Modelling Approach and Preliminary Results for Countermeasure - - PowerPoint PPT Presentation

Modelling Approach and Preliminary Results for Countermeasure Exercise

• Jan. 2011

EMRAS-2, Vienna, IAEA

Won Tae Hwang

2/25

 Overview of METRO-K (Korean Urban Radioactive Contamination Model)  Modelling Approach on Deposition  Modelling Approach on Behavior Following a Deposition  Modelling Approach on Countermeasure  Modelling Approch for Dose Assessment  Preliminary Results

Contents

Characteristics of METRO-K

 Based on analytical method using experimental and empirical data

• Easy to understand due to simple math.

structures

• Less input data

 Compose easily a complex urban environment using just 5 types of surfaces  Apply easily various remediation measures to different surfaces separately

3/25

Contamination Mechanisms

 Dry & wet depositions  Run-off  Retention on surface of radionuclide in run-off water  Environmental removals

• Natural processes such as wind, precipitation

and migration into soil

• Artificial processes such as traffic and walker

 Radioactive decay

4/25

5/25

Schematic Diagram of METRO-K

CAP : Critical Amount of Precipitation Radioactivity in Air P > CAP Dry/Wet Wet Fixed Run-off Fixed Dry Mobile Fixed Radioactivity on Surface Exposure dose Mobile Fixed Kerma Precipitation (P)

6/25

Modelling of Initial Deposition

d a s

v C C 86400 

p a d a s

w P C v C C

3

10 1 86400



  

 No rain (dry process)  Rain ≤ CAP (dry+wet processes)  Rain > CAP (wet process)

 

p ret c c a s

w f P P P C C ) (    

3

10 1

Time-integrated air concentration Dry deposition velocity daily rainfall

Washout ratio

CAP retained fraction

7/25

Urban Contamination

Exposure Dose

 



 

k j ijk j j k i i

k t D y DCF t H ) ( 10 64 . 8 ) (

14

 

Kerma is a function of receptor location (i), contaminated surface(j), gamma energy(k)

8/25

Application of Kerma (1)

1

K

1

K

2

K

2

K

3

K

3

K

A

K

A

K

B

K

B

K

C

K

C

K

Meckbach’s Results : Monte-Carlo Method 5 story building (METRO-K) 10 story building (Seoul scenario)

9/25

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Application of Kerma (2)

 Paved groundⅠ

A

K

A

K

Paved groundⅠ Paved ground Ⅱ

A

K

1 4

Paved ground Ⅲ

A

K

1 9

Environmental Removal

11/25

    ) exp( ) ( ) ( t D t D

d

 

) exp( ) ( ) exp(

, ,

t A t A

b w a w

      1

Application of Countermeasures

For the countermeasure effectiveness, a single DRF, which have been reviewed in previous EMRAS, is applied for each countermeasure

12/25

Radioactive Decay

60Co (5.3 yr) → 60Ni (Stable)

Energy (MeV) Yield (%) 0.69382 0.0163 1.1732 100 1.3325 100

239Pu (2 x 104 yr) → 235U (7 x 108 yr) →

Energy (MeV) Yield(%) 0.044141 0.0136 0.000476 0.11291

13/25

Resuspension

 Internal dose due to inhalation of resuspended particles is considered  Inhalation dose is evaluated from concentration of soil and sidewalk(paved surface) using a time-dependent resuspension factor  Seasonality of resuspsension is not considered, and the same resuspension factor is applied for all radionuclides

: resuspension factor (1/m) : time following a deposition (day)

14/25

 

9 6

10 01 10

 

   ) . exp( ) ( t t K

K

t

Assumptions

 External dose resulting from Pu-239 contamination is not considered  For internal dose due to inhalation, dose coefficients based on ICRP-60 are applied  For seasonal dependence of external dose, depositions onto trees on the street and in the park on Jan. are 10% and 50% of those on July, respectively  Environmental behaviors due to snow (in general) in winter are the same those due to rain in summer

15/25

16/25

Test Site – Region 1

Building 1

#1 : ground floor #2 : 10th floor #3 : 24th floor

(top floor)

#4 : outside

(block sidewalk)

17/25

Test Site – Region 2

Park Area

E1 : dirt pathway E2 : parking lot (concrete)

18/25

Results

60Co, No CM, Region 1, Outside, June

200 400 600 800 1000 1200 1400 1600 1800 2000 10

4

10

5

10

6

10

7

10

8

10

9

10

10

10

11

Contamination density of

60Co (Bq/m 2)

Time following an event (Julian day) Dry Light rain Heavy rain

19/25

Results

60Co, No rain, No CM, June

200 400 600 800 1000 1200 1400 1600 1800 2000 10

• 5

10

• 4

10

• 3

10

• 2

10

• 1

10

External dose rate (mGy/hr) Time following an event (Julian day) #1 #2 #3 #4 #5 #6

20/25

Results

60Co, Heavy rain, No CM, June

200 400 600 800 1000 1200 1400 1600 1800 2000 10

• 3

10

• 2

10

• 1

10 10

1

10

2

10

3

External dose rate (mGy/hr) Time following an event (Julian day) #1 #2 #3 #4 #5 #6

21/25

Results

60Co, No rain, No CM, Region 1, Ground floor, June

Year 0 Year 1 Year 5 10 20 30 40 50 60 70 80 90 100

Contribution to external dose rate (%) Time following an event wall street tree road

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Results

60Co, No rain, No CM, Year 0, June

#1 #2 #3 #4 10 20 30 40 50 60 70 80 90 100

Contribution to external dose rate (%) Location in Region 1 roof wall road street tree

23/25

Results

60Co, Heavy rain, No CM, Year 0, June

#1 #2 #3 #4 10 20 30 40 50 60 70 80 90 100

Contribution to external dose rate (%) Location in Region 1 roof wall road street tree

24/25

Results

60Co, No rain, Region 1, Ground floor, June

200 400 600 800 1000 1200 1400 1600 1800 2000 10

• 5

10

• 4

10

• 3

External dose rate (mGy/hr) Time following an event (Julian day)

No action Removal tree Removal tree+Washing road Washing road Washing wall + Washing roof Relocation Relocation + Washing road Vacuuming road Removal soil or Removal grass

25/25

Results

60Co, No rain, No CM, Region 1, Ground floor

200 400 600 800 1000 1200 1400 1600 1800 2000 10

• 4

10

• 3

External dose rate (mGy/hr) Time following an event (Julian day) July January