ML17194A117

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Forwards Final Evaluation of SEP Topic II-2.C, Atmospheric Transport & Diffusion Characteristics for Accident Analysis. X/Q Values Are Appropriate for Estimating Exposures from Postulated Accidents
ML17194A117
Person / Time
Site: Dresden 
Issue date: 08/26/1981
From: Crutchfield D
Office of Nuclear Reactor Regulation
To: Delgeorge L
COMMONWEALTH EDISON CO.
References
TASK-02-02.C, TASK-2-2.C, TASK-RR LSO5-81-08-064, LSO5-81-8-64, NUDOCS 8109040115
Download: ML17194A117 (7)
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August 26, 1981 l

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Docket No. 50l..4B7 L~SOS 08- 064..

Mr. L. OelGeorge Director of Nuclear Licensing Commonwe~lth Edison Company Post Office Box 767 Chicago, Illinois 60690

Dear Mr. OelGeorge:

SUBJECT:

  • SEP TOPIC 11-2.C, ATMOSPHERIC-TRANSPORT ANO DIFFUSION CHARACTERISTICS FOR ACCIDENT ANAi,. YSIS - DRESDEN UNIT 2 Enclosed is the staff's final evaluation of SEP Topic II-2.C, "Atmospheric Transport and Diffusion Characteristics for Accident Analysis" for Dresden Unit 2. The staff has concluded that the values provided in your safety analysis dated March 20, 1981 are appropriate with one exception as noted in our evaluation.

This evaluation will be a basic input to the integrated safety assessment for your fac11 ity unless you identify changes needed *to reflect the as-buil t conditions at your facility. This assessment may be revised in the future if your facility design is changed or if NRC criteria relating to this subject are modified before the integrated assessment is completed.

Enclosure:

As stated cc w/enclosure:

See next page Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing SP'1

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'i' Docket No. *so-;237 LS05 Mr. L. DelGeorge e

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Director of Nuclear Licensing Commonwealth Edison Company Post Office Box 767 Chicago, Illfhois 60690

Dear Mr. DelGeorge:

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SUBJECT:

SEP TOPIC II-2.e, ATMOSPHERIC TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS - DRESDEN UNIT 2

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Enclosed is the staff's final evaluation of SEP Topic II-2.c. "Atmospheric Transport and Diffusion Characteristics for Accident Analysis" for Dresden

. Unit 2.

The staff has concluded that the values provided in your safety analysis dated March 20, 1981 are appropriate with one exception as noted in our evaluation. Therefore, the values provided in the enclosed evalua-tion are to be used for all :accident radiological consequence calculations.

This evaluation will be a basic input to the integrated $,afety assessment for your f ac111 ty un 1 ess you 1 dent i fy c$.anges needed to reflect the as-.

built conditions at your facility. This assessment may be revised in the future if Your facility design is changed or if NRC criteria relating to this subject are modified before the integrated assessment is completed.

Enclosu~:

As stated cc w/enclosure:

See next page Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing

  • See previous yello,w for additional concurrences.

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DATE ****** 8/.19/.8.1........ 8,(.1.91.8.1.......... g/~.Q./g1....... S./*2-0/-8-1*.......... "8/*c~*f'8t*****..,* ~.... Btt* 8'l'" 0 NRC FORM 318 (10-BO) NRCM 0240 0 FF I c I AL RE c 0 RD c 0 PY USGPO: 1981-335'960..

Docket No. 50-237 LS05 08-064 Mr. L. DelGeorge e

UNITED STATES e

NUCLEAR REGULATORY COMMISSION.

WASHINGTON, D. C. 20555 August 26, 1981 Director of Nuclear Licensing Commonwea 1th Edi son CompanY... *...,

Post Office Box 767 Chicago, Illinois 60690

Dear Mr. DelGeorge:

SUBJECT:

SEP TOPIC II-2.C, ATMOSPHERIC TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS - DRESDEN UNIT 2 Enclosed is the staff's final evaluatJon pf SEP Topic II-2.C,. "Atmospheric Transport and Diffusion Characteristics for Accident Analysis" for Dresden Unit 2.

The staff has concluded that the values provided in your safety analysis dated Ma~ch 20, 1981 are appropriate with one exception as noted in our evaluation. Therefore, the values provided in the enclosed evalua-tion are to be used for all accident radiological consequence calculations.

This evaluation will be a basic input to the integrated safety assessment for your facility unless you identify changes needed to reflect the as-built conditions at your facility. This assessment may be revised in the future if your facility design is changed or if NRC criteria relating to this subject are modified before the integrated assessment is completed.

Enclosure:

As stated cc w/enclosure:

See next page

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Dennis M. Crutchfield, Ch' f.

Operating Reactors Branch No. 5 Divisirin of Litensing

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Mr. (.* DelGeorge cc Isham, Lincoln & Beale Counselor~ at Law One First National Plaza, 42nd Floor

Washington, D. c.

20005 U. S. Nuclear Regulatory Commission Resident Inspectors Office Dresden Station RR #1 Morris, Illinois 60450

  • Mary Jo Murray Assistant Attorney General Environmental Control Division 188 W. Randolph Street.

