting elements. Additionally, the design analysis uses anon-standard factor of safety for qualification of the concrete expansionanchors (CEA's) used to support the covers. This condition was initiallyidentified at Byron (IR's 653093 and 620080) and was found to be applicable to Braidwood (IR 654270). This condition affects thequalification of the following covers: 1AFFSO1-6, 1AFFSO1-7, 1AFFSO1-8,1AFFSO1-9, 2AFFSO1-6, 2AFFSO1-7, 2AFFSO1-8 and 2AFFSO1-9.Revision 1 of this OpEval changed the due dates of the items listedunder corrective action 1 and corrective action 2. Note that the date forfull qualification (design change installation date) has not changed.Revision 2 of this OpEval changed the due dates of the items listedunder corrective action 3 and corrective action 4. This changes theimplementation date of the modification to restore full qualification fromPage 10of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet 05/30/2008 to 12/31/2008 for both Unit 1 and Unit 2. This change isrequired to accommodate the late receipt of materials required toimplement the modification (Unit 2 materials have arrived; Unit 1materials have not yet been received). The new due date has been selected to ensure the job can be appropriately planned to minimize installation time, since the work will not be performed during a refueling outage. The degraded condition is not time-dependent; the change in implementationdate is judged acceptable.Revision 3 of this OpEval incorporates dynamic loading factors. TheNRC identified a concern related to the justification of operabilitycontained in Revisions 0 through 2 of this OpEval after reviewingCalculation 5.6.3-BRW-08-0045-S, Structural Evaluation of the Flood SealCover Support in the MSIV Rooms, Unit 1 Per EC 369245. This calculationsupports the modification to restore full qualification of the Unit 1 AF Tunnel Flood Seals and utilized a dynamic load factor of 2.0 to address the peak HELB accident impact load condition of the flood seal cover plateand supporting members. Revisions 0 through 2 of this OpEval did notaddress HELB accident impact load conditions. In addition, Revision 3 ofthis OpEval was completely reformatted to Revision 6 of OP-AA-108-115.Revision 4 of this OpEval addresses discrepancies identified in IR 789791 related to the HELB analysis of record, 3C8-0282-001. The HELB analysiscredited vent paths via blank off plates in the MSIV Rooms. However, thephysical construction of the blank off plates prevents them from acting as a vent path. In addition, a modified version on the AREVA (Framatone)computer model was used to determine the best estimate results to supportoperability. Further reviews of Calculation 5.6.3.9 identified additionalinconsistencies in the determination of factors of safety.2.0 EVALUATION:
2.1 Describe the safety function(s) or safety support function(s) ofthe SSC. As a minimum the following should be addressed, as applicable,in describing the SSC safety or safety support function(s):- Does the SSC receive/initiate an RPS or ESF actuation signal? No- Is the SSC in the main flow path of an ECCS or support system? No.- Is the SSC used to:
- Maintain reactor coolant pressure boundary integrity? No- Shutdown the reactor? No.- Maintain the reactor in a safe shutdown condition? No.
- Prevent or mitigate the consequences of an accident that could resultin offsite exposures comparable to 10 CFR 50.34(a)(1), 10 CFR50.67(b)(2), or 10 CFR 100.11 guidelines, as applicable. Yes.- Does the SSC provide required support (i.e., cooling, lubrication,etc.) to a TS required SSC? No.- Is the SSC used to provide isolation between safety trains, orbetween safety and non-safety ties? No.- Is the SSC required to be operated manually to mitigate a design basis event?- Have all specified safety functions described in TS been included?
