ML16165A028

Response to NRC Request for Additional Information Revise Current Licensing Basis to Use American Concrete Institute Ultimate Strength Requirements

ML16165A028
Person / Time
Site:	Fort Calhoun
Issue date:	06/09/2016
From:	Marik S M Omaha Public Power District
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML16165A032	List: LIC-16-0044, Calculation FC08499 Evaluation of FCS Concrete Compressive Strength Test Data ML16165A028
References
CAC MF6676, LIC-16-0044
Download: ML16165A028 (33)

Text

fljljjfl ._.._ --. Omaha Public Power District LIC-16-0044 June 9, 2016 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Fort Calhoun Station (FCS), Unit 1 Renewed Facility Operating License No. DPR-40 NRC Docket No. 50-285

Subject:

Response to NRC Request for Additional Information Re: Revise Current Licensing Basis to Use American Concrete Institute Ultimate Strength Requirements (CAC NO. MF6676)

References:

1. Letter from OPPD (L. P. Cortopassi) to NRC (Document Control Desk), "License Amendment Request 15-03; Revise Current Licensing Basis to Use ACI Ultimate Strength Requirements," dated August 31, 2015 (LIC-15-0077) (ML 15243A167)

2. Letter from NRC (C. F. Lyon) to OPPD (L. P. Cortopassi), "Fort Calhoun Station, Unit No. 1 -Supplemental Needed for Acceptance of Requested Licensing Action RE: Revise Current Licensing Basis to use American Concrete Institute Ultimate Strength Requirements (CAC NO. MF6676)," dated December 15, 2015 (NRC-15-104) (ML 15341A224)

3. Letter from OPPD (L. P. Cortopassi) to NRC (Document Control Desk), "Supplement of License Amendment Request 15-03; Revise Current Licensing Basis to Use ACI Ultimate Strength Requirements," dated December 23, 2015 (LIC-15-0142) (CAC NO. MF6676)(ML 15363A042)

4. Letter from NRC (C. F. Lyon) to OPPD (S. M. Marik), "Fort Calhoun Station, Unit No. 1 -Request for Additional Information RE: Revise Current Licensing Basis to use American Concrete Institute Ultimate Strength Requirements (CAC NO. MF6676)" Attached is the Omaha Public Power District (OPPD) response to a NRC request for additional information (RAI) (Reference

4) regarding License Amendment Request (LAR) 15-03 (Reference 1 ), which is to: "Revise Current Licensing Basis to Use ACI Ultimate Strength Requirements." This letter contains no regulatory commitments.

L -LI C-16-0044 Page 2 If you should have any questions regarding this submittal or require additional information, please contact Mr. Brad Blome at 402-533-7270.

Shane M. Marik Site Vice President and CNO SMM/epm Enclosure

-OPPD Response to NRC Request for Additional Information -OPPD Response Notes Attachment 2 -Steel Reinforcement Statistics -Calculation FC08499, "Evaluation of FCS Concrete Compressive Strength Test Data" c: M. L. Dapas, NRC Regional Administrator, Region IV C. F. Lyon, NRC Senior Project Manager S. M. Schneider, NRC Senior Resident Inspector LI C-16-0044 Enclosure 1 Page 1 REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION. UNIT NO. 1 DOCKET NO. 50-285 By letter dated August 31, 2015, as superseded by letter dated December 23, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML 15243A167 and ML 15363A042, respectively), Omaha Public Power District submitted a license amendment request (LAR) to revise the current licensing basis to use American Concrete Institute (ACI) ultimate strength requirements at Fort Calhoun Station, Unit No. 1 (FCS). The LAR intends to revise the FCS Updated Safety Analysis Report (USAR) to change the structural design methodology for Class I structures at FCS with several exceptions.

The exceptions are the containment structure (cylinder, dome, and base mat), the spent fuel pool, and the foundation mats. No change to the current licensing basis code of record is proposed for these structures.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided in the application and determined that additional information is required in order to complete its formal review of the request. RAI 1 Item 1 of the proposed changes in the LAR requests to replace the working stress design (WSD) method with the ultimate strength design (USO) method for normal operating/service loading conditions.

The LAR proposes to apply this change to new designs or re-evaluations of existing Class I structures at FCS other than the containment structure, the spent fuel pool, and the foundation mats for all Class I structures.

a. The proposed load combinations do not include operating thermal load and operating piping/equipment reaction loads. Please provide justification for excluding these relevant design load conditions considering the requirements of the FCS licensing basis Code of record ACI 318-63, "Building Code Requirements for Reinforced Concrete," the ACI 349-97, "Code Requirements for Nuclear Safety Related Concrete Structures" (Reference 6.11 in the LAR), the guidance in Regulatory Guide (RG) 1.142, Revision 2, "Safety-Related Concrete Structures for Nuclear Power Plants (Other than Reactor Vessels and Containments)" (Reference 6.22 in the LAR), and NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition" (SRP) Section 3.8.4, "Other Seismic Category I Structures" (Reference 6.12 in the LAR). OPPD Response The proposed USO load combinations for normal operating/service loading conditions are based on those in the original USAR, with the same loads considered.

When piping/equipment reaction loads are present, their dead load, live load, and OBE seismic loads must be considered in the new load combinations, as was done with the WSD load combinations.

LI C-16-0044 Enclosure 1 Page 2 The original design basis load combinations for normal operating/service loading conditions did not include operating thermal loads, which can be justified by the following:

• A review of Section 9.2 of ACI 349-97 indicates that in general, load combinations involving operating thermal loads are enveloped by those involving accident thermal loads.

• Accident temperature and thermal loads are included in the USAR for the function load combinations.

These are significantly higher than the operating temperature and thermal loads and thus govern structural design; therefore, use of the accident thermal loads meets the intent of the code of record, ACI 318-63. Footnote 4 in Section 2.1 of the LAR states the following: "Soil dynamic pressure and hydrodynamic pressure loading shall be accounted, where applicable in accordance with the current licensing basis." a. Considering soil dynamic pressure and hydrodynamic pressure loadings in the design of soil/water retaining structural components has been an established design practice.

As such, they should be considered for the design of new Class I structures and the evaluation of existing FCS Class I structures to maintain consistency with the proposed changes in this LAR. Thus, using the term "current licensing basis" appears redundant and unclear in the context of footnote 4 and in the context of this LAR which requests to change the current licensing basis. i. Please discuss the intent of the term "current licensing basis" in the context of this LAR and footnote 4. ii. Please confirm that soil dynamic pressure and hydrodynamic pressure loadings were considered in the original design of the FCS Class I structures.

iii. The mark-up of the USAR, Section 5.11 does not include a statement relative to consideration of soil dynamic pressure and hydrodynamic pressure loadings.

Please discuss the reason for excluding this relevant information from the USAR mark-up. OPPD Response The footnote refers to the design basis as it stands before submittal of this LAR. This LAR does not change the design basis regarding the application of soil dynamic pressure or hydrodynamic pressure loading. Soil dynamic pressure and hydrodynamic pressure loadings were not specifically included in the original design of FCS Class I structures.

Therefore, there is no intention to include the requirement for soil dynamic pressure and hydrodynamic pressure in the USAR.

LIC-16-0044 Enclosure 1 Page 3 Item 3 of the proposed changes in this LAR requests to use higher reinforcing steel yield strength values for the containment internal structure (CIS) that includes the reactor cavity and compartment (RC&C) walls and the CIS beams, slabs, and columns. Section 3.3 of the LAR references DIT-SA-13-005, "Use of Higher Reinforcement Yield Strength for Operability Calculations," and states that Quality records show that there were 115 heat code samples used in the construction of the CIS. Some of the heat code yield stress values could not be identified and 105 of the 115 samples are known. Based on 105 samples specifically used for CIS, the 95% confidence level is equal to 44.45 ksi. As a result, the current design steel yield strength (i.e. 40 ksi) is increased to 44 ksi with high confidence for the RC&C and for CIS. In addition, Section 2.10 of the LAR states that the FCS quality program during plant construction contained detailed procedures for controlling installation of reinforcing steel bars and included signoffs for each delivery, reinforcing steel test data, and the location where the steel reinforcement was placed in the Class I structures.

a. Please provide statistical analysis information, including mean, standard deviation and coefficient of variation for each individual bar size on a heat-by-heat basis, as well as for all bar sizes (entire 105 samples population).

