Text

Meeting Handouts April 22, 2013 Meeting with Omaha Public Power District to Discuss Potential Fort Calhoun Licensing Actions
	ML13112A052
Person / Time
Site:	Fort Calhoun
Issue date:	04/22/2013
From:	; Omaha Public Power District
To:	Joseph Sebrosky; Plant Licensing Branch IV
	Sebrosky J
References
	TAC MF0598
	Download: ML13112A052 (35)
	v • d • e

Fort Calhoun Station Potential NRC License Amendment April 22, 2013 1

Agenda

Purpose of the meeting - Bruce Rash

Tornado Missiles - George Wilhelmsen

Alternate Seismic Criteria and Methodologies -

George Wilhelmsen

Intake Structure - Chris Scofield

Piping Codes - Don MacIsaac

Equipment Reclassification - George Wilhelmsen

Closing comments - Bruce Rash 2

Tornado Missiles

OPPD implemented a modification that moved the condensing units from inside the control room to the roof.

NRC identified that a probabilistic analysis was used for tornado justification of these roof mounted control room condensing units.

All tornado missile vulnerabilities will be addressed prior to start up.

3

Existing Tornado Vulnerabilities Vulnerability Fix Reload or Restart Control Room Condensers1 Construct a cage around condensers Restart Room 81 Roof Opening1 Construct a cage around opening Restart FW-10 Stack1 Construct a cage around stack Restart Diesel Generator Fill Line 2 Grade beams and grating Restart Diesel Generator Vent Line2 None, Deterministic Approach Restart AC-10 Power Pull Boxes Concrete wall and grating Reload Intake Structure None, Deterministic Approach Restart Note 1: Missile threat include pipe and sphere (no car).

Note 2: Applies to both FO-1 and FO-10.

4

Tornado Protection Commitment

Omaha Public Power District (OPPD) plans on using the guidance in Regulatory Guide 1.76 Revision 1.

A License Amendment Request (LAR) is required.

- OPPD is changing the current licensing basis to account for differences in missile velocities that are contained in Regulatory Guide 1.76.

5

Implementing RG 1.76

Fort Calhoun is located in Region I of RG 1.76.

- Missiles include a six-inch pipe, an automobile, and a small sphere.

- Velocities listed in the Regulatory Guide will be used as inputs to calculations supporting mods.

- Automobile is limited to targets within 30 feet of grade.

6

Tornado Protection Plan is Comprehensive

Roof-mounted targets: The Control Room condensers, Room 81 roof opening, and the FW-10 stack will be protected from the six-inch pipe and sphere using a missile-resistant cage.

- Cage will use a small h-shaped metal frame and grating.

OPPD will use a deterministic approach for the evaluation.

7

Tornado Protection Plan is Comprehensive

Diesel generator fill lines will be protected with concrete grade beams and grating to protect against automobiles, pipe, and sphere.

- Grade beams will displace the forces from the automobiles to the grade around the tank.

- Grating will be bolted on top of concrete grade beams to protect fill lines against the pipes and spheres.

8

Tornado Protection Plan is Comprehensive

Diesel generator vent lines will be addressed using deterministic approach.

Targets associated with the raw water pumps (AC-10) will be addressed.

- Grating above the pumps will be reviewed for pipe and sphere protection.

- Power supply pull boxes will be protected using barriers.

9

Schedule and Summary

Schedule: All modifications are planned to be completed by May 31st for plant start up.

OPPD will determine operability based upon NRC Inspection Manual Section 9900 alternative methods for start up.

10

What is Alternate Seismic Criteria and Methodologies (ASCM)?

ASCM was initiated to address areas that did not have an NRC-approved seismic Floor Response Spectra (FRS).

- Turbine Building.

- Intake Structure.

ASCM used more advanced techniques for development of FRS.

11

Alternate Seismic Criteria and Methodologies

OPPD used ASCM FRS for structure, systems and components (SSCs) other than pipe and duct.

NRC identified that the ASCM FRS was used for SSCs outside the NRC approval, which is limited to piping and ducts.

OPPD will request approval to use ASCM FRS for all SSCs (LAR). Alternative to USAR FRS.

- This will not change methodologies.

12

Where FCS Used ASCM

Intake Structure

- Operability will be provided.

- Original USAR did not have floor response spectra.

HE-2

- Functionality will be provided.

Cage around FW-10

- Cage will be removed.

13

OPPD/NRC ASCM Correspondence

The initial ASCM LAR was submitted for NRC approval on 12/2/88.

There were numerous letters to the NRC and requests for information from the NRC. This issue was finalized with an SER (T71408) issued on 4/16/1993.

14

ASCM Included Many Topics

ASCM

- Future Designs.

- Modifications.

- Reanalysis of piping and supports.

- Electrical raceways HVAC systems.

- Anchor bolts.

