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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


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


3

Part I. Introduction


4

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


5

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


6

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


7

NRC Q&A Series: Three Minutes with an NRC Meteorologist (YouTube)

Introduction


8

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)


9

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)


Wind Rose


11

Part II. Onsite Meteorological Monitoring Program


12

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)


13

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)


14

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)


15

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



16

Classification of Atmospheric Stability



17

Precipitation

Precipitation should be measured near ground level near the base

of the mast or tower



18

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



19

Accuracy of Instrument (RG 1.23)


20

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


21

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


22

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)


Freestanding Tower

Guyed Tower

58m Tower

10m Tower

58m : Temp, Wind Speed/Direction




Sfc : Temp, precipitation Relative Humidity

Meteorological Tower (Korea)


Meteorological Tower (Korea)


25

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



26

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



27

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



28

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


29

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)


30

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)


31

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


32

Data Display (example)


33

Meteorological Data Format (example)


34

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


35

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


36

Part III. Design Basis Meteorological Conditions


37

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)


38

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)


39

Overview

Regional MeteorologicalCharacteristics

Onsite MeteorologicalCharacteristics

Atmospheric DiffusionLong termShort term

EAB & LPZLoad Combination

Extreme Events


40

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)


41

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)


42

Tornado

http://www.freakygossip.com/wp-content/uploads/2010/04/Yazoo-City-Tornado-pictures.jpg

http://www.freakygossip.com/wp-content/uploads/2010/04/Yazoo-City-Tornado-pictures.jpg


43

Tornado Scale


44

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)


45

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)


46

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)


47

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



48

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



49

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)


50

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)


51

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)


52

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)


53

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)


54

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)


55

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



56

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



57

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



58

Part IV. Long-Term Atmospheric Diffusion Estimates


59

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)


60

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



61

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



62

Gaussian Plume Model : Coordinate System

Source coordinate : (0, 0, H)Receptor Coordinate : (x, y, z)



63

Gaussian Plume Model : Horizontal Standard Deviation(σy) of Material in a Plume



64

Gaussian Plume Model : Vertical Standard Deviation(σz) of Material in a Plume



65

Gaussian Plume Model : Emission and Downwind Factors

Low Wind Speed High Wind Speed

QfactorEmissions u

factorDownwind 1



66

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



67

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



68

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)


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

)



70

Part V. Short-Term Atmospheric Diffusion Estimates


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)


72

Calculation of χ/Q on Exclusion Area Boundary(EAB)


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

#



73

Calculation of χ/Q on EAB


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)



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



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)



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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