The response should demonstrate random sampling plan was implemented, traceability of the bars to their respective heats, and traceability to the location where the reinforcing steel bars were placed in the RC&C and the CIS beams, slabs, and columns. b. Considering the design deficiencies of CIS beams (shear and/or flexure interaction ratios greater than one), as summarized in Table 8 of the LAR, please provide justification for proposing to use the yield strength associated with the 95 percent confidence level for the entire 105 samples of reinforcing steel population rather than using 95 percent confidence level for individual bar size(s) corresponding to the shear and flexural reinforcing steel bars. OPPD Response Response to Question 3a. The requirements regarding reinforcing steel from the FCS QA Program, LIC-15-0142 Reference 6.24, demonstrate that a random sampling plan was used and that the bars are traceable to their respective heats. The bars are traceable to the building in which they were installed, but not to the specific location in that building.

Excerpts from the QA Program are as follows: 8. 3. 5 Reinforcing Steel 8. 3. 5. 1 The steel supplier shall tag each bundle with the order number of the shipment.

The supplier, through the contractor, shall, supply a materials test report for each metal heat used in each shipment to the Q.A. Staff. 8.3.5.2 The Q.A. Staff will review each shipping order material certification for compliance to ASTM Specification A-615. Each heat number received will be logged by bar size and shipping order number.

LIC-16-0044 Enclosure 1 Page4 8. 3. 5. 3 The staff will randomly select one heat of each ten received per bar size to be tested and inspected by the laboratory.

Tests will consist of tensile tests and bend tests appropriate to the bar size per ASTM A-615 while the inspection will consist of verification of deformation criteria, also per A-615. The laboratory will furnish test and inspection reports to the staff who will be responsible for any required retests or corrective action. Exact rebar placement data was not collected during construction (i.e., which specific heat was placed into which specific beam, slab, or column). A formal OPPD calculation was developed and contains the data that identifies if the heat was located in the CIS and RC&C which is denoted as "Reactor Plant" in the data set. Only the data associated with the "Reactor Plant" are used to calculate the rebar strength for CIS and RC&C. In summary, the QA Program at the time of original construction sufficiently controlled the data such that rebar placement can be traced to building location and specifically to CIS and RC&C. Attachment 2 summarizes the key statistical information . . Response to Question 3b. The intent of using the yield strength associated with the 95 percent confidence level for the entire population of 105 samples is to provide a single strength value representative of the entire population rather than individual strength values for each rebar size. Size #3 and #7 bars were the only two sets found to have 95 percent confidence level strength values below the proposed 44 ksi. Every test located for #3 bars is greater than 44 ksi, and only one test out of 12 located for #7 bars was found to be less than 44 ksi. In addition, the single test falling below 44 ksi for #7 bars was on heat #13995. An additional test on heat #13995 reported a yield strength of 44.00 ksi. Based on this information, we have reasonable assurance that the strength for #3 and #7 bars meets or exceeds the proposed 44 ksi strength value, and therefore using the 95 percent confidence level for the entire population of 105 samples is appropriate.

Items 2 and 3 of the proposed changes in this LAR requests to use higher concrete compressive strength and higher reinforcing steel yield strength values using analysis of historical test data for a limited number and specific areas of Class I structures.

The language in the new Sections 5.11.3.8, "Concrete Compressive Strength," and 5.11.3.9, "Steel Reinforcing Capacity," included in the USAR mark-up in the LAR, gives an appearance that using analysis of historical test data as described in Sections 5.2.6 and 5.2.2.1 could be generically used for the FCS. In addition, these new sections appear to be redundant because Sections 5.2.6 and 5.2.2.1 of the LAR already describe the proposed changes. a. Please clarify the language and discuss the intent of new Sections 5.11.3.8 and 5.11.3.9 included in the USAR mark-up. b. The term "capacity" in the title of Section 5.11.3.9 and the term "steel reinforcing capacity allowable stress" in the proposed language of Section 5.11.3.9 are not consistent with the request in the LAR which relates to "reinforcing steel yield strength." Please clarify.

LIC-16-0044 Enclosure 1 Page 5 OPPD Response As stated, Sections 5.11.3.8 and 5.11.3.9 of the USAR markup are redundant.

OPPD FCS will exclude these sections from the final USAR revision since they provide no added value. Item 3 of the proposed changes in this LAR requests to use higher concrete compressive strength (fc) determined based on cylinder break test data for the Auxiliary Building (above Elevation 1007') and the CIS. The containment structure, intake structure, spent fuel pool, reactor cavity floor, and concrete around the reactor vessel will continue to use the re currently specified in the design basis documents.

a. Measured strengths of laboratory cured cylinders may be significantly different from the in-place strengths because it is difficult, and often impossible, to have identical bleeding, consolidation, and curing conditions for concrete in cured cylinders and concrete in structures.

In addition, the properties of concrete may vary with elevation due to differences in placing and consolidation procedures, segregation, and bleeding.

The ACI 318-63 (FCS Code of record), Section 504(a) indicates that additional test specimens cured entirely under field conditions may be required by the Building Official to check the adequacy of curing and protection of concrete.

i. Please provide cylinder break test data for the Auxiliary Building and the CIS for specimens cured under field conditions during the original construction of the FCS, if available.

ii. Considering the variabilities noted above, please provide a discussion to justify the request regarding the use of cylinder break test data of laboratory-controlled samples alone without performing an in-situ field test to establish a valid correlation between the statistical evaluation and the as-built concrete strength.

b. Please provide ACI 318-63, Section 504(c) strength test data analysis, and the 95 percent confidence level statistical analysis information.

The response should demonstrate that random sampling plan was implemented, and traceability of the samples to their respective structure and the location where the concrete was placed. OPPD Response Response to Question Sa. Calculation FC08499, "Evaluation of FCS Concrete Compressive Strength Test Data." (Attachment

3) is provided and performs the statistical analysis and provides the compilation of all retrievable cylinder break test data for the Auxiliary Building and the CIS. It includes data from laboratory cured cylinders and the field cured cylinders.

The field samples were not well controlled.

For example, some samples were reported as NOT @AREA PLACED, LOST ON JOB, or DAMAGED AT JOB SITE. Typically field cured samples are not as well maintained as lab cured samples. Per ACI 318-63 Section 504(a), "Specimens made to check the adequacy of the proportions for strength of concrete or as a basis for acceptance of concrete shall be made and laboratory cured in accordance with ... (ASTM C31)."

LIC-16-0044 Enclosure 1 Page 6 The statistical analysis of the available original lab cured test data supports the use of the actual concrete strength in accordance with Section 2.2 of LIC-15-0142 which meets the strength testing requirements of the FCS licensing basis concrete Building Code ACI 318-63 Section 504. Additionally, it is known that concrete compressive strength continues to increase with age when it is well maintained.

The request to use increased concrete strength is limited to locations which do not undergo prolonged exposure to high radiation, excessive moisture, or harsh chemicals.

Therefore, it is reasonable to conclude that the in situ concrete strength meets or exceeds the as-built concrete strength.

The statistical analysis is documented in a calculation.

OPPD has no plans for additional strength testing at this time. Response to Question 5b. The FCS QA Program demonstrates a random sampling plan was implemented and sample traceability exists with regard to specific sample pour locations.

Detailed pour location and sample data can be found within calculation FC08499 (Attachment 3). RAl-6 Please provide a discussion and a sample of quantitative data regarding reconciliation of bond and reinforcing steel anchorage requirements of ACI 318-63, when using higher concrete compressive strength, against the as-installed shear and flexural reinforcing steel arrangement.

OPPD Response Bond strength capacity is calculated in Sections 1301 and 1801 of ACI 318-63. The change in bond strength as it applies to the increase in concrete strength is proportionate to the square root of f'c since all other terms (i.e. 3.4, 4.8, 6. 7 or 9.5 and D for bars conforming to A307) are constants.

The requested increase in concrete compressive strength for the CIS corresponds with a 14% increase in concrete bond strength which is greater than the 10% requested increase in rebar yield strength.

Therefore, the development of rebar pertaining to bond strength remains adequate under the increased material properties.

