Guidance and EU experience on
Site Permit issuance of NPPs
Regulatory review of siting requirements for
meteorology and radioactive releases - Finnish
experience
VN/RA/01 Task 1&2 Workshop
Hanoi, October 2012
Confidential
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
Ilari Aro
STUK
Siting – list of topics to be reviewed
• Site effects in plant design
– site characterization: meteorology
• Radiation safety
– dispersion
• Emergency planning
– protection / evacuation
• Interaction with land use planning – population issues
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Nuclear power plants in Finland
Olkiluoto NPP (TVO)
• 2 operating units - ABB BWRs
• New EPR under construction
Loviisa NPP (Fortum)
• EIA completed for a new unit
• 2 operating units - VVERs
• EIA completed for a new unit
Fennovoima Ltd
• EIA completed for a new
unit
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RADIATION AND NUCLEAR SAFETY AUTHORITY
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Calculating and measuring radiation releases
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Guide YVL 7.1 sets out in more detail the Council of State's
regulations for radiation exposure and release limits. It sets forth the
general requirements for analysis methods, for exposure pathways
to be examined by dose calculation and for the evaluation of
individual and collective doses to the population.
Guide YVL 7.3 presents detailed requirements applicable to the
conducting of analyses on the dispersion of radioactive releases and
Guide YVL 7.2 sets forth detailed requirements for the calculation of
individual and collective doses to the population.
YVL 7.5 presents requirements for meteorological measurements.
YVL 7.6 and YVL 7.7 concerns radioactive release measurements
and radiation control in the environment.
When radiation doses to the surrounding population are calculated,
the region's special characteristics--hydrological, geological and
meteorological--as well as the living conditions and habits of the
population shall be considered.
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Objective of meteorological measurements
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Meteorological measurements in the vicinity of a nuclear power plant are
needed to assess the dispersion of the releases of radioactive materials
in the atmosphere in the following cases: the releases of radioactive
materials to be considered in the safety analyses of a nuclear power
plant; the releases caused by the normal operation and transients of a
nuclear power plant; the releases caused by accidents of a nuclear
power plant.
Safety and accident analyses, which are carried out as early as in the
design and construction phases of a nuclear power plant, utilize
meteorological data that represent the site concerned. These data are
complemented by meteorological measurements conducted in the
vicinity of the plant.
The data on meteorological conditions and radiation dose analyses are
needed to plan and conduct rescue operations in the emergency
planning zone and to assess the timing of a potential controlled release
of radioactive materials. In addition, the authorities make national
dispersion and dose predictions concerning a more extensive area and,
possibly, similar predictions affecting other countries.
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RADIATION AND NUCLEAR SAFETY AUTHORITY
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System requirements
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The meteorological measurement system of a nuclear power plant shall
have a sufficient and representative number of observation stations,
considering the local environmental factors. Observations of other
meteorological stations located in the near-field of the nuclear power
plant and of FMI can also be used to assess the dispersion of
radioactive materials in the environment.
The meteorological measurement system shall function reliably under all
anticipated environmental conditions. The power supply of the
measuring and data transmission systems shall be secured by an
independent system for a sufficiently long time. In addition, the
measuring and data transmission systems shall be doubled where
necessary. For this purpose, the functions that must tolerate a single
failure shall be specified. Ref. to YVL Guides 2.0 and 5.5.
The structures of the weather mast shall withstand a maximum load
caused by the extremely exceptional wind and freezing conditions (there
is a 95% probability that the frequency of occurrence is as high as or
higher than the statistically calculated load once in a hundred years).
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Measurements required by STUK
• Wind velocity:
– ±0.2 m/s at wind velocities of less than 2 m/s (lowest detection
limit of the measurement 0.4 m/s)
– ±5% at wind velocities higher than 2 m/s
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Wind direction: ±5°
Temperature: ±0.15 °C
Temperature difference: ±0.2 °C/100 m
Precipitation: ±0.2 mm
Time of precipitation: ±5 min
Air pressure: ±0.3 hPa (mb)
Relative humidity: ±5%
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Meteorological conditions described in SAR
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The PSAR shall contain a description of the meteorological conditions in
the area and the mesoclimate. The description shall include the wind
distributions, stability classifications and mixing height values at different
times of year, which indicate the dispersion conditions in the area.
Furthermore, the report shall include a plan for the meteorological
measurements to be conducted at the plant site and in its vicinity.
