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Frontiers of Earth Science

Front Earth Sci    2013, Vol. 7 Issue (1) : 1-27     DOI: 10.1007/s11707-012-0342-y
RESEARCH ARTICLE |
Short-term emergency response planning and risk assessment via an integrated modeling system for nuclear power plants in complex terrain
Ni-Bin CHANG1(), Yu-Chi WENG2
1. Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, FL 32816, USA; 2. Division of Environmental Engineering, Graduate School of Engineering, Hokkaido University, Hokkaido, Sapporo 060-8628, Japan
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Abstract

Short-term predictions of potential impacts from accidental release of various radionuclides at nuclear power plants are acutely needed, especially after the Fukushima accident in Japan. An integrated modeling system that provides expert services to assess the consequences of accidental or intentional releases of radioactive materials to the atmosphere has received wide attention. These scenarios can be initiated either by accident due to human, software, or mechanical failures, or from intentional acts such as sabotage and radiological dispersal devices. Stringent action might be required just minutes after the occurrence of accidental or intentional release. To fulfill the basic functions of emergency preparedness and response systems, previous studies seldom consider the suitability of air pollutant dispersion models or the connectivity between source term, dispersion, and exposure assessment models in a holistic context for decision support. Therefore, the Gaussian plume and puff models, which are only suitable for illustrating neutral air pollutants in flat terrain conditional to limited meteorological situations, are frequently used to predict the impact from accidental release of industrial sources. In situations with complex terrain or special meteorological conditions, the proposing emergency response actions might be questionable and even intractable to decision-makers responsible for maintaining public health and environmental quality. This study is a preliminary effort to integrate the source term, dispersion, and exposure assessment models into a Spatial Decision Support System (SDSS) to tackle the complex issues for short-term emergency response planning and risk assessment at nuclear power plants. Through a series model screening procedures, we found that the diagnostic (objective) wind field model with the aid of sufficient on-site meteorological monitoring data was the most applicable model to promptly address the trend of local wind field patterns. However, most of the hazardous materials being released into the environment from nuclear power plants are not neutral pollutants, so the particle and multi-segment puff models can be regarded as the most suitable models to incorporate into the output of the diagnostic wind field model in a modern emergency preparedness and response system. The proposed SDSS illustrates the state-of-the-art system design based on the situation of complex terrain in South Taiwan. This system design of SDSS with 3-dimensional animation capability using a tailored source term model in connection with ArcView? Geographical Information System map layers and remote sensing images is useful for meeting the design goal of nuclear power plants located in complex terrain.

Keywords emergency response      nuclear power plants      diagnostic model      particle model      source term model      spatial analysis      Spatial Decision Support System     
Corresponding Authors: CHANG Ni-Bin,Email:nibinchang@gmail.com   
Issue Date: 05 March 2013
 Cite this article:   
Ni-Bin CHANG,Yu-Chi WENG. Short-term emergency response planning and risk assessment via an integrated modeling system for nuclear power plants in complex terrain[J]. Front Earth Sci, 2013, 7(1): 1-27.