The below comparison between proposed and existing material strengths is made based on bond strength capacity as calculated in ACI 318-63. Ratio of increased bond strength:

.../5200 psi : .../4000 psi = 1.14 Ratio of increased yield strength:

44 ksi : 40 ksi = 1.10 LIC-16-0044 Enclosure 1 Page 7 The footnote for Table 7 of the LAR indicates that the application of actual concrete compressive strength in lieu of the original specified design values is not allowed where structures undergo prolonged exposure to high radiation, excessive moisture, or harsh chemicals.

Table 7 of the LAR indicates that the increased compressive strength of concrete will not be used for reactor cavity floor and concrete around the reactor vessel. a. Please provide a discussion and the rationale for requesting to allow increased compressive strength for the reactor cavity walls and other compartment walls relative to the footnote for Table 7. OPPD Response OPPD requests an increase in concrete strength for the walls of the fuel transfer canal, the reactor cavity pool walls, the steam generator and reactor coolant pump walls, and the pressurizer compartment floor and walls. These areas of the CIS are not exposed to excessive moisture or chemicals.

The transfer canal and reactor cavity pool walls are protected by the stainless steel liner from moisture and chemical exposure.

The transfer canal is dry except during refueling outages. Worst case radiation exposure levels from survey data correspond with 60-year plant life total estimated gamma and neutron doses, 4.73.E+06 rad and 1.58.E+13 n/cm 2 respectively, which are lower than the critical levels listed in NUREG/CR-7171 Section 5.2, 2.00.E+10 rad and ' 1.00.E+19 n/cm 2 respectively.

Therefore, no loss in concrete compressive strength due to prolonged exposure to high radiation, excessive moisture, or harsh chemicals is expected for the areas of the CIS for which OPPD has requested increased concrete strength.

According to Section 2.7 of the LAR, it is the NRC staffs understanding that (1) FCS currently inspects the Auxiliary building per procedures SE-PM-AE-1001, Auxiliary

-.. Building Structural Inspection, and the CIS in accordance with procedure SE-PM-AE-1004, Containment Building Structural Inspection; (2) each procedure has an inspection frequency of 3 years with caveats to increase or decrease the frequency as accumulated inspection findings warrant, but shall not exceed 5 years; and (3) a review of the results from recent inspections did not identify any significant structural deterioration that would invalidate the use of the current licensing basis or proposed licensing basis items requested by this LAR. Considering the brevity of the above statements in the LAR: a. Please provide a general description of the FCS inspection program for the Auxiliary building and the CIS. The response should, as a minimum, identify and discuss the industry standard(s) used to develop the FCS inspection procedures, current inspection frequency, the scope and the method of inspection, and the criteria used for classification of inspection findings.

LIC-16-0044 Enclosure 1 Page 8 b. Please discuss the highlights of findings of the last three inspections of the Auxiliary building and the CIS, and any corrective actions taken to disposition them. c. Please discuss the definition of "significant structural deterioration" noted in Section 2. 7 of the LAR. Also, discuss the threshold where an inspection finding (crack, etc.) will be designated as "significant structural deterioration".

OPPD Response Response to Question Ba. Procedures SE-PM-AE-1001, "Auxiliary Building Structural Inspection," and SE-PM-AE-1004, "Containment Building Structural Inspection," monitor the structural condition of the auxiliary building and containment internal structure.

The structures are assessed and are documented in a manner sufficient to give reasonable assurance that the structure, components, supports, and fasteners are capable of fulfilling their intended design function.

This is achieved by performing a visual inspection of accessible surfaces (interior and exterior) of the buildings (broken down by area/room with reference drawings).

The inspection includes all exposed surfaces of the structure, joints and joint material, interfacing structures and material (e.g., abutting soil), embedments, and attached components such as base plates and anchor bolts. In addition, the inspections include a representative sampling of Critical Quality Equipment (CQE) components such as support pedestals; piping and snubber seismic supports; cable tray seismic supports; HVAC seismic supports; "seismic gap" between Containment Building and Containment structure and a representative sampling of component supports and component support fasteners; pipe supports and equipment anchorage; supports for cable trays, conduits, HVAC ducts, tube track and tubing; anchorage of racks, panels, cabinets, and enclosures for electrical equipment.

Specific industry codes and standards used in the development of the FCS inspection procedures SE-PM-AE-1001 and SE-PM-AE-1004 include ACI 349.3R-96, ACI 201.1 R-92, ASCE 11-90, RG 1.127 Rev. 1, and Generic Aging Lessons Learned (NUREG-1801, Rev. 0). The Structures Monitoring Program (SMP), which includes SE-PM-AE-1001 and SE-PM-AE-1004, is consistent with the requirements of GALL Chapters Xl.S5, Xl.S6 and applicable criteria in Xl.S7. A previous Staff review concluded, per NUREG-1782, that FCS has demonstrated the SMP will effectively manage aging in structures and components in which this program is credited.

The current frequency for performance of SE-PM-AE-1001 and SE-PM-AE-1004 is 144 weeks and every other RFO, respectively, which meet or exceed the frequency requirements established in ACI 349.3R-96.

Criteria used to classify inspection findings is broken into three categories; Acceptable, Acceptable after Review, and Unacceptable.

Table 1 contains a general breakdown of the criteria as listed within the inspection procedures; quantitative limits used to determine the classification of findings are contained within ACI 349.3R-96.

LI C-16-0044 Enclosure 1 Page9 Table 1; Criteria for Classification of Inspection Findings Acceptable Acceptable after Review Absence of leaching and Appearance of leaching or chemical attack chemical attack Absence of abrasion, erosion Areas of abrasion, erosion and cavitation and cavitation Absence of dummy areas Dummy areas which may (poorly consolidated concrete, exceed the cover concrete with paste deficiencies per ACI thickness in depth 201.1R) Minor spalling, scaling, popouts Excessive spalling, scaling, and voids, and passive cracks popouts and voids, and passive cracks Absence of any signs of Corrosion staining of corrosion in reinforcing steel undefined source on system or anchorage concrete surfaces components Absence of excessive Passive settlements or deflections, settlements or other deflections within the physical movements that may original design affect structural performance Absence of corrosion of Presence of spalling, exposed embedded metal scaling, popouts and voids, surfaces and corrosion stains or other signs of around embedded metal deterioration around anchorage embedments Absence of detached Evidence of corrosion or embedments or loose bolts degradation of reinforcing steel, anchors, or exposed embedded metal surfaces Absence of indications of Indications of separation, degradation due to vibratory environmental degradation, loads from piping and or water leakage in joints or equipment joint materials No signs of separation, Indications of degradation environmental degradation, or in waterproofing water in-leakage are present in membranes joints or joint material Absence of degradation in any waterproofing membrane protecting below-grade concrete surfaces (within the inspected area) Non-structural elements appear to be serving their desired function Unacceptable Conditions which exceed the limits described in Step 10.2, or other evidence of significant structural deterioration of accessible concrete liner or other building features which may affect structural integrity or leak tightness Indications of widespread adhesion/cohesion problems, environmental attack or poor performance indicators on joints, joint materials, or waterproofing membranes LIC-16-0044 Enclosure 1 Page 10 Response to Question Sb. The past three inspections for both the Containment Internal Structure and Auxiliary Building did not identify any significant structural deterioration.

Detailed observations are documented for each building, elevation, and equipment inspected.

Each of the inspections document the presence of cracks and other minor conditions which were determined to be acceptable as is. Per the procedure, any conditions that are classified as "Acceptable after Review" or "Unacceptable" would require a Condition Report to be generated in the station's Corrective Action Program. Table 2 provides a summary of the findings applicable to concrete structures which required corrective actions and work performed to resolve the noted conditions.

To date, all findings requiring corrective actions have been resolved or are planned/scheduled to be resolved during the upcoming RFOs. Table 2; Structural Findings from Past Inspections 2005 Inspection (W0131761}

-Containment Internal Structure Condition Finding Corrective Action(s)

Work Completed Report 2005019 Multiple grease trails None Grease trails on the exterior 04 observed on the outside walls of the containment of Containment Structure building are caused by from various rooms in the leakage from upper tendon Auxiliary Building end grease can seals. The mechanism for these grease trails is well understood and documented, they occur/recur when ambient temperature increases cause tendon grease to relieve volume. They have no effect on the ability of the tendon grease to inhibit corrosion to the tendons and has no detrimental effect on the concrete.

