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Joint IAEA-KINS Workshop on Site Evaluation for Nuclear Facilities,
16-20 April 2018, Daejeon, Korea
Meteorological Hazards
Dr. Kwanhee LEE
Korea Institute of Nuclear Safety
Korea Institute of Nuclear Safety
2
Part I. Introduction
Part II. Onsite Meteorological Monitoring Program
Part III. Design Basis Meteorological Conditions
Part IV. Long-Term Atmospheric Diffusion Estimates
Part V. Short-Term Atmospheric Diffusion Estimates
Table of Contents
Korea Institute of Nuclear Safety
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Part I. Introduction
Korea Institute of Nuclear Safety
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Meteorology?
The science of the atmosphere : embracing both weather and climate.
It is concerned with the physical, dynamical and chemical state of the
earth's atmosphere, and with the interactions between the earth's
atmosphere and the underlying surface.
Weather : conditions of the atmosphere over a short period of time
(hour to day, rain, snow, thunderstorms)
Climate : description of the long-term pattern of weather in a
particular area (usually taken over 30-years)
Major focus on weather forecasting
Introduction
Korea Institute of Nuclear Safety
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Role of Meteorology in the Nuclear Industry
Site acceptability studies for construction of NPPs
local climatology (including both normal and extreme conditions)
Estimating the potential annual doses to the public resulting from
routine effluent releases
Determining when protective measures should be considered to protect
the health and safety of the public in the event of an accidental release
of radioactive materials
Assessing potentially adverse environmental effects of a radiological or
non-radiological nature resulting from the construction or operation of
a NPP
Introduction
Korea Institute of Nuclear Safety
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Purpose of the Onsite Meteorological Monitoring System
Provide meteorological conditions for safe design, operation and
proper emergency planning & preparedness of NPPs
Meteorological data collected at nuclear facilities play an important
role in determining the effects of radiological effluents on workers,
facilities, the public, and the environment
Onsite meteorological measurement program at a nuclear site should
be capable of providing the meteorological information needed to
make the following assessments
a conservative assessment of the potential dispersion of radioactive
material
a conservative assessment of the habitability of the control room
during postulated design-basis radiological accidents
Introduction
Korea Institute of Nuclear Safety
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NRC Q&A Series: Three Minutes with an NRC Meteorologist (YouTube)
Introduction
Korea Institute of Nuclear Safety
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Temperature(˚C) : A measure of the hotness or coldness of the ambient
air, as measured by a suitable instrument
Vertical temperature difference (ΔT)
Measured difference in ambient temperature between two elevations on the same tower
It is defined as the upper level temperature measurement minus the lower level temperature measurement
Calm : Any wind speed below the starting threshold of the wind speed
or direction sensor, whichever is greater
Starting Threshold: The minimum wind speed above which the measuring instrument is performing within its minimum specification
Precipitation (mm) : Any of the forms of water particles, whether liquid
or solid, that fall from the atmosphere and reach the ground
Definitions (1/2)
Korea Institute of Nuclear Safety
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Wind Direction(˚):
The direction from which the wind is blowing
Wind direction is reported in degrees azimuth, measured clockwise from true north and ranging from 0E to 360E (e.g., north is 0˚ or 360 ˚, east is 90 ˚)
Wind Speed(m/s) : The rate at which air is moving horizontally past a given point
Relative Humidity(%) : The ratio of the vapor pressure to the saturation vapor pressure with respect to water
Pasquill Stability Class: A classification of atmospheric stability, or the amount of turbulent mixing in the atmosphere and its effect on effluent dispersion
Wind Rose : A graphic tool used by meteorologists to give a succinct view of how wind speed and direction are typically distributed at a particular location
Definitions (2/2)
Korea Institute of Nuclear Safety
Wind Rose
Korea Institute of Nuclear Safety
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Part II. Onsite Meteorological Monitoring Program
Korea Institute of Nuclear Safety
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NSSC(Nuclear Safety and Security Commission) Notice No. 2017-26
“Technical Standards for Investigation and Evaluation of
Meteorological Conditions of Nuclear Reactor Facility Sites”
General Provisions, Investigation of Data, Method of Analysis,
etc.
