ML20049A823
| ML20049A823 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/29/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| References | |
| TASK-02-02.C, TASK-2-2.C, TASK-RR LSO5-81-09-075, LSO5-81-9-75, NUDOCS 8110020305 | |
| Download: ML20049A823 (5) | |
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September 29, 1981
/ q, Docket No. 50-245 kO LS05 09-075 Q
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Mr. W. G. Counsil, Vice President 7s 8
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Nuclear Engineering and Operations g
Northeast Nuclear Energy Company N
Post Office Box 270 Hartford, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
SEP TOPIC II-2.C. ATi10'.?HERIC TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS - HILLSTONE UNIT 1 Enclosed is the staff's final evaluation of SEP Topic II-2.C.
We have reviewed your submittal of May 19, 1981 and performed an independent evaluation to verify the reported values. You based your analysis on five years of t'ata (1975-1979), calculated the relative concentrations for each year, then selected the highest calculated value. Our indepen-dont analysis used two years of data (1974-1975), calculated the relative concentracions for the complete data set, then selected the highest values for corparison wMh those given by the applicant. Both analyses followed the guidance of Regulatory Guide 1.145. The staff values were, however, generally greater than those presented in your submittal. Possible reasons for this lack of agreement were discussed in a July 10, 1981, telephone conversation between Mike Bain, Joe Santovasi and Ray Crandall, Northeast Utilities, and Bob Abbey and Jim Fairobent of the staff and are identified in tiie attached evaluation. The staff values are more conservativa and are thought to be more in agreement with the guidance presented in Reculatory Guide 1.145 and are presetned in this evaluation as the appropriate values for use in accident dose calculations.
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This evaluation will be a basic input to the integrated safety assessment'
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f for your facility unless.vou 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 HRC criteria relating to tgq s.3 6
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this subject are modified before the integrated assessment is completed.
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Sincerely, 8110020305 810929 PDR ADOCK 05000245 P
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h'wC Ah/MDL Dennis H. Crutchfield, Chief 0
DC1 chfield GLdinas Operating Reactors Branch No. 5 9/$ 81 9/[p/81 Division of Licensing
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Mr. W. G. Counsil cc William H. Cuddy, Csquire Connecticut Energy Agency Day, Berry & Howard ATTN: Assistant Director Counselors at I.aw Research and Policy One Constitution Plaza Development Hartford, Connecticut 06103 Department of Planning and Energy Policy Natural Resources Defense Council 20 Grand Street 91715th Street, N. W.
Hartford, Connecticut 06106 Washington, D. C.
20005 Northeast Nuclear Energy Company ATTN: Superintendent Millstone Plant P. O. Box 128 Waterford, Connecticut 06385 Mr. Richard T. Laudenat
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Manager, Generation Facilities Licensing Northeast Utilities Service Company.
P. O. Box 270 Hartford, Connecticut 06101 Resident Inspector c/o U. S. WRC P. O. Box Drawer KK Niantic, Connecticut 06357 Waterford Public Library Rope Ferry Road, Route 156 Waterford, Connecticut 06385 First Selectman of the Town of Waterford H.;1 of Records 200 Boston Post Road Waterford, Connecticut 06385 John F. Opeka Systems Superintendent Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101 U. S. Environmental Protection Agency Region I Office ATTN: EIS COORDINATOR
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SEP TOPIC II-2.C ATMOSPHERIC TRANSPORT AND DIFFUSION CHARACTERISTICS
'f0R ACCIDENT ANALYSIS MILLST0!!E UNIT 1 I.
INTRODUCTION The safety objective of this review is to determine the appropriate on-site and near-site abnospheric transport and diffusion characteristics necessary to establish conformance with the 10 CFR Part 100 guidelines.
In particular, the short-term relative ground-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, " Reactor 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 Topic II-1.A, " Exclusion 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 conseq4ences of postulated accidents.
IV.
REVIEW GUIDELINES "ihe 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 source, during periods of low wind speeds (<6 meters /sec) and neutral and stable atmospher.ic l
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l l (2) Exclusion area boundary distance as a function of direction from the planc; (3) Atmospheric dispersion conditions when the wind is blowing in a specific direction; and (4) The feliction of time that the wind can be expected to blow into each of the 16 compass directions.
V.
EVALUATION By letter dated May 19, 1981, the licensee submitted an analysis of the atmospheric transport and diffusion characteristics for the Millstone f
site.
For the purpose of this evaluation, a comparison was made between the values submitted by t!ie applicant arid values determined independently by the staff; the applicant utilized five years y data (1975-1979) and the staff used two yeais of data (1974-1975).
The applicant computed the concentrations for each year seuarately, then selected the highest value. that occurred in any year; the staff combined the two years of dats and computed the values accordingly. The wind speed and wind direc-tion were measured at the 10 m (33 ft) and 114 m (374 ft) levels; atmospheric stability was defined by the applicant and the staff using the vertical temperature gradient between the 10 m and 43 m (142 ft) levels for ground level releases.
For the elevated releases, the applicant determined the horizontal stability by computing the wind direction varicnce at the 136 m (446 f t) level and the vertical stability by the vertical temperature gradient between the 10 m and 136 m levels; the staff determined the horizontal and vertical stabilities by the l
vertical temperature gradient between the 10 m and 114 m (374 ft) levels. The calculational methodology of the applicant produced generally smaller values than those calculated by the staff even though they used five years of data compared to two years.
The staff values are the more conservative and are thought to be more in agreement with the guidance presented by Regulatory Guide 1.145. Therefore, we have determined that the staff values are appropriate for use in accident dose calculations.
The following relative concentraticn values for assumed ground-level and elevated releases have been determined at distances corresponding to the exclusion area boundary distancesin each sector (EAB) and the coter boundary-of the low population zone (LPZ) in an onshore direction;'the building wake correction factor for the off-gas building of 82 m was used in the ground level reiease calcd ations'and topographic vari-ations were considered for the elevated release calculations.
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. GROUND LEVEL RELEASE STAFF 3
Time Period Distance & Direction XlQ(r.itc/m) 0-2 hours EAB(566m)NE 6.1 x 10-4 0-8 hours LPZ (3860 m) SSW/ENE 1.9 x 10-5 8-24 hours LPZ (3860 m) SSW/ENE 1.3 x 10-5
-6 1-4 days LPZ (3860 m) SSW/ENE 5.5 x 10
~0 4-30 days LPZ (3860 m) SSW/ENE 1.7 x 10 ELEVl. LED RELEASE 0-2 hours fumigation EAB (496 m) NE 9.2 x 10-5 0-4 hours fumigation LPZ (3860 m) N 1.8 x 10-5
-6 4-8 hours LPZ (3860 m) N 1.3 x 10 8-24 hours LPZ (3860 m) N
CONCLUSION 4
The staff concludes that the X/Q valves presented in Section V are appropriate for estimating exposures from postulated accidents and should be used in all accident calculations.
This completes the evaluation of this SEP topic.
Since this evaluation conforms to current licensing practice, no additional SEP review is required.
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