Tend on grease leakage is routinely monitored by inspections conducted IAW ASME Code Section XI, SUBSECTION IWL. A hair line to slightly Track completion of WR 82497 This work order has been larger crack observed on (WO 218196), which has been tracked to completion.

WO the underside of the floor written to clean and investigate 218196 is coded as complete.

slab at elev. 1045' which further the source of the The surface was cleaned with contained a white particulate in the cracks on the lime away and left clean. particulate underside of the slab on the 1045' elev. Rust stains were Track completion of WR 82496 This work order has been observed around two (WO 218192), which has been tracked to completion.

WO hairline cracks on the written to clean the rust stains 218192 is coded as complete.

underside of the floor and investigate further the source The system engineer slab at elev. 1060'; of the moisture in the cracks on performed a walkdown of the the underside of the slab on the underside of containment 1060' elev. 1060' floor slab and LI C-16-0044 Enclosure 1 Page 11 A shallow spall None approximately 1 SF in size was observed on concrete beam supporting elev. 1013' floor slab 2009 Inspection (W0318189)

-Containment Internal Structure Condition Finding Corrective Action( s) Report 2009-Rust evidence was noted WO 549129 is currently in 5711 on the face of "PLAN" Status containment columns 14 and 1 (the second and third column clockwise from the PAL door. The rust discoloration is widespread in this area and easily visible from the adjacent 1022 platform.

The corrosion source is not easily apparent; multiple structural steel items in the area appear to be affected.

A portion of the steel on the containment side of penetration M-93 (near Column 14) has notable rust, as does a portion of the steel on the containment side of penetration M-96 (near Column 1). 2015 Inspection (W0360747)-

Containment Internal Structure Condition Finding Corrective Action Report N/A No Structural Conditions N/A requiring Corrective Actions were identified 2003 Inspection (W0109603)-Auxiliary Building Condition Finding Corrective Action Report determined no additional cleaning required at this time. This area will be monitored by SE-ST-CONT-0001 for further deterioration.

See the work order for further details The shallow spall area noted on the concrete beam supporting the 1013' elev. Floor slab has been noted in previous inspections and has been assessed to not be an operability issue. CR 200303808 evaluated this spalled area on this beam. Work Completed Wrote WR 143491 (WO 549129) for investigation of the source and cause of the corrosion and the extent of condition.

This is related to CR 2009-5714.

The CRG changed the condition level to B due to concern for the source. They closed this CR to Level B CR 2009-5714.

Work Completed N/A Work Completed LIC-16-0044 Enclosure 1 Page 12 2003019 65 A section of expand-a-flash along the east side of the room 81 roof was found to be torn Document cause and work accomplished on WO 148953. WO 148953 is closed. 2008 Inspection (W0259063)

-Auxiliary Building Condition Finding Corrective Action Report 2008-Aging indications on the Initiated WR 128723 -6516 roof area of Rm. 69 Repair/Replace Roof Area Above Rm. 69. Aging indications in the Initiated WR 128724 -Recaulk Rm. 69 roof area flashing the Roof Area Flashing Above caulk Rm. 69. A section of 1 inch Initiated WR 128726 -Reattach conduit is unattached, Section of 1 Inch Conduit located on the Rm. 69 Located on Rm. 69 Roof. roof Debris on the roof area Initiated WR 128727 -Clean of Rm. 69 Debris From Roof Area Above Rm.69. Signs of seepage on the Initiated WR 128729 -Repair the ceiling of the Diesel Air Roof Flashing Above Diesel Air Intake Enclosure Intake Enclosure.

Peeling paint and signs Initiated WR 128731 (WO of seepage on the Rm. 321586)-Repaint the Ceiling of 82 ceilinQ Rm. 82. Peeling paint on wall Initiated WR 128732 -Repaint areas of Rm. 69 Wall Areas of Rm. 69. Peeling paint on ceiling Initiated WR 128734 -Repaint areas of Rm. 69 Ceiling Areas of Rm. 69. 2013 Inspection (W0365092) -Auxiliary Building Condition Finding Corrective Action Report 2011-Water dripping from Performed walkdown, hairline 06051 ceiling in Corridor 4. The crack will be documented under crack is approximately 3 SE-PM-AE-1001 and monitored ft long. The current for growth. From a flooding leakage coming from the perspective, leak is well within crack is approximately 5-capacity of aux building sump 6 drops per minute at this pumps and will not require time. The crack is repairs at this time. Ceiling area located adjacent to has been and will continue to be column E-7A. monitored under the Auxiliary Building Structural Inspections (SE-PM-AE-1001

). CR The work order associated with this action item is being tracked in the integrated plant schedule.

Since it has no safety significance and is a level 6 CR; closing this action item. The cause of any failures and the actions taken to correct the problem will be documented in the associated work order. Work Completed WO 321564-01 Closed WO 321564-02 Closed Replaced one inch straps on conduit. It is no longer sagging (WR 128726). Debris removed (WR 128727) WO 321564-03 Closed WO 321586 Cancelled WO 321587-01 Complete WO 321587-02 Complete Work Completed Wrote WR 166811. Completed walk downs (two different times) of the area noted in the Condition Description, could not find any leakage source. This is an interior location with no ground water. Reviewed SE-PM-AE-1001, "Auxiliary Building Structural Inspection" procedure.

Review of recently completed Auxiliary Building Structural Inspections (SE-PM-LIC-16-0044 Enclosure 1 Page 13 2013-04777 2013-04779 2011-06051 determined no AE-1001) performed to actions are required.

determine if the hairline crack found in Corridor 4 ceiling has been previously identified.

There are numerous observations of fine cracks in Corridor 4. Also noted are fine ceiling cracks in the area of the 7 A column line. -1/8" crack was found in Track WR 192983 to completion.

Wrote this CR and Initiated the pyrocrete in front of W0476857 tasks 1, 2 and 3 were WR 192983. This is not a 1A4-13 in the West completed and the pyrocrete structural concern, function of switchgear room. This is cracks identified were sealed the pyrocrete is to provide on the East wall where separation of redundant trains there fire doors are of switchgears, load centers, located. and associated electrical

-1/4" crack was found equipment.

under the girder above T18-48 on the East wall in the West switchgear room. -1/4" crack was found on the pyrocrete wall above Door 1011-19 in the East switchgear room. Signs of past leakage on CR 2009-4099 resolved the Wrote WR 193429 and placed M-28 in DG-2 Room leakage issue. WR 193429 (WO a WR tag on the wall. This is 478174) is currently in "PLAN" not a DNC. The only issue is Status that there is currently a stain on the wall that indicates past leakage. WR 193429 will paint the wall and cover up the leakage. This way any future leakage can be seen. The Work Management Process will drive the completion of the WR Response to Question 8c. Significant Structural Deterioration is defined as measurable structural deterioration which, when compared with past inspections, shows strong evidence of an increase of structural degradation which could affect a building or component's structural integrity or leak tightness.

Evidence of cosmetic or superficial deterioration, unless determined by sound engineering judgement to be significant, is not considered significant structural deterioration.

Threshold will be based on previous findings and codes/standards referenced in procedures.

Previous inspections, did not identify any signs of significant structural deterioration and the structures were capable of performing their specified safety functions.

LIC-16-0044 Enclosure 1 Page 14 Section 2.0 of the LAR states that in 2012, two latent engineering errors were discovered during preparations for a planned extended power uprate of FCS and a detailed extent of condition concluded that several concrete beams in the CIS do not meet the current design basis. In addition, Section 2.8 {Table 8) of the LAR provides summary of analysis results for CIS beams. The LAR does not discuss the operating experience that prompted for structural re-evaluation of intake structure, Auxiliary Building, and the RC&C walls. a. Please provide a discussion regarding the operating experience (design deficiencies, etc.) that prompted the RC&C structural re-evaluation and the proposed request to use the limit state design method. ' b. Please provide a discussion regarding the operating experience (design deficiencies, etc.) that prompted the intake structure and Auxiliary Building structural re-evaluation and the proposed requests in the LAR. OPPD Response At FCS, Class 1 structures are the concrete Internal Structures of Containment, Containment, Auxiliary Building, and Intake Structure.