Onsite Meteorological Measurement Program (parameters shall
be measured, Meteorological Measurement Period, Accuracy of
Maintenance, Data Processing, Special Meteorological
Measurement and Analysis)
Diffusion Characteristics of Radioactive Materials (Evaluation of
Diffusion and Dilution)
Regulations and Guidance (1/2)
Korea Institute of Nuclear Safety
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US NRC Reg. Guide 1.23 Rev. 1(2007)
“Meteorological Monitoring Programs for Nuclear Power Plants”
Definitions
Meteorological Parameters : Wind Speed and Direction, Vertical
Temperature Difference, Ambient Temperature, Precipitation,
Atmospheric Moisture
Siting of Meteorological Instruments
Instrument Accuracy and Range
Instrument Maintenance and Servicing Schedules
Data Reduction and Compilation
Special Considerations for Complex Terrain Sites
Regulations and Guidance (2/2)
Korea Institute of Nuclear Safety
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Wind Speed and Direction
Wind speed and direction should be measured on one open-lattice
tower or mast
Measured at heights of approximately 10, 58(60) meters above
ground level
Meteorological Parameters (1/5)
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Vertical Temperature Difference
Vertical temperature difference should be measured on the same
open-lattice tower or mast as wind speed and wind direction (10,
58(60) m levels)
Vertical temperature difference is the preferred method for
determining Pasquill stability classes at NPP for licensing purposes
it is an effective indicator for the worst-case stability
conditions
Meteorological Parameters (2/5)
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Classification of Atmospheric Stability
Meteorological Parameters (3/5)
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Precipitation
Precipitation should be measured near ground level near the base
of the mast or tower
Meteorological Parameters (4/5)
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Atmospheric Moisture
At sites utilizing cooling towers, cooling lakes and ponds, or spray
ponds as the plant’s normal heat sink, the pre-operational
monitoring program should include ambient temperature and
atmospheric moisture measurements
Meteorological Parameters (5/5)
Korea Institute of Nuclear Safety
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Accuracy of Instrument (RG 1.23)
Korea Institute of Nuclear Safety
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The minimum amount of onsite meteorological data to be provided at
the time of application
for a construction permit is a representative consecutive 12-month
period (PSAR)
for an operating license is a representative consecutive 24-month
period (FSAR)
However, 3 or more years of data are preferable and, if available,
should be submitted with the application
Meteorological Measurement Period
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Significant lead time will be required
to design a complete meteorological monitoring system
installation of the tower, securing site power and communications
installation of instrumentation and equipment on the tower, field
testing of instrumentation
This process can often require 3 to 12 months from the start of the
system design process to the start of data collection
Schedule and Lead Times
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Siting the Tower
Tower or mast should be sited at approximately the same elevation
as finished plant grade(~10 m)
Monitoring tower shall be located in an area that is representative
of the site, with terrain and meteorological exposure similar to that
of the proposed facility. This requires that the following potential
influences be considered when siting the monitoring tower:
Surrounding terrain and vegetation should be similar in the vicinity of the tower to the location where the plant will be located
No unusual natural or man-made obstructions that would unduly influence wind flow or other meteorological parameters. tower be located at least 10 obstruction heights from potential flow-modifying obstructions such as wooded areas, structures
Siting of Meteorological Instruments (1/4)
Korea Institute of Nuclear Safety
Freestanding Tower
Guyed Tower
58m Tower
10m Tower
58m : Temp, Wind Speed/Direction
