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Docket No. 50-424 MEMORANDUM FOR: Jacques Read. Acting Leader Section B, AES FROM:
Irwin Spickler, Leader Meteorology Section, METB I
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SUBJECT:
ACCIDENT X/Q VALUES FOR V0GTLE We have performed an independent assessmenc of short-term (less than 30 i
days) accidental releases from buildings and vents at the Vogtle site using the direction-dependent atmospheric dispersion model described in Regulatstry Guide 1.145. A three-year composite set of onsite meteorological data (April 4,1977-April 4,1979 and April 1,1980-March 31, 1981) was used for this evaluation. Wind speed and direction data were based on measurements at the 10m level, and atmospheric stability was defined by the vertical temperature gradient measured between the 45.7m and 10m levels. From information provided.in I
Section 2.3.4 of the applicant's Final Safety Analysis Report,2 a ground-level release with a building wake factor, cA, of 1184m was assumed.
.In accordance with instructions from M. Wohl of your section, the exclusion area boundary was assumed to be circular with radii of 1097m (3600 ft) for Unit 1 and 1189m (3900 ft) for Unit 2.
The Low Population Zone (LPZ) distance was assumed to be 3218m in accorcance with information presented in the FSAR.
The relative concentration (X/Q) value for the 0-2 hour time period was determined to be 1.8 x 10-4 sec/m3 for the 5% overall limit X/Q at the exclusion area boundary. Virtually identical X/Q values were calculated at the exclusion area boundary in the east-northeast, south, south-southwest, and southwest sectors. The 5% overall limit X/Q at the LPZ distance was also slightly higher than the X/Q values in individual sectors. The following X/Q values were determined for appropriate time periods at the LPZ distance:
Time Period X/Q (sec/m3) 5 5
0-8 hours 3.1 x 10 5 5
8-24 hours 2.2 x 10 5 1-4 days 1.0 x 10-l 4-30 days 3.4 x 10-0
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I The X/Q values at the exclusion area boundary for the 0-2 hour time period is identical to that calculated by the applicant (see Table 2.3.4-1 i
of the FSAR) and that calculated previously by the staff (see the January 16, 1980 memorandum from Hulman to Rubenstein). The X/Q values for various time periods at the LPZ distance are very similar to those calculated by the applicant and previously by the staff. The X/0 value for the 4-30 day time period is about 25% larger than the value calculated by the applicant and previously by the staff..The differences are most likely attributable to the availability of the expanded data base (i.e., through March 1981).
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The X/Q values identified above are considered appropriate for use in i
assessments of the consequences of design basis accidents included in the l
draft Safety Evaluation Report for Vogtle. This assessment was performed l
by J. Fairabent (x29427) and any questions should be directed to him.
l OB435.c31 d u rA t@E Irwin Spickler, Leader Meteorology Section Meteorology and Effluent Treatment Branch cc:
W. Gammill L. Hulman j
M. Whol l
J. Fairobent I
DISTRIBUTION:
Docket File 50-424 1
METB Docket File METB Reading File Z Spickler 1
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