Yes.Page 11of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet
- Have all safety functions of the SSC required during normal operationand potential accident conditions been included? Yes.- Is the SSC used to assess conditions for Emergency Action Levels(EALs)? No.There are two AF tunnel covers in each Main Steam Isolation Valve (MSIV)room. The covers provide a flood barrier and a HELB barrier between the MSIV room and AF tunnel. The barrier protects the AF013 valves from the effects of flooding or a HELB in the MSIV rooms. The AF013 valves aremaintained in the open position. If exposed to a harsh environment, thesevalves may not be able to close to provide their containment isolation function.2.2 Describe the followi ng, as applicable:(a) the effect of the degraded or nonconforming condition on theSSC safety function(s)(b) any requirements or commitments established for the SSC and anychallenges to these(c) the circumstances of the degraded/nonconforming condition,including the possible failure mechanism(s)(d) whether the potential failure is time dependent and whether thecondition will continue to degrade and/or will the potential consequencesincrease(e) the aggregate effect of the degraded or nonconforming condition inlight of other open Op Evals(a) The covers are designed to perform a sealing function (leak-tight)between the MSIV rooms and AF tunnel for all design loads includingseismic. Based on the design analysis (calculation 5.6.3.9), the CEA'sfor the AF tunnel cover support members do not meet the structural design criteria requirements with respect to safety factor. The design criteriarequire a factor of safety of 4 while the design analysis uses a factor ofsafety of 1. The effect of this condition is that the design margin forthe CEA's is reduced. Additionally, the design analysis does not addressthe loading on the cover and support members due to a high energy line break. Failure of the cover or supporting members could expose the AF013 valves (located in the AF tunnel) to a harsh environment, which couldadversely impact their cont ainment isolation function.(b) The AF tunnel covers are required to remain intact and in place to ensure that the AF013 valves are protected against the environments due toflooding and HELB within the MSIV rooms. Additionally, the structuraldesign criteria require a factor of safety of 4 to be maintained for CEA's.(c) The possible failure mechanisms associated with this condition area catastrophic failure of the plate or supporting member, or the plasticdeformation of the cover or supporting member. Either of these scenarioscould expose the AF013 valves to an environment for which the AF013 valveshave not been qualified.(d) The AF tunnel covers and associated support components have been Page 1 2 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet qualified independently for the worst case HELB and the worst case floodin the MSIV room. Since worst-case conditions are used, the potentialfailure is not time-dependant. Additionally the potential consequenceswill not change over time since worst-case conditions were used.(e) No other OpEvals at Braidwood are associated with the AF tunnelcovers. Thus, this non-conforming condition has no impact on thepreviously evaluated degraded conditions associated with currently openOpEvals.YES NO2.3 Is SSC operability supported? Explain basis (e.g., analysis,test, operating experience, X¨ ¨ engineering judgment, etc.):The original design analysis (Calculation 5.6.3.9) for the AF tunnel coverand supporting members was reviewed to determine the impact of the HELBloading on qualification of the plate, shelf angle CEAs, and the C6(channel) CEAs. Per this design analysis, the minimum calculated factorsof safety are as follows:
Plate = 1.34Shelf Angle CEA = 1.08 C6 (channel) CEA = 1.47These factors of safety are associated with a loading of 15.83 psig due toa seismic/flood loading. The AF tunnel covers were not originallydesigned to HELB loading conditions.A re-evaluation of the HELB peak pressures was performed by Sargent &Lundy as a result of the discrepancies identified in IR 789791 for eachunit. Preliminary results from this evaluation indicated that it may be prudent to temporarily modify the blank off plates in the MSIV rooms to provide additional relief paths in the event of a HELB. ECs 371256 (Unit1) and 371262 (Unit 2) were issued to install foam panels to replace theexisting panels as a Compensatory Measure. These installations arecomplete for both units. Further results from this evaluation indicated that it may also be prudent to reinforce the AF tunnel covers to provideadditional margin as a Compensato ry Measure. ECs 371281 (Unit 1) and371283 (Unit 2) were issued to install tube steel bracing on the AF tunnelcovers. These TCCs were designed based on a peak pressure of 20 psig witha dynamic load factor of 2.0 (effective peak pressure of 40 psig) toensure all factors of safety are greater than 2. Both compensatory measures were initiated to enhance an operable, but degraded condition toensure that the AF tunnel covers will continue to perform their specifiedsafety function.The re-evaluation of the HELB peak pressures utilized new mass-energyvalues as documented in EC 371293. The re-evaluation determined that thepeak pressure for Unit 1 is 21.7 psig and for Unit 2 the peak pressure is19.4 psig. Dynamic load factors consistent with the new peak pressure andload history were determined by Sargent & Lundy to be 1.01 for both units.In addition, further margin was recovered from conservatisms inCalculation 5.6.3.9. EC 371345 was approved which captures all the changes related to the HELB loading and determined the following factorsof safety for the CEAs:Unit 1 Unit 2 Shelf Angle CEA = 1.25 Shelf Angle CEA = 1.39C6 (channel) CEA = 1.28 C6 (channel) CEA = 1.43The above factors of safety are applicable with the blank off platesmodified and prior to the installation of the tube steel bracing on the AF Page 1 3 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet tunnel covers. As of the date of this OpEval revision, the tube steelbracing of the Unit 1 AF tunnel covers has been installed under EC 371281.With this EC installed all factors of safety are nearly 4 and designmargin is restored.As indicated above, the factors of safety for the Unit 2 CEAs are lessthan 2 and the installation of the tube steel