The Root Cause Analysis (RCA) and associated Extent of Condition (EOC) evaluation conducted for the Containment Internal Structures concluded that "FCS did not comply with the design load combination criteria for working stress and No Loss of Function for Containment internal concrete structures as required by USAR Section 5.11.3." and that the condition extended to the RC&C and Auxiliary Building.

RC&C During the Extent of Condition review it was discovered that calculations for the Reactor Cavity and Compartments (RC&C) were deficient or nonexistent.

The RC&C includes all internal concrete walls within containment including the reactor cavity, fuel transfer canal, pressurizer compartment, and steam generator/reactor coolant pump (SG/RCP) compartments.

Though the internal walls are integral with the beams, columns, and floor slabs of the Containment Internal Structures (CIS), the two scopes were deliberately kept separate to simplify modeling and qualification.

The request to allow use of the Limit Design Method is required because there is no equivalent method in the ACI 318-63 Code. The original design of the reactor cavity and compartment walls (RC&C walls) was based on the limit state of the reinforced concrete structure.

Design forces and moments at the limit state, which were used to determine sizes and placements of reinforcing bars (rebar), cannot be replicated by linear finite element analysis (Linear Design Method). Design forces and moments at the limit state can only be computed by using linear (or step-wise linear) finite element analysis (Limit Design Method). While the Limit Design Method is able to reasonably reproduce the original design forces and moments at the limit state by simulating load redistribution behavior, the Linear Design Method is not. Application of the limit design method helps resolve overstress issues. The limited clearances available in the RC&C makes placement of additional concrete or other support structures difficult and would impact the ability to perform routine maintenance and inspections.

Use of the proposed changes significantly reduces or eliminates the need for modifications in the RC&C. The safety benefit that would be gained by the installation of additional structures in this area is small when compared to the increased radiation exposure to workers during installation.

LIC-16-0044 Enclosure 1 Page 15 Auxiliary Building The Extent of Condition review of the calculations of record for 11 members within the Auxiliary Building was performed.

The more highly loaded members were selected for review. The structural design calculations of record were checked against design drawings and reviews of the calculations were performed to assess the quality of the evaluations.

The reviews identified discrepancies similar to those identified for the Containment Internal Structure.

Therefore, a reconstitution effort was warranted.

The change to USD for normal service loads (in lieu of WSD) will increase the consistency between normal operating/service conditions and no loss-of-function conditions.

Projects requiring new designs or reevaluations of existing reinforced concrete structures can be conducted more efficiently with less chance for error as design calculations will only require USD member capacities.

The current method requiring both WSD and USD calculations, is unnecessarily complex, and results in over-designed and over-engineered concrete structures.

Use of the proposed changes significantly reduces or eliminates the need for modifications in the Auxiliary Building.

The safety benefit that would be gained by the installation of additional structures is small when compared to the increased difficulty of performing maintenance activities resulting from reductions in work space. Intake Structure The original design basis calculations for the Intake Structure are not available (CR 200504328, 200504345, 2009-3769).

This deficiency was discovered during the NRC Safety System Design and Performance Capability team inspection of the raw water system. As a result, analyses were performed in 2009 and 2010 using Finite Element Analysis.

The structure was checked against both Working Stress Design criteria and Ultimate Strength Design criteria.

The evaluation indicated that the Intake Structure is structurally adequate.

As a result, a reconstitution effort is not planned for the FCS Intake Structure.

The Intake Structure meets the current design basis of WSD and USD. The use of USD for future analysis is also being requested for the Intake Structure to provide a consistent approach for *all reanalysis work for CIS, RC&C, or Auxiliary Building.

RAl-10 Item 4 of the proposed changes in this LAR requests to use the limit state design method for evaluating the RC&C walls, including the use of dynamic increase factors (DIF) for impulsive loads, according to equations in commentary of Appendix C of ACI 349-97. Section 2.9 of the LAR attempts to perform a gap analysis of ACI 318-63 (FCS Code of record) to ACI 349-97. Section 2.9.4 of the LAR states the following: "Based on the comparison of ACI 349-97 Code and the dissimilarities to ACI 318-63 it has been determined that use of DIF as described in ACI 349-97 and RG 1.142 would be advantageous for re-evaluation of the RC&C. Use of the USO methodology is adequate to evaluate the RC&C."

LI C-16-0044 Enclosure 1 Page 16 Section 3.4 of the LAR states the following:

The request to allow the inclusion of the Limit Design Method is required because there is no equivalent method in the ACI 318-63 Code. The original design of the reactor cavity and compartment walls (RC&C walls) was based on the limit state of the reinforced concrete structure.

Design forces and moments at the limit state, which were used to determine sizes and placements of reinforcing bars (rebar), cannot be replicated by any form of linear finite element analysis, herein called the Linear Design Method. They can only be computed by using non-linear (or wise linear) finite element analysis, herein called the Limit Design Method. While the Limit Design Method is able to reasonably reproduce the original design forces and moments at the limit state by simulating load redistribution behavior, the Linear Design Method is not. Please provide further clarification on the following items: a. Contrary to Section 3.4 of the LAR where it is requested to allow the use of the limit design methodology, the conclusion of Section 2.9 of the LAR states that the use of the USO methodology is adequate to evaluate the RC&C. Please clarify. OPPD Response to 10a. The intent of the conclusion of Section 2.9 of the LAR was to indicate that the application of DIF, in accordance with ACI 349-97, would be beneficial for the reevaluation of the RC&C; however, the application of DIF may not necessarily be required for the reevaluation of the RC&C. The use of USD in conjunction with the Limit Design Method might produce satisfactory results for the RC&C reevaluation under the proposed licensing basis. The conclusion of Section 2.9 of the LAR is silent concerning the use of the Limit Design Method. There was no intent to imply that the use of USD without the Limit Design Method would produce satisfactory results for the RC&C reevaluation.

USD is a design methodology in ACI 318 and the Limit Design Method (LDM) is a general analysis approach the LAR requests for use to determine load distribution in a structure.

Internal loads from LDM are used in USD for design. b. Section 3.4 of the LAR states that when the limit design method is applied, where flexure controls design of the RC&C walls, rotations of the walls in any yield zone must be less than the rotational capacity of the zone, as expressed by Equations 3.4.1 and 3.4.2 in Section C.3.4 of ACI 349R-97, Appendix C (ACI 349-97 Commentary).

The NRC staff notes that the premise of using the provisions of the ACI 349, Appendix C and the limit state design methodology hinges upon the member ductility at critical section(s) and consideration of limited plastic hinge rotation.

i. Please provide information related to ductility of the RC&C walls and reconciliation of reinforcing steel detailing requirements of ACI 349-97. ii. The LAR does not discuss/justify an appropriate acceptance criterion/limit for the rotational capacity of yield (plastic) hinge. Please clarify. iii. Partial adoption of a more up-to-date code (ACI 349) is not consistent with the industry practice.

Please provide justification.

LIC-16-0044 Enclosure 1 Page 17 OPPD Response to 10b. ACI 349-97 is referenced to show precedence and how later codes ultimately adopted a similar approach.

Attachment 1, Notes 1 provides justification and discusses acceptance criteria.

Ductility factors in ACI 349-97 will not be used in the analysis of the RC&C walls and thus reconciliation of the reinforcing steel detailing is not planned. Instead, rotations or maximum compressive strains due to bending at critical sections of the finite element model are checked against the rotational capacity or the concrete ultimate strain of 0.003 to confirm that they are less than the limits for critical sections to be ductile. c. It is the NRC staff's understanding that finite element analysis is used for the RC&C walls structural re-evaluation.

Please provide a discussion relative to the application of the limit state design methodology as it relates to the RC&C walls and the applicable load combinations.

The response should, as a minimum, include the description of (1) RC&C finite element model/analysis (element type, stress-strain relationship of concrete and reinforcing steel, type of nonlinearity associated with the RC&C wall analysis, incremental and iterative procedures used in the analysis, computer software, benchmarking and model validation, etc.); and (2) how the transverse shear forces and twisting moments, in addition to bending moments, are taken into account. OPPD Response to 1 Oc. The specific details of the methodology, design inputs, and assumptions are part of a formal calculation that supports the Operability Evaluation associated with the RC&C. That analysis can be provided if requested.

In summary, the elastic design methodology leads to every section (member) being proportioned to provide adequate strength.

See Attachment 1, Notes 2 for a summary of the approach.

