ML20039C045
| ML20039C045 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/23/1981 |
| 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 LSO5-81-12-076, LSO5-81-12-76, NUDOCS 8112280352 | |
| Download: ML20039C045 (8) | |
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December 23, 1981 i
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Docket No. 50-245
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S Mr. W. G. Counsil,' lice President TW/F Nuclear Engineering and Operations A
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Northeast Nuclear Energy Company Post Office Box 270
'[j llartford, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
SEP TOPIC II-2.C. ATMOSPHERIC-TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS - MILLSTONE UNIT 1
. By letter dated November 19, 1981, you infomed us of an error in our final evaluation of SEP Topic II-2.C.
Therefore,-we are reissuing the final evaluation with the suggested corrections incorporated. The w
evaluation is enclosed.
Your letter stated that the staff did not include an explanation for the lack of agreement of staff and licensee value's. You further stated that the staff has not provided a basis for our statement that the staff values are more in agreement with Regulatory Guide (R.G.) 1.145.
In reference to your first concern our evaluation clearly states:
1) the licensee utilized five years of data and the staff used two years of data, 2) the licensee computed concentrations for each year separately and selected the highest value whereas the staff combined the two years
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and computed the values accordingly and 3) for elevated releases the licensee determined the horizontal stability by computing wind dirsction at the 136 meter level and the vertical stability by the vertical tempera-ture gradient between the 10 meter and 136 meter levels while the staff determined both the horizontal and vertical stability by the vertical temperature gradient between the 10 meter and 114 meter levels.
1 The difference in data base and data handling will easily result in l
different values. Therefore, your statement regarding the staff providing no explanation for the differences in calculated values is unfounded.
Regarding the second statement, a phone conversation was held on July 10, l
1981, between members of your staff and NRC staff meterologists. During this conversation it was pointed out that the staff calculates X/Q values yd folk
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Q for time periods greater than two hours by assuming a logarithmic interpolation between the plume centerline X/Q for the 0-2 hour period and an annual average X/Q value as described in Section 2.2.1 of Regu-latory Guide 1.145.
It is-our understanding that the X/Qs provided in your evalnation used the plume centerline kalue for the o-2 hour.
X/Q and used sector-spread values for. time periods greater than eight hours. The differences in calculational procedures could account for the differences in X/Q values.
Particularly for the 8-24 hour and -
1-4 day time periods. As previously discussed in the July 10, 1981, telephone conversation with your staff, we feel the staff values are more in' agreement with the guidance of R.G. 1.145.
This evaluation will be a basic input to the integrated safety assess-ment 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 co@leted.
Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division _of Licensing
Enclosure:
As stated cc w/ enclosure:
See next page
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UNITED STATES 8
N NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20555 g
December 23, 1981
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Docket No. 50-245 LS05 12-076 Mr. W. G. Counsil Vice President Nuclear Engineering and Operations
- Northeast Nuclear Energy Company Post Office Box 270 Hartford, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
SEP TOPIC II-2.C, ATMOSPHERIC TRANSPORT AND DIFFUSION CHARACTERISTICS FOR ACCIDENT ANALYSIS - MILLSTONE UNIT 1 By letter dated November 19, 1981, you infomed us of an error in our final evaluation of SEP Topic II-2.C.
Therefore, we are reissuing the final evaluation with the suggested corrections incorporated.
The evaluation is enclosed.
Your letter stated that the staff did not include an explanation for the lack of agreement of staff.and licensee values.
You further stated that the staff has not provided a basis for our statement that the~ staff values are more in agreement with Regulatory Guide (R.G.) 1.145.
In reference to your first concern our evaluation clearly states:
1) the licensee utilized five years of data and the staff used two years of data, 2) the licensee computed concentrations for each year separately and selected tha highest value whereas the staff combined the two years and computed the values accordingly and 3) for elevated releases the licensee determined the horizontal stability by computing wind direction at the 136 meter leve: and the vertical stability by the vertical tempera-ture gradient between che 10 meter and 136 meter levels while the staff determined both the horizontal and vertical stability by the vertical temperature gradient between the 10 meter and 114 meter levels.
The difference in data Lue and data handling will easily result in different values.
Therefore, your statement regarding the staff providi.ng no explanation for the differences in calculated values is unfounded.