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http://journal.hep.com.cn/fesci/EN/10.1007/s11707-012-0342-y
http://journal.hep.com.cn/fesci/EN/Y2013/V7/I1/1
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Ni-Bin CHANG
Yu-Chi WENG
Countries or RegionsFeatures
USA(Ritchie et al., 1983)● MIDAS (Meteorological Information and Dose Assessment System)● three dimensions● dry/wet deposition● real time control
Japan(Yoshikawa et al., 1990)● SPEEDI● Euler system● three dimensions and terrain – following coordinates● partial differential equations system for wind field prediction and pollutants transport● real time model
Italy(Bonelli et al., 1992)● STRALE● Lagrangian trajectory model● three dimensions multiple puff● pollutant transport in vertical and horizontal scales● wet/dry deposition
Holland(Verver and De Leeuw,1992)● Lagrangian trajectory● three dimensions multiple puff● multiple layers above and beneath mixing layer● pollutant transport in vertical and horizontal scales● wet/dry deposition
Hong Kong SAR(Yeung and Ching, 1993)● RADIS (Regional Nuclear Accident Consequence Analysis Model)● Lagrangian trajectory● two dimensions● wet/dry deposition
England(Maryon and Buckland,1994)● NAME (Nuclear Accident Dispersion Model)● Monte Carlo-based Lagrangian trajectory● multi-particle● multiple layers above and beneath mixing layer● three dimensions terrain – following coordinates● pollutant transport in vertical and horizontal scales● wet/dry deposition
Norway(Saltbones et al., 1996)● SNAP (Sever Nuclear Accident Program)● Monte Carlo-based Lagrangian trajectory
Germany(Eder et al.,1997)● Monte Carlo-based Lagrangian trajectory● terrain – following coordinates● real time model● spatially distributed deposition/dose graphic user-interface (GUI)
Tab.1  Design features of SDSS for nuclear emergency preparedness and response in the literature
Fig.1  Modular design of evaluation subsystems in SDSS
Fig.2  Operation procedures of SDSS ()
No.Description of malfunction
1.Loss of Coolant Accident (Hot Leg)
2.Loss of Coolant Accident (Cold Leg)
3.Steam Line Break Inside Containment
4.Steam Line Break Outside Containment
5.Loss of Feedwater Accident
6.Main Steam Isolation Valve Closure
7.Loss of Flow (Locked Rotor)
8.Anticipated Transient Without Scram
9.Turbine Trip (Loss of Load)
10.Steam Generator A Tube Rupture
11.Steam Generator B Tube Rupture
12.Inadvertent Rod Withdrawal
13.Inadvertent Rod Insertion
14.Moderator Dilution
15.Load Rejection
16.Containment Failure
17.Fuel Failure at Power
18.Fuel Handling Error in Containment
19.Fuel Handling Error in Auxiliary Building
20.Letdown Line Break in Auxiliary Building
Tab.2  Scenario planning of accidental contaminant release in PCTRAN
AtmosphericStabilityABCDEF
a0.800.700.600.450.300.20
b1.701.601.200.700.600.40
c0.900.840.800.770.590.48
Tab.3  Coefficients of dispersion parameters
RadionuclidesVd /(m·s-1)
Ru-1030.0045
Te-1320.0046
I-1330.002
Cs-1370.0042
Ba-1400.0036
Others0.00378
Tab.4  Dry deposition velocity, /(m·s)
Radionuclidesa /s-1b
Ru-1034 × 10-40.72
Ru-1062 × 10-41.2
Te-1291.3 × 10-40.4
Te-1321.8 × 10-40.71
I-1317 × 10-40.69
I-1331.6 × 10-40.5
Cs-1342.8 × 10-40.51
Cs-1362.4 × 10-40.43
Cs-1373.4 × 10-50.59
Ba-1403 × 10-50.3
Others1.0 × 10-40.64
Tab.5  Scavenging coefficient, s
Fig.3  Pathways of exposure assessment
ConsequenceEmergency conditionDescription
NegligibleNotification of unusual event(Emergency standby)Negligible on-site and off-site impact on people or the environments
LowPlant alert emergencyMinor on-site and negligible off-site impact on people or the environments
ModerateSite area emergencyConsiderable on-site impact on people or the environments; only minor off-site impact
HighOff-site emergencyConsiderable on-site and off-site impact on people or the environments