Though not explicitly codified, the ACI Code does contain provisions for adjustments to these simplified elastic analysis outcomes.

In the 1963 Code this is addressed in Code section ACI 1502. The advent of sophisticated analysis tools for continuous statically indeterminate structures had not yet occurred.

Forces can now be precisely followed (element by element) such that load redistribution can be irrefutably established with no need of simplifying, conservative assumptions.

Limit design and yield line theory are used to safely design concrete structures and realize cost savings over the results produced by simplified, elastic member design. Transverse shear loads at all critical sections are checked against code allowables.

Twisting moments are conservatively added absolutely to each of two normal bending moments. j d. Please provide the pertinent RC&C force/moment demand versus capacity for individual load cases (e.g., seismic loads, compartmental pressurization) prior and subsequent to the application of limit state design methodology and identify critical load combinations and the areas of high demand.

LIC-16-0044 Enclosure 1 Page 18 OPPD Response to 1 Od. Since the analysis of the RC&C walls using the LAR conditions has not yet been performed no pertinent data are available at the point of time. However, the inelastic behavior of the RC&C walls is mainly due to compartmental pressurization, which is shown in the existing operability calculation mentioned in response to RAI 10(9). The RC&C walls exhibit elastic behavior in the primary load-carrying direction under all loads and load combinations including seismic loads except accident pressures.

The major difference in the interaction ratios prior and subsequent to the application of limit state design methodology will be seen in the secondary direction due to load redistribution.

For the explanation of why results prior and subsequent to the application of limit state design methodology are different, see the response to RAI #10 (f). e. The inelastic deformation/rotational capability of RC&C walls, adequate shear resistance in critical sections, and adequate reinforcement anchorage length to support the use of limit state design methodology have not been discussed in the LAR. Please provide a discussion with quantitative data related to these items. OPPD Response to 1 Oe. The acceptance criteria of the inelastic deformation/rotation of the RC&C walls are described in Attachment 1, Notes 1. Shear loads at all critical sections are checked against code allowable.

If a wall section has shear loads greater than the allowable, a modification will be required.

As explained in the response to RAI #6, as long as an existing anchorage (for rebar) meets the anchorage requirement in ACI 318-63 it is deemed acceptable to use the Limit Design Method (LDM). Since the analysis of the RC&C walls using the LAR conditions has not yet been performed, no quantitative data are available at this point. f. Considering the statement in Section 3.4 of the LAR, it is the NRC staff's understanding that the request to use limit state design methodology is being proposed for all load combinations applicable to the RC&C walls including the normal/service load combinations.

The ACI 349 Code and NRC staff guidance (SRP Section 3.8.3, "Concrete and Steel Internal Structures of Steel or Concrete Containments, " and Section 3.8.4), referenced in this LAR, require elastic design for service load and seismic load conditions.

Therefore, the request to use limit state design methodology for all load combinations has not been technically justified in this LAR. Please provide further information to demonstrate that this request is consistent with the industry codes/standards and the NRC staff regulatory guidance.

OPPD Response to 10f. The inelastic behavior of the RC&C walls is mainly due to compartmental pressurization.

This is shown in formal calculation associated with operability of the RC&C. The calculation can be provided if requested.

LI C-16-0044 Enclosure 1 Page 19 Walls carry loads in two-way action. The original design of the RC&C walls at the Fort Calhoun Station (FCS) was based on the limit state of the reinforced concrete structure (i.e., accident pressure is carried primarily in the horizontal direction).

This limit state cannot be replicated by any simple form of linear analysis.

The design forces and moments at the limit state can only be computed by using step-wise linear finite element analysis, herein called the Limit Design Method, or by non-linear analysis.

Attachment 1, Notes 3 shows an example problem to illustrate the concept of the Limit Design Method (LMD). The step-wise linear analysis of the LDM requested in this LAR is justified by the following,

• The step-wise linear analysis consists of multiple steps, at each of which a linearly elastic model and gross-section properties of the elements are considered.

The multiple steps are used primarily to track load redistribution rather than material inelasticity.

Further, as allowed by Section 8.3 of ACI 349-97, the maximum effects of factored loads are determined by the theory of elastic analysis along with the use of simplifying assumptions for computing the relative flexural and torsional stiffnesses of columns, walls, floors, and roof system. The multiple steps in the step-wise linear analysis are used for tracking load redistribution and changes in the relative stiffnesses from step to step.

• Except for the fuel canal walls which need further analysis to determine if modification is required for hydrostatic loads when flooded, the RC&C walls exhibit elastic behavior in the primary load-carrying direction under all loads and load combinations including seismic loads except for loads associated with accident pressures.

• The RC&C walls were designed in accordance with ACI 318-63 and the time of their construction is well before ACI 349-97 was issued as the governing code for nuclear safety related concrete structures.

ACI 318-89, which is a later edition of ACI 318-63, permits a seismic design based on loads corresponding to an inelastic response to strong ground motion earthquake if the design exhibits a robustness characterized by retention of substantial proportion of its strength as it is inelastically cycled. As explained in Section R21.2 of ACI 349-97 Commentary, ACI 349-97 recognizes that significant differences in design and structural forms exist in the applications of respective codes and adopts the high seismic risk provisions of ACI 318-89, Chapter 21. These later codes allow for a degree of inelasticity so long as rebar is fully developed by anchorage, maximum compressive strain of concrete is less than 0.003, and shear loads of all types are less than their respective allowable.

• In the elastic design, sizes and placements of reinforcing bars (rebar) are determined by internal forces and moments from a linear analysis.

Since a linear finite element analysis is very much different from the simplified analysis by hand calculation performed for the RC&C walls back in 1960's (note: the document of the hand calculation is either incomplete or missing), it produces different internal forces and moments than were originally used for the design of the RC&C walls. For example, If OPPD were required to meet ACI 349-97's requirement of the elastic design based on a linear analysis, the RC&C walls would need modification.

This is driven primarily by the differences in the design loads due to two different types of linear analyses.

By using a step-wise linear analysis to replicate the original design forces and moments it is possible to capture the actual load redistribution behavior.

In conclusion, the step-wise linear analysis is considered safe and appropriate for existing structures.

LIC-16-0044 Enclosure 1 Page 20 g. Considering the methodology of limit state design and formation of plastic hinge: i. Please discuss the effects of change in stiffness on the dynamic characteristics of the RC&C walls, which may affect (1) the level of accelerations induced in the RC&C structure due to seismic loading; and (2) the structural response of the RC&C walls to the impulse loading due to compartmental pressurization.

ii. Please justify that the additional deformation/rotation, crack formation, and stiffness degradation of the RC&C wall structure, resulting from such an analysis approach, does not adversely affect those safety-related structures, systems, or components adjacent to or supported from the RC&C walls, including the component support anchorages.

OPPD Response to 1 Og. RC&C walls under seismic loads act primarily as shear walls and their in-plane shear stiffnesses barely change. Even though out-of-plane bending stiffness of some of the walls does change, their fundamental frequencies still remain well above 3 Hz, which is the 1st soil-structure frequency of the dynamic stick model for the combined Containment Building, Internal Structure, and Auxiliary Building as described in USAR Appendix F. Their masses consist primarily of weights and are small relative to their stiffness.

Therefore, (1) the effects of change in stiffness on accelerations induced in the RC&C structure due to seismic loading are insignificant, and (2) the USAR-specified maximum dynamic Load factor (DLF) of 1.5 due to compartmental pressurization applied in RC&C evaluation is conservative without considering the beneficial effect of dynamic response's decreasing with decreasing wall stiffness.

The major equipment supported by RC&C walls are the Reactor, the Steam Generators, the Pressurizer, and the Reactor Coolant Pumps. The additional deformation/

rotation, crack formation, and stiffness degradation of the RC&C walls due to the out-of-plane action do not adversely affect their safety function because support loads/reactions are in the plane of the supporting walls and in-plane shear stiffnesses of the supporting walls barely change. It is important to note that the additional deformation/rotation is still small, since it is limited by the acceptance criteria.

RAl-11 According to RG 1.142 {Reference 6.22 in.the LAR), Regulatory Position 10.6, increase in the material strength (i.e., DIF) could be realized only when the material is subjected to very high strain rates of loading, normally associated with impactive/impulsive loadings.