10m : Temp, Wind Speed/Direction
58m : Temp, Wind Speed/Direction
10m : Temp, Wind Speed/Direction
Sfc : Temp, precipitation Relative Humidity
Meteorological Tower (Korea)
Korea Institute of Nuclear Safety
Meteorological Tower (Korea)
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Wind
Wind measurements should be made at locations and heights that
avoid airflow modifications by obstructions such as large structures,
trees, and nearby terrain
Wind sensors should be located on top of the measurement tower
or mast or extended outward on a boom to reduce airflow
modification and turbulence induced by the supporting structure
itself
Wind sensors on the side of a tower should be mounted at a
distance equal to at least twice the longest horizontal dimension of
the tower
Sensors should be on the upwind side of the mounting object in
areas with a dominant prevailing wind direction
Siting of Meteorological Instruments (2/4)
Korea Institute of Nuclear Safety
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Temperature and atmospheric moisture
Measurements should be made to avoid air modification by heat
and moisture sources (e.g., ventilation sources, cooling towers,
water bodies, large parking lots)
Temperature sensors should be mounted in fan-aspirated radiation
shields to minimize the adverse influences of thermal radiation and
precipitation
Siting of Meteorological Instruments (3/4)
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Precipitation
Precipitation gauges should be equipped with wind shields to
minimize the wind-caused loss of precipitation
Where appropriate, precipitation gauges should also be equipped
with heaters or an antifreeze to melt frozen precipitation
If heaters are used, they should be operated to minimize
underestimation attributable to evaporation caused by the
heater device
Siting of Meteorological Instruments (4/4)
Korea Institute of Nuclear Safety
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Meteorological instruments should be inspected and serviced at a frequency that will ensure data recovery of at least 90 percent on an annual basis
90-percent rate applies to the composite of all variables (e.g., the joint frequency distribution of wind speed, wind direction, stability class) needed to model atmospheric dispersion for each potential release pathway
90-percent rate applies individually to the other meteorological parameters
Channel checks should be performed daily for operational monitoring programs
Channel calibrations should be performed semiannually for both pre-operational and operational monitoring programs
For guyed towers, guyed wires should be inspected annually, and
anchors should be inspected once every 3 years in accordance with
industry standards
Instrument Maintenance
Korea Institute of Nuclear Safety
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Meteorological monitoring systems should use electronic digital data
acquisition systems as the primary data recording system
Backup recording system (either analog or digital) may be used to
provide a high assurance of valid data
The digital sampling of data should be at least once every 3 seconds.
The digital data should be compiled as 10(15)-minute average values
for real-time display in the appropriate emergency response facilities
(e.g., control room, technical support center)
For precipitation, the hourly value should represent the total amount of
precipitation (water equivalent) measured during the hour
Data Reduction and Compilation (1/2)
Korea Institute of Nuclear Safety
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Examples of how wind speed and direction can be processed
electronically by a data logging device
Examples of Vector and Scalar Averaging Schemes
Data Reduction and Compilation (2/2)
Korea Institute of Nuclear Safety
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Modern meteorological systems become much more versatile due to
the advances of electronics
Electronic data management systems can be programmed to
sample the instrumentation at a near instantaneous rate and to
store the data in independent channels for remote downloading or
follow-up processing on a periodic basis
Data can be processed and stored at the time of collection in a variety
of ways including the conversion of instrument output signals to the
