ML16165A376
| ML16165A376 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 08/05/2016 |
| From: | Tekia Govan Japan Lessons-Learned Division |
| To: | Bryan Hanson Exelon Nuclear |
| References | |
| CAC MF6111 | |
| Download: ML16165A376 (19) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 August 5, 2016 Mr. Bryan C. Hanson President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville , IL 60555
SUBJECT:
NUCLEAR REGULATORY COMMISSION REPORT FOR THE AUDIT OF EXELON GENERATION COMPANY, LLC'S FLOOD HAZARD REEVALUATION REPORT SUBMITIAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR OYSTER CREEK NUCLEAR GENERATING STATION (CAC NO. MF6111)
Dear Mr. Hanson:
By letter dated July 21 , 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15148A286), the U.S. Nuclear Regulatory Commission (NRC) informed you of the staff's plan to conduct a regulatory audit of Exelon Generation Company, LLC's (Exelon , the licensee) Flood Hazard Reevaluation Report (FHRR) submittal related to the Near-Term Task Force Recommendation 2.1-Flooding for Oyster Creek Nuclear Generating Station. The audit was intended to support the NRC staff review of the licensee's FHRR and the subsequent issuance of a staff assessment.
The audits conducted on August 18, 2015, and January 14, 2016, were performed consistent with NRC Office of Nuclear Reactor Regulation , Office Instruction LIC-111 , "Regulatory Audits,
dated December 29, 2008 (ADAMS Accession No. ML082900195) . The purpose of this letter is to provide you with the final audit report which summarizes and documents the NRC's regulatory audit of the licensee's FHRR submittal.
B. Hanson If you have any questions, please contact me at (301) 415-6197 or by e-mail at Tekia.Govan@nrc.gov.
Tekia V. Govan , Project Manager Office of Nuclear Reactor Regulation Japan Lessons-Learned Division Hazards Management Branch Docket No. 50-219
Enclosure:
Audit Report cc w/encl : Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 NUCLEAR REGULATORY COMMISSION REPORT FOR THE AUDIT OF EXELON GENERATION COMPANY, LLC'S FLOOD HAZARD REEVALUATION REPORT SUBMITTALS RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR OYSTER CREEK NUCLEAR GENERATING STATION BACKGROUND AND AUDIT BASIS By letter dated March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued a request for information to all power reactor licensees and holders of construction permits in active or deferred status, pursuant to Title 1O of the Code of Federal Regulations (1 O CFR) ,
Section 50.54(f), "Conditions of license" (hereafter referred to as the "50.54(f) letter). The request was issued in connection with implementing lessons-learned from the 2011 accident, at the Fukushima Dai-ichi nuclear power plant, as documented in The Near-Term Task Force review of insights from the Fukushima Dai-ichi accident. Recommendation 2.1 in that document recommended that the NRC staff issue orders to all licensees to reevaluate seismic and flooding for their sites against current NRC requirements and guidance. Subsequent staff requirements memoranda associated with SECY-11-0124 and SECY-11 -0137, instructed the NRC staff to issue requests for information to licensees pursuant to 10 CFR 50.54(f).
By letter dated March 12, 2015, Exelon Generation Company, LLC (Exelon, the licensee) submitted its Flood Hazard Reevaluation Report (FHRR) for Oyster Creek Nuclear Generating Station (Oyster Creek) (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15085A046). The NRC is reviewing the aforementioned submittal and has completed a regulatory audit of the licensee to better understand the development of the submittal, identify any similarities/differences with past work completed, and ultimately aid in its review of the licensee's FHRR. This audit summary was completed in accordance with the guidance set forth in NRC Office of Nuclear Reactor Regulation , Office Instruction LIC-111 , "Regulatory Audits, dated December 29, 2008 (ADAMS Accession No. ML082900195).
AUDIT LOCATION AND DATES The audit was completed by document review via a webinar session in conjunction with the use of the licensee's established electronic reading room (ERR) and teleconferences on August 18, 2015, and January 14, 2016.
