ML20133H296

Forwards Staff Evaluation Supporting Proposed Change in Methodology for Emergency Dose Assessment Model (Edam), Involving Replacement of TI-59 Based Method W/Edam as Backup Method to RM-21 Dose Assessment Computer Method

ML20133H296
Person / Time
Site:	Comanche Peak
Issue date:	08/06/1985
From:	Noonan V NRC - COMANCHE PEAK PROJECT (TECHNICAL REVIEW TEAM)
To:	Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
References
NUDOCS 8508090279
Download: ML20133H296 (7)

Text

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Docket Nos.: 50-445 and 50-446 AUG 0 61985 Mr. W. G. Counsil Executive Vice President Texas Utilities Generating Company 400 N. Olive Street, L. B. 81 Dallas, Texas 75201

Subject:

NRC Staff Evaluation of CPSES Emergency Dose Assessment Model (EDAM) Methodology This is in response to your letter (TXX-4452) dated March 29, 1985, trans-mitting your manual for the Emergency Dose Assessment Model (EDAM). We understand that you intend to replace your TI-59 based method with EDAM as the backup method for projecting offsite doses during a radiological emergency should your RM-21 Dose Assessment Computer be unavailable.

The staff has performed a detailed evaluation (copy enclosed) of your pro-posed change and determined that the methodology meets the requirements of 10 CFR 50.47(b)(9) and 10 CFR Part 50, Appendix E(V). The staff further finds that implementation of the proposed change will not degrade your capability to effectively respond to an emergency. The staff expects that the use of this change will be demonstrated during your next exercise.

0hlGINAL SIG3ED BY Vincent S. Noonan, Director for Comanche Peak Project Division of Licensing Office of Nuclear Reactor Regulation

Enclosure:

ISTRI8 tit-ION:

Staff Evaluation of CPSES Docket fy e SBurwell DRohrer JCalvo EDAM Methodology DH OELD DMatthews LPDR ACRS (16) RVollmer cc: See next page NSIC EJordan BGrimes PRC System JPartlow CTrammell LB#1 R/F BGrimes AVietti MRushbrook VNoonan R/F LShao Sbbme .

C, T:DL CP:TR :0 LB#1:DL LB)1

SBurwell:kab BJY lood 'rammell Vf] n 07/f//85 07/ /85 Oh/-( /85 0 / /85 8508090279 850806 PDR ADOCK 05000445 F PDR

, AUG 0 61985

, W. G. Counsil Comanche Peak Steam Electric Station Texas Utilities Generating Company _ Units 1 and 2 cc:

Nicholas S. Reynolds, Esq. Resident Inspector / Comanche Peak Bishop Liberman, Cook, Nuclear Power Station Purcell & Reynolds c/o U.S. Nuclear Regulatory' Commission 1200 Seventeenth Street, NW P. O. Box 38 Washington, D.C. 20036 Glen Rose, Texas 76043 i Robert A. Wooldridge, Esq. Regional Administrator, Region IV Worsham, Forsythe, Sampels & U.S. Nuclear Regulatory Connission Wooldr.idge 611 Ryan Plaza Drive, Suite 1000 2001 Bryan Tower, Suite 2500 Arlington, Texas 76011

Dallas, Texas 75201 Mr. Homer C. Schmidt Larry A. Sinkin Manager - Nuclear Services 3022 Porter Street, NW #304 r -

Texas Utilities Generating Company Washington, D.C. 20008 Skyway. Tower 400 North Olive Street, L.B. 81 Dallas, Texas 75201

'Mr. Robert E. Ballard, Jr. Ms. Billie Pirner Garde Director of Projects Citizens Clinic Director Gibbs and Hill, Inc. Government Accountability Project 11 Pen Plaza 1901 Que Street, NW New York, New York 10001 Washington, D.C. 20009 David R. Pigott, Esq.

Mr. A. T. Parker Orrick, Herrington & Sutcliffe Westinghouse Electric Corporation 600 Montgomery Street P. O. Box 355 San Francisco, California 94111 Pittsburgh, Pennsylvania 15230 Anthony Z. Roisman, Esq.

Renea Hicks, Esq. Trial Lawyers for Public Justice Assistant Attorney General 2000 P. Street, NW ,

Environmental Protection Division Suite 611 l P. O. Box 12548, Capitol Station Washington, D.C. 20036 Austin, Texas 78711 Nancy E. Wiegers Mrs. Juanita Ellis, President Spiegel & McDiarmed Citizens Association for Sound Energy 1350 New York Avenue, NW 1426 South Polk Washington, D.C. 20005-4798 Dallas, Texas 75224 Ms. Nancy H. Williams CYGNA 101 California Street San Francisco, California 94111

AUG 0 61985 Texas Utilities Electric Company Comanche Peak Electric Station Units 1 and 2 cc:

Resident Inspector - Comanche Peak c/o U.S. Nuclear Regulatory Commission P. O. Box 1029 Granbury,~ Texas 76048 Mr. John W. Beck Manager - Licensing Texas Utilities Electric Company Skyway Tower 400 N. Olive Street, LBf81 ,

Dallas, Texas 75201 Mr. Jack Redding Licensing T

Texas Utilities Generating Company 4901 Fairmont Avenue Bethesda, Maryland 20814 William A. Burchette, Esq.

