ML061290460

May 5, 2006 Meeting Slides

ML061290460
Person / Time
Site:	Cooper
Issue date:	05/05/2006
From:	Roberts J Nebraska Public Power District (NPPD)
To:	Office of Nuclear Reactor Regulation
References
TAC MC8236
Download: ML061290460 (5)

Text

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CNS DIESEL GENERATOR (DG) -ORNADO COPING ANALYSIS May 5, 2006 2-1 PRESENTATION BACKGROUND

• SSD&PC Inspection Question Regarding Tomado Design of DG

• BACKGROUND Rooms at CNS.

• CNS Re-verified and Validated the Tornado Design of the DG

• DG ROOM HIIAC AND VIRTUAL Rooms.

TOUR - The DG Structures per USAR are Designed for:

Class I (seismic)

• TORNADO SEQUENCE Tomado p

and Wind Generated MissileProtection 3 si Differential Pressure Load from Atmospheric Pressure Change.

• TIA ISSUES - By Design, the DG Structures are Vented

- The DG Ccmponents Located Within hose Structures are Vented

• CNS CALCULATION and per the SRP,

• "AdequatelyProtectedandMayb.ErqectedtoPedonn

• CONCLUSIO1S NecessarySafety-ReatedFunclons.1

- Tomado Event isRecove ableCondiion in that Actions Can be

• QUESTIONS/DIALOGUE Taken to Mantain or Restore DG's 4

BACKGROUND, cont. BACKGROUND, cont.

- DG Components Cutside Structure VAII Not Prevent Engine - CNS Provided Calculation NEDC 05-021, Rev. 1 to Start and Load Atetr Tomado Demonstrate DG Ventilation Ductwork Integrity Is Maintained ExtaustMufflerAistys Bypassed During Tomado Induced Atmospheric Pressure Changes in Separate Alr Intakesfor EngineandBuikding ventiltion June of 2005.

- Based on Field Ins 3ection of Venting, OE and Engineering CNS Calculatbn of 2005 Not Performed for Desin.

Analysis, Other Ro 3m Components are not Affected by

• Calculationwas Performed for Showing Reasonable Atmospheric Pressure Changes. Expectationof Duct Inegrity.

• Electrical, Mecthanimat.Instnrumentation

• Calculation Utlized Venting of Rooms for Diftirential Pressure

- Question Still Existed Regarding Failure of DG Room on Duct Comporents.

Ventilation Ductwok that Could Potentially Result In Room Sound Engineering PracticesUsed in Calculathg Duct Overheating. Component Stresses.

• CNSDGSructnure; Not HamrhEnvirtnment, EO Is NotApplicable.

• Recognized thatSome Deformation May Occur Due to Faufted ElevatedRoomTenperatures CouldAffectElectricalcomponents. Condition.

• Calculation Cmtsistent wth Industry Practice(OE) 0 1

HVAC Schematic DG in Standby BACKGROUND, cont. Normal Spring/Summer Operation

- Familiarity with CNS Specific Design is Necessary to Understand the Calculations.

- Calculation was Revised Utilizing More Recent Methodology.

• Venting of Rooms Still Utilized

• 1984 Rectangular Ductwork Analysis (ASCE Paper)

- DG Ventilation Components with Highest Vulnerability tc Tornado Damage:

• Supply Plenuri Ducts Dunng Depressurization Phase

• Exhaust Backiraft Dampers During Re-pressurization Phase HVAC Schematic DG Running Spring/Summer Operation VIRTUAL TOUR

• SITE LAY OUT AND OVERVIEW

• DG ROOM 903' OUTSIDE

• DG ROOM VESTIBULE

• DG ROOM 903' WEST

• DG ROOM 903' EAST

• DG MEZZANINE 915'

• DG ROOF

• DG PENTHOUSE 9 IC SITE LAY OUT I 4fE:0 X

...0E 0' nd X i 2

DEPRESSURIZATION SEQUENCE DEPRESSURIZATION SEQUENCE WUE DURINGTUNADO

_ MUFR RYPA5S AMWJEWF.IIMP..

ENSSR ASNA7E5 F, I~~EquASTTL 13 14 DEPRESSIJRIZATION SEQUENCE DEPRESSURIZATION

SUMMARY

• MAXIMUM PRESSURE DIFFERENTIAL IS 0.83 PSID

• MOST LIMITED PRESSURE CAPABILITY OF DUCT IS 1.25 PSID

- Duct Work Flow Path Remains Intact

• LOCATION IS IN VESTIBULE SECTION OF SUPPLY PLENUM

• NOTES:

- Having the normal Fi/AC suppl tan in operation during the depressurization phase Is inconsequenel since I provides litle additionrl resistance to the venting airflav pat) based on the resistance contribution of the other co onents nithe path. The fan capacty isinsufficisntto overcomehe presasre d erenti otfa tornado. The compressible ngture of air predudes damage b fan itself. The fan motor could trip on overload. Theefore the Calculation modeled the fan as'OFF-I1 1s RE-PRESSIJRIZATION SEQUENCE RE-PRESSURIZATION SEQUENCE DURINGT(RNADO MWTlEBYPASS AM4EBIIPI1 7ip.