Section 3.4 of the LAR is not clear relative to the application of DIF to various load combinations.

Please clarify. OPPD Response DIF will be used only for RC&C materials that are subjected to very high strain rates of loading. These loads are caused by rapid increases in differential pressure and jet impingement and are the result of the design basis High Energy Line Breaks (HELBs) accidents.

LIC-16-0044 Enclosure 1 Page 21 RAl-12 Section 2.9.2 of the LAR states that special seismic requirements for steel reinforcing detailing of ACI 349-97, Chapter 21 adds special detailing provisions for seismic that are not related to impactive or impulsive conditions.

Section 21.2.1.1 of ACI 349-97 states that the reinforcing bar detailing requirements of Chapter 21 shall be the design practice for nuclear plants within the purview of this code. In addition, the ACI 349-97 Commentary (Section R21.2) provides a discussion regarding the intent of Chapter 21. Considering the above, the NRC staff does not consider the statement in Section 2.9.2 of the LAR consistent with the intent of ACI 349 Code. Please provide further clarification regarding the statement in Section 2.9.2 of the LAR. OPPD 'Response Dynamic Increase Factors (DIFs) are not in the existing code of record. ACI 349-97 is referenced only as a source for DIFs. A comparison between the design requirements of ACI 349-97 and ACI 318-63 is performed within LAR section 2.9 to justify the use of DIFs when considering impactive or impulsive load scenarios in the analysis of the RC&C. The intent of the statement in question was to note that the requirements of ACI 349-97 Chapter 21 need not apply when considering impactive or impulsive loading and therefore do not apply to the conditions of this request. RAl-13 The mark-up of the USAR, Section 5.11 indicates changes to Section 5.11.3.2, "Operating Basis Load Combinations for Class I Steel Structures," and Section 5.11.3.3, "Design Basis Load Combinations for Class I Steel Structures." The scope of the LAR is related to concrete structures and the proposed changes to Section 5.11.3.2 and Section 5.11.3.3 are not discussed in the LAR. These changes are considered outside the scope of the submitted LAR and will not be reviewed.

Please discuss and clarify this inconsistency in the LAR submittal.

OPPD Response USAR Sections 5.11.3.2 and 5.11.3.3 will not be changed by this LAR. OPPD agrees that these sections are outside the scope of the LAR and need not be reviewed.

LI C-16-0044 Enclosure 1 Page 22 RAl-14 The mark-up of the USAR, Section 5.11.3.6 indicates that the use of DIF for RC&C comply with ACI 349-97, Appendix C. RG 1.142 has not been incorporated in this mark-up as discussed in the LAR. Please clarify. OPPD Response Based on review of the comment, the reviewer is correct. .The Markup to USAR section 5.11.3.6 references ACI 349-97 Appendix C for DIF; the LAR write up also discusses the provisions of RG 1.142 being applicable (specifically LAR enclosure page 33). OPPD agrees that in addition to ACI 349-97, RG 1.142 should have been included in the USAR section 5.11.3.6 markup.

LI C-16-0044 Attachment 1 Page 1 Attachment 1 OPPD Response Notes LI C-16-0044 Attachment 1 Page 2 Attachment 1 OPPD Response Notes Notes 1. Acceptance Criteria for a Ductile Section To avoid brittle failure of a critical cross section, the maximum compressive strain due to bending must be less than the concrete ultimate strain of 0.003. If the finite element software used for modelling the RC&C walls can output the maximum compressive strain due to bending, the concrete ultimate strain of 0.003 can be used as the acceptance criteria.

Otherwise, the rotational capacity derived below can be used as the acceptance criteria for rotations at critical sections, Per Figure 1, curvature 4-'u at the ultimate strength of a section is, n1 _ Eu Tu -c Where Eu is the concrete ultimate strain (0.003) and c is the distance from the extreme compressive fiber to the neutral axis at the ultimate strength determined per ACI 318-63. The rotational capacity ru of a yield zone can be expressed by: Where Dh is the length of the yield zone which can be determined from output of the finite element software.

Rotations at critical sections of the RC&C walls must be less than ru for the sections to preclude concrete failure. c I I f i I I /. I I E* u Figure 1 -Strain Distribution in a Section at Ultimate State LI C-16-0044 Attachment 1 Page 3 Notes 2. Limit Design Method (LDM) The Reactor Cavity & Compartment (RC&C) walls at the Fort Calhoun Station (FCS) will be analyzed using a linear finite element model with a step-wise linear analysis procedure.

The procedure is illustrated using the simple example shown in Figure 2. The top of the figure shows a structure consisting of three springs in parallel.

For convenience, the springs' stiffnesses are assumed equal, but they vary in strength from F/4 to F. Model 1 consists of all three springs. In Step 1, the model is loaded until the strength of the weakest spring (top spring) is reached. This would be the end of a linear analysis, achieving a capacity of 0.75F. The nonlinear analysis proceeds by removing the top spring and applying a load increment until the residual capacity of the next weakest spring (the bottom spring) is reached (see Model 2). At the end of Step 2, both the top and bottom spring have reached their maximum strength and a load of 1.25F has been applied. Implicit is the assumption that the top spring has sufficient ductility to maintain the F/4 load through the additional displacement.

The analysis continues by removing the lower spring (Model 3) and applying another load increment required to use up the residual strength of the strongest (middle) spring. At the end of Step 3, all three springs are at their maximum strength and a load of 1. 75F has been achieved.

This method is called Limit Design Method (LDM), which is similar to the Yield Line Theory widely used for slabs in industry.

The RC&C walls are modeled using the finite element model (FEM). The elements are organized into groups, each of which has same rebar design and same wall thickness in the same wall plane. When elements reach their capacities, their stiffnesses are set to a small number and the analysis proceeds to the next step. In general, each group of elements is loaded primarily in one direction.

The use of the step-wise linear analysis procedure allows the stiffness in the direction of rebar yielding to be set to a small value at the end of an analysis step; the other direction may continue to take load as the analysis proceeds.

The criteria for 'removing' elements with yielding rebar is per the code of record ACI 318-63. The mechanics of the computation required for RC&C wall analyses are briefly detailed as follows: at each step, the load combination being evaluated is applied to the linear finite element model. The amplitude of the load combination is essentially arbitrary.

The element force/moments are then dumped into a database which also houses the results from the previous steps. The analyst guesses a scale factor to be applied to the current model's analysis results; the results are then combined with those of the previous steps (whose loading scale factors have already been established) and the results are checked against ACI code requirements.

The scale factor is then adjusted up or down until one or more elements is at the code limits. A new model is then created in which the stiffness for those elements reaching code \ limits is set to a small number, and the analysis continues.

The analysis stops if enough elements are 'removed' so that small increases in loads result in large increases in displacements.

Otherwise, it will continue until 100% of load is applied. The method described above will be applied to the following No-Loss of Function load combinations for RC&C walls, as required by FCS USAR, U = 1.00 + 1.0E' U = 1.00 + 1.0L + 1.0E' U = 1.00 +/- 0.050 + 1.5Pc + 1.0Tc U = 1.00 +/- 0.050 + 1.25Pc + 1.25E + 1.0Tc U = 1.00 +/- 0.050 + 1.0Pc + 1.0E' + 1.0Tc LI C-16-0044 Attachment 1 Page 4 In the above load combinations, D and L refer to Dead and Live Loads, Tc to thermal load caused by temperature gradient across the concrete section, Pc to accident pressure loading, E to Operating Basis Earthquake (OBE) loading, and E' to Maximum Hypothetical Earthquake (MHE) loading. It is important to note that no reduction in seismic demand is allowed. The method will also be applied to the following Normal/Operating Service Load combinations requested in the LAR, u = 1.40 + 1. 7L U = 1.00 +/- 0.050 + 1.25L + 1.25E k, F/4 Fmax? k, F k, F/2 Model 1 F/4 Step 1 0.75F Step 2 F/4 F/4 Model 2 1.25F F/2 F/2 0.50F Step 3 F/4 Model 3 1.75F F F/2 0.50F F/2 Figure 2 -Schematic of Step-Wise Linear Analysis Procedure LI C-16-0044 Attachment 1 Page 5 Notes 3. Example Problem Solve by Limit Design Method (LDM) Shown below is a one-way slab with all sided fixed. Fixed Fixed Fixed Fixed In the design of the slab, the reinforcing bars (rebar) required in the short direction are determined by designing a unit-wide beam and small (minimal) temperature rebar is used in the long direction.