Heron, Burchette, Ruckert & Rothwell Suite 700 1025 Thomas Jefferson Street, NW Washington, D.C. 20007 Mr. James McGaughy Southern Engineering Company of Georgia 1800 Peachtree, Street, NW Atlanta, Georgia 30367-8301 l

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4 ENCLOSURE i

STAFF EVALUATION OF CPSES EDAM METHODOLOGY Standard 4

Adequate methods for assessing and monitoring actual or potential offsite consequences of a radiological emergency condition are in use.

_ . Evaluation A rapid, microcomputer based methodology for assessing the potential and actual consequences of a release of airborne radioactivity is described in the appli-cant's March 29, 1985 submittal of a program document entitled: " Emergency Dose Assessment Model (EDAM)." The applicant proposes to use this EDAM metbidology, which is run on a KAYPR0 portable microcomputer, as a back-up system to the primary systems which uses the General Atomic RM-21 computer. The applicant plans to replace the currently approved manual /back-up dose assessment method-ologies described in Procedures No. EPP-300 (Rev. No. 2) and No. EPP-302' (Rev.

No. 3) with the EDAM methodology. Another approved manual / backup procedure using overlays, nomograms, isopleths and manual calculation sheets will be left intact and available for use at appropriate emergency response facilities.

The KAYPRO system will be used to perform rapid dose assessments using the EDAM program if the RM-21 primary system is inoperable. -

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The EDAM program is essentially the NRC's Interactive Rapid Dose Assessment Model (IRDAM) program which has been modified to reflect Comanche Peak site specific data. The EDAM methodology calculates radiation dose rates and integrated doses for the total body and infant thyroid at four downwind receptor distances. The four downwind receptors are assumed to be at the exclusion area boundary (EAB)

. and at 2, 5 and 10 miles. These distances have been chosen because of their convenience for taking offsite survey data and also to aid protective action recommendation decisions such as sheltering or evacuation.

Various methods are provided for determining key parameter values for the dose calculations should certain information be unavailable. For example, four different methodologies for determining atmospheric stability class for meteoro-logical dispersion calculations are available in EDAM. The plume dispersion calculations assume a ground level release because Comanche Peak's plant stacks is less than 2.5 times the height of the tallest structure. The atmospheric dis-persion factors, X /Q, u

used in the EDAM program are based on a semi-infinite cloud geometry and were obtained from IRDAM Vol. 2 for the 2, 5, and 10 mile distances and were calculated for the various exclusion area boundary (EAB) dis-tances surrounding CPSES. A table of the X u/Q values used by EDAM is given in Appendix I of the EDAM document.

The EDAM program has three basic accident scenario options for determining radio-active effluent release rates: stack releases, containment leakage, and steam generator tube leaks. The " stack releases" are divided into two sub-options:

1) when available, the user may input specific isotopic release concentrations for up to twenty different radionuclides, including the ones listed in IRDAM; and 2) when only the gross noble gas or the gross iodine activity concentration is available, it may be used. The " containment leakage" pathway option assumes a specific leak rate from a uniformly dispersed source within cont-inment. The

__ , EDAM program uses either the containment monitor reading in R/hr or a default data option. The steam generator (S/G) tube leak pathway option calculates release rate in C1/sec of both noble gases and iodines by simply multiplying the activity concentration Ci/cc by the (S/G) leak rate in cc/sec.

The EDAM program adjusts the source terms in each of the above three pathway options by first determining the iodine release fraction or the iodine to noble gas ratio and then, if the age of the released material is greater than one day, a noble gas and thyroid decay correction is applied to the release. The EDAM program assumes that the plume consists of only Xe-133 and I-131 and corrects for decay appropriately. For releases where an isotopic concentration is avail-able, EDAM corrects for decay of each radionuclide independently.

Finding i

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The applicant's proposed EDAM methodology and its relationship to the appli-cant's existing methodology in their procedures EPP-300 through EPP-303 was evaluated against the standards in NUREG-0654 (Revision 1),Section II.I. The

applicant's proposed EDAM methodology meets the standards of NUREG-0654 (Revision 1) and is compatible with the currently approved manual /back-up method-ologies for rapid dose assessment in Procadure Nos. 300 and 302. 'The staff finds that the applicant's dose assessment methods in the EDAM Program documentation submittal are adequate for planning purposes and may replace the existing method

,_ , which uses the TI-59 calculator. The applicant's ability to implement the revised backup dose assessment techniques and methods should be demonstrated during the next emergency preparedness exercise.

_. . _ . _ .