Enclosure
AUDIT TEAM Title Team Member Organization Team Leader, NRR/JLD Tekia Govan NRC Technical Monitor Michael Willingham NRC Technical Staff Mike Lee NRC Technical Deputy Division Andy Campbell NRC Director Technical Branch Chief Aida Rivera-Verona NRC Technical Branch Chief Christopher Cook NRC NRC Contractor Philip Meyer Pacific Northwest National Lab A list of the licensee's participants can be found in Attachment 2.
DOCUMENTS AUDITED of this report contains a list which details the documents that were reviewed by the NRC staff, in part or in whole, as part of this audit. The documents were located in an electronic reading room during the NRC staff's review. The documents, or portions thereof, that were used by the NRC staff as part of the technical analysis and/or as reference in the completion of the staff assessment, were submitted by the licensee and docketed, as necessary, to complete the staff assessment. These documents are identified in Table 1.
AUDIT ACTIVITIES In general, the audit activities consisted mainly of the following actions:
- Review background information on site topography and geographical characteristics of the watershed.
- Understand the selection of important assumptions and parameters that would be the basis for evaluating the individual flood causing mechanisms described in the 50.54(f) letter.
- Review model input/output files to computer analyses such as FL0-2D to have an understanding of how modeling assumptions were programmed and executed.
Table 1 summarizes specific technical topics (and resolution) of important items that were discussed and clarified during the audit. The items discussed in Table 1 may be referenced/mentioned in the staff assessment in more detail.
EXIT MEETING/BRIEFING On April 29, 2016, the NRC staff closed out the discussion of the technical topics described above. The NRC staff requested that the licensee provide a revised local intense precipitation (LIP) analysis report and model input/output files on the docket for the NRC staff's use to develop the staff assessment, and place the revised LIP
calculation in the ERR for the NRG staff to reference. As of April 28, 2016, all requested documents relevant to this audit have been received on the docket.
Table 1: Oyster Creek Information Needs - Audit/Post-Audit Summary INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED 1 Consistency between Water Elevation Conversion In response to this information need request, the ERR file Factors document was provided entitled, "OYS FHRR Audit IN Responses 8-14-15.pdf." The licensee confirmed that FHRR Enclosure 1 (the Evaluation of the effects of flooding on water surface elevations evaluation of flooding from LIP) used the correct conversion at the Oyster Creek site is requested in the 50.54 letter. In the between elevations using the MSL and NAVD88 vertical datums.
Oyster Creek FHRR, two conversions were used between The licensee described the verification of the FHRR Enclosure 1 NAVD88 and mean sea level (MSL): conversion using the National Geodetic Survey benchmark and the NOAA Orthometric Height Conversion tool. The licensee also feet NAVD88 = feet MSL - 0.02 ft (in Enclosure 1) confirmed during the August 18, 2015, audit that the elevation feet MSL = feet NAVD88 - 0.02 ft (in Enclosure 2) conversion factor used in FHRR Enclosure 2 is incorrect. The licensee stated in "OYS FHRR Audit IN Responses 8-14-15.pdf",
Examination of the National Oceanic and Atmospheric that this would not have a significant impact on elevations reported Administration (NOAA) Tide Benchmark page for the in FHRR Enclosure 2.
reference tide gage (Reference 9 of Enclosure 1) shows that the Enclosure 1 conversion is correct. The Enclosure 2 The NRC staff concluded that the information provided by the conversions are incorrect. In addition, the embedded licensee in response to this information need request was reference to the NOAA benchmark webpage in Enclosure 2 sufficient.
does not work. The discrepancy between Enclosures 1 and 2 does not appear to affect the analysis of local intense precipitation (LIP), which used the correct conversion.
It is requested that the licensee clarify the reported flood elevations in Enclosure 2 of the Oyster Creek FHRR.