bracing of the Unit 2 AF tunnel covers is pending.Load capacities for CEAs are determined by testing numerous anchors undercontrolled conditions. Ultimate loads are based on a mean average ofthese test results and are normally reduced for design applications toaccount for any differences from the controlled conditions that may exist in the field. Safety factors for concrete expansion anchors are introduced to account for three key issues; 1) loose bolts/undertorque; 2) inaccurate load distribution/modeling; and 3) cyclic loading. None ofthese issues are applicable to the CEAs installed in the support detailsfor the AF tunnel covers as discussed below:Loose Bolts/Undertorque:The anchors used in this installation were installed to the requirementsof Byron/Braidwood Specification F/L-2722, Form 1778 and SpecificationBY/BR/CEA, the installation specifications in place at that time of installation. Conformance to the requirements of these specifications were ensured by an approved Quality Assurance program, which included inspections to ensure each anchor was installed to required specificationsincluding minimum embedment depth, angularity, minimum spacing, andminimum installation torque. Each of these parameters provide additionalassurance that the conditions present in field are consistent with thetested conditions. Therefore, loose anchor bolts are not expected and visual inspections verified that the installed anchors show no indication of localized degradation or cracking that could adversely impact the CEAperformance.Inaccurate Load Distribution/Modeling:The shelf angle configuration at one edge of the plate consists of asingle row of bolts resisting the vertical load from the plate. The calculations contained in Calculation 5.6.3.9 account for the vertical load and resulting moment causing both shear and tensile force on the anchors. The single row of bolts is not conducive to load distribution due to plate flexibility that is normally considered in a typical multiple bolt base plate arrangement. Similarly, the CEAs for the channel supportmember are loaded in direct shear and are not subject to additional forces caused by base plate flexibility.Cyclic Loading:The CEAs used in this application (closure plate support) experiencesignificantly different conditions than those used in a typical piping system or equipment support applications. For example, piping supportsare typically subject to cyclic loading due to changing operating conditions experienced during heat-up or cool-down, or due to flow inducedvibration. For the closure plate, there are no significant loads appliedduring normal operation. Therefore, the installed condition of the CEAsat the time of the postulated HELB event would not be appreciablydifferent than when they were originally installed.A HELB load is not a normal working load or sustained load. When takinginto account the higher loading conditions due to a one-time,non-recurring and short duration accident load such as a HELB event, a minimum factor of safety of 1.25 for Unit 1 and 1.39 for Unit 2 isadequate to provide reasonable assurance that the CEAs will perform asrequired on the AF tunnel covers. Thus, although the CEAs do not conformto the administrative limit for safety factors applicable to CEAs (safetyfactor of 4), operability is supported.
Page 1 4 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet From Calculation 5.6.3.9, the original FOS for the ?" plate (1.34) wasbased on the collapse load determined from the Formulas for Stress andStrain. As cited in the reference, the equation used to determine thecollapse load used is subject to a 30% error. Therefore, based on the lowFOS, further analyses is required to justify the continued acceptabilityof the ?-inch plate for the revised HELB pressure load.
Preliminary Elastic Plastic Large Displacement Time History Finite ElementAnalyses were performed using the pressure time histories for both Byron and Braidwood Units 1 and 2. The resul ts of this analytical work showthat there is reasonable assurance that the steam tunnel cover plates willwithstand the applicable pressure loading without failure. The results ofthis work also show that the stress in the central section of the plate is at yield value of 36 ksi (i.e, the stress in the rest of the plate is under the material yield value of 36 ksi and additional margin exists).The maximum displacement anywhere in the plate is 0.4". Therefore, operability is supported for the ?-inch plate.Operability for both the plate and the CEAs is supported. Fullqualification will be restored by the installation of permanent designchanges EC 369245 for Unit 1 and EC 369246 for Unit 2.If 2.3 = NO, notify Operations Shift Management immediately.If 2.3 = YES, clearly document the basis for the determination.
YES NO 2.4 Are compensatory measures and/or corrective actionsrequired? X¨ ¨See Section 3.0 for required corrective actions and compensatorymeasures. These actions are required in order to ensure compliance with the structural design criteria.If 2.4 = YES, complete section 3.0 (if NO, N/A section 3.0).2.5 Reference Documents:2.5.1 Technical Specifications and Bases Section(s):3.7.5 Auxiliary Feedwater (AF) System3.6.3 Containment Isolation Valves2.5.2 UFSAR Section(s):3.0 Design of Structures, Components, Equipment, and Systems3.6 Protection Against Dynamic Effects Associated with the Postulated Break of Piping Attach. C3.6 Main Steamline Break in Main Steam Tunnel3.11 Environmental Design of Mechanical and Electrical Equipment15.1.5 Steam System Piping Break at Zero Power 15.1.6 Steam System Piping Break at Full Power2.5.3 Other:Dwg S-895, Rev AD Dwg S-896, Rev. W
Dwg S-969 Rev. AFDwg S-970, Rev AB Dwg S-1062, Rev. X
Dwg S-1088, Rev. N
Dwg S-1093, Rev. U
Dwg S-1502, Rev. G Calc. 5.6.3, Rev. 005 Section 9 Calc. 5.6.3-BRW-96-608, Rev. 001 Calc. 3C8-0282-001, Rev. 003DIT S040-BRW/BYR-8011, Dynamic Load Factors For Aux. Feedwater Hatch CoverEC 371293, B/B MSLB Outside Containment Mass and Energy ReleasesEC 371345, Evaluation of Auxiliary Feedwater Tunnel Fl ood Barrier for Page 1 5 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet Revised HELB Loads -Operability ReviewSpecification F/L-2722, Concrete StructuresDIT S040-BYR/BRW-8013, Analysis of Line Break in Lower Safety Valve RoomDIT S040-BRW/BYR-8012, Aux Feedwater Tunnel Hatch Cover Operability forByron and Braidwood.
