ML20031F343

Assessment of Tornado Venting Sys for Comanche Peak Steam Electric Station,Units 1 & 2

ML20031F343
Person / Time
Site:	Comanche Peak
Issue date:	10/07/1981
From:	Cavanagh C, Costabile T, Trons J GIBBS & HILL, INC. (SUBS. OF DRAVO CORP.)
To:
Shared Package
ML20031F340	List: ML20031F339 ML20031F343
References
REF-PT21-81-503-000 NUDOCS 8110190563
Download: ML20031F343 (20)

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GIBBS & HILL, INC.

ASSESSMENT OF THE TORNADO VENTING SYSTEM FOR COMANCHE PEAK STEAM ELECTRIC STATION UNITS 1 AND 2 1/d PREPARED BY:

8M THOMAS'CDSTABfLE CHRISTDPHE'R CAVI4@bH SENIOR ENGINEER - MECHANICAL ASSISTANT ENGINEER - MECHANICAL N

REVIEWED BY:

JOHNJIRONS SUPERVISING ENGINEER - MECHANICAL APPROVED BY:

e OUIS F.

GfANNUZZI l/ U CHIEF ENGINEER - MECHANICAL

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OCTOBER 7, 1981 t

8110190563 811008 PDR ADOCK 05000445

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O TABLE OF CONTENTS Page

1.0 INTRODUCTION

1

2.0 BACKGROUND

1

3.0 CONCLUSION

S 1

4.0 CORRECTIVE ACTIONS 2

5.0

SUMMARY

OF REVIEW 3

ATTACHMENTS 1.

G&H LETTER TO N.R.C. JULY 31, 1983 2.

R.J. KWIK MEMO TO P.P. DeRIENZO JULY 29, 1981 3.

LIST OF DOCUMENTS REVIEWED 4.

FIGURE OF BLOWOUT PANELS FOR THE CONTROL ROOM i

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1.0 INTRODUCTION

This re' port summarizes an engineering investigation of the Tornado Venting System for the Comanche Peak Steam Electric Station Units 1 and 2.

The investigation was performed to respond to the concerns expressed by R.J. Kwik in his memo to P.P. DeRienzo who subsequently filed a notification of a potential defect relating to the rules of 10CFR21 (included as Attachment 1).

The NRC acknowledged receipt of the notification and was advised that the design would be investigated to determine if, in fact, a defect did exist.

2.0 BACKGOUND The potential defects relating to the rules of 10CFR21 with regards to the C.P.S.E.S.

Tornado Venting System were identified by G&H Engineer R. J. Kwik in his memo to P.

P.

DeRienzo dated July 29, 1981 (ir.cluded as ).

In order to evaluate the concerns enumerated by R. J. Kwik, the documents listed in were reviewed.

3.0 CONCLUSION

S The concerns enumerated by R. J. Kwik were investigated.

A summary of the conclusions resulting from the investigations is given below:

The C.P.S.E.S.

Tornado Venting System with modifications noted in this report will be acceptable under current licensing criterim.

The size and location of the tornado vents are appropriate for venting of the buildings in the event of a Design Basis Tornado (DBT).

The G&H Engineering calculations for the Tornado l

Venting system should be updated to reflect final l

plant design information.

Doors located throughout the plant should be reviewed and modified, if necessary, to conform to the updated engineering calculations.

Additional tornado vents should be provided in the control room false ceiling and internal non-load-bearing partition walls. _.

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The glass panels located in the control room are capable of withstanding the tornado design conditions and will not blow out during the DBT.

The electronic equipment cabinet analyzed is capable of withstanding the tornado design conditions.

Based on this

analysis, other electrical / electronic cabinets should also be capable of withstanding the tornado design conditions.

A review of all electrical / electronic cabinets should be performed to confirm similarity of design and capability to withstand the DBT.

There is sufficient register area in the HVAC ductwork for venting during the DBT to assure that the ductwork required for safe shutdown will not rupture or collapse.