2 Local Intense Precipitation - Availability of Light In response to this information need request, the ERR file Detection and Ranging (LiDAR) Data document entitled, "OYS FHRR Audit IN Responses 8-14-15.pdf,"
was provided. The licensee stated that 2-meter or 5-meter LiDAR Evaluation of the effects of flooding of LIP on water surface data were available for the site, and that these data were not used elevations at the Oyster Creek site is requested in the 50.54 in the LIP floodinq analysis. The licensee clarified that the site
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED letter. Page 20 of the LIP Calculation Sheet ("10.0 ground surface elevations used in the LIP flooding analysis were Attachments") contains a caption for Figure A-01 of, "Existing based on a combination of photogrammetric data obtained in 2004 ground surface elevations based on LiDAR data and site field and supplemental field survey data obtained in 2012. The licensee survey." The text of the Oyster Creek FHRR states that stated that the vertical error in the photogrammetry-based photogrammetric data and a field survey were used to elevations was 0.17 ft, based on a comparison with the field survey determine surface elevations. data. The licensee confirmed that the Figure A-01 caption was in error and should read as follows: "Existing ground surface It is requested that the licensee clarify whether LiDAR data elevations based on photogrammetric and site field survey." The were available for the Oyster Creek site and if so, whether they NRC staff noted that the referenced text in the LIP calculation were used. In either case, the NRC staff also requests that the package (ERR file entitled "LI P-121 .6 OYS LIP Calculation licensee provide an estimate of the vertical error associated Package-Rev 5_Final") was subsequently revised to read as with the surface elevation data. follows: "Ground surface elevations in feet (NAVD88)."
The NRC staff concluded that the information provided by the licensee in response to this information need request was sufficient.
3 Local Intense Precipitation - Grid Resolution In response to this information need, the ERR file document entitled, "OYS FHRR Audit IN Responses 8-14-15.pdf," was Evaluation of the effects of flooding of LIP on water surface submitted. The licensee clarified that the photogrammetric data elevations at the Oyster Creek site is requested in the 50.54 provided 1-ft contours of the site topography from point letter. For the purposes of the LIP-based FL0-20 analysis, measurements of elevation that were horizontally spaced 10- to the licensee reported that it relied on topographic data that 100-ft apart, and that the supplemental field survey data were used possessed resolution level of 1 square foot and later averaged to capture local topographic grade variations as well as those data into a single elevation value corresponding to the depressions (low points) in the site topography. During the August 10 square foot grid cells that formed the basis of the FL0-20 18, 2015, audit, the licensee confirmed that the combined computational domain. photogrammetric and field survey topographic point measurements were averaged when multiple points were co-located within a It is requested that the licensee describe how the 1 square single 1Oft-by-1 Oft FL0-20 model grid cell, and were interpolated foot level-of-resolution topographic data were mathematically to grid cells between topographic points. The licensee confirmed treated (averaged) to defined the elevations of the 1O square that the averaging/interpolation was completed as part of the FLO-foot grid cells used in the FL0-20-based LIP model. 20 model development.
The NRC staff concluded that the information provided by the licensee in response to this information need request was sufficient.
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED 4 Local Intense Precipitation - Treatment of Building Roofs In response to this information need, the ERR file document entitled, "OYS FHRR Audit IN Responses 8-14-15.pdf," was Evaluation of the effects of flooding of local intense submitted. The licensee confirmed the use of WRF and ARF precipitation on water surface elevations at the Oyster Creek values as stated in the information need request description. The site is requested in the 50.54 letter. For the purposes of the licensee stated that the ARF value of 0.94 was used to ensure that LIP analysis, the licensee relied on a FL0-2D computer precipitation falling on roofs was not removed from the modelling model. Buildings were represented in that model by width domain. The licensee also stated that some precipitation was reduction factor (WRF) values of 1.0 and area reduction factor allowed to pond on the roofs due to the presence of parapet walls .