In addition, the FSAR shall contain an account of the meteorological
conditions in the area, which is drawn up on the basis of measurements
conducted during a period of at least one year and other available data,
as well as an updated climate report.
The data contained in the FSAR shall be complemented at regular
intervals on the basis of measurements carried out in the nuclear power
plant area during operation.
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Meteorology for emergency preparedness
Ref to Markku Seppänen, Finnish Meteorological Institute
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STUK uses Finnish Meteorological Institute (FMI) for meteorological
support during emergencies.
There is a direct link from FMI super computer to STUK to get real-time
weather information and dispersion estimates for all Northern NPP’s four
times per day to have a realistic, immediate release estimate in case
there is an accident going on in NPP.
This helps a lot for planning the immediate response to such an event or
accident. Accurate weather information including rain is crucial in dose
estimation during emergencies.
STUK has developed its own release models / programs and utilizes
European RODOS model as well in radiation exposure calculations. FMI
/VTT has also developed its own dispersion model SILAM that is
publicly available through FMI web-pages. FMI is also willing to consult
on installation if/when assistance is needed.
Weather mast is needed at NPP site for measuring meteorological
conditions such as wind speed and direction, temperature, stability class
definition, precipitation etc
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RADIATION AND NUCLEAR SAFETY AUTHORITY
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Principle picture
Weather Mast
at NPP
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Measuring methods for stratification in the
surface layer of atmosphere and for rain
• Stability (class) is an important parameter in a emergency
situation that describe turbulent conditions at the site. It can
be calculated of temperature and wind observations. Different
calculation methods give different results. Finnish solution: on
line-calculations on the mast station and at FMI.
• In a emergency situation it is also important to know rain
conditions over the whole potential risk area. Rain wash out
radioactive particles of the atmosphere.
• There are in situ measurements on the weather stations.
Station observation don't know anything what is happening
between stations. Weather radars are available for areal
observing of rain. Extrapolation is possible.
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Example of weather radar network picture (FMI)
Light
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RADIATION AND NUCLEAR SAFETY AUTHORITY
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Moder.
Heavy
Dispersion modelling:
SILAM – system in Finland (FMI)
• Forecasts for potential risk area, dose rate, doses etc. Simulate
turbulent transport and dispersion of nuclear gases and particles
in atmosphere. Can be calculated with long time weather model
data. As good as the numerical weather data used in dispersion
model. SILAM-model home page: silam.fmif.i
• FMI makes automatic model runs for Finnish and near by NPP’s
4 times/day – results to STUK
• Every duty meteorologist can make calculations. Nuclear
situation center officers can make more calculations. STUK’s
experts can use SILAM to test and calculate with different source
terms.
• Easy to supply model products to Rescue Officers and other
relevant authorities. FMI Consulting Services has used SILAMsystem with success with some site evaluation project in Europe.
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RADIATION AND NUCLEAR SAFETY AUTHORITY
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SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Acceptance criteria for radioactive releases /
max doses to general public
– needed meteorological data
• Normal operation: radiation dose limit 0,1 mSv / year
– Reliable statistical meteorological data over the year
• Anticipated events: radiation dose limit 0,1 mSv
• Design basis accidents: radiation dose limit 5 mSv
• Design extention conditions: radiation dose limit 20 mSv
– Conservative stability class for radiation dose calculation
• Severe accidents: no acute health effects, tolerable long term
contamination: Cs-137 release < 100 TBq
– Growing season and non-growing season
• PSA Level 3
– Reliable statistical meteorological data over the year
• Emergengy response
– Real time weather data
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Dose assessment models developed by
VTT
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ARANO (PRA3-code): was developed and used for NPP site
evaluation studies in 1975-76 in co-operation with the Finnish
Meteorological Institute (FMI). The model can be applied within
distances up to 100 km).
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ROSA: emergency preparedness support tool for real time dose
assessments in the vicinity of the plant (up to 20 km distance).
Model is based on ARANO code and utilizes real time weather data
with 10 minutes intervals. Model is still operational at Olkiluoto
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TRADOS: 1983; long-range dispersion and dose assessment tool
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SILAM: long-range dispersion and dose assessment tool; first
applications in 1996. Atmospheric dispersion model is based on a
Monte Carlo type random walk method
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VALMA. A simplified and more flexible user interface to apply the
dispersion estimates calculated by SILAM or by a simple model
based on weather data derived from a single measurement tower.
