Gaussian Plume and Puff Models for Offsite Dose Rates Evaluations

國立清華大學工程與系統科學系Engineering & System Science, NTHU

Gaussian Plume and Puff Modelsfor Offsite Dose Rates Evaluations

Department of Engineering and System ScienceNational Tsing-Hua University

Chunkuan Shih

MST NJ, July 12, 2006


Gaussian Steady State Plume Model

NPP effluents dispersion is based on site’s meteorology

Concentration of effluent is determined by the usual diffusion equation

Gaussian plume model for dispersion in transverse directions

Dispersion coefficients determined from Pasquill conditions (A thru G)


Local Meterorology


Pasquill Conditions

Pasquill category (˚C/100 m) (degree) Remarks

A Extremely unstable

B Moderately unstable

C Slightly unstable

D Neutral

E Slightly stable

F Moderately stable

G Extremely stable

zT /

9.1/ zT

7.1/9.1 zT

5.1/7.1 zT

5.0/5.1 zT

5.1/5.0 zT

0.4/5.1 zT

zT /0.4

5.22

5.175.22

5.125.17

5.75.12

8.35.7

1.28.3

1.2


Diffusion Equation and Solution

2

2

2

2

' 2

)(

2exp

1

zyzy

hy

vQ

xzK

yK zy

2

2

2

2


Dispersion Coefficients (Horizontal)


Dispersion Coefficients (Vertical)


Dispersion Coefficients for Type G

)(3

2)();(

5

3)( FGFG yyzz


Dose Rates Values and Presentations


Type B


Type D


Type F


Gaussian Puff Model

Account for the time of travel of effluents and dispersions in all directions

Effluents are releases as successive puffs at every end of a preset duration of time (ex. 30 sec)

Code keeps track of dose rates and integrated doses at every downwind location (50m X 50m square) within 5 km radius .

tQQ


The concentration due to the puff at the receptor (xr, yr, zr) relation to the center of a puff located at (xp, yp, zp)

Effluent Concentration Distribution

22

2222/3

)(2

1exp)(

2

1exp

)(2

1exp)(

2

1exp

)2(),,(

z

rp

z

rp

h

rp

h

rp

zh

rrr

zzzz

yyxxQzyx

ground level

+ y r

- y r

xr

z r

H

wind direction

xp

z p

+ yp


For ground level concentration, zr is replaced by –H,

Ground Level Concentration

22

2222/3

)(2

1exp)(

2

1exp

)(2

1exp)(

2

1exp

)2(),,(

z

p

z

p

h

rp

h

rp

zh

rr

HzHz

yyxxQHyx


Time Varying Thyroid Dose Rates

1000 s2000 s

3000 s

4000 s


Time Varying Thyroid Dose Rates

0.001

0.01

0.1

1

10

0 1000 2000 3000 4000 5000

m

mS

v/h

1020 s2010 s

3000 s

3990 s


Accident Classifications事故類別級別分級原則廠界最大個人全身劑量率

異常事件之警示通知

　異常事件無影響

緊急戒備 A級無放射性物質外釋的緊急戒備事故無影響

B級有放射性物質外釋的緊急戒備事故，細分成左方三種狀況有不同的行動準則。

大於等於 0.02mSv/hr



廠區緊急事故 A級無放射性物質外釋的緊急戒備事故　

B級有放射性物質外釋的緊急戒備事故，但最大個人全身劑量率小於 0.5mSv/h，又細分成左方三種狀況有不同的行動準則。




C級有放射性物質外釋的緊急戒備事故，但最大個人全身劑量率大於等於 0.5mSv/h

0.5mSv/hr

全面緊急事故　　

A級指已下令執行民眾防護行動之全面緊急事故

0.01 Sv/hr（或甲狀腺劑量率大於等於 0.05 Sv/hr）　　B級指突發性之全面緊急事故（事故發生或演

變突然，而無法循序準備與下令執行各項民眾防護行動）

Gaussian Plume and Puff Models for Offsite Dose Rates Evaluations

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