The wind velocities in the control room are not significant and do not prevent the operators from shutting down the plant.

Small missiles which may enter the control room are not potential hazards and will not prevent the operators from effecting a

safe Phutdown of the pinnt.

l 4.0 CORRECTIVE ACTIONS l

The results of this investigation indicate that the following corrective actions are required:

The engineering calculations for the Tornado Venting System should be verified and updated to include the latest design conditions.

The revised calculations should include a computer model of the entire as-built plant design considering the actual room volumes and the normal position of the connecting doors.

The doors and corresponding door hardware should be modified where needed to ensure that the doors are consistant with the updated engineering calc'ulations and that the doors will not be potential missiles.

Additional internal tornado vents in-the Control Room false ceiling and non-load-bearing partitf.on walls should be provided to obtain a lower internal '

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wind speed and differential pressure across the ceiling and walls.

Safety-related electrical / electronic cabinets required for shutdown should be identified and verified to have sufficient vent area to ensure that the cabinets do not deform or rupture during the DBT.

5.0

SUMMARY

OF REVIEW The rcview and investigation consisted of two major tasks:

Review of the Existing Tornado Venting System Design Calculations Review of the Concerns Enumerated by R.J. Kwik 5.1 Review of the Existing Tornado Venting System Ddsign Calculations Review of the existing calculations for the Tornado Venting System (Mechanical Calculations 2323-512-1 Revision 1 and 2323-512-2) indicated that the analysis was performed utilizing a

simplified approach.

The calculations considered gross volumes throughout the plant; however, in actuality the volumes are comprised of many small volumes.

The analytical approach was applied to one half of the plant, which was considered acceptable based on symetry of the two units.

This type of analysis is acceptable for determining vent paths and for initial sizing of vent openings.

However, the normal positions of doors and additional vent paths created by the total plant geometry were not factored in tt.e analysis.

Consideration of the above will yield I

more realistic results and larger design margins.

5.2 Review of the Concerns Enumerated by R.J.

Kwik Each of the concerns emunerated by R.

J. Kwik (in ) were reviewed.

The findings are presented and discussed below ir. the same sequence.

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5.2.I.

Internally Generated Missiles i

5.2.I.A Normally Closed Doors not Capable of Withstanding Tornado Design Pressure A

review of the door schedule indicates that there are various types of doors located throughout the plant which are normally closed.

The majority of the doors are fire rated.

The balance of the doors are either missile resistant, penetration resistant, watertight or roll-up doors.

A review of the specifications and vendor drawings for the missile resistant, penetration resistant and watertight doors indicates that the tornado design conditions are specified and included in the door design.

The tornado design requirements are specified in the specification for the roll-up doors to ensure that these doors blow out during the DBT (the roll-up doors are used as primary vent paths to the atmosphere).

Tornado design requirements are not specified in the i

fire rated door specification.

Preliminary analysis has shown that a

number of the fire rated doors do not experience a sufficient tornado generated differential pressure to cause concern.

Following final analysis, the balance of the fire rated doors will either be specified as normally open or will be modified to ensure that the doors will not be potential missiles or will be analyzed to show that as potential missiles they will not cause damage to essential equipment.

5.2.I.B Normally Closed Doors Capable of Withstanding 3 PSI Differential Pressure The areas provided with watertight doors are equipment compartments on the 778' elevation of the Safeguards Buildings and the 790' elevation of the Auxili ary Building.

A review of these areas indicated that they contain safety-related equipment (pumps, valves and tanks).

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These areas are designed for the tornado conditions.,

Clogging of vents will not occur as existing housekeeping requirements do not allow storage of any items noted in R.J. Kwik's memo in these areas.

This is based on the potential for radiation exposure and the expected radition level for the compartment.

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5.2.I.C Miscellaneous Objects The miscellaneous objects referred to are primarily located in the Control Room Complex.