Tab.6  Consequences analysis
Z0/mTerrain characteristic descriptions
≈ 0.03Flat terrain with short grass; no obstacles upwind
≈ 0.10Little nonuniform terrain; scattered tree cover upwind
≈ 0.30Nonuniform field; low density residential for urban areas
≈ 0.03Flat terrain with forest; a city without tall buildings
Tab.7  An empirical guideline for the roughness length () of different types of land surface in this study
Fig.4  The Holzworth method, which utilized the hourly surface temperature rising along the dry adiabatic lapse curve until crossing the vertical temperature curve
Atmospheric stabilityThe transient temperature in terms of height (ΔTz)/(°C10-2m-1)Standard deviation of wind directions
A<-1.925
B-1.9 ~ -1.720
C-1.7 ~ -1.515
D-1.5 ~ -0.510
E-0.5 ~ 1.55
F1.5 ~ 4.02.5
Tab.8  Selection of atmospheric stability
Pasquill-Turner atmospheric stability
Roughness/mABCDEF
0.030.030.050.090.140.200.27
0.10.050.070.120.180.250.33
0.30.070.100.160.250.350.45
1.00.100.150.250.350.450.55
Tab.9  Exponents of wind velocity
Protective measuresMain exposure pathways
Sheltering● External irradiation from facility, plume and ground deposits● Inhalation of radioactive material in plume● Deposition on skin and clothes
Administration of stable iodine compounds● Inhalation of radioiodine● Ingestion of radioiodine
Urgent evacuation● External irradiation from facility, plume and ground deposits● Inhalation of radioactive material in plume● Deposition on skin and clothes
Temporary relocation and permanent resettlement● External irradiation from ground deposits● Ingestion of contaminated food and water● Inhalation of resuspended radionuclides
Food and water control, restriction and discarding of foodstuffs● Ingestion of contaminated food and water
Decontaminationof persons and clothing● External irradiation and/or internal irradiation
Tab.10  Protective measures for averting exposure via various pathways (; )
Because the largest value of off-site dose is over the limits, the following protection actions for the emergency response should be taken into account.
ReleasedConditionsPuff Release or Released time less than 2 hContinuous Release or Released time more than 2 h
0 - 4 hEmergency response in protective zone:● Sheltering● Distributing iodine tablet● Access limit
4 - 8 hEmergency response in protective zone:● Distributing iodine tablet● Access limitEmergency response in protective zone:● Evacuation or Sheltering● Distributing iodine tablet● Access limit
After 8 hEmergency response in protective zone:● Distributing iodine tablet● Access limitEmergency response in protective zone:● Evacuation or sheltering● Distributing iodine tablet● Access limit
Radiological contaminated control zone:● Control of products (milk, food, water, crop and etc.)Radiological contaminated control zone:● Control of products (milk, food, water, crop and etc.)
After the end of accidental eventRadiological pollution control zone:● Sampling air, water, soil, food/feed● Detection and monitoring● Re-enter, clean and recovery
Tab.11  Protective actions for the emergency response in various released conditions (; )
The exposure dose of assessmentProtection guides
Whole BodyThyroid
5-50 mSv50-500 mSvInfant, children, and pregnant women should enter a shelter like a house and close doors and windows to prevent radionuclide permeation.
50-100 mSv500-1000 mSvInfant, children, and pregnant women should enter a shelter like a concrete building or evacuate from the affected area. Adults could stay in the house and close doors and windows to prevent radionuclide permeation.
>100 mSv>1000 mSvInfant, children, pregnant women and adults should enter a shelter like a concrete building or evacuate from the affected area.
