strategies for the selection of substitute meteorological data ken sejkora entergy nuclear northeast...
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Strategies for the Selection of Substitute Meteorological Data
Ken SejkoraEntergy Nuclear Northeast – Pilgrim
Station
Presented at the 14th Annual RETS-REMP WorkshopSyracuse, NY / 28-30 June 2004
Basis of Problem Pilgrim Station was experiencing problems
with the upper-level wind direction indication on the primary tower
Question: Can Pilgrim substitute data from its backup tower to meet data recovery goals?
Proposed Solution: Compare various multiple measurements of meteorological parameters to determine suitability for substitution
Pilgrim Meteorological Towers Primary Tower
220-ft tall, based at ~80 ft above sea level on vegetated area 270m from ocean
Effective height = 300 ft Wind and temperature at top and 10m
Secondary (Backup) Tower 160-ft tall, based at ~20 ft above sea level in parking
lot 100m from ocean Effective height = 180 ft Wind and temperature at top and 10m
Hourly averages for 2-year period, yielded ~17,500 observations
Tower Placement Guidance Safety Guide 23… minimal guidance
Minimize effects from plant structures ANSI/ANS-2.5-1984
Represent release point Minimize effect from manmade
structures Avoid downwind from plant Distance from structures should be
>10 times the structure height
Tower Placement Guidancecontinued
ANSI/ANS-3.11-2000 More detailed than other guidance Avoid asphalt/concrete surfaces Not endorsed/’required’ by NRC Post-dates most pre-existing nuclear plant
meteorological installations Backup tower fails to meet many
criteria Downwind, nearby buildings, asphalt
Stability Class Frequencies
Stability Class Distribution
0%
10%
20%
30%
40%
A B C D E F G
Stability Class
Fre
qu
en
cy
Primary Backup
Problem with Frequency Data Relative frequencies for two sources do
not reflect the comparability of simultaneous measurements
Identified need for comparing paired measurements through time to determine how well they compare
Summarize comparisons of paired data to determine degree of differences
Agreement Matrix: Stability Class
A B C D E F G
A 1128 426 154 350 64 9 3B 218 171 72 124 14 3 0C 213 152 96 205 28 4 0D 479 429 405 3191 365 29 9E 170 135 105 2041 2996 396 78F 29 10 8 118 557 669 348G 7 8 7 25 85 158 299
Primary Tower
Backup Tower
Agreement Matrix Summary: Summation of Diagonals
Stability Class
Difference
Match 8550 51.5% 8550 51.5%1 3531 21.3% 1812 10.9%2 950 5.7% 413 2.5%3 647 3.9% 377 2.3%4 187 1.1% 67 0.4%5 37 0.2% 9 0.1%6 7 0.0% 3 0.0%
Total 5359 32.3% 2681 16.2%
Primary Tower Conservative
Backup Tower Conservative
Stability Class Differences
Primary vs. Backup Stability
0%10%20%30%40%50%60%
P:T
P:6
P:5
P:4
P:3
P:2
P:1
Ma
tch
B:1
B:2
B:3
B:4
B:5
B:6
B:T
Stability Class Difference
Fre
qu
en
cy
Candidate for Substitution?Delta-T
Primary tower delta-T yields more conservative stability class ~30% of cases
May be good substitute, but consider… Backup tower is in middle of parking lot, and
does not meet ANSI meteorological standards Heating from blacktop, cars, adjacent
buildings, etc. could bias readings, and would be expected to yield more negative delta-T values and lower stability classes
Temperature Frequencies
Temperature Class Distribution
0%5%
10%15%20%25%
-10
-0
0-1
0
10
-20
20
-30
30
-40
40
-50
50
-60
60
-70
70
-80
80
-90
90
-10
0
Temperature Class
Fre
qu
en
cy
Primary Backup
Temperature Differences
Primary vs. Backup Temperature
0%10%20%30%40%50%60%
T:S
>P -8 -6 -4 -2 0 2 4 6 8
T:P
>S
Temp.Difference: Primary - Backup
Fre
qu
ency
Candidate for Substitution?Temperature
>75% readings from both towers are within ±2 degrees of each other
Acceptable substitute, but consider… Backup tower is in middle of parking lot,
and does not meet ANSI meteorological standards
Heating from blacktop, cars, adjacent buildings, etc. could bias readings
Wind Speed Frequencies
Wind Speed Distribution
0%10%20%30%40%50%60%
Calm-0.95
0.95-3.5 3.5-7.5 7.5-12.5 12.5-18.5
18.5-24 >24
Wind Speed Class - mph
Fre
qu
en
cy
Primary Upper Backup Upper Primary Lower Backup Lower
