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

Contents  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 2/25

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

Schematic Diagram of METRO-K Radioactivity in Air Dry Precipitation (P) P > CAP Mobile Fixed Dry/Wet Wet Mobile Fixed Fixed Run-off Fixed Radioactivity on Surface Kerma Exposure dose CAP : C ritical A mount of P recipitation 5/25

Modelling of Initial Deposition  No rain (dry process)  C 86400 C v s a d Time-integrated air Dry deposition concentration velocity  Rain ≤ CAP (dry+wet processes)     3 C C v C P w 86400 1 10 s a d a p daily rainfall Washout ratio  Rain > CAP (wet process)      3   C C P P P f w 1 10 ( ) s a c c ret p CAP retained fraction 6/25

Urban Contamination 7/25

Exposure Dose       14  H ( t ) 8 . 64 10 DCF y D ( t ) k i i k j j ijk k j Kerma is a function of receptor location (i), contaminated surface(j), gamma energy(k) 8/25

Application of Kerma (1) Meckbach’s Results : Monte-Carlo Method K 1 K 2 K 3 K K K 1 A A K K B B K 2 K K C C K 3 5 story building 10 story building (METRO-K) (Seoul scenario) 9/25

Application of Kerma (2)  K K A A Paved groundⅠ Paved groundⅠ 1 K A 4 Paved ground Ⅱ 1 K A 9 Paved ground Ⅲ 10/25

Environmental Removal     D ( t ) D ( 0 ) exp( t ) d         A exp( t ) ( 1 A ) exp( t ) w , a w , b 11/25

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 60 Co (5.3 yr) → 60 Ni (Stable) Energy (MeV) Yield (%) 0.69382 0.0163 1.1732 100 1.3325 100 239 Pu (2 x 10 4 yr) → 235 U (7 x 10 8 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        6 9 K ( t ) 10 exp( 0 . 01 t ) 10 : resuspension factor (1/m) K : time following a deposition (day) t 14/25

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

Test Site – Region 1 Building 1 #1 : ground floor #2 : 10 th floor #3 : 24 th floor (top floor) #4 : outside (block sidewalk) 16/25

Test Site – Region 2 Park Area E1 : dirt pathway E2 : parking lot (concrete) 17/25

Results 60 Co, No CM, Region 1, Outside, June 11 10 Dry 10 2 ) Light rain 10 60 Co (Bq/m Heavy rain 9 10 Contamination density of 8 10 7 10 6 10 5 10 4 10 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Time following an event (Julian day) 18/25

Results 60 Co, No rain, No CM, June 0 10 #1 #2 #3 -1 10 External dose rate (mGy/hr) #4 #5 #6 -2 10 -3 10 -4 10 -5 10 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Time following an event (Julian day) 19/25

Results 60 Co, Heavy rain, No CM, June 3 10 #1 #2 2 10 #3 #4 External dose rate (mGy/hr) #5 1 10 #6 0 10 -1 10 -2 10 -3 10 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Time following an event (Julian day) 20/25

Results 60 Co, No rain, No CM, Region 1, Ground floor, June wall 100 street tree 90 road Contribution to external dose rate (%) 80 70 60 50 40 30 20 10 0 Year 0 Year 1 Year 5 Time following an event 21/25

Results 60 Co, No rain, No CM, Year 0, June 100 90 Contribution to external dose rate (%) roof 80 wall road 70 street tree 60 50 40 30 20 10 0 #1 #2 #3 #4 Location in Region 1 22/25

Results 60 Co, Heavy rain, No CM, Year 0, June 100 90 Contribution to external dose rate (%) roof 80 wall road 70 street tree 60 50 40 30 20 10 0 #1 #2 #3 #4 Location in Region 1 23/25

Results 60 Co, No rain, Region 1, Ground floor, June No action Removal tree Removal tree+Washing road Washing road Washing wall + Washing roof External dose rate (mGy/hr) -3 10 Relocation Relocation + Washing road Vacuuming road Removal soil or Removal grass -4 10 -5 10 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Time following an event (Julian day) 24/25

Results 60 Co, No rain, No CM, Region 1, Ground floor July January External dose rate (mGy/hr) -3 10 -4 10 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Time following an event (Julian day) 25/25