Regarding the second statement, a phone conversation was held on July 10, 1981, between members of your staff and NRC staff meterologists.
During this conversation it was pointed out that the staff calculates X/Q values O
e
4
. for time periods greater than two hours by assuming a logarithmic interpolation between the plume centerline X/Q for the 0-2 hour period and'an annual average X/Q value as described in Section 2.2.1 of Regu-latory Guide 1.145.
It is our understanding that the X/Qs provided in your evaluatic' used the plume centerline value for the 0-2 hour X/Q and used sect..r-spread values for time periods greater than eight hours. The differences in calculational procedures could account for the differences in X/Q values.
Particularly for the 8-24 hour and 1-4 day time periods.
As previously discussed in the July 10, 1981, telephone conversation with your staff, we feel the staff values are more in agreement with the guidance of R.G. 1.145.
This evaluation will be a basic input to the integrated safety assess-ment 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.
Sincerely, C/
Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing
Enclosure:
As stated cc w/ enclosure:
See next page
o, Mr. W. G. Counsil i
CC William H. Cuddy, Esquire Connecticut Energy Agency Day, Berry & Howard ATTN: Assistant Director Counselors at Law Research and Policy One Constitution Plaza Development Hartford, Connecticut 06103 Department of Planning and Energy Policy Natural Resources Defense Council 20 Grand Street i
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 Manager, Generation Facilities Licensing Northeast Utilities Service Company.
P. O. Box 270 Hartford, Connecticut 06101 Resident Inspector c/o U. S. NRC 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 Hall of Records 200 Boston Post Road Waterford, Connecticut 06385 John F. Opeka Systems Superintendent l
Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101 1
U. S. Environmental Protection Agency Region I Office ATTN: EIS C0ORDINATOR JFK Federal Building
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i Boston, Massachusetts 02203 r
SEP TOPIC II-2.C ATMOSPHERIC TRANSPORT AND DIFFUSION CHArtACTERISTICS FDR ACCIDENT ANALYSI5 MILLST0!!E UNIT 1
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1.
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 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 shoind 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-
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mine the offsite radiological consequences of postulated accidents.
IV.
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, cs a function of. atmospheric stability, l
wind speed, and distance from the source, during periods of low wind speeds (<6 meters /sec) and neutral and stable atmospher.ic conditions;
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.., (2) Exclusion area boundary distance as a function of direction from the plant; (3) Atmospheric dispersion conditions when the 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 directio'ns.
V.
EVALUATION By letter dated May 19, 1981, the licensee submitted an analysis of the atmospheric transport and diffusion characteristics for the Millstone site.
For the purpose of this evaluation, a comparison was made between the values submitted by the licensee and values determined independently by the staff; ':he licensee utilized five years of data (1975-1979) and the staff used two years of data (1974-1975). The licensee computed
, the concentrations for each year separately, then selected the highest value that occurred in any year; th.e staff combined the two years of data and computed the values accordingly. The wind speed and wind direc-tion were measured at the 10 m (33 ft) and 136 m (446 ft) levels; atmospheric stability was defined by the licensee 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 licensee determined the horizontal stability by computing the wind direction variance at the 136 m (446 ft) 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 vertical temperature gradient between the 10 m and 114 m (374 ft) levels.
The calculational methodology of the licensee 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 con-servative and are thought to be more in agreement,with the guidance pre-sented by Regulatory Guide 1.145. Therefore, we have determined that the staff values are appropriate for use in accident dose calculations.
The following relative concentration values for assumed ground-level and l
elevated releases have been determined at distances corresponding to the i
exclusion area boundary distances in each sector (EAB) and the outer 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 l
used in the ground level release calculations and topographic variations were considered for the elevated release calculations.
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GROUNO LEVEL RELEASE STAFF 3
Time Period Distance & Direction X/Q (sec/m )
0-2 hours EAB (566 m) 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
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1-4 days LPZ (3860 m) SSW/ENE
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5.5 x 10
-6 4-30 days LPZ (3860 m) SSW/ENE 1.7 x 10 ELEVATED 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 8.5 x 10-7
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1-4 days LPZ (3860 m) N
- 3. 6 x 10-7 '
4-30 days LPZ (3860 m) SE/NE 1.1 x 10-7 VI.
CONCLUSION 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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