units of desired measurement.
This greatly simplifies the conversion of “raw” instrument data to
the parameters of interest
System Operation
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Data Display (example)
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Meteorological Data Format (example)
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Data quality can be increased by maintaining and calibrating all
instrumentation on a periodic basis
For electro-mechanical instrumentation (such as wind speed and
direction sensors), a good practice is to install new or factory
rebuilt and calibrated instrumentation at a minimum of six-month
intervals to ensure that data are within manufacturer specifications
Safeguards and precautions to increase data recovery include
maintaining sufficient spare equipment to permit the interchange of
equipment at the first sign of instrument failure or abnormal/suspect
operation
Data Quality
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At some sites, because of complex flow patterns in non-uniform terrain,
additional wind and temperature instrumentation and more
comprehensive programs may be necessary
the representation of circulation for a hill-valley complex or a site
near a large body of water may need additional measuring points
to determine airflow patterns and spatial variations of atmospheric
stability
Special Considerations for Complex Sites
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Part III. Design Basis Meteorological Conditions
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Meteorological phenomena can cause several hazards that singly or in
combination could affect the safety of nuclear installations
Adequate measures that apply the concept of defence in depth should
be taken for the protection of nuclear installations against such hazards
Meteorological phenomena may affect all the structures, systems and
components important to safety on a nuclear installation site
Meteorological phenomena may also affect the communication
networks and transport networks around the site area of a nuclear
installation
Meteorological Hazards (1/2)
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Extreme values of meteorological parameters, as well as rarely
occurring hazardous meteorological phenomena should be considered
Normal meteorological variables : air temperature, wind speed,
precipitation, snowpack
Hazardous, rarely occurring phenomena : lightning, tropical cyclones,
typhoons and hurricanes, tornadoes, waterspouts
Other possible phenomena : dust storms, hail, freezing precipitation
Meteorological Hazards (2/2)
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Overview
Regional MeteorologicalCharacteristics
Onsite MeteorologicalCharacteristics
Atmospheric DiffusionLong termShort term
EAB & LPZLoad Combination
Extreme Events
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General Climate
Types of air masses
Synoptic features: high- and low-pressure systems, frontal systems
Temperature
humidity
Precipitation: rain, snow, and sleet
Relationships between synoptic-scale atmospheric processes and local (site) meteorological conditions
Seasonal and annual frequencies of severe weather phenomena
Hurricanes, waterspouts, and tornados
Thunderstorms and lightning
Hail
Air pollution potential
Regional Climatology (1/2)
Korea Institute of Nuclear Safety
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Meteorological Conditions for Design & Operating Basis
Max. snow and ice load (water equivalent) that roofs of safety-related structures must be capable of withstanding during plant operation
Ultimate heat sink (UHS) meteorological conditions resulting in the max. evaporation and drift loss of water and min. water cooling, if applicable
Tornado parameters, including translational speed, rotational speed, and Max. pressure differential with the associated time interval
100-year return period of wind, including vertical velocity distribution and gust factor
Probable annual frequency of occurrence & time duration of freezing rain (ice storms) and dust (sand) storms where applicable
Max. rainfall rate
Other regional meteorological and air quality conditions used for design and operating basis considerations
Regional Climatology (2/2)
Korea Institute of Nuclear Safety
