A few points on Dispersion Analysis for The Dominion Site

The site has a complex topography with large water body in the central and eastern

sides. It is expected that such complex terrain leads to non-stationary and non-

homogenous meteorological conditions leading to variation in the plume trajectory and

the spatial distribution of concentration / deposition patterns around the release point.

Hence a simulation is carried out with a nested 3-d non-hydrostatic mesoscale

atmospheric model (WRF) and a lagrangian particle dispersion model (FLEXPART) to

represent the complexity in dispersion and radiological impact due to accidental

releases.

A typical day 14th Dec 2012 is selected for simulation.

Configuration of the WRF Meteorological Model

Dynamics Primitive equations, non-hydrostatic ARW 3.4

Domains , Horizontal

resolution, no. of grids

Domain 1 – 27 km (50 x 50 grids along x, y directions)

Domain 2 – 9km (49x 49 grids along x, y directions)

Domain 3 – 3 km (88 x 88 grids along x, y directions)

Domain 4 – 1 km (151x 151 grids along x, y directions)

Size of the domains Domain 1 – 1350 km x 1350 km

Domain 2 – 441 km x 441 km

Domain 3 – 264 km x 264 km

Domain 4 – 151 km x 151 km used in dispersion analysis

Vertical Levels 50 levels

Model Physics Radiation : Dudhia (1989) scheme for shortwave;

Rapid radiative transfer model (RRTM) for longwave

Surface processes : NOAH land surface scheme

Boundary layer : Hong and Pan non-local diffusion

Convection - Kain-Fritsch mass flux scheme

Microphysics : WSM6 class simple ice scheme

Initial/boundary conditions NCEP GFS analysis, forecasts

(National Centers for Environmental Prediction Global Forecast

Model 50 km resolution meteorological analysis for initial

condition and 3 hourly forecasts for boundary conditions)

Distribution of Wind Flow, Temperature and Humidity

Analysis of Simulated Meteorological Parameters for a typical station in the simulation domain

JGG

Mixing

height(m)