The Control Room Complex is already constructed and utilizes a hung ceiling with a refective light grid.

All of the ceiling tiles located in the Control Board Console area are above the suspended light grid.

The light grid is a metal structure constructed of one inch by one inch And/or half inch by half inch squares.

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lights are provided with steel cables to ensure that j

they will not fall.

The Tornado Venting System Analysis for the Control Room Complex indicates that the internal pressures across the walls and ceiling during a

tornado are appoximately 0.25 PSI.

The wind speed in the Control Room was calculated using the maximum mass flow rate of air exiting the Control Room Complex.

Considering the differential pressure and wind speed in the Control Room proper, the number of ceiling tiles that could become windborne is minimal.

During the tornado the ceiling tiles which fall will impinge on the light grid and not enter the Control Board Console area.

The lights will not fall as they are restrained by steel cables.

Review of the glass vision panels in the Control Room Complex indicates that the glass panels are tempered glass in the Observation Area and plate glass in the Shift Supervisor's Office and Kitchen.

Review of the G&H specification and the manufacturer's data for the glass verified that the glass can withstand

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the 0.25 PSI pressure differential with considerable margin.

Reanalysis of the Control Room Complex has shown that the potential problems can be further minimized by adding additional vent area in the internal non-load bearing partition walls and hung ceiling of the Control Room.

This additional vent area will be provided..

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5.2.II Damage Due to Decompression and Recompression of Components 5.2.II.A Electrical / Electronic Cabinets The primary concern is deformation of electrical / electronic cabinets during a

tornado.

In order to addreso this concern the Solid State Safeguards Sequencer, a cabinet located in the Control

Room, was analyzed.

The analysis verified that the differential pressure across the sequencer cabinet walls was 0.01 PGI.

This translated to a load of 22 lbf on the cabinet door, which is acceptable.

Based on the analysis of the eaguencer cabinet, an empirical equation was derived relating cabinet volume to a vent area acceptable for venting during a tornado.

A review of electrical / electronic cabinets required for safe shutdown will be performed using this criteria to confirm that the cabinets are adequately vented to ensure that the effects of depressurization and repressurization do not affect their performance.

5.2.II.B Differential Pressure Effects on HVAC Ducta A

review of the Control Room ductwork indicated that no specific pressure relief dampers are included in the design.

An analysis was performed relating the volume of the ductwork to the vent area of the~ register grills located within.

The results of this calculation verify that there is sufficient vent area to ensure that the ductwork will not rupture or collapse.

5.2.III High Wind Velocities The wind velocity in the stairwells and other sensitive areas is an industrial safety concern and not a nuclear safety concern.

Personnel required for shutdown are located in the Control Room at all times.

During a

tornado personnel required for shutdown will not be in the stairwells or any other sensitive areas.

The plant operating procedures for operation in the event of a tornado (which are written by the utility) include appropriate instructions and warnings to be followed during tha event.

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A 5.2.IV Small Missiles The concern is missiles entering the Control Room through the tornado vents.

All tornado dampers and blowout panels are located in concrete missile barriers.

This type of layout is typical for all exterior tornado dampers and blowout panels located throughout the plant.

The attached figure (Attachment 4) shows the configuration of the tornado vents for the Control Room.

The Control Room tornade vents are located at the extreme ends of the Control Room roof at a considerable distance from the Control Board Console area.

As shown for the Control Room tornado vents, the wind must travel through a minimum of three 90* turns before entering the Control Room.

The average wind speed through the tornado vent path is 205 feet per second.

The momentum of the missiles entering the missle barrier, combined with the turns in the barrier will tend to force the missiles against the barrier.

Small mis-iles may stay entrained in the air steam.

However, at snuation of these missiles can be expected as they encounter the lower air velocities in the Control Room.

Considering the design of the missile barrier, the missiles entering the Control Room will most probably be small missiles (i.e.,

roof gravel, dust and dirt).