Formulas for Stress and Strain, Young -5th Edition.
EC 369245, AF Tunnel Flood Seal Cover Modification, Unit 1EC 369246, AF Tunnel Flood Seal Cover Modification, Unit 23.0 ACTION ITEM LIST:If, through evaluating SSC operability, it is determined that thedegraded or nonconforming SSC does not prevent accomplishment of the specified safety function(s) in the TS and the intention is to continue operating the plant in that condition, then record below, as appropriate,any required compensatory measures to support operability and/orcorrective actions required to restore full qualification. For corrective actions, document when the actions sh ould be completed (e.g., immediate,within next 13 week period, next outage, etc.) and the basis fortimeliness of the action. Corrective action timeframes longer than thenext refueling outage are to be explicitly justified as part of the OpEval or deficiency tracking documentation being used to perform the corrective action.
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Corrective Action #1: Determine scope and extent of change (modification), Get installation estimate. Feed this info to WC for their ATI.Responsible Dept./Supv.: DEM Action Due: Action Complete Basis for timeliness of action: There is no time-dependent degradation concern with this issue. The due date is a reasonable amount of time.
Action Tracking #: 654270-03
____________________________________________________________________________________Corrective Action #2: Determine installation completion date andgenerate appropriate corrective actions.Responsible Dept./Supv.: Work Control Action Due: Action Complete Basis for timeliness of action: There is no time-dependent degradation concern with this issue. The due date is a reasonable amount of time.
Action Tracking #: 654270-04____________________________________________________________________________________
Corrective Action #3: Install a design change on the Unit 1 AF tunnel covers to restore full design margin Responsible Dept./Supv.: MMD Action Due: 12/31/2008 Basis for timeliness of action: There is no time-dependent degradation concern with this issue. The due date is a reasonable amountof time to plan and implement the work.Action Tracking #: 654270-05
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Corrective Action #4: Install a design change on the Unit 2 AF tunnel covers to restore full design margin Responsible Dept./Supv.: MMD Action Due: 12/31/2008Basis for timeliness of action: There is no time-dependentdegradation concern with this issue. The due date is a reasonable amount of time to plan and implement the work.
Action Tracking #: 654270-06 Page 1 6 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet
______________________________________________________________________________________________________________________________________________________________________Compensatory Measure #1: Install temporary design changes EC 371256and EC 371262 to modify blank off plates in the MSIV Rooms.
Responsible Dept./Supv.: MMD Action Due: Complete Basis for timeliness of action: The due date is a reasonableamount of time to plan and implement the work.
Action Tracking #: N/A Effects of the Compensatory Action: Provides an additional reliefpath from the MSIV rooms and margin in the analysis._______________________________________________________________________
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Compensatory Measure #2: Install temporary design changes EC 371281 and EC 371283 to reinforce the AF tunnel covers.
Responsible Dept./Supv.: MMDAction Due: 07/07/2008Basis for timeliness of action: The due date is a reasonableamount of time to plan and implement the work.
Action Tracking #: 789791-04 Effects of the Compensatory Action: Provides additional margin onall factors of safety for the plate and concrete expansion anchors.
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__4.0 SIGNATURES:4.1 Preparer(s) Date 7/1/084.2 Reviewer Date7/1/08 HU-AA-1212 was reviewed and the high est Consequence Risk Factor wasMED (C.4). The probability of error was determined to be low and ExistingProcess Reviews are adequate. EC 371345 contains the analytical basis foroperability. EC 371345 received an ITPR by an off site specialist.4.3 Sr. Manager Design Engg/Designee Concurrence Date 7/1/084.4 Operations Shift Management Approval Date 7/1/084.5 Ensure the completed form is forwarded to the OEPM for processingand Action Tracking entry as appropriate.5.0 OPERABILITY EVALUATION CLOSURE:
Page 1 7 of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet 5.1 Corrective actions are complete, as necessary, and the OpEval isready for closure
Date(OEPM)5.2 Operations Shift Management Approval
Date 5.3 Ensure the completed form is forwarded to the OEPM for processing, Action Tracking entry, and cancellation of any open compensatory measures, as appropriate.Completion Notes:Page 18of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet Assign #: 04 AR #: 00789791 Aff Fac:BraidwoodAssign Type:
CA Status:COMPLETE Priority:Assigned To:
Due Date:07/07/2008Schedule Ref:
Prim Grp:A8922MMOrig Due Date:07/07/2008Unit Condition:Sec Grp: Assignment DetailsSubject/Description:Install ECs 371281 (Unit 1) and 371283 (Unit 2). Tube steel bracing on AF tunnel covers.
