ML15114A386

Licensee Slides - 4/23/15 Public Meeting, License Amendment Request for Class I Structures

ML15114A386
Person / Time
Site:	Fort Calhoun
Issue date:	04/23/2015
From:	Omaha Public Power District
To:	Division of Operating Reactor Licensing
Lyon C
References
Download: ML15114A386 (19)

Text

OPPDs Fort Calhoun Station Driving to Excellence Public Meeting with the U.S. Nuclear Regulatory Commission License Amendment Request (LAR) for Class I Structures April 23, 2015 1

Agenda

• History

• Overall Goal

• 4 Elements

• Closing Remarks 2

History

• The CIS project started in 2012 where the investigation of the structure for a pipe support resulted in a self identified corrective action and complete structural re-evaluation of Class I Structures.

3

FCS License Basis

• FCS USAR (Section 5.11) License Basis:

• Allowable Stress Design (ASD) for Normal operations.

• Ultimate Strength Design (USD) for faulted conditions.

• Operability Analysis Completed in 2012

• It was noted that the current License Basis is conservative.

4

Options to License Basis

• Many options to change the FCS license basis were evaluated.

• ACI 318-63 is the code of construction (Design Basis).

• ACI 318-71 is one of the updated codes that was evaluated carefully as a replacement to the 1963 code.

But was finally rejected because of the exhaustive evaluations required to address all the new detailing in the code.

• Best option is to revise License Basis using the current code of record.

5

Overall Goal of the LAR

• Change License Basis

• Replace Working stress with Ultimate Strength. This is a license basis change.

• Change Design Basis

• Replace Design Basis Concrete Design Strength (fc) in specification (4000 psi) with 28 day break strength.

• Adopt methods that are not in the1963 code

• Use Finite Element Analysis for more accurate results.

• Credit Dynamic Increase Factors to increase capacity.

• This applies to all Class I Structures other than Containment shell.

LAR has 4 Elements 6

Elements of the LAR

1. Replace Allowable Stress Design (ASD) with Ultimate Strength Design (USD) for normal operating/service conditions.

2. Use of 28 day test strength of concrete (not age hardening) for Class I Structures other than Containment Shell.

3. Use of Ductility (finite element analysis) as defined in ACI 349-01 Appendix C.

4. Use of Dynamic Increase Factors (DIF) for impulse loads as defined in ACI 349-01 Appendix C.

7

FCS LAR: Element 1

• ACI 318-63 Replace ASD with USD for normal/service operating conditions.

- Allowable stress design (ASD) commonly known as working stress design has four equations. Four USD equations will be developed that are analogous to the ASD Design Basis.

- The USD equations will be developed from codes and License Basis.

• For faulted, the approach remains unchanged.

8

Element 1: ASD vs. USD Eqns.

• Final Load Combinations for Normal/Service Operating Conditions.

Working Stress Design (WSD) Replacement Ultimate Strength Design (USD)

Current License Load Combination Equations Basis S=D+L U = 1/ (1.4 D + 1.7 L)

S=D+L+W U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 W)

S=D+L+E U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 E)

S=D+F U = 1/ (1.4 D + 1.4 F) 9

Element 1: Develop USD 1st Eqn.

• ASD basic equation is S = D + L

• Equivalent Ultimate Strength Design to the basic eqn.:

[ACI 318-63 Equation 15-1] U = 1.5D + 1.8L

• ACI 318-71 and beyond uses a different basic equation.

[ACI 318-71 Equation 9-1] U = 1.4D + 1.7L FCS is proposing to use the updated version with 1.4 factor S = Required section capacity for WSD W = Wind load U = Required ultimate strength capacity E = Design earthquake (OBE)

D = Dead load, including hydrostatic load F = External hydrostatic load L = Live load = Capacity strength reduction factor 10

Element 1: Develop USD 2nd/3rd Eqn.

• USD method for normal service conditions needs to address the following: Wind, Earthquake, and Hydrostatic loads.

• FCS UFSAR currently utilizes USD factored loads for SSE and OBE:

U = 1/ (1.0D +/- 0.05D + 1.5Pc + 1.0Tc)

U= 1/ (1.0D +/- 0.05D + 1.25Pc + 1.25E + 1.0Tc) for OBE case U = 1/ (1.0D +/- 0.05D + 1.0Pc + 1.0E + 1.0Tc) for SSE case

• Second equation is used to develop the USD equations for the optional normal service conditions and implement the earthquake and wind load factors.

11

Element 1: Develop USD 2nd/3rd Eqn.

• From the USAR Section 5.11 (Current License Basis):

• U= 1/ (1.0D +/- 0.05D + 1.25Pc + 1.25E + 1.0Tc) for OBE case

• The resulting USD load combinations for wind and earthquake are as follows:

U = 1/ (1.0D +/- 0.05D + 1.25 L + 1.25 W)

U = 1/ (1.0D +/- 0.05D + 1.25 L + 1.25 E)

Note: This is similar to the ACI 318-71 code Equation 9-2: U = 0.75(1.4D + 1.7L + 1.7W) 12

Element 1: Develop USD 4th Eqn.

• The USD load combination for Hydrostatic loads is a simple conversion of the ASD equation plus the phi factor.

ASD U=D+F Use the 1.4 factor to convert ASD to USD USD U = 1/ (1.4 D + 1.4F) 13

Element 1: ASD vs. USD Eqns.

• Final Load Combinations for Normal/Service Operating Conditions.

Working Stress Design (WSD) Replacement Ultimate Strength Design (USD)

Current License Load Combination Equations Basis S=D+L U = 1/ (1.4 D + 1.7 L)

S=D+L+W U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 W)

S=D+L+E U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 E)

S=D+F U = 1/ (1.4 D + 1.4 F) 14

FCS LAR: Element 2

• Use of 28 day test strength of concrete for Class I Structures.

- This is NOT age hardening as discussed in NRC Information Notice 2012-17.

day concrete break strength information was documented.

- Actual 28-day strength ranges are approximately 4700 psi to 5500 psi.

15

FCS LAR: Element 3

• Allow the use of Ductility (Finite Element Analysis) to bridge generation gap of concrete analysis.

- There is a difference with conventional analysis and finite element (FE) analysis. We can now model shapes with small increments to come closer to actual values.

- This is not a margin issue but improves accuracy. There is no impact on margin.

- Ductility methodology is defined in ACI 349-01 Appendix C.

16

FCS LAR: Element 4

• Allow for use of dynamic increase factors (DIF) using ACI 349-01 Appendix C for impulse effects.

- Impulsive loads are time-dependent loads which are not associated with collision of solid masses. The pressure raises quickly and then stabilizes. The pressure difference across walls equalize quickly.

- Appropriate dynamic increase factors (DIF) address changing strain rates applied to a static analysis. Material strengths are increased to appropriately reflect the response of concrete to the dynamic condition.

- This is not a margin issue but improves accuracy. There is no impact on margin.

- DIF methodology is defined in ACI 349-01 Appendix C.

17

FCS LAR: Schedule

• LAR Submittal: 2nd Quarter 2015

• Requested Approval: 2nd Quarter 2016

• Design Correction and Install Columns (RF028):

3rd Quarter 2016 18

Closing Remarks

• History

• Overall Goal

• 4 Elements

• ASD v. USD (License Basis Change)

• 28 day break strength (Capacity)

• Finite Element Analysis (Accuracy)

• Dynamic Increase Factors (Capacity) 19