It is not likely that these small missiles and/or dust and dirt entering the Control Room during the short time period that the plant experiences the repressurization phase of the tornado, will render the plant inoperative.

These missiles do not directly enter the Control Board Console area which is normally occupied by the operators.

They must be carried by the slower moving air in the Control Room to this area.

Based on this, direct impact of the operators is unlikely.

Also, during a turbine or reactor trip the plant is sequenced automatically and initially requires no operator action.

The same type of missiles entering other areas of the plant will not effect the equipment required for safe shutdown.

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ATTACHMENT 1 r

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Gibbs & Hill,Inc.

E NGIN E E RS DE&lSNERS CONSTRUCTOR 5 DIRECT DIAL EXTENSION 82121 TSO-July 31, 1981 Mr. Karl V.

Seyfrit Director-Region IV Nuclear Regulatory Commission 611 Eyan Plaza Dr.

Suite 1000 Arlington, Texas 76011

Subject:

Notification of a Potential Defect Relating to the Rules of 10CFR21 This wil.L confirm my telephone call to your office with Mr. Cliff Hale on Thursday, July 30, 1981 at approximately 4:15 p.m.,

in which I notified you of a potential defect relating to the rules of 10CFR21 with regard to the Tornado Venting System for Comanche Peak, Units No. 1 and No. 2 as identified by one of our employees.

We have performed an initial review of the bases for the employee's concerns from which we believe that these concerns will not compromise the plants ability to withstand the effects of a tornado.

Nevertheless, because available design documentation does not presently address all of the concerns that have been raised and because we have not been able to document the bases for our engineering judgement within the time constraints of the 10CFR21 regulatichs, we have notified you of this potential defect.

The description of the pote r tial defect is presented in the attached documents.

We int e nd to complete our inhouse assessment by September 10, 1981 at w'./.ch time we will notify you of the results and the bases for our judgement as to the safety impli-cations.

This matter arose out of our work on the Comanche Peak Project, a.nd we have informed the appropriate official of the licensee.

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l Mr. Karl V. Seyfrit July 31, 19P1 Page 2 As it also l'as possible implicat.ons to the Ft. Calhoun Unit il that we designed, we have similarly adyised that licensee of this notification.

Sincerely, GIB

& HILL, INC.

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Paul P. deRieni.:

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f Vice President Consulting Eagineering PPD:paf and Quality Assurance cc: B. R. Cleraents (TUGCO)

R. Andrews (OPPD) 6 m

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i OPD-1 Rev. 2 Page 24 of 30 Dater 7/30/81 APPENDIX'V l

REPORT OF A POTENTIAL DEFECT UNDER 10 CFR PART 21 Evaluation Number:

81-01 Date:

7/30/81 To:

rirector, NRC Region 7.V

.11 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011 i

From:

Vice President, 'Consditing Engineering and QA Gibbs & Hill, Inc.

Dravo Utility Constructors, Inc.

l 393 7th Avenue i

New York, N.Y.

10001 Facility Name and Location:

1.

Comanche Peak SES Units 1&2 - Glen Rose, Texa."

2.

Ft. Calhoun Unit No. 1 - Omaha, Nebraska Licensees 1.

Texas Utilities Generating Co. (TUGCO) 2.

Omaha Public Power District Co. (OPPD)

Docke t Number: 1.

50-445 and 50-446 Date:

1.

7/20/73 2.

50-285 2.

4/18/67 License Type:

1.

Construction Permit Date:

1.

12/19/74 l

(CPPR126 & 127)

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5/23/73 2.

Operation Permit (DPR 40)

Constructor:

(If Applicable)

Not Applicable Construction Subcontractors (If Applicable)

Not Applicable Component Vendor:

(If Applicable)

Not Applicable Component Subvendor:

(If Applicable)

Not Applicable G&H Design:

(If Applicable)

Tornado Venting System

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, - - - w OPD-1 Rev. 2 Page 25 of 30 Date: 7/30/82 Description of Potential Defect During a tornado event, the building housing safety related equip-ment will be depressuri' zed by 1.5 psi for a few seconds and then repressurized back to normal ambient conditions.

