ML061290460

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May 5, 2006 Meeting Slides
ML061290460
Person / Time
Site: Cooper Entergy icon.png
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)
v • d • e


Text

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

  • BACKGROUND
  • DG ROOM HIIAC AND VIRTUAL TOUR
  • TORNADO SEQUENCE
  • CNS CALCULATION
  • CONCLUSIO1S
  • QUESTIONS/DIALOGUE BACKGROUND
  • SSD&PC Inspection Question Regarding Tomado Design of DG Rooms at CNS.
  • CNS Re-verified and Validated the Tornado Design of the DG Rooms.

- The DG Structures per USAR are Designed for:

Class I (seismic)

Tomado and Wind Generated Missile Protection 3

psi Differential Pressure Load from Atmospheric Pressure Change.

- By Design, the DG Structures are Vented

- The DG Ccmponents Located Within hose Structures are Vented and per the SRP,

  • "AdequatelyProtectedandMayb.ErqectedtoPedonn NecessarySafety-R eatedFunclons.1 Tomado Event isRecove ableCondiion in that Actions Can be Taken to Mantain or Restore DG's 4

BACKGROUND, cont.

DG Components C utside Structure VAII Not Prevent Engine Start and Load Atetr Tomado ExtaustMufflerAistys Bypassed Separate Alr Intakes for Engine and Buikding ventiltion Based on Field Ins 3ection of Venting, OE and Engineering Analysis, Other Ro 3m Components are not Affected by Atmospheric Pressure Changes.

  • Electrical, Mecthani mat. Instnrumentation

- Question Still Existed Regarding Failure of DG Room Ventilation Ductwok that Could Potentially Result In Room Overheating.

  • CNS DG Sructnure; Not Hamrh Envirtnment, EO Is Not Applicable.

Elevated Room Tenperatures Could Affect Electrical components.

BACKGROUND, cont.

- CNS Provided Calculation NEDC 05-021, Rev. 1 to Demonstrate DG Ventilation Ductwork Integrity Is Maintained During Tomado Induced Atmospheric Pressure Changes in June of 2005.

CNS Calculatbn of 2005 Not Performed for Desin.

  • Calculationwas Performed for Showing Reasonable Expectationof Duct Inegrity.
  • Calculation Utlized Venting of Rooms for Diftirential Pressure on Duct Comporents.

Sound Engineering PracticesUsed in Calculathg Duct Component Stresses.

  • Recognized thatSome Deformation May Occur Due to Faufted Condition.
  • Calculation Cmtsistent wth Industry Practice(OE) 0 1

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

- 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'

SITE LAY OUT

...0E X 0'

nd X i 4fE:0 I

2

DEPRESSURIZATION SEQUENCE DEPRESSURIZATION SEQUENCE WUE DURING TUNADO

_ MUFR RYPA5S AMWJEWF.II MP..

ENSSR AS NA7E5 F,

I~~EquASTTL 14 13 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 ni the path. The fan capacty is insufficisntto 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-1s I1 RE-PRESSIJRIZATION SEQUENCE RE-PRESSURIZATION SEQUENCE DURING T(RNADO MWTlEBYPASS AM4EBIIPI1 7ip.

PRESSWEEA5 Burro NDlTrPA*5 F 1e 17 3

RE-PRESSURIZATION

SUMMARY

MAXIMUM PRESSURE DIFFERENTIAL IS 2.50 PSI

  • DUCT WORK REMAINS INTACT with POSITIVE INTERNAL PRESSURE

- 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

- Allowable Stress of 3 SM from ASME Not Appropriate

  • PRESSURE D)IFFERENTIAL UTILIZED

- Should have used 3 psi Design Pressure (Non-vented vs. Vented Structure)

  • MATERIAL PROPERTIES

- Source of Material Yield Strengths Not Identified 21 PIPING CODE USE

  • ASME Code Allowable Stress (3 SM) Invoked for 'Faulted' Condition Based on Similarity of Order of Magnitude for Tomadoes and DBA LOCA as Low Probability Events.
  • Plate Bending Formulae are 'Textbook' Tools for Analysis of Stressed Members.
  • Industry Code Expert (Reedy Engineering)

Confirms Acceptability of Use of ASME (3 SM)

  • CNS Methodology Provides Similar, but Conservative Results to ASCE Alternative Methodology.

22 TORNADO DATA CNS Desbtn Bsis Tomato of 300 MPH Rotational Wind Speed, BC MPH Translational Wind S meed and 3.0 PSID is Low Pflbability Event

.15-0.

'04.06 t00tlen aeQUIoP eaO 0045 10661605.1 Sli

~ ~

tt O.CnN 6-tlaee-4 p4

-E 612

  • 04E4 4.6004 0 5Z t.1 F4 S

na

  • 41N IIII44 t

s2 ALTERNATIVE METHODOLOGY A Revised Analytical Method

-ASCE Paper 1984

- Methodology Based on Testing (ANO)

- 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

- Actual Material Properties Used for Duct 24 4

PRESSURE DIFFERENTIALS

  • Structure Design Conservatively Assumes Non-vented
  • Structure is Snot intentionally sealed"
  • Components ir Structure are Vented

+ Depressurization of Room Calculated Based on USAR 3.0 psi at 1.0 psi/second rate.

  • Re-pressurization of Room Calculated Based on Same Rate.
  • Best Estimate 'K" Factors Used for Entrance Losses.
  • DG Fans Modeled in Standbys to Maximize Pressure Differantials.

25 MATERIAL PROPERTIES

  • Worst-Case Material Properties Assumed

- ASTM-A-36 36 ksi yield

  • Actual Duct Material

- 42.5 ksi minimum yield (by test)

  • Stiffener Angle Properties Not Clearly Identified
  • Duct Thickness of 0.1875" Used (Error)
  • Actual Duct Thickness is 0.0747"

- Calculation Continues to Demonstrate Acceptability.

CONCLUSIONS

  • 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.

27 QUESTIONS/DIALOGUE 28 5

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