(ARF) values of 0.94. The WRF values of 1.0 prevent flow The licensee noted the presence scuppers on the reactor, turbine to/from building grid cells that would be adjacent to cells that building roof, and provided estimated flow rates through the would be used to simulate overland flow within the power scuppers for a 27-inch, 6-hour probable maximum precipitation block yard. The ARF values reduce by 94 percent the cell event. The licensee stated that flow through the scupper drains area available for water storage on the tops of buildings and would minimally affect the peak flood elevations on the site.
other structures. Consistent with American Nuclear Society During the August 18, 2015, audit, the licensee confirmed that the (ANS) 2.8 Section 11.4, the NRC staff expects that the roof configuration of the FL0-2D model used in the LIP flood analysis drain contribution to surface runoff would be evaluated to (described in FHRR Enclosure 1 and ERR file document entitled determine a worst case for site surface drainage effects. "LI P-121 OYS LIP Calculation Package-Rev 4") resulted in no drainage from building roofs to the ground surface adjacent to It is requested that the licensee clarify how the FL0-2D those buildings.
computer model described in the FHRR handles rainfall occurring on grid cells where the WRF and ARF parameters The NRC staff determined that the information provided by the values were set to 1.0 and 0.94, respectively. It is also licensee regarding water flow off of building roofs was not requested that the licensee describe how drainage associated consistent with ANSl/ANS-2.8 Section 11.4 standard for worst case with Oyster Creek facility roofs, as represented in FL0-2D effect on site drainage. The licensee's modeling resulted in all analyses, is consistent with the guidance found in American precipitation being stored on the roofs. Information provided by the National Standards Institute (ANSl)/ANS-2.8-1992, Section licensee on roof design features indicated that the LIP event would 11.4. result in some flow of water from the roofs to the ground surface.
The licensee agreed to address this issue as part of a revision to the FHRR LIP analysis.
Following the August 18, 2015, audit the licensee provided detailed drawings of the reactor building roof (within ERR file document entitled: "BR 4502, Sheet 1, Rev 001 , REACTOR BLDG ROOF PLAN DETAILS WALL SECTIONS") as well as a ponding calculation on the reactor and turbine buildinQ roofs with
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED subsequent flow through the parapet wall scuppers (within ERR file document entitled: "C-1302-576-5320-001 , Rev 0, 19841018, PONDING OF REACTOR BUILDING - TURBINE BUILDING ROOF LOADING ANALYSIS") . The NRC staff reviewed these documents.
On October 16, 2015, the licensee submitted a revised LIP calculation (ERR file document entitled: "LI P-121.6 OYS LIP Calculation Package-Rev 5_Final") as well as a supplemental response to Information Need 4 on October 21, 2015, as a second ERR file document entitled: "OYS FHRR Audit IN Updated Responses 4 and 6 10-21-15." In its supplemental response, the licensee stated that the FL0-2D model used in the LIP flood analysis had been revised to raise the elevation of grid cell locations corresponding to building locations to obviate the need to use ARFs. The licensee stated that building roofs were flat and set at 1Oft per story above the ground elevation , with the exception of the reactor and turbine buildings which were given sloped roofs.
As a result of this modeling decision, the licensee stated that the revised LIP model now assumed that all runoff from the buildings was conveyed directly to the adjacent ground surface and took no credit for roof storage from parapet walls or runoff diversion from roof drainage systems. The licensee also provided to the NRC staff FL0-2D model input files corresponding to the revised LIP flood analysis.
The NRC staff reviewed the supplemental information and the revised LIP flood calculation provided on the ERR. The staff used the licensee-provided FL0-2D model input files to confirm that the revised model did not use ARF values for the model grid cells representing building. The NRC staff confirmed that buildings were represented in the model as described in ERR file document entitled "LIP-121.6 OYS LIP Calculation Package-Rev 5_Final ,"
with the exception that model grid elevations for cells corresponding to the turbine and reactor building locations
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED appeared to now represent the building parapet walls on the east and west sides of those buildings. The NRC staff determined that building grid cell elevations were consistent with information in ERR files entitled "BR 4502, Sheet 1, Rev 001, REACTOR BLDG ROOF PLAN DETAILS WALL SECTIONS" and "C-1302-576-5320-001, Rev 0, 19841018, PONDING OF REACTOR BUILDING-TURBINE BUILDING ROOF LOADING ANALYSIS," and that flow off the north and south sides of the buildings would limit water
- storage on the roofs and provide conservative flood depths adjacent to the buildings.