Tab.12  Protection Actions Guides (PAGs) for the public in Taiwan
Emergency conditionEmergency event classDefinition
First class emergency event (Notification of unusual event and emergency standby)The emergency alarm of notification of unusual event
Second class emergency event (Plant alert emergency)2ANo radionuclides releasing of plant alert emergency
2BRadionuclides releasing of plant alert emergency
Third class emergency event (Site area emergency)3ANo radionuclides releasing of site area emergency
3BRadionuclides releasing of site area emergency and the maximum of whole body dose rate (Heff) less than 0.5 mSv/hr
3CRadionuclides releasing of site area emergency and the maximum of whole body dose rate (Heff) more than 0.5 mSv/hr
Forth class emergency event(General emergency)4AImmediately command and execute the protective actions for public (from the evolution of Class 3B or Class 3C event)
4BImmediate general emergency, not in the procedure of command and execution of protective actions for public
Tab.13  Classification of emergency accidental events of nuclear power plant in Taiwan
Fig.5  Maanshan Windows Mimic
ParametersOn-site dose assessment evaluationLocal dose assessment evaluationRegional dose assessment evaluation
ConditionsNuclear power plant’s observations& diagnostic modelPlant’s and met-station’sobservations& diagnostic modelPlant’s and meteorological-station’sobservations& prognostic model (e.g., MM5 or WRF)
Domain10 × 10 (5 km × 5 km)20 × 20 (20 km × 20 km)60 × 60 (60 km × 60 km)
Simulating period0 - 90 min0 - 6 h0 - 96 h
Releasing durationUTC 0000 - 0130UTC 0000 - 0600UTC 0000 - 2400
Source termPCTRAN:l Loss of Coolant Accident [Hot leg] 100% of 100 cm2l Loss of Coolant Accident [Cold leg] 100% of 100 cm2l Containment Failure 100% per day leakage rate at design pressure
Atmospheric stabilityBBB and C (day)D (night)
Calculated vertical levelsSelection of seven levels:10.0, 86.4, 208.3, 515.7, 1015.6, 1464.4, 2000.0 (m).
Tab.14  Parameters settings in case study
Fig.6  Study Domain (a) and Satellite image (b)
ObservationsMeteorological stations
Time intervalOn-siteHengchunTawuLan-YuChienchenHsiaokang
0 - 1 h4.0 m/s,189.2°3.3 m/s,180.0°3.0 m/s,135°3.7 m/s,202.5°2.7 m/s,180.0°4.5 m/s,220.0°
1 - 2 h4.3 m/s,191.8°3.2 m/s,180.0°2.0 m/s,135°3.5 m/s,202.5°3.3 m/s,180.0°5.0 m/s,210.0°
2 - 3 h4.5 m/s,192.4°2.9 m/s,157.5°2.3 m/s,157.5°4.6 m/s,202.5°3.2 m/s,180.0°5.0 m/s,200.0°
3 - 4 h3.1 m/s,173.9°2.8 m/s,157.5°0.7 m/s,270°3.8 m/s,202.5°2.9 m/s,180.0°5.0 m/s,220.0°
4 - 5 h3.0 m/s,169.8°2.6 m/s,180.0°0.6 m/s,135°3.7 m/s,202.5°2.4 m/s,180.0°5.0 m/s,220.0°
5 - 6 h2.3 m/s,162.3°2.8 m/s,180.0°0.8 m/s,270°4.1 m/s,202.5°2.5 m/s,180.0°4.0 m/s,190.0°
Tab.15  Meteorological observations
Dose contour colorsDose rate value on the surface/ (mSv·hr-1)
>0.5
0.2 - 0.5
0.05 - 0.2
0.02 - 0.05
0.015 - 0.02
0.01 - 0.015
0.005 - 0.01
<0.005
None
Tab.16  Dose contour colors and dose rate value
Fig.7  Whole body dose (a) and wind field (b) at 0 - 15 min
Fig.8  Whole body dose (a) and wind field (b) at 15 - 30 min
Fig.9  Whole body dose (a) and wind field (b) at 30 - 45 min
Fig.10  Whole body dose (a) and wind field (b) at 45 - 60 min
Fig.11  Whole body dose (a) and wind field (b) at 60 - 75 min
Fig.12  Whole body dose (a) and wind field (b) at 75 - 90 min
Fig.13  Integrated whole body dose at 0-90 min
Fig.14  Whole body dose (a) and wind field (b) at 0 - 1 hr
Fig.15  Whole body dose (a) and wind field (b) at1 - 2 hr
Fig.16  Whole body dose (a) and wind field (b) at2 - 3 hr
Fig.17  Whole body dose (a) and wind field (b) at3 - 4 hr
Fig.18  Whole body dose (a) and wind field (b) at 4-5 hr
Fig.19  Whole body dose (a) and wind field (b) at 5-6 hr
Fig.20  Whole body dose at 0-6hr
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