Scope reduced:

- Floor response spectra

- Piping and HVAC.

15

Why is the Floor Response Spectra Acceptable? Per SER (T71408)

Housner Ground Response Spectrum.

- The NRC staff agreed with the Housner ground response spectra.

- The actual time histories used in the analysis.

Overturning and Sliding.

- The NRC staff agreed that the difference in pile stresses is not significant.

Accidental Torsion

- The NRC staff agrees that the FRS introduces sufficient margin of conservatism.

16

Why is the Floor Response Spectra Acceptable? Per SER (T71408)

Upper Bound (UB) Soil Properties:

- The NRC staff agrees that the use of 1.3 times the best estimate value for the UB value is adequate.

Radiation Damping:

- NRC staff considers that the use of 6.7% radiation damping conservative.

Liquefaction

- NRC staff is satisfied with the action taken by OPPD to achieve a relative density of 86%.

17

Safety Evaluation Report NRC-93-0150 April 16, 1993

The FRS is the main issue:

- The SER stated that the ASCM is approved for pipe and duct.

- This also approves the ASCM developed FRS for pipe and duct methodology.

- The SER did not specifically state that the FRS was approved.

18

ASCM Going Forward

The ASCM FRS developed is acceptable as an alternative to the USAR Appendix F FRS.

ASCM FRS is acceptable for use on any SSC.

OPPD will submit an LAR to clarify that the ASCM FRS can be used as an alternative to the USAR Appendix F.

- This does not change any methodologies.

19

Intake Structure Flood Control

Topics:

- Licensing Basis

- Current Intake Structure Flood Control

- Future Bypass Modification Cell Control

- Modification Safety Classification 20

Licensing Basis

Draft Description provided to District in response to AEC question in 1970:

- For any water levels above 1007.5, the water level inside the intake structure is controlled by positioning the exterior sluice gates to severely restrict the inflow into the wet wells, along with pumping out at a rate equal to the inflow. Because of the wide head variation available, sluice gate and pump settings are self balancing with reasonable limits

PSAR / FSAR 9.8 (1972):

- For water levels above 1007.5 feet, the water level inside the intake structure is controlled by positioning the exterior sluice gates to restrict the inflow in to the wet wells to match the rate of pumped outflow. Because of the wide head variations possible, the sluice gate and pump settings are automatic self-balancing within reasonable limits. - Underlined language removed during USAR Verification Project (CR1999-01469)

USAR 9.8 (Current):

- The water level inside the intake cells can be controlled by pre-positioning the exterior sluice gates (i.e., before floodwater reaches the elevation that prevents access to the sluice gate actuators) to severely restrict the inflow into the cells. Intake cell level is then controlled by varying the raw water pump output to remove the inlet flow.

21

Current Intake Structure Flood Control

Sluice Gates (incorporated flood barriers) are prepositioned per AOP-01 by 1004

- Five of six gates fully closed

- One gate partially open

One Raw Water Pump run continuously, second pump cycled 22

Future Bypass Modification Control

AOP-01 Acts of Nature - Flood:

- Open new flood control throttle valves and close sluice gates

- Manually control in-leakage with four 10 inch throttle valves 23

24 Modification Safety Classification

Flood Barriers:

inch butterfly valve

Class break

Normally closed inch pipe

- Sluice gates

Incorporated flood barrier

Flood Control Valves:

- Four 10-inch butterfly valves

- Manually controlled

- Single failure 25

Piping Code Issue

OPPD used ASME Section III analysis in safety-related piping design calculations.

FCS safety-related piping Design Codes are USAS B31.1 (1967) and USAS B31.7 DRAFT (1968).

Use of alternate Design Codes, such as ASME Section III (1974, 1980), requires NRC approval (10CFR50.55a).

OPPD has not submitted an LAR to obtain NRC approval. This issue was discovered by NRC and is documented by Condition Report 2013-05206..

26

Operability

NRC Inspection Manual Part 9900, Appendix C, Section C.4 allows the use of Alternate Analytical Methods in Operability Determinations.

OPPD used an NRC-approved Alternate Analytical Method (ASME Section III Code) in safety-related calculations.

These calculations have been performed, checked, verified and are analytically acceptable as an Alternate Analytical Method to determine operability.

27

Operability

FCS calculations using ASME Section III piping design methodology:

- Meet the Allowable Stress Criteria of ASME Section III for design of piping systems at FCS.

- Meet the increased Allowable Stress Criteria of ASME Section III Appendix F as specified by NRC Inspection Manual 9900, Section C.10 for operability determination.

Therefore, FCS calculations using ASME Section III design code methodology document piping system operability.

28

Path Forward

OPPD will prepare an operability evaluation prior to fuel load.

Based on the requirements of 10 CFR 50.55(a),

OPPD will submit an LAR to the NRC requesting approval to use ASME Section III as an optional Design Code.

29