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DETRA: Radionuclide transport in biosphere & food chains
(terrestrial & aquatic) and estimation of radiation doses.
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Calculation of radiation doses in the SILAM
model
In the development of the SILAM
model by FMI and VTT the radiation
dose assessment models are using
similar methods as in TRADOS &
ARANO.
The real time prediction of dispersion
of releases employs a completely
different approach.
The dispersion and dose calculation
models are coupled to each other,
but the model includes the possibility
to employ the once calculated
dispersion analysis results data base
to sensitivity analyses regarding
dose estimates.
The versatile modelling system allows
the production of estimates of
dispersion and dose forecasts with
gradually
increasing
accuracy.
SÄTEILYTURVAKESKUS
• STRÅLSÄKERHETSCENTRALEN
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RADIATION AND NUCLEAR SAFETY AUTHORITY
Results of dispersion calculation (concentration in
air and in deposition) either in central memory or in
separate data base
Radioactive decay and production of
daughter nuclides
Activity
in air
Activity in air
C(x,y,z=1 m)
C(x,y,z)
Internal
dose via
inhalation
External
dose
from
plume
Activity in
deposition
CA(x,y,0)
External
dose
from deposition
Internal
dose via
foodchains
Radiological impact modelling for
emergency response analyses
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Emergency preparedness exercises and advance & real-time simulations for
preparing the situation description for exercises
Deterministic and probabilistic safety analyses.
Research use (for example model validation against experimental measurement
data; for this purpose the 137Cs-release from Algeciras iron foundry and specific
tracer experiment in ETEX project has been modelled by SILAM)
Different kinds of source terms: Besides the main purpose (= releases from
nuclear facilities as a results of transients and accidents and normal operation)
other source terms can also be modelled, such as transportation accidents, dirty
bombs etc. Provided that the radionuclide composition, time behaviour of release,
release height and so on are known
What are the important key output (default) quantities ?
Nuclide-specific concentrations in air [Bq/m3] and deposited amounts [Bq/m2]
External dose rates [e.g. μSv/h, mSv/yr]
Integrated external doses within 24 h, week, month etc
Committed internal doses (within 50 yrs) [Sv] or short-term internal doses within 24
h, 1 week etc
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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User interface (www-based) for the SILAM
model
VTT has developed a www-based graphical user interface (GUI) for SILAM.
The GUI is operated over internet and does not require programme
installations by users (to client work stations)
The central server has 8 processors and is managed by the Finnish
Meteorological Institute (FMI).
Several users and multiple calculation processes for each user can be
handled simultaneously (in parallel)
Main methods applied for GUI are PHP-language and MySQL-data base
management system.
Main objective is to have reliable access by all relevant emergency
preparedness organisations (such as STUK, FMI, meteorologist on duty
etc) to the same system. Several user classes have been defined
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Simplified interface (VALMA) for employing the SILAM model for
dose assessments and example applications
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The interface provides easier
access to the dispersion calculation
results by SILAM and gives
possibility to flexible adjustment of
input parameters and assumptions
for dose assessment
The example results obtained for
total external dose rate (from the
plume and deposition) visualized by
the VALMA model interface
The picture corresponds to an
assumed release from the Kola NPP
and shows dose rate in mSv/h.
The situation is 48 h after the
release start
The yellow colour for example
corresponds to 0.4 µSv/h
Corresponding calculations have
been performed for the Finnish NPP
sites and other location close to
Finland.
SÄTEILYTURVAKESKUS • STRÅLSÄKERHETSCENTRALEN
RADIATION AND NUCLEAR SAFETY AUTHORITY
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Application areas of radiological impact
assessments for nuclear facilities
• Dose assessments as a necessary final stage in deterministic
and probabilistic nuclear safety analyses
– In most cases the safety requirements are expressed in the form of annual
doses or committed doses
• Emergency preparedness exercises
– also in case of real time weather conditions
– The leader of the exercise can flexibly change the assumed dispersion
conditions and assumptions for the temporal behaviour of the release
– With modelling one can also simulate “surveillance measurement” results for
the automatic measurement stations and air sample locations (for the
Loviisa drill in November 2003 this option was employed)
• Advance planning of emergency preparedness
– The effectiveness of alternative countermeasures can be evaluated
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RADIATION AND NUCLEAR SAFETY AUTHORITY
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