Suite 2315 Chicago, Illinois 60601 Morris Pubiic Library 604 Liberty Street Morris, Illinois 60451 Chairman Board of Supervisors of Grunqy County Grunqy County Courthouse Morris, Illinois 60450 John F._Wolf, Esquire 3409 Shepherd Street Chevy.Chase, Maryland 20015

  • Dr. Lirida*w. Little 500 Hermitage Drive Ral~igh, North Carolina 27612

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EIS COORDINATOR

-230 South Dearborn Street Chicago, Illinois 60604 Dr. Forrest J. Remick

  • 305 East Hamilton Avenue State College, Pennsylvania 16801 The Honorable Tom Corcoran United States House of Representatives

. Washington, D. C.

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SEP TOPIC 11-2.C ATMOSPHERIC TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS DRESDEN UNIT 2.*

I.

INTRODUCTION The safety objective of this review is to determine the appropriate on-

.site and near-site atmospheric transport and diffusion characteristics necessary to establish conformance with the*10 CFR Part 100 guidelines.

In particular, the short-term relative vround-level air concentrations (x/Q) are determined for use in estimating offsite exposures resulting from postulated accidents.

II *.

REVIEW CRITERIA Section 100.10 of 10 CFR Part 100, "Reactot Site Criteria," states that meteorological conditions at the site and surrounding area should be*

considered in determining the acceptability of a site for a power reactor.

III.

RELATED SAFETY TOPICS IV.

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Topic 11-1.A, "Exel usi on Area Authority and Control" provides the proper exclusion boundary distance over which the licensee has control. Various section XV topics utilize the atmosphere dispersion coefficients to deter-mine the offsite radiological consequences of postulated accidents.

REVIEW GUIDELINES The atmospheric dispersion.factors were calculated using the direction dependent method described in Regulatory Guide 1.145, *"Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants." This model incorporates the results of recent atmospheric tracer tests, and considers the directionally dependent

. atmospheric dispersion conditions.

Specifically, the modified dispersion model considers the following effects:

(1)

Lateral plume meander, as a function of atmospheric stability, wind speed, and distance from the sot.irce 0

, during periods of low wind speeds (<6 meter~/sec) and neutral and stable ~tmospheric condi ti.ans;

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Exclusion area bolmdary distance as a function of direction from the plant;

~) Atmospheric dispersion conditions when ~he wind is blowing in a specific direction~ and

4) *The fraction of time that the wind can *be expected to blow into each of the 16 compass directions~'

V.

EVALUATION The staff has reviewed and evaluated the ColT!lTlonwealth Edison Company's (licensee) assessment dated March 20, 1~81~. Meteorological data collected from the Dresden site.for the 1974 and 1975 calendar years

~ere used to determine the atmospheric transport and diffusion charac-teristics. For releases from the 94.5 m stack, wind from the 91.5 meter-level was used and for releases near ground.level, wind from the 10.5

.meter-level was used.

Atmospheric stability was determined from measurements of vertical temperature difference between the 91.5 and 10.5 meter-levels.

The licensee's relative concentration (X/Q) estimates were based on a directionally independent assessment for the 5% probability level at circular exclusion area boundary (EAB) and low population zone (LPZ) distances. The staff compared the licensee's estimates with estimates made using the direction dependent methodology of Regulatory Guide 1.145. All of the licensee's values were in reasonable agree-ment with the staff~s estimates except for the (X/Q) value during* a two hour period at the EAB from an elevated release. Discussions with Conmonwealth Edison and its consultant revealed that the licensee considered only ground level concentrations *at the EAB whereas the staff considered the maximum ground level co'ncentrati.otis at or beyond the EAB.

The licensee agreed that the staff!s method was reasonable.

The* following X/Q valves have been determinep-by the staff~~: _____

a*ppropri ate--for~fhe ___ Dresden-~site-:-*-**-:---:-***.,. " - *-.....

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. Location Type of Release Time Period.*

X/Q (sec/m3)

EAB (805m)

Elevated w/fumigation 0-~ hr.

6.9(-5)a Elevated w/o fumigation lz-2 hr.

6.6(-6)*

Ground level

  • 0-2 hr.

2.6 (-4).

LPZ (8050m)

Elevated w/fumigation 0-~ hr.

8.7(~6)

  • Elevated w/o fumigation

~-8 hr.

1.3(-6) 8-24 hr.

7.6(-7) 1-4 days:

3.2(-7)

  • 4-30 days 9.4(-8)

Ground level 0-2 hr.

2.5(-5)

VI.

CONCLUSION The staff concludes that the X/Q valves presented in-Section V are appro-priate for estimating exposures from postulated accidents and should be used in all accident calculations.

This ~ompletes the evaluation of this SEP topic.

Since this evaluation conforms to current* licensing practice, no additional SEP review is required.

a6.9(-5) ~ 6.9 x lo-5

  • Staff's value using Regulatory Guide L 145 model.

All other values are from the licensee's assessment.

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