There is some concern that the cycle will cause damage to safety related equip-ment and will prevent the plant from being shutdown and maintained in a safe shutdown condition.

Date information obtained:

July 28, 1981 - 4:45 p.m.

Description of Potential Safety Hazard In the event of a major tornedo, no structure failure will occur; however, there is concern that the capability to shut the plant down and maintain it in a safe shutdown condition might be im-paired.

The impairment is assumed to occur because of electronic equipment cabinet depressurization, internally generated mis-siles, and from externally generated missiles enterir.g the control room.

Defective Basic Component Safeguards, Auxiliary Buildings includ-ing control room.

Number:

-In use:

At:

-Supplied for Use:

At:

-On Order:

For:

Other Facilities:

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a OPD-1 Rev. 2 Page 26 of 30 Da te : 7/30/81 Corrective ;ction By:

(See Note Below)

Organization - Gibbs & Hill, Inc.

Individual - Chief' Mechanical Engineer Corrective Action Dates:

Final assessment of the potential defect will be made by 9/10/81.

Advice to Licensee:

B. R.

Clements, TUGCO; Vice President -Operation and R. Andrews, OPPD; Section Manager-Operation were notified by phone at approximately <4:30 p.m. on 7/30/81.

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/G&H Vice President, Consultinp/

Da te

' Engineering and QA ( Designated Responsible Officer)

Note:

This report confirms the verbal notification made by P.

P.

DeRienzo of G&H to Cliff Hale of NRC Region IV at 4:15 p.m. of 7/30/81.

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ATTACHMENT 2 l

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d TO: Ikul P. DeRienso July 29,1961 FRGt Robert J. Kwik

Subject:

10CFR21 Sukittal Concerning Tornado Venting I wish to thank ycn for your attention to ar previous submittal and for the clarificati s of the function of a 10CFR21 report. I su bit this memo as a substitute for all previous explanations of ar objections (7/15/81,7/27/81). I confinn myself to specific complaints and offer what I believe to be appropriate remedies. Due to time constraints I am unable to sup;b drawing and equi xnent rzumbers, 3

but I am sure that these can be aetermined within a reasonable period of time, I.

Internally Generated Missiles

1. Normally closed doors not capable of witha+mnding design pressure.

Response: No such door should exist, but a check of the ourrent door schedule should be ande to ensure that it is correct.

B. Normally closed doors not capable of withstanMng 3 poi differential pressure. R ese doors have been desi6ned and specified to certain differential precsurec. Vent areas have been provided to maintain pressure at or below these design pressures. Rese vents may be cloge(maif loose material is permitted d

b2 hind viese doors mal s, etc. ).

Response

Provide statement that general housekeeping rules would eliminate such hazards.

Zssue appropriate statement in plant specs.

Be use of falso oeilings in washrooms, or other use of easily displaced materials must be eliminated.

C. Miscellaneous objects. False ceilings, glass panels in the control room and other objects may have been located in areas of either high wind apped or between areas of differing pressure.

Response: A check of the architectural drawings, particularly of the control room is advised. A memo to the architectural department warning that no such installations be permitted is required. A plant walk-thru to assure h t no such installations are made by local personnel is requ' ired, as is mention in the tech specs.

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Damage due to decompression and recomprecsion of components.

A.Electrieml/ElectronicCabinets Since a deoompression of up to 3 poi (depending upon the specific locatica) may occur in % seconds, cabinets with inadequate venting may suffer deformation. Filters installed to assure a dirt-free interior would be potential causes of such problems.

Response: Provide appropriate departments with memo calling attention to the relevant PJLR sectien(3 3 2) and request statement that in the judgment of those responsible no problem will occur under these ciroumstances.