Assignment CompletionIn Progress Notes:****COMPLETE FOLLOWING STEPS PRIOR TO COMPLETION OF ASSIGNMENT****1. Prior to start of work on the completion of any CA, ensure you havereviewed the associated CR, investigation, this assignment, and ifnecessary contact the originator to ensure a complete understanding of therequested action.2. Implement the requested actions. (e.g. Procedure should beimplemented not submitted for change)
- 3. Document completion of action by completing each field in thefollowing form or marking NA.
- 4. Additional guidance is provided by clicking here : ClickingHereRecord of Extensions: (Note: Record the date, justification and approvalreceived for each extension)Document Corrective Action: (Note: Restate the requested action)Install ECs 371281 (Unit 1) and 371283 (Unit 2). Tube steel bracing on AFTunnel CoversDocument the Resolution: (Note: Clearly document the implementation ofthe Corrective Action to the requirements of LS-AA-125 Attachment 3."That which is not documented is not done.")Document any changes to the intent of the original Actions (Includeappropriate Department Head Approv al): (Note: Document any deviationfrom the specific action and document the name of the SeniorManager/Director that authorized the deviation)
Document additional assignment determined during evaluation: (Note(s):Do not close to a promise - CA Type Assignments can only be closed toanother CA Type Assignment on a CR)
Page 1 9 of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet Quality Signoff: (Note: Document the name of the person who isaccountable for the completion of this assignment.)
Name: Date:
Document Additional Details here:Completion Notes:ECs 371281 (Unit 1) and 371283 (Unit 2). INSTALLATION COMPLETED ON 07/03/08 11:59 AM. Page 20of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet Assign #: 05 AR #: 00789791 Aff Fac:BraidwoodAssign Type:ACIT Status:COMPLETE Priority:Assigned To:
Due Date:08/25/2008Schedule Ref:
Prim Grp:A8952DEROrig Due Date:08/22/2008Unit Condition:Sec Grp: Assignment DetailsSubject/Description:Per MRC, track and document past operability in CAP.
Assignment CompletionIn Progress Notes:8/20/08 () The results of EC 371692 support a past-operabilitydetermination of the AF013 valves for a postulated MSLB. Note that the AFTunnel covers have since been modified to provide additional structuralsupports such that their current configuration represents a significantincrease in margin beyond that reviewed within this evaluation. Inaddition, blowout panels in the upper areas of the valve rooms (neglectedin this evaluation) have also been provided to minimize the pressuretransient in the valve rooms.The following text is from EC 371692:
Purpose:The purpose of this evaluation is to determine the effect of a postulateddouble-ended Main Steam Line Break (MSLB) event originating in the SafetyValve Rooms, on the steel closure plate assembly protecting the flooropening between the valve room and the Auxiliary Feedwater (AF) Tunnel.This effort represents a best-estimate evaluation to support apast-operability determination for the Byron and Braidwood Units 1 and 2AF013 valves (1 & 2AF013A thru H).Summary of Results:The results of this evaluation support a past-operability determination ofthe AF013 valves for a postulated MSLB. Note that the AF Tunnel covershave since been modified to provide additional structural supports suchthat their current configuration represents a significant increase inmargin beyond that reviewed within this evaluation. In addition, blowoutpanels in the upper areas of the valve rooms (neglected in thisevaluation) have also been provided to minimize the pressure transient inthe valve rooms.Detailed Evaluation:The AF Tunnel covers provide a closure for the access opening between the lower level of the Safety Valve Rooms at Elevation 377'an d the AF Tunnel.This closure plate is intended to protect the components, specifically the AF013 valves, located in the AF Tunnel from the effects of postulated pipebreaks. The MSLB event is considered the most limiting of the pipe breaks with respect to the closure plates.Description:Per References 1 and 2, the floor opening closure plate assembly consistsof a ?-inch thick checkered steel plate supported on all four edges. Oneedge of the closure plate is supported by a shelf angle attached to thetunnel wall using 3/8-inch concrete expansion anchors (CEAs). The otherPage 21of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet three edges are supported by the 3-feet thick (minimum) concrete floorslab between the valve room and the AF Tunnel.(Note: The shorter edge for several of the plates is supported by a 6-inchsteel channel that is in turn supported at the wall and long edge of theconcrete opening. The area adjacent to this channel is filled withconcrete (Refs. 1f & 2F.))The closure plate is fastened to the supporting surfaces with 1/4" minimumdiameter cap screws at 24 inch maximum spacing around its perimeter. A1/8-inch thick rubber/neoprene gasket is provided beneath the plate toprovide a seal between the contact surfaces.