The NRC staff concluded that the supplemental information and revised LIP flood analysis provided by the licensee in response to this information need request was sufficient. However, the NRC staff issued follow-up question numbers 1a, 1b, and 2 (below) to obtain additional information about the revised LIP flood model.
5 Local Intense Precipitation - Specification of Boundary In response to this information need, the ERR file document Conditions entitled, "OYS FHRR Audit IN Responses 8-14-15.pdf," was submitted. The licensee stated that the photogrammetric survey Evaluation of the effects of flooding of local intense coverage of the intake/discharge canals represents the side slopes precipitation on water surface elevations at the Oyster Creek and water surface of the canals at the time of the survey. The site is requested in the 50.54 letter. For the purposes of the licensee confirmed that the intake/discharge canals were modeled LIP analysis, the licensee relied on a FL0-2D computer as an overland flow surface. The licensee also stated that a model. In the matter of how the boundary conditions in that Manning's n coefficient for a water surface was used for model grid model were treated, the licensee specified an outflow cells representing the intake/discharge canal's bottom and a boundary condition for the entire periphery of the modeling Manning's n coefficient for asphalt was used for model grid cells domain , including the outer bank of the intake and discharge representing the side slopes. The licensee stated that any canal locations. When examining the discharge canals , for overflow from the discharge canals would be directed toward the example, it would appear that they were modeled as an outer boundaries of the modeling domain because the powerblock overland flow surface, since the licensee assigned Manning's and switch yard areas represent topographic high ground within n values to a water surface land cover type (Table 1 of the the modelling domain . The licensee stated that, because of this Oyster Creek FHRR Enclosure 1). The effect (and reasoning) elevation difference, the modeling choices for the intake/discharge of these modeling choices is unclear in the text of the Oyster canals and model boundary would have no effect on the estimated Creek FHRR. LIP flood elevations.
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED It is requested that the licensee describe the use of an outflow The NRC staff concluded that the information provided by the boundary around the entire model and for modeling the canals licensee in response to this information need request was as an overland flow surface, and the possible effect of these sufficient.
modeling decisions on the estimated flood hazard elevation.
6 Changes to Power Block Site Lay-Out In response to this information need, the ERR file document entitled , "OYS FHRR Audit IN Responses 8-14-15.pdf," was Evaluation of the effects of flooding on water surface elevations submitted. The licensee described the photogrammetric and field at the Oyster Creek site is requested in the 50.54 letter. In surveys performed to obtain undated site elevations, and stated connection with that evaluation , the 50.54 letter requests that that site visits in 2012 verified the locations of buildings, security the licensee describe any changes to the power block site that barriers, and other important site features. The licensee also might influence current licensing basis flood water elevations. stated that administrative procedures are in place to control This would include but not be limited to changes to existing site changes to the site layout as well as the evaluation of those topography (and grading) as well as modifications to the changes potentially to estimated flood elevations. During the footprint of existing on-site structures or the addition of new site August 18, 2015, audit, the licensee confirmed that the VBS structures (such as vehicle barrier systems - vehicle barrier present at the site was not included in the FL0-20 LIP flood system (VBS) or other type temporary structures). analysis model (described in FHRR Enclosure 1 and ERR file "LIP-121 OYS LIP Calculation Package-Rev 4"). The licensee stated It is requested that the licensee describe any changes to the that an engineering judgement was made initially that the VBS site layout that have occurred since the last update to the Safety would either not affect the flood hazard, or that its inclusion in the Analysis Report for the Oyster Creek site consistent with the LIP model would not be conservative because it would not allow 50.54 letter. flow from the east to cross the site. The NRC staff determined that the VBS should be evaluated for possible impacts to the estimated LIP flood hazard elevation. The licensee agreed to address this issue as part of a revision to the FHRR LIP analysis.