3. HVAC ducts may rupture or crumple if differential pressure exceeds design limits.

Response: Check that apprpriate pressure relief dampers have been specified for the safety-related lines.

III.

High wind velocity may bowl over and injure persons in stairwells and in other sensitive areas. hre ares can be specified upon ernmhtion of C0!GARE: code aJ1alyses.

Response: Warning signs should be Ixrovidtd stating that these areas are to be avoided during periods of tornado alert.

A ntatement of engineering judanent by a p reon familiar with plant operation that no persew essential to safe shutdown will be in such areas during plant operation.

i IV.

Small missiles.

Personnel susceptibility to missileu depends upon the mass and upon the velocity of the missile. Samuel Glasstone in EE EFFEC 7S OF NUCLEAR VEAIOltS, U.S.A.E.C.,

1962 gives the following threshold values (pp.560-1):

Nes 1%

50%

99%

Damage

.lgram 235f s 41ofps 730 fps Glaas into abdomen P

l' gram ~

160 275 485 5sram 140 245 430

10. gram 115 180 355 10 lb.

12-13 fps can cause skull fracture.

Tornadic winds carry dirt and small objects and may enter the building through tornado vents, assuming the tornado possesses winds in excess of 119 m.p.h.

In addition, reflux of air into the depressurized *.:u11 ding will occur at sppeds roughly similar to those calculated for the depreemization phase (up to 150 mph, or 220 fps).

Esturning air will be as dirty as other air f rom the same tornado, since the air which es:ited will have been moved elsewhere.

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Be momentum of hse missiles will tend to force them against the missile barriers, while air drag will tend to keep them in W air stream. A certain critical velocity must exist for each missile barrier. Eis can be dat: mined.

Some attenuation of missile speed in the less rapidly moving air within the building can be expected. Gatings exist in some vents (FSAR Figures 3 3-3), but not in others(Fig. 3 5-2,3 3-4). - nese limit the =nrs=>=

size of potential missiles.

Remedy:

Ad$1st tornado dampers and gratings,as needed, so ht reflux of air into building is inhibited to value which no longer carries significant missile risk. Bis may require that building compressive loads in excess of l'.5 psig be tolerated. Outward pressure of 15 psig ='<== can be saintained.

Ors A statement by an engineer responsible for specifying control room operating procedures that influx of h =vi=m size missiles at the expected velocity would not interfere with control room operation to the extent of preventing safe shutdown of the plant.

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ATTACHMENT 3 O

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LIST OF DOCUMENTS REVIEWED

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Final Safety Analysis Report for the Comanche Peak Steam Electric Station; Section 3.3 and Figures 3.3.1 through 3.3.4.

U.S.A.E.C.

Regulatory Guide 1.76, April 1974, Design Basis Tornado for Nuclear Power Plants U.S.N.R.C.

Regulatory Guide 1.117, April 1978, Revision 1, 4

" Tornado Design Classification".

Gibbs & Hill Calculation No. 512-1, Revision 1, 1978 Gibbs & Hill Calculation No. 512-2, 1979

" Wind Performance", PPG Industries, Technical Service Report No. 10A COMPARE:

A Computer Program for the Transient Calculation of a System of Volumes Connected by Flow Vents, Los Alamos Scientific Laboratory, LA-NUREG-6488, MS, 1976 Gibbs & Hill Specification 2323-MS-96, 1978 " Tornado Vents" Gibbs & Hill Specification 2323-AS-17, 1976 " Aluminum Doors and Frames" Gibbs & Hill Specification 2323-AS-18, 1975

" Hollow Metal Doors and Frames" Gibbs & Hill Specification 2323-AS-61, 1975 " Bullet Resistent and Penetration Resisting Doors" Gibbs & Hill Architectural Drawings

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Gibbs & Hill Tornado Vent Layout Drawings Gibbs & Hill Control Room HVAC Ductwork Composite Drawings n

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