Ustar(m/s) Inverse.obukhov(m) Wstar(m/s) WS(m/s) WD(m/s) Pasquill

stability

14_08 100 0.18353 0.02007 0.31707 1.22 320.68 F

14_09 100 0.1334 0 0 1.46 320.35 E

14_10 100 0.2732 0.01748 0.61125 1.49 327.71 E

14_11 100 0.12232 0.03839 0.20772 1.45 330.15 F

14_12 100 0.1 0 0 1.42 324.57 D

14_13 100 0.17668 0.00419 0.14842 1.09 322.4 D

14_14 100 -0.22052 0.05019 0 1.52 304.82 F

14_15 183.5952 0.22272 0 0 1.35 286.56 F

14_16 327.8984 -0.3385 0.02943 0 1.49 265.9 F

14_17 407.7824 0.18835 0 0 2.38 251.02 D

14_18 457.3471 0.31703 0 0 2.39 249.91 D

14_19 478.1546 0.30302 0 0 2.61 252.91 D

14_20 435.3577 0.15577 0.00785 0.3138 2.76 255.46 D

14_21 428.5682 0.18614 0.00339 0.27642 1.39 250.41 D

14_22 301.2212 0.1 0.114 0.21649 1.64 250.38 E

14_23 196.8753 0.1 0.07158 0.1848 1.7 245.86 F

15_00 120.5875 0.1 0.10595 0.2112 1.48 251.67 D

15_01 100.5301 0.1 0 0 1.33 268.15 D

15_02 100 0.1 0.08456 0.19551 1.02 299.18 F

15_03 100 0.1 0.08748 0.19778 0.89 288.92 F

15_04 100 0.1 0.11751 0.21871 1.01 301.77 E

15_05 100 0.1 0.11769 0.21884 1.3 314.83 E

15_06 100 0.1 0.12473 0.22306 1.12 328.22 E

15_07 100 0.1 0.12113 0.22098 0.99 346.79 E

15_08 100 0.1 0.02753 0 0.93 56.99 F

15_09 100 0.1242 0 0 0.86 134.26 D

15_10 100 0.1 0 0 0.77 354.81 D

15_11 100 0.1 0.05674 0.17112 0.73 352.43 F

15_12 100 0.1 0.00862 0.09115 0.78 14.6 F

15_13 100 0.1 0.00845 0.09044 1 20.71 F

15_14 100 0.18797 -0.03739 0 0.97 59.42 B

15_15 100 0.23742 0 0 0.62 220.25 D

15_16 168.8325 0.26298 -0.05581 0 0.73 72.53 B

15_17 366.1367 0.22883 -0.07548 0 1.82 103.31 B

15_18 453.4218 0.35182 0 0 1.9 145.11 D

15_19 461.1819 0.3268 0 0 2.17 142.05 D

15_20 325.5932 0.14246 0.01031 0.30816 1.83 155.12 E

15_21 338.9031 0.18249 0.00318 0.26616 1.04 152.35 E

15_22 183.5108 0.1 0.07638 0.35293 1.65 119.6 F

15_23 129.1479 0.1 0 0 1.58 124.64 D

16_00 247.3658 0.1 0.07628 0.28018 2.08 179.94 F

16_01 195.2075 0.1 0.07797 0.24115 1.81 193.53 F

16_02 181.1512 0.1 0.12453 0.22281 1.72 184.35 E

16_03 185.5431 0.10146 0.06348 0.23964 1.92 173.54 F

16_04 161.2278 0.11671 0.02187 0.24271 2.28 169.04 E

16_05 157.7259 0.12502 0.0231 0.27353 2.09 150.06 E

16_06 173.1626 0.1664 0.01183 0.28191 1.85 168.42 E

Simulated meteorology indicated large diurnal variation in the flowfield and the stability

of the atmosphere. Both observations and met simulations show surface level

atmospheric flow continuously changes as northerly, northwesterly, westerly,

northeasterly, easterly and southeasterly. This may be due to the land-water contrast

and the resulting temperature gradients that drive the local scale flows.

Hourly trajectories for 24 h duration from the assumed source point at Dominion

Trajectory analysis shows wind flow is not stationary and changes atleast by 100 deg

over a day

For the 14-15 December case that we considered we found the atmospheric condition

as mostly stable (E/F), winds are moderate 1.0-2.0 m/s, mixed layer heights are noted to

vary as 100 m -450 m. These parameters show very poor diffusive conditions of the

atmosphere.

Mixing Height Variation

Flexpart Model Configuration

Model Parameter Parameter values

Horizontal grids 100 in the east-west direction; 100 in the north-south direction

Size of the domain – 60 km x 60 km

Grid resolution 600 m

Vertical levels 15 levels

0m, 15m, 25, 50m, 100m, 150m, 200m, 300m, 400m, 600m, 800m,

1000m, 1200m, 1500m, 2000m, 2500m, 3000m

Model integration,

Computational

particles

December 14-15; 100000 particles

Release point -76.697465 E; 37.165465 N (Dominion Power Plant)

Turbulence diffusion Hanna’s semi-empirical method based on surface layer scaling and local

stability.

Source

Characteristics

INPRO -ENV

Release Height – 8 m

Input Meteorology 1-km resolution WRF predictions between 18 UTC 14 Dec to 18 UTC

15 Dec; Parameters - u,v,w, Ө, rh ,cloud fractions, accumulated rain,

u*,surface fluxes, mixed layer height

Dry Deposition Deposition velocity (vd) with the resistance method

Wet Deposition Scavenging exponential decay process considering the cloud and rain

mechanisms.

Source Term Considered in the calculation using GPM

Nuke Rel (Bq) Bq/s AvEnerg(Mev) EffEnerg (Mev)

Sr-89 2.70E+14 3.13E+09 0.748 0.748

Sr-90 2.10E+13 2.43E+08 0.748 0.748

Te-127m

2.43E+14 2.81E+09 0.025

0.011

Te-129m

8.40E+14 9.72E+09 0.100

0.038

Te-132 1.82E+16 2.10E+11 0.127 0.234

I-131 1.59E+16 1.84E+11 0.361 0.381

I-132 2.04E+16 2.36E+11 0.762 2.275

I-133 1.11E+16 1.28E+11 0.585 0.606

Xe-133 5.76E+18 6.67E+13 0.050 0.045

Xe-135 1.31E+18 1.52E+13 0.249 0.249

Cs-134 2.44E+14 2.83E+09 0.796 0.796

Cs-137 1.73E+14 2.00E+09 0.607 0.533

Ce-144 5.24E+13 6.07E+08 0.134 0.134

Pu-238 1.28E+11 1.48E+06 0.748 0.748

GPM Dispersion Model Configuration

Distances for calculation 0.20, 0.30, 0.50, 0.70, 1.00, 1.60, 3.00, 4.00, 5.00, 6.00, 8.00, 10.00, 16.00, 20.00, 32.00 km