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Tornado
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Tornado Scale
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Description of Local (Site) Meteorology
Airflow
Temperature
Atmospheric water vapor
Precipitation
Fog
Atmospheric stability
Air quality
Assessment of the Influence of the Plant on the Above Factors
Effects of plant structures
Effects of terrain modification
Effects of heat and moisture sources due to plant operation
Local Meteorology (1/2)
Korea Institute of Nuclear Safety
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Topographical Description
Description of the site and its environs, as modified by the plant
structures
Includes site boundary, exclusion zone, and low population
zone(LPZ)
Local Meteorology (2/2)
Korea Institute of Nuclear Safety
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IAEA SSG-18 : Meteorological and Hydrological Hazards
in Site Evaluation for Nuclear Installation (2011)
Objective:
Provides guidance on complying with safety requirements on
assessing the hazards associated with meteorological and
hydrological phenomena that may affect the safety of nuclear
installations
Scope:
Site selection and evaluation
Design of new installations
Operational stages of existing installations
Meteorological Hazard Analysis (1/3)
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Hazards considered in the IAEA-SSG 18 include those
associated:
wind, water, snow, ice or hail, wind driven materials, extreme water
levels around or at the site
dynamic effects of water
extreme air temperature and humidity
extreme water temperature
extreme groundwater levels
Meteorological Hazard Analysis (2/3)
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Meteorological and hydrological phenomena may affect:
All SSC(System, Structure, Component) and could lead to the risk of
common cause failure for systems important to safety(emergency
power supply systems)
Communication networks and transport networks around the site
may jeopardize the implementation by operators of safety related
measures
may hinder emergency response by making escape routes
impassable and isolating the site in an emergency
Meteorological Hazard Analysis (3/3)
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Extreme values of the following meteorological variable
should be considered :
Air temperature
Precipitation
Wind speed
Snow pack
Rare meteorological phenomena that should be considered :
Lightning
Tornadoes
Tropical Cyclones (Typhoon, Hurricane)
Waterspouts
General Considerations (1/2)
Korea Institute of Nuclear Safety
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Other possible meteorological phenomena with potential
adverse effects that should be considered:
Dust storms and sandstorms
Hail
Freezing precipitation (ice storms)
High intensity winds (tropical storms, tornadoes) may
produce flying debris and projectiles
General Considerations (2/2)
Korea Institute of Nuclear Safety
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Divided into two broad categories (deterministic methods
and probabilistic methods)
Deterministic methods : based on the use of physical or empirical
models to characterize the impact of an event in a specific scenario on
a system
Statistical methods are typically based on time series analysis and
synthesis
Probabilistic methods : to make use of the probabilistic descriptions of
all involved phenomena to determine the frequency of exceedance of
any parameter
☞ The general approach to meteorological evaluations should be directed towards reducing the uncertainties at various stages of the evaluation process so as to obtain reliable results
Methods for assessment of hazards (1/2)
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Meteorological Data
Climatic normal and extreme values to be collected include:
Annual extreme values : wind speed, precipitation, snow pack
Frequencies of certain air temperature conditions
Dry-bulb temperature, wet-bulb temperature for establishing heat
load, HVAC
Minimum period of continuous observation should be at least 30 years,
since the hazard cannot be estimated with sufficient accuracy for
values more than three to four times the length of the sample period
Methods for assessment of hazards (2/2)
