ML20043H554

Forwards Supplemental Info to Tech Spec Rev Request Re Auxiliary Bldg Filtered Ventilation Sys

ML20043H554
Person / Time
Site:	Mcguire, McGuire
Issue date:	06/18/1990
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9006260102
Download: ML20043H554 (7)

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. (iMI373 4Lil DUKE POWER June 18,1990 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555

Subject:

McGuire Nuclear Station Units 1 and 2 Docket Nos. 50-369 ani' 50-370 Supplement to Technicaa Specification Revision Request Centlemen By letters dated October 15, 1987 and May 11, 1989 I requested revisions to the McGuire Technical Specifications regarding the Auxiliary Building.

Filtered Ventilation (VA) system. Supplements to my proposal were provided by letters dated June 14 and December 8, 1989. In Ma'y 1990, the staff requested a summary of the McGuire control room dose calculation.

Accordingly, find attached the requested information.

Any questions pertaining to this m tter should be directed to Steve LeRoy at 704-373-6233.

Very truly yours, fG- . C ug Hal B. Tucker Attachments SEL552 0 0\

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xc: . Mr.-S.D. Ebneter, Administrator U.S. Nuclear Regulatory Commission, Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323

-Mr. Dayne Brown, Chief Radiation-Protection Branch, Division of Facility Services Department of Human Resources-701 Barbour Drive-Raleigh, N.C. 27603-2008.

Mr. D.S. Hood, Project Manager

. Office of Nuclear' Reactor. Regulation, USNRC Washington, D.C. 20555 Mr. P.K. Van Doorn Senior Resident. Inspector, USNRC McGuire Nuclear' Station l

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• MCC-1227000-00-0041 by H E Vanpelty/ff FOR INFORMATION June 15, 1990 page 1 of 4 Problem - Explain the assumptions and methods used to calculate the Control Room Dose for McGuire Nuclear Station.

O A condition - This is a non QA Calculation. This calculation summarizes the results of other calculations and is not used to support any safety related work.

Method - The assumptions and methodology used in determining the <

Control Room dose is summarized from calculations which are used as the design basis for licensing the station.

Aeolicable Codes and Standards - None FSAR Criteria - None Other Desian Criteria - None Assumotions - See Summary References 1 MCC-1227.00-00-0002 Control Room Dose Calculation rev. 1, July 10, 1986.

2 MCC-1227.00-00-0032 Design Basis Accident with Revised Annulus Pressure Setpoint Rev. 3 November 8, 1989 3 MCC-1227.00-00-0035 Design Basis Analysis for Removal of VE Supply Ring Header Summary of the Control Room Dose Calculation The Dose to the McGuire Control Room is calculated using the conservative monnoas ano assumptions outlined in the Standard Review Plan (NUREG 0800). The Source Terms are derived from '

conservative fission product inventory calculations and assumed to be released immediately at the initiation of the Design Basis i Accident. Assumptions on the fractions of Iodine and Noble Gasses released are those prescribed in Reg Guide 1.4. Partition Factors are assumed in accordance with the Reg Guides also.

The release paths from containment are: ,

1) Leakage from containment into the annulus and discharge through the filtered Annulus Ventilation (VE) exhaust into the unit vent.

2) Containment Leakage which bypasses the Annulus and leaks directly to the environment.

3) Leakage from Post Accident ECCS systems into the Auxiliary building and through the Auxiliary Building Ventilation System (VA).

o MCC-1227000-00-0041 j FOR INFORM' ATioN H E Vanpelt g June 15, 1990 page 2 of 4 l l

The paths of contaminated air entry to the Control Room ares ~

1) Inleakage through Control Room openings such as doors which may be opened periodically during accident mitigation

2) Contaminated Air filtered through the Control Room j Ventilation Filters.

)

The major assumptions made in calculating the Control Room Dose are i One hundred percent of Maximum Core Noble Gas and twenty  !

five percent Maximum Core Iodine release into the containment atmosphere at accident initiation.  ;

Fifty percent of Core Iodine is released into the containment sump. Sump Water mass is calculated using a temperature of 160 degrees Fahrenheit.

Containment Leak rate is assumed to be .3% of Containment volume the first day and .15% the following days.

Bypass Leakage is Seven Percent credit is taken for removal of Iodine from the containment atmosphere by the Ice Condenser from 10 minutes to 42.33 min. after the accident initiation.

Credit for Iodine removal by containment Spray is also <

taken in accordance with NUREG 0800.

One train of Containment Air return, Annulus Ventilation, and Control Room Air is assumed to be failed.

ECCS Leakage is assumed at twice the normal rate. The rate is based on Westinghouse estimated leakage of 1 GPH. The Luanagu uegins at cne ear 11est cimo possloie sump recirculation can be made available. The Iodine partition g factor for ECCS leakage is assumed to be 0.1.