PRESSWEEA5Burro NDlTrPA*5 F 17 1e 3

RE-PRESSURIZATION

SUMMARY

. MAXIMUM PRESSURE DIFFERENTIAL IS 2.50 PSI

• DUCT WORK REMAINS INTACT with POSITIVE INTERNAL PRESSURE

• WEAK LINK LOCATION IS EXHAUST BACKDRAFT DAMPER

- CAPABIUTY OF DAMPER IS1.60 PSID

- SELF-RELIEVING (Actual dP will be much less than 2.5 psi)

- WILL NOT CAUSE ANY SIGNIFICANT FLOW BLOCKAGE

- MAY NOT IMPACT EXHAUST FAN, HOWEVER..

- EXHAUST FAN NOT NEEDEDWITH SUPPLY FAN RUNNING TO MAINTAIN ROOM COOUNG AND REDUCED DG LOAD.

• CNS REVIEWING REMOVAL OF DAMPERS TO PROVIDE ADDITIONAL DESIGN MARGIN FOR PRESSURE VALUES AND EXHAUST FAN PROTECTION.

TIA COMMENTS PIPING CODE USE

• PIPING CODE_ USE

• ASME Code Allowable Stress (3 SM) Invoked for 'Faulted' Condition Based on Similarity of

- Allowable Stress of 3 SM from ASME Not Order of Magnitude for Tomadoes and DBA Appropriate LOCA as Low Probability Events.

• PRESSURE D)IFFERENTIAL UTILIZED

• Plate Bending Formulae are 'Textbook' Tools

- Should have used 3 psi Design Pressure for Analysis of Stressed Members.

(Non-vented vs. Vented Structure)

• Industry Code Expert (Reedy Engineering)

Confirms Acceptability of Use of ASME (3 SM)

• MATERIAL PROPERTIES

• CNS Methodology Provides Similar, but

- Source of Material Yield Strengths Not Conservative Results to ASCE Alternative Identified Methodology.

21 22 TORNADO DATA CNS Desbtn Bsis Tomato of 300 MPH Rotational Wind Speed, BCMPH Translational Wind S meed and 3.0 PSID is Low Pflbability Event ALTERNATIVE METHODOLOGY A Revised Analytical Method

-ASCE Paper 1984

.15-0. '04.06 t00tlen aeQUIoP eaO

- Methodology Based on Testing (ANO) 0045 10661605.1 Sli ~ ~ tt O.CnN 6-tlaee-4 - Specific for Nuclear Rectangular Ducts

- Yield Line Theory utilized (plastic behavior)

• Similar 'Textbook' Plate Formulae Provided

- Negative Internal Pressure of Duct is Most Limiting Scenario

• Room Vent Paths Utilized p4 612 *04E4 4.6004

-E 05Z t.1 F4 naS *41N IIII44 t s2 - Actual Material Properties Used for Duct 24 4

PRESSURE DIFFERENTIALS MATERIAL PROPERTIES

• Structure Design Conservatively Assumes

• Worst-Case Material Properties Assumed Non-vented - ASTM-A-36 36 ksi yield

• Structure is Snot intentionally sealed"

• Actual Duct Material

• Components ir Structure are Vented - 42.5 ksi minimum yield (by test)

+ Depressurization of Room Calculated Based

• Stiffener Angle Properties Not Clearly on USAR 3.0 psi at 1.0 psi/second rate. Identified

• Re-pressurization of Room Calculated Based

• Stiffener Angles ASTM-A-36 on Same Rate.

• Duct Thickness of 0.1875" Used (Error)

• Best Estimate 'K" Factors Used for Entrance

• Actual Duct Thickness is 0.0747" Losses. - Calculation Continues to Demonstrate

• DG Fans Modeled in Standbys to Maximize Acceptability.

Pressure Differantials.

25 CONCLUSIONS QUESTIONS/DIALOGUE

• ORIGINAL CALC BASED ON SOUND ENGINEERING PRINCIPLES.

• VENTING IS CNS DESIGN.

• MATERIAL PROPERTIES KNOWN.

• ALTERNATIVE METHODOLOGY FOR DUCTS, NUCLEAR SPECIFIC, STRAIGHTFORWARD AND SHOWS MORE MARC IN.

• DUCT INTEGRITY MAINTAINED.

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