Korea Institute of Nuclear Safety
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Determination of Design Basis Parameters
General Procedure
Obtain representative data series available for the region
Evaluate its quality (representativeness, completeness, QA/QC)
Select the most appropriate statistical distribution
(Gumbel, Frechet, Weibull)
Process the data to estimate Mean Recurrence Interval (MRI)
Korea Institute of Nuclear Safety
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100 MRI Max. Wind Speed by Storms
IAEA Safety Series No. 50-SG-S11A Annex I provides the Gumbel-Chow
method for maximum wind speed and maximum instantaneous wind
speed for MRI as follows
The long term meteorological data more than 30 years shall be used in
order to reduce uncertainties
Determination of Design Basis Parameters (1/4)
Korea Institute of Nuclear Safety
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100 MRI Max. Wind Speed by Storms (Case study)
Yearly Max. Instant. Wind Speed at Busan and Ulsan Met. Station Year 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946
Busan 29.1 29.0 22.7 29.3 30.3 36.9 33.6 30.4 33.5 28.3
Ulsan - - - - - - - - - -
Year 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956
Busan 30.2 29.2 29.6 33.5 32.1 31.0 29.8 28.9 28.1 34.4
Ulsan - - - - - - - - - -
Year 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966
Busan 38.3 33.1 42.7 30.1 34.7 32.0 39.0 29.8 30.2 35.7
Ulsan - - - 24.0 27.4 25.5 30.1 26.5 24.0 25.0
Year 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976
Busan 28.9 32.4 29.9 28.2 28.3 29.9 29.7 33.4 29.5 29.5
Ulsan 22.3 24.6 22.3 23.3 26.4 24.4 27.5 27.1 21.5 25.1
Year 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986
Busan 27.6 29.4 33.0 36.0 25.1 27.5 30.5 25.7 26.8 32.1
Ulsan 20.0 21.5 26.0 24.0 25.0 26.5 22.0 22.1 27.0 23.6
Year 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996
Busan 43.0 25.3 28.1 27.0 38.0 28.4 31.1 30.3 42.3 29.0
Ulsan 36.7 25.1 19.1 21.1 26.8 20.2 27.9 21.1 27.3 20.7
Year 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Busan 25.3 22.8 21.2 32.7 27.9 34.7 42.7 25.0 26.4 32.5
Ulsan 23.4 27.0 23.0 19.0 19.0 24.3 33.2 29.1 24.9 24.1
Year 2007 2008 2009
Busan 25.0 21.4 26.3
Ulsan 21.0 20.7 21.0
100 MRI Max. Instant. WS by Storm
- Busan : 45.4 m/s
- Ulsan : 35.4 m/s
Determination of Design Basis Parameters (2/4)
Korea Institute of Nuclear Safety
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100 MRI Max. Wind Speed by Typhoon (Case study)
at Busan Met. Station at Ulsan Met. Station
100 MRI Max. Instant. WS by Typhoon
- Busan : 53.1 m/s
- Ulsan : 45.9 m/s
Year No. Name DateInstantaneous
Max. WS(m/sec)
1979 10 IRVING 8.15~18 33.0
1983 10 FORREST 9.26~30 30.5
1984 10 HOLLY 8.20~22 25.7
1986 13 VERA 8.27~29 32.1
1987 12 DINAH 8.29~31 43.0
1991 19 MIREILLE 9.27~28 38.0
1992 19 TED 9.22~26 28.4
1993 7 ROBYN 8.8~11 31.1
1994 29 SETH 10.10~12 30.3
1995 3 FAYE 7.22~24 42.3
1996 12 KIRK 8.5~16 16.6
1997 19 OLIWA 9.14~17 32.9
1998 10 ZEB 10.11~18 22.8
1999 7 OLGA 8.2~4 24.3
2000 12 PRAPIROON 8.31~9.1 23.0
2002 15 RUSA 8.30~9.1 34.7
2003 14 MAEMI 9.12~13 42.7
2004 15 MEGI 8.17~19 23.0
2005 15 NABI 9.6~7 26.4
2006 13 SHANSHAN 9.17~18 32.5
2007 11 NARI 9.16~17 21.3
Year No. Name DateInstantaneous
Max. WS(m/sec)
1979 10 IRVING 8.15~18 26.0
1980 13 ORCHID 9.10~11 24.0
1984 10 HOLLY 8.20~22 22.1
1987 12 DINAH 8.29~31 36.7
1993 7 ROBYN 8.8~11 27.9
1994 29 SETH 10.10~12 30.7
1995 3 FAYE 7.22~24 27.3
1996 12 KIRK 8.5~16 15.9
1997 19 OLIWA 9.14~17 19.8
1998 10 ZEB 10.11~18 15.4
1999 7 OLGA 8.2~4 17.0
2000 12 PRAPIROON 8.31~9.1 16.0
2002 15 RUSA 8.30~9.1 24.3
2003 14 MAEMI 9.12~13 33.2
2004 15 MEGI 8.17~19 37.1
2005 15 NABI 9.6~7 24.9
2006 13 SHANSHAN 9.17~18 21.9
2007 11 NARI 9.16~17 18.0
Determination of Design Basis Parameters (3/4)
Korea Institute of Nuclear Safety
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100 MRI Max. Wind Speed (Case study)
100 MRI Max. WS
(m/sec)
100 MRI Max. Instant. WS
(m/sec)
by Storm by Typhoon by Storm by Typhoon
Busan 37.0 36.3 45.4 53.1
Ulsan 29.3 23.2 35.4 45.9
Design
Basis37.0 53.1
Determination of Design Basis Parameters (4/4)
Korea Institute of Nuclear Safety
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Part IV. Long-Term Atmospheric Diffusion Estimates
Korea Institute of Nuclear Safety