Loading:The pressure loading acting downward on each of the tunnel cover plates was determined per Reference 3. The loading is represented by a time history plot of the maximum effect of a postulated MSLB. These plots wereused as input to finite element analyses (FEA) performed on each of thetunnel cover assemblies.Analysis:Finite element analysis was performed on each of the AF Tunnel cover assemblies as documented in Reference 4. The results of these analyses are provided below:Per Reference 4, p. 4:Three finite element models were defined to bound all 16 flood plateopenings at Byron and Braidwood stations; the models are designated Model A, Model BC, and Model D. Model A bounds all "A" openings, model BC boundsall "B" and "C" openings, and model D bounds all "D" openings. Analysis of these models concludes that the capacity of the flood plates during a pressure transient due to MSLB conditions is limited by the capacity of concrete expansion anchors supporting a single structural steel anglebolted to the wall along the long edge of the plate.Specific results are as follows:? The small capscrews used to secure the flood plates to the floor arenot adequate to carry the full pressure loading. Deflection of the floodplates is sufficient to cause the capscrews to fail at approximately one-half of the peak transient pressure. Once the capscrews have failed,each flood plate is supported by concrete and/or grout on three edges anda shelf angle bolted with four concrete expansion anchors (CEAs) to a wall along the fourth edge.
? The detailed analyses are conducted assuming the capscrews are failed.? Scoping evaluations were performed assuming failure of the CEAs andconsequent loss of the support provided by the shelf angle. Theseevaluations indicate that when the flood plate is supported on only threeedges, the pressure loading results in large vertical deflections thatlead to eventual failure of the plate. However with the shelf angle intact, the flood plate deflections are moderate and the plate will notfail even under the maximum pressure loading. Thus, the CEAs supportingthe shelf angle are the critical structural components in the flood plateclosure assembly.? The ultimate pressure capacity of the flood plate assembly is limited by the ultimate strength of the CEAs. Figures 2-1, 2-2, and 2-3 show theCEA interaction ratios vs. time, along with the pressure time-historiesfor the three models evaluated. The interaction ratio is an ellipticalinteraction equation with 1.0 defined as ultimate capacity, with no additional margin of safety. Margin to failure is the inverse of the interaction ratio.? For grouted openings, the channels supporting the grout and theanchors supporting the channels are less limiting than the shelf angle andthe shelf angle CEAs.
? The number and spacing of the shelf angle CEAs are unverified design Page 2 2 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet inputs. These parameters should be verified by Exelon. Differences betweenthe as-built configurations and those assumed in this calculation mayrequire additional evaluation.The limiting anchor bolt interaction ratios for the shelf angle are provided in Table 5-1 of Reference 4. The maximum interaction ratio determined is 0.90. As discussed above, this value is with respect toultimate anchor capacity.Discussion:The results summarized above demonstrate adequacy of the AF Tunnel coversto withstand the effects of a postulated MSLB; however, this evaluationrequires that additional review of these results be performed. Twospecific aspects of this analysis that will be further discussed are: 1) the effect of the loss of contact pressure at the corners of the plates and 2) the use of the ultimate capacity for the CEAs.1) Loss of Contact Pressure at Corners of Plates:Due to the momentary loss of contact pressure at the corners of the plateduring the MSLB event, the possibility exists that the 1/8-inch thickrubber/neoprene gasket will be dislodged at these locations. Since thecorners do not permanently deform, a maximum gap equal to the thickness of the displaced gasket was assumed to result.
The effect of postulated cover plate corner gaps following the initialMSLB pressure event was evaluated in Reference 5 to demonstrate thecapability of the AF Tunnel cover to limit the environmental effects inthe AF Tunnel below the cover. The results of this evaluation determined that the postulated gaps would result in a temperature no greater thanapproximately 233 oF.As demonstrated in Refe rence 6, the AF013 valves are expected to functionin an environment of 100% relative humidity and at a temperature of atleast 266 oF. Therefore, the presence of the postulated gaps followingthe initial pressure event will not result in an environment such that the AF013 valves would not be capable of performing their design function.2) Use of Ultimate Capacity for CEAs:Load capacities for CEAs are determined by testing numerous anchors undercontrolled conditions. Ultimate loads are based on a mean of these testresults and are normally reduced for design applications to account for any differences from the controlled conditions that may exist in the field. For example, tensile capacity may be reduced by the presence of cracking in the concrete in the vicinity of the anchor, with the magnitude of this effect dependent on the location, quantity and size of the cracking.A field walkdown conducted of the concrete in the area of the AuxiliaryFeedwater Tunnel hatch covers has determined that there is no cracking in the general vicinity of these hatches that would impact the CEAs. Inaddition, the location of the anchors is within the portion of the wall where it intersects with the floor slab (i.e., a support point for the wall). Under MSLB pressure, this portion of the wall will have no tensileforces that would tend to create or open any cracks in the concrete.