In a linear finite element analysis of this one-way slab, the slab is commonly shown overstressed along the short sides since the calculated moment about the short side is greater than moment capacity provided by minimal temperature rebar. This implies the slab is under-designed and additional rebar is needed in the long direction.

Actually, the main rebar in the short direction is perfectly capable of picking up all of the loads and redistributes them to the short direction after the temperature rebar yields. While a linear finite element analysis is not capable of showing this sequence of load redistribution behavior, the redistribution behavior is correctly simulated by a step-wise linear finite element analysis or a non-linear analysis.

LI C-16-0044 Attachment 2 Page 1 Attachment 2 Steel Reinforcement Statistics

1. Order#(s)

Heat# Bar Size Supplier CMTR Steel Independent Test Agency Average Test Std Dev Mean (ksi) 95% (ksi) Coefficient Strength (ksi) Strength (ksi) Strength (ksi) (ksi) of Variation 1 F-5228 14049 3 44.64 44.64 3.77 49.29 43.10 0.08 2 F-5500 14657 3 52.81 52.81 3 F-63X4 14598 3 53.18 53.18 4 F-63X8, F-6387, F-6390 15371 3 46.54 46.54 5 F-9343 16359 3 6 2790 32720 4 50.00 50.00 3.33 50.11 44.62 0.07 7 F-3922 26209 4 49.75 51.50 50.63 8 F-4997 C29170 4 57.00 57.00 9 F5228 A29428 4 52.00 52.00 10 F-5499 34016 4 47.00 47.00 11 F-6384 34043 4 50.00 50.00 12 F-6385 34026 4 48.75 48.75 13 F-6388 S3327 4 56.49 56.49 14 F-7154 27795 4 45.50 48.00 46.75 15 F-7153 M9161765 4 45.50 45.50 16 F-8245, 8246, 828 15699 4 49.75 49.75 17 F-7897, 8247 27799 4 47.25 47.25 18 F-8924 27794 4 50.25 50.25 19 F-9343 16111 4 20 F-3922 14510 5 49.84 49.70 49.77 3.94 51.89 45.41 0.08 21 F-4987 33520 5 48.39 48.39 22 F-5231 14710 5 50.65 50.65 23 F-5492 33351 5 51.61 51.61 24 F-6384 S3203 5 51.50 51.50 25 F-6385 S3245 5 51.34 51.34 26 F-6388 S1674 5 54.60 54.60 27 F-6384, 6392, 7151, 7148 S3398 5 28 F-6386 S3464 5 58.18 58.18 29 F-7154 S3452 5 51.17 51.17 30 F-7153 28078 5 47.74 47.74 31 F-8246 34697 5 48.55 48.55 32 F-8247 16209 5 47.75 47.75 33 F-8249 S3954 5 53.13 53.13 34 F-8924 16463 5 62.10 62.10 35 F-9343 40098 5 36 2790 32678 6 48.41 48.41 4.00 50.84 44.25 0.08 37 2791 S1534 6 49.78 49.78 38 F-3922 M9160732 6 47.04 45.00 46.02 39 F-4987 33377 6 50.11 50.11 40 F-3921 32853 6 48.52 48.52 41 F4988 M9151167 6 45.80 45.80 42 F-6383 S2552 6 56.12 56.12 43 F-6384 S2477 6 53.86 53.86 44 F-6385 14805 6 57.05 57.05 45 F-6388 S2547 6 59.97 59.97 46 F-6387 S3195 6 54.31 54.31 47 F-7153 34515 6 48.41 48.41 48 F-8245 40100 6 49.09 49.09 49 F-8246 30100 6 49.09 49.09 50 F-7897 40100 6 49.09 49.09 51 F-8924 40196 6 47.84 47.84 52 2790 M9030377 7 45.33 45.33 4.90 49.16 41.10 0.10 53 2791 M9020322 7 44.50 44.70 44.60 54 F-4987 13995 7 44.00 41.67 42.84 55 F-5228 14013 7 44.91 44.91 56 F-6384 S2395 7 54.06 54.06

1. Order#(s)

Heat# Bar Size Supplier CMTR Steel Independent Test Agency Average Test Std Dev Mean (ksi) 9S% (ksi) Coefficient Strength (ksi) Strength (ksi) Strength (ksi) (ksi) of Variation S7 F-638S S2396 7 SS.06 SS.06 S8 F-6388 S277S 7 S4.39 S4.39 S9 F-6387 H-49834 7 SS.OD SS.00 60 F-71S4 34207 7 47.50 45.67 46.59 61 F-7153 34181 7 46.25 46.25 62 F-8246 34391 7 55.75 5S.75 63 F-7897, 8247 34225 7 45.17 45.17 64 F-9343 40193 or 7 40113 65 2790 26058 8 49.93 49.93 2.43 51.71 47.71 0.05 66 F-3922 M9150780 8 49.31 42.40 45.86 67 F-X987 14058 8 50.18 50.18 68 F-3921 S0890 8 51.31 51.31 69 F-6383 S2902 8 52.33 52.33 70 F-XXXX 52857 8 54.75 S4.75 71 F-6385 52901 8 52.58 S2.58 72 F-6XXX 52907 8 52.84 S2.84 73 F-6384AD, F-8S39 52199 8 51.31 51.31 74 F-7501 X597 8 55.28 55.28 7S F-7897, 8247 52198 8 52.46 52.46 76 F-9343 27878 8 77 2790 51313 9 49.66 49.66 2.24 50.75 47.07 0.04 78 2791 51317 9 50.03 50.03 79 F-6384, 7898 27446 9 80 F-6XX5, 6XX6, 6384AD 52316 9 53.80 53.80 81 F-63XX 52196 9 50.40 50.40 82 F-6387 52166 9 53.80 53.80 83 F-71S4 S2172 9 54.30 54.30 84 F-6XXX 2 52318 9 85 F-7153 52747 9 52.00 52.00 86 F-8344 27441 9 47.66 47.66 87 F-7897, 8247 33589 9 49.06 49.06 88 F-XXX4 27415 9 49.03 49.03 89 F-9343 34495 9 90 F-895 34052 9 48.50 48.50 91 2791 50027 10 52.15 52.15 3.00 49.86 44.93 0.06 92 F-X922 12011 10 46.99 46.10 46.55 93 F-4987 52283 10 S2.30 52.30 94 26834 51815 10 50.17 50.17 95 F-5228 S1804 10 51.5S 51.S5 96 F-6386 13515 10 S3.18 53.18 97 F-6388 S2962 10 53.25 53.25 98 F-7897, 8247, 8566, 8476A 34375 10 44.47 44.47 99 F-8924 34714 10 48.50 48.50 100 F-897 34383 10 46.50 46.50 101 899Add 25091 11 48.04 48.04 2.47 48.78 44.71 0.05 102 2791 59829 11 48.25 48.25 103 3496 59832 11 53.36 53.36 104 F-3922 M9150787 11 50.03 45.20 47.62 105 F-3505Add XX256 11 45.96 45.96 106 F-4987 52218 11 51.96 Sl.96 107 F-5228 M9161343 11 56.66 42.63 49.65 108 F-6383 M9151340 11 44.39 44.39 109 F6387 52833 11 51.38 51.38 110 F-7153 15423 11 46.90 46.90 111 F-8244 M9150771 11 112 F-7897 16023 11 49.02 49.02 113 F-9343, F-703AD 40178 11 46.82 46.82 114 F-897 27907 11 50.80 50.80 Heat# Bar Size Supplier CMTR Steel Independent Test Agency Strength (ksi) Strength (ksi) # Order#(s) 115 F-3922AD2 14149 14 51.38 Average Test Std Dev Mean (ksi) 95% (ksi) Coefficient Strength (ksi) (ksi) of Variation 51.38 0.00 51.38 51.38 0.00 Min: 41.10 Max: 51.38 SAMPLE POPULATION STANDARD DEVIATION, a= 3.61 SAMPLE MEAN, µ = 50.38 SINGLE TAIL 95% CONFIDENCE, µ -1.6450 = 44.44 COEFFICIENT OF VARIATION=

0.07