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General
Long-term atmospheric diffusion estimate applies to normal operation of NPP
The transport and dilution of radioactive materials are function of
state of the atmosphere along the plume path
topography of the region
characteristics of the effluents themselves
For a routine airborne release (long-term annual basis), the concentration of radioactive material in the surrounding region depends on
amount of effluent released
height of the release
momentum and buoyancy of the emitted plume
wind speed, atmospheric stability, and airflow patterns of the site
various effluent removal mechanisms
Long-Term Atmospheric Diffusion (1/11)
Korea Institute of Nuclear Safety
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Diffusion Model
Variable Trajectory Models
allow conditions to vary spatially and temporally over the region of interest
Particle-in-Cell (PIC) Model
Plume Element Models
Constant Mean Wind Direction Models
assume that a constant mean wind transports and diffuses effluents, within the entire region of interest, in the direction of airflow at the release point
could not describe the effects of spatial and temporal variations in airflow in the region of the site
Long-Term Atmospheric Diffusion (2/11)
Korea Institute of Nuclear Safety
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Gaussian Plume Model
A basic atmospheric dispersion model that assumes that the plume
spread has a Gaussian distribution in both the horizontal and
vertical directions
Q : Source Strength, U : Mean wind speed, σy, σz : horizontal & vertical standard deviation of plume
Long-Term Atmospheric Diffusion (3/11)
Korea Institute of Nuclear Safety
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Gaussian Plume Model : Coordinate System
Source coordinate : (0, 0, H)Receptor Coordinate : (x, y, z)
Long-Term Atmospheric Diffusion (4/11)
Korea Institute of Nuclear Safety
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Gaussian Plume Model : Horizontal Standard Deviation(σy) of Material in a Plume
Long-Term Atmospheric Diffusion (5/11)
Korea Institute of Nuclear Safety
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Gaussian Plume Model : Vertical Standard Deviation(σz) of Material in a Plume
Long-Term Atmospheric Diffusion (6/11)
Korea Institute of Nuclear Safety
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Gaussian Plume Model : Emission and Downwind Factors
Low Wind Speed High Wind Speed
QfactorEmissions u
factorDownwind 1
Long-Term Atmospheric Diffusion (7/11)
Korea Institute of Nuclear Safety
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Release Mode
Elevated release
For effluents released from points at least twice the heights of
adjacent solid structures : Very tall stack release
use meteorological data measured at representative release
height
Ground-level release
Other than elevated release
Vent or building penetration release
Long-Term Atmospheric Diffusion (8/11)
Korea Institute of Nuclear Safety
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Removal Mechanism
Radioactive decay : dependent on the half-life and the travel time
of the radioactive effluent
2.26 days for short-lived noble gases
8 days for all radio-iodine
Dry deposition
always applicable
deposition velocity
Wet deposition
applicable only for the rain period
dependent on precipitation intensity
Long-Term Atmospheric Diffusion (9/11)
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Computer Code : XOQDOQ (based on RG. 1.111)
Available at RSICC, ORNL, USA
Meteorological Data for XOQDOQ Model
Wind speed
Wind direction
Atmospheric stability
Joint Frequency Data(JFD) with combination of atmospheric
stability(7), wind direction(16), wind speed class(~14)
Long-Term Atmospheric Diffusion (10/11)
Korea Institute of Nuclear Safety 69
Sample of JFD
.0362.0536.0555.0742.0729.1078.0941.1010.1166.1278.1415.1577.1814.1191.0704.0580
.0576.0769.1222.1967.2590.2436.3780.4458.2992.2870.2952.2523.4553.4202.1407.0930
.1837.2436.6043.89281.1631.1831.3371.605.7147.6662.3477.3181.95311.111.3150.2255
.2472.2968.8570.8041.4703.3981.4127.4955.2239.2172.0453.1037.4671.9610.4474.2270
.1585.2602.5633.5664.1675.0915.0587.0177.0181.0311.0055.0777.1596.6662.5420.1502 Stability A
.0619.1794.2535.2235.0603.0363.0150.0000.0008.0012.0095.1112.0662.2282.3843.0796