Therefore, the effect of cracking on the anchor ultimate capacity isjudged to be negligible.Closely spaced anchors also negatively influence capacities. PerReferences 1 & 2, there are no anchors spaced closer than 14-anchordiameters. This spacing is adequate to eliminate any negative impact of spacing on anchor capacity.Historically, industry concerns for CEA capacity have centered on threekey issues; 1) loose bolts (undertorqued), 2) inaccurate base platestiffness/rigidity and load distribution assumptions or modeling, and 3)the potentially adverse impact of cyclic loading on installed anchors. Asdiscussed below, none of these issues are applicable to the CEA's Page 2 3 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet installed in the support details for the Auxiliary Feedwater Tunnel accesshatch plates. Similarly, the mixing, placement and testing of theconcrete used in the structure are tightly controlled to ensure that theconcrete is sound and will provide conditions similar to the testedconditions.1) Loose Bolts/Undertorque:The anchors used in this assembly were installed to the requirements of Byron/Braidwood Specification F/L - 2722, Form 1778 and SpecificationBY/BR/CEA, the installation specifications in place at that time ofinstallation.Conformance to the requirements of these specifications were ensured by anapproved Quality Assurance program, which included inspections to ensure each anchor was installed to the required specifications including;minimum embedment length, angularity, minimum spacing, and minimum installation torque. Each of these parameters provides additional assurance that the conditions present in the field are consistent with the tested conditions.Therefore, loose anchor bolts due to installation deficiencies are notexpected.2) Inaccurate Load Distribution/Modeling:This concern typically results from the use of simplified models using rigid plate assumptions. The support angle was included with the models developed for the finite element analysis performed in Reference 4. Since any load redistribution due to angle or anchor stiffness will be automatically accounted for in these analyses, there is no inaccuracyintroduced into the load determination for these CEAS.3) Cyclic Loading:The CEAs used in this application (closure plate support) experiencesignificantly different loading conditions than those used in a typical piping system or equipment support applications. For example, pipingsupports are normally subject to cyclic loading whether due to changing operating conditions experienced during heat-up or cool-down, orflow-induced vibration.For the closure plate, there are no significant loads applied duringnormal operation. Therefore, the condition of the CEAs at the time of thepostulated HELB event would not be appreciably different than when theywere originally installed. Furthermore, the postulated pressure event isa one-time load of limited duration, with no cyclic component.Document Summary:The following documentation provides the input and results that supportthe various aspects of this review:
? EC 371547 - Best-Estimate Ma ss & Energy (M&E) Releases? TODI No. EC-371547 - Transmittal of Results of M&E to Sargent & Lundy (S&L)
? Document # 2008-12134 - S&L Calculation of Pressure Time-History Data? TODI No. ENSAF ID# ES0800025 - Tran smittal of Pressure Time-Historyto MPR for Structural Analyses? TODI No. BYR-08-027 - Transmittal of AF Tunnel Cover Details to MPR? Calculation 3101-0025 MPR Structural Analyses / FEA Modeling ofAF Tunnel Cover
? EC 371656 - An Evaluation of Past Auxiliary Feedwater AF013 Valves Environment with Respect to the B/B AF Tunnel MSLB Accident Conditions
==
Conclusion:==
It can be concluded based on the discussion provided above, reasonableevidence exists that the closure plate assemblies for the floor openings between the Safety Valve Room floor and the Auxiliary Feedwater Tunnelwould have remained intact following a MSLB event originating in the Page 2 4 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet Safety Valve Room.Furthermore, the effect of the MSLB event on the closure plates would nothave resulted in any significant adverse environmental conditions that would have prevented the AF013 valves from performing their intended design function.Thus, the results support a best-estimate past-operability determinationfor the AF013 valves for a postulated Main Steam Line Break.
References:
- 1) Byron Design Drawingsa. S-895, Rev. AA
- b. S-896, Rev. U
- c. S-969, Rev. AA
- d. S-970, Rev. AB
- e. S-1062, Rev. X
- f. S-1093, Rev. Q
- g. S-1502, Rev. G2) Braidwood Design Drawingsa. S-895, Rev. AD
- b. S-896, Rev. W
- c. S-969, Rev. AF
- d. S-970, Rev. AB
- e. S-1062, Rev. X
- f. S-1093, Rev. U
- g. S-1088, Rev. N
- 3) Sargent & Lundy Document # 2008-12134, Rev. 0 "Analysis of LineBreaks in Lower Safety Valve Rooms without Blow Out Panels"4) MPR Associates, Inc. Calculation No. 3101-0025-01, Rev. 15) EC# 371656, Rev. 0 "An Evaluation of Past Auxiliary Feedwater AF013Valves Environment with Respect to the B/B AF Tunnel MSLB Accident Conditions"
- 6) EC# 365163, Rev. 0 "Past Operability Review of a Gap in Flood Seal 1DSFSO08"Note: As identified in Reference 4, an unverified assumption was maderegarding the spacing and number of CEAs for the support angle at thewall. Although this assumption is supported based on the informationprovided in the design drawings, shop (i.e, fabrication) drawings andphotographs, due to access requirement s, the as-built spacing and numberof CEAs could not be verified at the time of this analysis.Therefore, the verification of this information will be made as each AFTunnel becomes accessible during planned maintenance activities requiringthe removal of the covers. These verifications are being tracked via AT #00789344-04 and -05 (Byron Unit 1 & 2) and # 00789791-06 and -07 (Braidwood Unit 1 & 2).