Wind Speed Differences: Primary vs. Backup, Upper Level
Primary vs. Backup Upper Wind Speed
0%10%20%30%40%50%60%
P:T
P:6
P:5
P:4
P:2
P:2
P:1
Ma
tch
B:1
B:2
B:3
B:4
B:5
B:6
B:T
Upper Speed Class Difference
Fre
qu
en
cy
Wind Speed Differences: Primary vs. Backup, Lower Level
Primary vs. Backup Lower Wind Speed
0%10%20%30%40%50%60%
P:T
P:6
P:5
P:4
P:2
P:2
P:1
Mat
ch B:1
B:2
B:3
B:4
B:5
B:6
B:T
Lower Speed Class Difference
Fre
qu
enc
y
Wind Speed Differences: Primary, Upper vs. Lower Level
Primary Upper vs. Lower Wind Speed
0%
20%
40%
60%
80%
100%
U:T
U:6
U:5
U:4
U:2
U:2
U:1
Ma
tch
L:1
L:2
L:3
L:4
L:5
L:6
L:T
Speed Class Difference
Fre
qu
en
cy
Wind Speed Differences: Backup, Upper vs. Lower Level
Backup Upper vs. Lower Wind Speed
0%
20%
40%
60%
80%
100%
U:T
U:6
U:5
U:4
U:2
U:2
U:1
Ma
tch
L:1
L:2
L:3
L:4
L:5
L:6
L:T
Speed Class Difference
Fre
qu
en
cy
Candidate for Substitution?Wind Speed
Upper readings > lower readings… expected
Differences in wind speeds as a function of height would make substitution difficult Possible correction factors by extrapolation
The fact that the lower level of primary tower shows lowest wind speeds may indicate influence of nearby trees Implications to wind direction at this location
Wind Direction Frequencies
Wind Direction Distribution
0%
5%
10%
15%
20%
N
NE E
SE S
SW W
NW
Wind Direction
Fre
qu
en
cy
Primary Upper Primary Lower Backup Upper Backup Lower
Wind Direction Differences: Primary vs. Backup, Upper Level
Primary vs. Backup Upper Wind Direction
0%10%20%30%40%50%60%
CC
W:T
CC
W:5
CC
W:4
CC
W:3
CC
W:2
CC
W:1
Ma
tch
CW
:1
CW
:2
CW
:3
CW
:4
CW
:5
CW
:T
Upper Direction Difference
Fre
qu
en
cy
Wind Direction Differences: Primary vs. Backup, Lower Level
Primary vs. Backup Lower Wind Direction
0%10%20%30%40%50%60%
CC
W:T
CC
W:5
CC
W:4
CC
W:3
CC
W:2
CC
W:1
Mat
ch
CW
:1
CW
:2
CW
:3
CW
:4
CW
:5
CW
:T
Lower Direction Difference
Fre
qu
ency
Wind Direction Differences: Primary, Upper vs. Lower Level
Primary Upper vs. Lower Wind Direction
0%10%20%30%40%50%60%
CC
W:T
CC
W:5
CC
W:4
CC
W:3
CC
W:2
CC
W:1
Mat
ch
CW
:1
CW
:2
CW
:3
CW
:4
CW
:5
CW
:T
Direction Difference
Fre
qu
ency
Wind Direction Differences: Backup, Upper vs. Lower Level
Backup Upper vs. Lower Wind Direction
0%10%20%30%40%50%60%
CC
W:T
CC
W:5
CC
W:4
CC
W:3
CC
W:2
CC
W:1
Ma
tch
CW
:1
CW
:2
CW
:3
CW
:4
CW
:5
CW
:T
Direction Difference
Fre
qu
en
cy
Candidate for Substitution?Wind Direction
Primary tower seems to indicate slight counterclockwise bias compared to backup at both levels Alignment? Topography effect?
Candidate for Substitution?Wind Direction
Primary tower upper level shows clockwise bias compared to lower level Alignment? Potential effects of nearby trees? Lower level of primary tower exhibits
greatest fluctuations… evidence of influence of trees?
When coupled with low wind speeds at this level, may point to influence from trees
Candidate for Substitution?Wind Direction
Backup tower upper and lower levels show good agreement
Acceptable substitute, but consider… Backup tower is in middle of parking lot,
and does not meet ANSI meteorological standards
The good agreement may indicate minimal influence from nearby structures, but difficult to quantify
Summary Delta-T, temperature, and wind direction
show potential for substitution, but need to consider placement of backup tower (non-ANSI)
Wind speed is poor candidate for substitution
Lower wind speed and direction readings at primary tower may indicate influence of nearby trees and topography
Summary - continued Of all readings from backup tower,
upper wind direction would likely be least affected by adjacent structures, and would be most suitable for substitution Need to resolve potential bias? Upper wind speed may also be candidate,
but would need to be adjusted for height difference
Summary - continued Although backup tower location does not
meet ANSI standards in regard to ground cover, adjacent buildings, etc., its readings appear reasonable and acceptable for backup use if primary is lost Local data is better than alternate data from
a remote site Most remote sites (airport, NWS) are not
equipped to provide met data for emergency operations