Release height (m) 35 m

Wind speed (m/s) 2.525 m/s

Atmos.Stability Pasquill – E category

Parameters Dry deposition using source depletion model with a deposition velocity of 0.01 m/s

Simulated Dose distribution with the Weather-Dispersion model (WRF-Flexpart)

Spatial simulated radiological dose over 1-day shows widely distributed dose in the

southern sectors from the release point with a maximum along the southeast sector.

Highest dose is near the release point and it decreases rapidly away from the source

Calculation using the Gaussian Plume Model

Inhalation Dose

The highest inhalation dose is by I-131 (high dose conversion factor as well relatively

large amount of release followed by Te-132 and I-133)

0.00E+00

5.00E-01

1.00E+00

1.50E+00

2.00E+00

2.50E+00

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

Sr-89

Sr-90

Te-127m

Te-129m

Te-132

I-131

I-132

I-133

Cs-134

Cs-137

Ce-144

Pu-238

Total (Sv/day)

Downwind distance (km)

Inh

alat

ion

do

se (

Sv)

Cloudshine Dose

Highest cloudshine dose is due to Xe-135 followed by Xe-133 and I-132

Groundshine Dose

Highest ground shine is due to Te-132 and I-131

1.00E+05

2.00E+05

3.00E+05

4.00E+05

5.00E+05

6.00E+05

7.00E+05

8.00E+05 Sr-89

Sr-90

Te-127m

Te-129m

Te-132

I-131

I-132

Clo

ud

shin

e d

ose

(u

Sv)

Downwind Distance (km)

0.00E+00

1.00E+00

2.00E+00

3.00E+00

4.00E+00

5.00E+00

6.00E+00

7.00E+00

8.00E+00

9.00E+00

1.00E+01

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

Te-127m

Te-129m

Te-132

I-131

I-132

I-133

Cs-134

Cs-137

Ce-144

Total (uSv/day)

Downwind distance (km)

Gro

un

dsh

ine

do

se (

uSv

)

5.00E-01

1.00E+00

1.50E+00

2.00E+00

2.50E+00

3.00E+00

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

Downwind distance (km)

Tota

l d

ose

(Sv

)

Total dose

5.00E-01

1.00E+00

1.50E+00

2.00E+00

2.50E+00

3.00E+00

3.50E+00

4.00E+00

4.50E+00

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00

GPM

Flexpart

Total dose

Tota

l d

ose

(Sv

)

Downwind distance (km)

Total Dose (Sv)

Distance (m) GPM Flexpart

0.20 6.89E-01 1

0.30 6.98E-01 1.5

0.50 1.36E+00 3

0.70 2.30E+00 4

1.00 2.83E+00 2

1.60 2.48E+00 0.75

3.00 1.41E+00 0.75

4.00 1.03E+00 0.5

5.00 8.02E-01 0.3

6.00 6.47E-01 0.25

8.00 4.60E-01 0.2

10.00 3.52E-01 0.075

16.00 1.98E-01 0.025

20.00 1.51E-01 0.01

32.00 8.49E-02 0.001

Dose computed using FLEXPART along the maximum plume trajectory (in southeast

sector) is compared with corresponding values from GPM

The computed dose with GPM is higher than that computed using FLEXPART

Flexpart values are higher by a factor of 2 at about 0.7 km distance. The release height

used in the FLEXPART is 8m against the GPM model value of 35m.

At all other points GPM value are higher than the FLexpart values by a factor of 3.

This is because the Flexpart considers the variation in the wind speed , stability apart

from variation in the wind direction which leads to distribution of plume in all sectors as

well a higher dilution due to variable diffusion and advection.