The DAR questions of CC-AA-102, Attachment 1A have been reviewed and nonewere determined to be applicable to this activity. This evaluation is fora past-operability determination of the AF013 valves and does not affectthe design basis of any SSC.Completion Notes:
Page 2 5 of 28 Full Action Request Report 8/31/201 7 http://eamgenco.ceco.c om/cap/servlet/ReportFullARServlet Assign #: 06 AR #: 00789791 Aff Fac:BraidwoodAssign Type:ACIT Status:COMPLETE Priority:Assigned To:
Due Date:01/16/2009Schedule Ref:
Prim Grp:A8952DEROrig Due Date:12/19/2008Unit Condition:Sec Grp: Assignment DetailsSubject/Description:Verify CEA spacing on U1 AF Tunnel Covers-Braidwood EC # 371692 documents a structural analysis performed by MPR. The analysis used an assumption for the actual spacing on the shelf angle CEAs. This ATI is to perform verification that the actual spacing is bounded.
Assignment CompletionIn Progress Notes:Status as of 12/12/09:
.
The CEA spacing on three of four hatches has been verified. The remaining AFW tunnel hatch for the 1C MSIV room is scheduled to be performed in
January 2009. The verification of the anchor bolts for the 1C hatch platewill be performed at this time. The due date for this assignment ischanged to 1/16/09.
., Site Engineering, 12/18/08ATI 789791-06The field verification of CEA spacing for shelf angle supporting Aux FeedTunnel hatch covers located in unit 1 A/B/C/D MSIV rooms is completed. Thesummary of results is documented below.Tunnel Hatch No.of CEAs Minimum spacing between CEAs Maximumspacing between CEAs Remarks 1A 4 13.375" 16" 1B 4 12" 12" 1C 4 12" 12" 1D 3 18" 18"The field information for the spacing and number of CEAs for 1A, 1B and 1CMSIV rooms tunnel hatch meets the assumption made in the MPR Analysisdocumented in EC 371692 to support past operability except for 1D MSIV room tunnel hatch where 3 CEAs are installed in lieu of 4. Because theassumption made in the analysis could not be validated for 1 hatch out ofthe four hatches, past operability could not be substantiated. IR 852425is initiated to track this issue and determine additional correctiveactions. Therefore, this ATI may be closed to IR 852425. This item iscomplete.Page 2 6 of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet 1/16/2009** See next page for field information for reference.Completion Notes:See in-progress notes for resolution.
Page 2 7 of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet Assign #: 07 AR #: 00789791 Aff Fac:BraidwoodAssign Type:ACIT Status:COMPLETE Priority:Assigned To:
Due Date:01/21/2009Schedule Ref:
Prim Grp:A8952DEROrig Due Date:12/19/2008Unit Condition:Sec Grp: Assignment DetailsSubject/Description:Verify CEA spacing on U2 AF Tunnel Covers - Braidwood EC# 371692 documents a structural analysis performed by MPR. The analysis used an assumption for the actual spacing on the shelf angle CEAs. This ATI is to perform verification that the actual spacing is bounded.
Assignment CompletionIn Progress Notes:(1/2/09 ) ATI was reopened. The attachment will not be electronicallyarchived since it is an attachment. If the information is critical, pleasedocument the results, otherwise delete the attachment.ATI 789791-07The field verification of CEA spacing for shelf angle supporting Aux FeedTunnel hatch covers located in unit 2 A/B/C/D MSIV rooms is completed. Thesummary of results is documented below.Tunnel Hatch No.of CEAs Minimum spacing between CEAs Maximumspacing between CEAs Remarks 2A 5 10" 11-1/4" 2B 3 12" 14" Total of 4 CEAs including 1st anchor at channel2C 4 13-7/8" 15-1/4"2D 5 12" 12-5/8"The field information for the spacing and number of CEAs for 2A, 2B, 2Cand 2D MSIV rooms tunnel hatch meets the assumption made in the MPRAnalysis documented in EC 371692 to support past operability for unit 2.
There are no further actions. This item is complete.01/21/2009** See next page for field information for reference.Completion Notes:See in-progress notes for the resolution. See in-progress notes for resolution. Page 28of 28 Full Action Request Report 8/31/201 7http://eamgenco.ceco.com/cap/servlet/ReportFullARServlet