ML15114A386
| 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
1 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
2 Agenda
- History
- Overall Goal
- 4 Elements
- Closing Remarks
3
- 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.
History
4
- 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.
FCS License Basis
5
- 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.
Options to License Basis
6
- 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.
Overall Goal of the LAR LAR has 4 Elements
7 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.
8 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.
9 Element 1: ASD vs. USD Eqns.
- Final Load Combinations for Normal/Service Operating Conditions.
Working Stress Design (WSD)
Current License Basis Replacement Ultimate Strength Design (USD)
Load Combination Equations S = D + L S = D + L + W S = D + L + E S = D + F U = 1/ (1.4 D + 1.7 L)
U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 W)
U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 E)
U = 1/ (1.4 D + 1.4 F)
10 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 S = Required section capacity for WSD U = Required ultimate strength capacity D = Dead load, including hydrostatic load L = Live load W = Wind load E = Design earthquake (OBE)
F = External hydrostatic load
= Capacity strength reduction factor FCS is proposing to use the updated version with 1.4 factor
11 Element 1: Develop USD 2nd/3rd Eqn.
- USD method for normal service conditions needs to address the following: Wind, Earthquake, and Hydrostatic loads.
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.
12 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)
13 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)
14 Element 1: ASD vs. USD Eqns.
- Final Load Combinations for Normal/Service Operating Conditions.
Working Stress Design (WSD)
Current License Basis Replacement Ultimate Strength Design (USD)
Load Combination Equations S = D + L S = D + L + W S = D + L + E S = D + F U = 1/ (1.4 D + 1.7 L)
U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 W)
U = 1/ (1.0 D +/- 0.05 D + 1.25 L + 1.25 E)
U = 1/ (1.4 D + 1.4 F)
15 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.
16 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.
17 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.
18 FCS LAR: Schedule
- LAR Submittal: 2nd Quarter 2015
- Requested Approval: 2nd Quarter 2016
- Design Correction and Install Columns (RF028):
3rd Quarter 2016
19 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)