METI-LIS Technical Manual

B. Validation using Available Results of Field Experiment
1. Millstone Experiment
Documents of air dispersion phenomena influenced by buildings are collected, and
examined the field dispersion experiments and wind tunnel experiments in the past. Existing
field observation data 13 from overseas were applied to the METI-LIS model to examine the
accuracy. By applying field data to the METI-LIS and ISC model, it was confirmed that the
METI-LIS model has more accuracy than the ISC model. In this section, such results are
described.
The field observation data used for examination were from survey at Millstone Nuclear
Power Station in United States. The observed concentrations were in hourly average,
whereas the METI-LIS and the ISC models use 3-10 minute average. The concentrations of
the METI-LIS and the ISC models were corrected to hourly average by using the following
simple correction method.
Set concentration distribution calculated with representative wind direction as C. Shift the
wind direction (right and left) by standard deviation of wind direction within 1 hour. Set
calculated concentration with the shifted wind directions as C + and C - . The wind frequency
of C, C + , and C - were used to calculate the weighted average of concentration, which
represent the hourly average.
Specifically, the equation below is used.
C 1hr = ( C + 0.61 x C + + 0.61 x C - ) / (1+0.61+0.61)
Here, 0.61 is the frequency of shifted wind direction by amount of standard deviation; while
frequency of representative wind direction is set as 1.
Gas tracer study (SF 6 ) was carried out in field observation of Millstone Nuclear Power
Station to examine the downwash influence by buildings. Dispersion source is the vent
(Vg 14 /U is roughly 1) set at the roof of reactor building (UNIT2). Total of 36 cases were
observed. As shown in figure B1-1, the samples were taken in 3 rows in arc shape from the
source location (approximately 350m, 800m and 1,000m leeward of the source). From 36
cases, 8 cases were chosen that thought to have small fluctuations in wind direction and
stability of neutral condition. In calculation, reactor building (UNIT2) was selected as the
main building.
Compared result is shown in Figure B1-2 and Table B1-2. Meteorological condition is
14
Vg indicates exit gas velocity.
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