The licensee provided on October 16, 2015, a revised LIP calculation in the ERR entitled "LIP-121.6 OYS LIP Calcu lation Package-Rev 5_Final ," and a supplemental response to Information Need 6 on October 21 , 2015, in the ERR file document entitled, "OYS FHRR Audit IN Updated Responses 4 and 6 10 15." In the supplemental responses, the licensee stated that the FL0-20 LIP flood analysis model had been revised consistent with the NRC staff's earlier request. That revised model now
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED included four different sizes of security barriers ranging from 40 to 48 inches high, 32-inch high Jersey barriers, a landscaping area and rock wall near the Office Building , and a metal security barrier around the Diesel Generator Building (DGB). The licensee stated that these features, which could affect flow patterns during the LIP event, were identified during a September 11, 2015, walkdown of the site conducted in response to the NRC staff's information need request. In the supplemental information, the licensee provided a summary of LIP flood results and reported that the maximum water surface elevations at main door locations across the site had increased by up to 0.60 ft, but remained below the protection elevations at all doors other than Door #9 (of the Reactor Building).
The licensee stated that the maximum flood elevation increased by 0.07 ft at Door #9. The licensee also provided to the NRC staff FL0-2D model input/output (1/0) files corresponding to the revised LIP flood analysis. The N RC staff reviewed the supplemental information and the revised LIP flood calculation provided in the ERR . Using a satellite image of the site, the NRC staff determined that the security and landscaping features were properly located in the model. The NRC staff used the licensee-provided FL0-2D model input files to confirm the LIP flood results reported in an ERR file document entitled "LIP-121 .6 OYS LIP Calculation Package-Rev 5_Final."
In reviewing the revised LIP analysis the NRC staff observed that the licensee had revised the DGB door sill elevations. In the ERR file document entitled "LIP-121 OYS LIP Calculation Package-Rev 4," the DGB door sill elevations reported were based on earlier information described in Updated Final Safety Analysis Report (UFSAR) Section 2.4.8. In the revised analysis provided in an ERR file document entitled "LIP-121 .6 OYS LIP Calculation Package-Rev 5_Final," the DGB door sill elevations being reported were now based on a document entitled "Exelon Nuclear, Oyster Creek Nuclear Generating Station (2009), Drawing DRC 06-121-203, Rev 0, As-Built Survey Diesel Generator Building Security."
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED The NRC staff noted this difference, but neither verified nor validated the revised DGB door sill elevations because this revision had no effect on the estimated flood water surface elevations. The NRC staff concluded that the supplemental information and revised LIP flood analysis provided by the licensee in response to this information need request was sufficient. However, the NRC staff did issue follow-up questions designated 1a, 1b, and 2 (below) in an effort to obtain additional information about the revised LIP flood model.
FOLLOW-UPS TO ORIGINAL INFORMATION NEED REQUESTS 1a Revised LIP Flood Model, Flow around the Northeast The licensee responded to this Information Need Request on Corner of the Reactor Building (Follow-up Question to December 15, 2015, in the ERR file document entitled, "OYS Information Need Requests 4 and 6) FHRR Responses to Staff Follow Questions 12-15-15." The licensee stated that the revised FL0-2D model described in a In response to earlier Information Needs Requests 4 and 6, second ERR file document entitled "LIP-121.6 OYS LIP Calculation the licensee revised its FL0-2D LIP analysis. The figure Package-Rev 5_Final," treated the area along the east side of the shows detail from the licensee's updated grid for the FL0-2D Reactor Building as obstructed to water flow. The licensee model construction in the vicinity of the reactor containment provided a figure of the buildings in this general area and stated building. In connection with its review of the revised LIP that, although the Reactor and Old Radwaste Buildings do not analysis, the N RC staff observed that the north corner of the connect, other structures exist between the two buildings that Reactor Building and a building believed to be the old rad would constrict flow.
waste storage appears to have been "joined" as part of the development of the FL0-2D computational grid. The Using the revised FL0-2D model input files provided by the northeast corner of the Reactor Building is identified by the licensee in response to Information Need Requests 4 and 6, the yellow circle in the figure. Reactor Building Door #9 is NRC staff evaluated flow at the corner of the Reactor Building and identified by the teal-colored square and was previously determined that the licensee's initial response to this Information identified as location of LIP ingress. Need Required additional clarification. The NRC staff sent the licensee a request for clarification.