.0398.0985.1167.0946.0434.0213.0004.0000.0004.0004.0244.1360.0339.0796.2625.0359
.0043.0008.0169.0169.0173.0035.0004.0000.0000.0000.0158.0150.0008.0020.0670.0099
.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0110.0000
.0100.0095.0100.0148.0148.0169.0190.0137.0153.0206.0184.0279.0380.0264.0137.0063
.0146.0126.0272.0410.0516.0307.0367.0643.0371.0402.0430.0461.0757.0552.0264.0102
.0374.0611.1269.1336.1837.0733.0840.1301.0481.0461.0347.0398.1324.1380.0390.0213
.0288.0505.1486.0883.0757.0213.0166.0307.0221.0110.0071.0237.0713.0729.0485.0284
.0134.0367.1112.0441.0177.0110.0059.0028.0012.0020.0012.0213.0556.0548.0414.0118 Stability B
.0102.0158.0406.0284.0106.0083.0032.0000.0004.0004.0012.0461.0296.0280.0292.0099
.0051.0024.0197.0181.0087.0024.0000.0000.0000.0000.0028.0654.0102.0095.0189.0059
.0008.0004.0110.0087.0020.0000.0000.0000.0000.0000.0071.0063.0004.0004.0020.0016
.0000.0000.0024.0000.0000.0000.0000.0000.0000.0004.0004.0000.0000.0000.0000.0000
Wind Direction Class(16)
Win
d S
pe
ed
Cla
ss(9
)
Long-Term Atmospheric Diffusion (11/11)
Korea Institute of Nuclear Safety
70
Part V. Short-Term Atmospheric Diffusion Estimates
Korea Institute of Nuclear Safety
71
General
Short-term atmospheric diffusion estimate applies to accidental conditions
The transport and dilution of radioactive materials are function of
state of the atmosphere along the plume path
topography of the region
characteristics of the effluents themselves
For an accidental airborne release (2 hrs basis), the concentration of radioactive material in the surrounding region depends on
amount of effluent released
height of the release
momentum and buoyancy of the emitted plume
wind speed, atmospheric stability, and airflow patterns of the site
various effluent removal mechanisms
Short-Term Atmospheric Diffusion (1/5)
Korea Institute of Nuclear Safety
72
Calculation of χ/Q on Exclusion Area Boundary(EAB)
Ground-level release
①
②
③
: atmospheric diffusion factor (s/m3)
: average wind speed at 10 m above the ground (m/s)
: diffusion coefficient in the #-direction (m)
: minimum vertical cross-section of a building (m2)
: correction factor in the #-direction for meandering effect
)2/(
1/
10 AUQ
zy
)3(
1/
10 zyUQ
)(
1/
10 zyUQ
Q/
10U
#
A
#
Short-Term Atmospheric Diffusion (2/5)
Korea Institute of Nuclear Safety
73
Calculation of χ/Q on EAB
Ground-level release
For neutral or stable atmospheric condition, and U<6m/s
Meandering effect may be considered
Use χ/Q = min[③, max(①, ②)]
Otherwise
Use χ/Q = max(①, ②)
Short-Term Atmospheric Diffusion (3/5)
Korea Institute of Nuclear Safety
74
Calculation of χ/Q on EAB
Elevated release
for non-fumigation condition
for fumigation condition
: effective stack height (m)
]2
exp[1
/2
2
z
e
zyh
h
UQ
0,)2(
1/
2/1 e
eyh
hhU
Q
e
eh
Short-Term Atmospheric Diffusion (4/5)
Korea Institute of Nuclear Safety
75
Calculation of χ/Q on Low Population Zone (LPZ)
For the first 2 hrs
The calculation methods are the same as those for EAB
After 2 hrs
Calculating χ/Q for 0~8 hrs, 8~24 hrs, 1~4 days, and 4~30
days
Logarithmic interpolation between short-term χ/Q and long-
term χ/Q
Computer Code : PAVAN (based on RG. 1.145)
Input meteorological data : JFD (same as XOQDOQ)
Short-Term Atmospheric Diffusion (5/5)
Korea Institute of Nuclear Safety
76
NSSC(Nuclear Safety and Security Commission) Notice No. 2017-26, “Technical Standards for Investigation and Evaluation of Meteorological Conditions of Nuclear Reactor Facility Sites”
US NRC Regulatory Guide 1.23 rev 1, "Meteorological Monitoring Programs for Nuclear Power Plants"
US NRC Regulatory Guide 1.111, "Methods for Estimating Atmospheric Transport and Dispersion of Gaseous Effluents in Routine Releases from Light-Water-cooled Reactors"
US NRC Regulatory Guide 1.145, "Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear power Plants“
IAEA SSG-18, “Meteorological and Hydrological Hazards in Site Evaluation for Nuclear Installation”
Determining Meteorological Information at Nuclear Facilities, American National Standards Institute/American Nuclear Society, ANSI/ANS-3.11-2015
Meteorological Considerations for Nuclear Power Plant Siting and Licensing, George C. Howroyd & Paul B. Snead, 12th NUMUG Meeting, 2008
References
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