No credit is taken for Annulus Ventilation system operation until Annulus pressure is calculated to be drawn to .25 in WG. (112 sec)

Only one percent mixing in the Annulus is assumed based on removal of the VE supply ring header.

The Annulus Filters are assumed to be clogged after 900 seconds of operation and are operated at 85 percent capacity after this time.

No credit for use of the Auxiliary Building (VA) filters is taken for calculating the dose consequence of ECCS leakage.

No Hydrogen Purge is required because of use of the hydrogen recombiners.

MCC-1227.00-00-0 41' 1 1

by H E Vanpelt FOR INFORMATION June 15, 1990 page 3 o 4 Inleakage to the Control Room is 600 cfm prior to operation of the Control Room Ventilation System and 10 cfm after the system is in operation due to leakage through opened doors.

The Control Room Ventilation is considered operable 20 sec.

after the initiation of the accident.

The calculation is performed using a Duke written computer code ACTDOSEM which models the operation of post accident mitigation systems and structures for airborne release of iodines and noble gasses. The model calculates the projected offsite and control room dose for a variety of plant configurations and dose paths with time. The principal parameters of interest are as follows.

Chemical makeup of iodine in containment atmosphere. I 91% elemental, 5% particulate, 4% organic Filter efficiency for removal of iodine in the air leaked l from containment, j

VE filters. 95% for each species of iodine with- l air flowing through filters with heater i controlled humidity. l 90% for elemental, 95% particulate and i 30% organic for air flowing through filters without humidity control.

VC filters 994 for each species of iodine VA filters 95% for each species of iodine (The Auxiliary Building Filters are not assumed to be used during a Design

, Basis Accident for Offsite Dose or control Room Dose calculations.)

Annulus Ventilation 8000 cfm for first 900 sec.

Flow Rate 6800 cfm afterward.

Control Room 1000 cfm outsido air through the Ventilation filters Flow Rate 1000 cfm recirculated air through the filters.

Containment Volume 1,038,000 cubic feet Annulus Volume 422,361 cubic feet Control Room Volume 116,000 cubic feet Atmospheric 3 1.0E-03 sec/m 0 - 8 hrs Dispersion 7.0E-04 sec/m 3 8 - 24 hrs Factors 4.5E-04 sec/m 3 1 - 4 days 2.4E-04 sec/m 4 + days

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. 0 l MCC-1227.00-00-0041 FOR INFORMATION by H E Vanpelt 3/ 7 June 15, 1990 page 4 of 4

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The Annulus Ventilation System cycles between exhausting Annulus air through the Unit Vent and recirculating Annulus air through j

the VE filters. Cycling is controlled such that a negative pressure is maintained in the Annulus at all times. This cycling is modelled into the dose calculations.

The Control Room Ventilation System isolates the Control Room from other areas of the plant by pressurizing the control Room l l to 1/8 in. W G or greater pressure relative to outside air. l This system operates continuously, taking supply from two remote vents located on the Auxiliary Building roof.

The Control Room Dose Calculated based on these assumptions and input data is 21.3 Rem Thyroid and .3 Rem Whole Body. Since filter operation has no effect on Noble Gas dose contribution the whole body dosc to control room workers will be unaffected by VA filter operetion. The Thyroid dose is contributed nearly equally by the assumed inleakage to the control room of 10 cfm contaminated air from outside sources and contaminated air I filtered through the VC system. The contaminated air source is l 58% containment bypass leakage, 19% filtered exhaust from the l Annulus and 23% Exhaust of ECCS leakage through the Auxiliary Building Ventilation System.

No credit is taken for VA filters in mitigating the ECCS leakage l source, but this system is automatically switched to the filtered exhaust mode of operation on an accident or Blackout signal or if radiation is detected by the exhaust monitor. The VA system has two trains (unit 1 and unit 2) both of which respond to an accident on either unit thus providing essentially '

redundant protection. The operation of the VA system is not considered in calculating Control Room Doses but operation in the filtered exhaust mode by either train of the system would serve to reduce the calculated dose to Control Room personnel.

The VA system is designed to prevent spreading of air from the potentially ECCS leakage contaminated areas to areas which are uncontaminated. All the potentially ECCS contaminated areas are exhausted through the Unit i

Vant as assumed in the Control Room Dose calculations. The switching of other non ECCS contaminated areas away from the.

unit vent exhaust as proposed by the modification to add the waste solidification area will not have any affect on the

[ control room dose calculation. Since the flow through the L

filters will be slightly reduced the expected result in reality will be an improvement in filter performance.

The calculated Control Room Dose is thus not affected by the l proposed changes to the VA Tech. Specs or by modifications the system to remove sor.e non ECCS Contaminated areas from the filtered exhaust trains exhausting through the Unit Vent.

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