The NRC staff would like clarification as to whether these two structures are physically joined or whether there is an open In response to the NRC staff's request for clarification, on passage way between the two structures that would permit the January 14, 2016, the licensee provided an updated response to conveyance of LIP-generated surf ace water along the east this information request in an email to the NRC staff (ADAMS face of the Reactor Buildinq. The model results shown in Accession No. ML16015A001) and discussed this updated
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED Appendix A of LIP-121.6 Rev. 5 suggest the absence of a flow response with the NRC staff during a clarification telephone call. In path at this location by the absence of model results at the updated response , the licensee stated that when the FL0-2D building locations (see, for example, Figure A-05b on Sheet model was revised to remove ARF values , a gap (space) was 29 of 49 in LIP-121.6) . inadvertently created between the Reactor and Old Radwaste Buildings allowing fluid flow between the two structures. The If the licensee chooses to treat this location as an obstruction licensee stated that the FL0-2D computer model was revised to for the purposes of modeling , the NRC staff believes it might fill this gap and prevent flow from passing between the structures.
possibly lead to a higher (more conservative) estimated flood The licensee provided a table of revised flood depths and durations elevation at Door #9 compared to modeling treatment as an at the door locations, and stated that this revision of the LIP unobstructed location. analysis increased the maximum flood depth at Door #9 by 0.36 ft, to a maximum water surface elevation of 24.37 ft MSL, which is If the licensee proposes to treat this location as an 0.87 ft above the door sill elevation. The licensee stated that the obstruction , what is the LIP-related flood elevation at Door #9? revision increased the flooding duration at Door #9 by 0.58 hr, to a total duration of 1.52 hr. On January 22, 2016, the licensee The NRC staff seeks clarification as to how the licensee provided a revised LIP flood calculation in the ERR file document intends to treat this location for the purposes of modeling and entitled , "LIP-121 _7 OYS LIP Calculation Package-Rev 6_Full ultimately Mitigating Strategies Flood Hazard Information Binder."
reporting.
The licensee's updated response and revised LIP calculation were reviewed by the NRC staff and it was determined that the revised LIP flood results were consistent with NRC staff's calculations using FL0-2D model input files provided by the licensee in response to Information Need Requests 4 and 6.
The NRC staff received supplemental information dated April 25, 2016, from the licensee. The supplemental information included a letter stating that responding to the NRC staff's information needs resulted in the addition of a reactor building door to the results of the LIP flood evaluation. Enclosure 1 of the licensee's letter was a revised LIP Evaluation Report (Rev. 8) that incorporated the licensee's responses to all of the NRC staff's information needs discussed in the audit. Enclosure 2 of the letter was a set of FLO-2D model files for the calculations described in the revised LIP report. The NRC staff received the supplemental information on April 28, 2016. The NRC staff reviewed the revised report and
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED used the licensee's model files to confirm the licensee's calculations of flood elevation and duration. The maximum flood elevation *at the additional door in the Reactor Building (Door 14) was 24.38 ft MSL, 0.88 ft above the door sill elevation. Flooding duration at Door #14 was 1.41 hrs. The NRC staff concluded that the supplemental information and revised LIP flood analysis provided by the licensee in response to this information need request was sufficient.
1b Revised LIP Flood Model, Apparent Inconsistency in The licensee responded to this information need request on Flood Results (Follow-up Question to Information Need December 15, 2015, in an ERR file document entitled, "OYS FHRR Requests 4 and 6) Responses to Staff Follow Questions 12-15-15." The licensee stated that Table 8-3 of the ERR file document entitled "LIP-121 .6 As mentioned above, the updated FL0-2D model OYS LIP Calculation Package-Rev 5_Final" provides the correct construction appears to show the northeast corner of the DGB maximum water surface elevations. The licensee stated that the just touching the corner of the adjacent Old Radwaste Building maximum water surface elevations in the Appendix A figures located immediately to the northeast. In reference to that referred to in the information need request may be lower because general area, Figures A-15f and A-15g in LI P-121 .6, Rev. 5 do the figures were generated from FL0-2D computer code results not appear to reflect the margins listed in Table 8-3 (also reported at 6-minute time steps, which may not coincide with the Table A of the updated audit response to information need time of maximum water surface elevation .
requests 4 and 6, dated October 21 , 2015). Margins are 0.00 ft at Door #12 and 0.04 ft at Door #13, but appear larger in the The NRC staff concluded that the information provided by the Appendix A figures. The NRC staff seeks clarification on what licensee in response to this information need request was are the appropriate flood elevations to report based on the sufficient.
apparent inconsistency identified.
2a Revised LIP Flood Model, Manning's n Sensitivity The licensee responded to this information need request on (Follow-up Question to Information Need December 15, 2015, in the ERR file document entitled , "OYS FHRR Requests 4 and 6) Responses to Staff Follow Questions 12-15-15." The licensee stated (in the ERR file document entitled "LIP-121 OYS LIP Upon review, the NRC staff found that the licensee apparently Calculation Package-Rev 4") that the sensitivity of the FL0-2D LIP did not repeat the Manning 's n sensitivity analysis using the results to Manning's n values had been found to be small and that updated FL0-2D computer model. On Sheet 12 of 50 in LIP- both elim inating the use of ARF values while adding the security and 121 .6, it is stated that the sensitivity analysis performed on VBS features to the model would not affect the Manning's n Manning 's n values used a FL0-2D model with buildings sensitivity.
accounted for using ARF. However, ARFs were not used in the
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED updated model. The NRC staff seeks clarification concerning Using the revised FL0-20 model input files provided by the this ambiguity. licensee in response to Information Need Requests 4 and 6, the NRC staff evaluated the sensitivity to Manning's n value of the revised LIP model results, as described in the ERR file document entitled "LIP-121.6 OYS LIP Calculation Package-Rev 5_Final." The NRC staff determined that the revised model was not sensitive to the magnitude of the Manning's n value. The NRC staff concluded that the information provided by the licensee in response to this information need request was sufficient.
ATTACHMENT 1 Oyster Creek Audit Document List
- 1. Exelon , Calculation Number LIP-OYS-001 : Oyster Creek Local Intense Precipitation Evaluation ,
Revision 4, 2013.
- 2. Exelon , Calculation Number LIP-OYS-001 : Oyster Creek Local Intense Precipitation Evaluation, Revision 5, 2015.
- 3. Exelon , Calculation Number LIP-OYS-001 : Oyster Creek Local Intense Precipitation Evaluation ,
Revision 6, 2016.
- 4. GPU Nuclear, Calculation Number 1302-576-5320-001: Ponding of Reactor Building and Turbine Building Roof Loading Analysis , Oyster Creek, Revision O, 1984.
ATTACHMENT 2 List of Oyster Creek Audit Participants Name Organization
- 1. Chuck Behrend Exelon
- 2. Vinod Aggarwal Exelon
- 3. Joseph Bellini Exelon
- 4. David Distel Exelon
- 5. George Wrobel Exelon
- 6. John Traynor Exelon 7 . Cynthia Fasano AREVA
- 10. Ken Hunu GZA
B. Hanson If you have any questions, please contact me at (301) 415-6197 or by e-mail at Tekia.Govan@nrc.gov.
Sincerely, IRA/
Tekia V. Govan, Project Manager Office of Nuclear Reactor Regulation Japan Lessons-Learned Division Hazards Management Branch Docket No. 50-219
Enclosure:
Audit Report cc w/encl: Distribution via Listserv DISTRIBUTION :
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