The Automatic Weather Monitoring System of NPP "Kozloduy" (ASMM) is designed and operates in accordance with the requirements of Safety Standards Series of the International Atomic Energy Agency (IAEA) and the National Nuclear Regulatory Agency. Built in 1995 and is the first carried out major project of the Consortium "MS&E". It was modernized in 2003 and 2010.
When choosing the number and location of the measuring equipment the characteristics of topography, the requirements for reliable transmission of digital information in FM radio channel and the available infrastructure are under review.The three automatic weather stations MS&E-4 (AMC) are located in three specific for the region areas:
1. AMS1 is located on a plateau southern of the NPP.It has a displacement of +90 meters to the site of the NPP. This place is typical for most of the area around the NPP.
2. AMS2 is located in the lower part, to the Danube and has a displacement of -15 m. This AMS is representative for the wind in cases of calm weather in the region, because it is recording the channel effect of the river.
3. AMS3 is located near the confluence of the rivers Skat and Augusta into the Danube River and has a displacement of + 20 m. This AMS registers the effect of the two deep basins of the rivers on the wind in the area. With this choice of location of AMS true recovery of the wind field throughout the whole controlled area is possible by the data from the three local measurements.The wind preprocessing is imposed by the fact that diffusion models are working with summarized data at the point of mission.The differences in the characteristics of wind in the three measuring points are a function that depends simultaneously on wind speed and on its direction. The preprocessing is based on empirical statistical model that transforms wind data from three points in aggregate for the region value that is used by diffusion models.
It is similar with the precipitation.
To obtain the necessary data for speed and direction of the basic air transport in the atmosphere and the height of mixing layer an Automatic System for Upper Air Sounding of the atmosphere (ASAS) is used. ASAS is located west of Kozloduy, considering the predominant transmission in the region. Aerological digital radiosondes with GPS positioning are used. ASAP is integrated into ASMM information and the data from it is automatically included in the total radio transfer.
In the regulations of IAEA and materials of the World Meteorological Organization concerning the meteorological aspects of the normal operation of NPPs and in accident mode were formulated the main requirements for dispersion models to assess the spread of radioactive substances into the atmosphere.
It is important to know the restrictions on the use of the model, since for different applications, depending on the task and the search results, may be selected an appropriate model. For example, in practice, to assess exposure to radiation for distances up to 10 km from the source, the most widely used are Gaussian models. But there are specific situations, such as: presence of complex orography, coastal areas and major rivers, very high chimneys, taking into account the transformation of meso-scale tasks, and others. where Gaussian models are not appropriate. Then are used more complex Eulerian or Lagrange models.
In ASMM of NPP "Kozloduy" until 2007 for assessment of radiation exposure are used the numerical realization of the classical Gaussian model.
In 2007 as a separate module of the ASMM is an integrated version of the model EMAP (Eulerian Model for Air Pollution), developed by Prof. E. Sirakov. This is a three-dimensional Eulerian dispersion model for assessment of concentrations and deposition of radionuclides in the region of Kozloduy, as in normal operation and in case of accident. The model uses the Cartesian coordinate system, with uniform sampling in the horizontal and uneven in the vertical. Horizontal coordinate surfaces that follow the form of relief, are more dense at ground level and are diluted in height, which corresponds to the typical profiles of meteorological elements in the boundary layer of the atmosphere - rapid changes in land and smooth running at altitude.
Diffusion schemes in EMAP are different. Horizontally is used obvious scheme with "open" borders. In the vertical implicit scheme is used with an opened upper border. The reason for applying the implicit scheme is the variability of the vertical network. Wet deposition in Aymar is recorded by a formula similar to that for radioactive decay.
In the EMAP version used in ASMM of NPP is added preprocessing for wind and precipitation.
Means of ground meteorological measurements AMS1, AMS2 and AMS3 work in "on-line" mode and are connected to a common network. ASAP only works in emergency mode. Overall management of the measurement of vertical profiles of meteorological elements, archiving raw data and the automatic start of the meteorological models for determining the height of mixing layer and the speed and direction of the main transmission is done by ASAP computer. When you turn on ASAP it is automatically recognized and integrated into ASMM.
In point of control of environmental parameters, located in the NPP, is the basic meteorological computer. It has been installed with special software to manage the operating modes of measuring, monitoring and diagnostics of the work of ASMM, telecommunications management, visualization and archiving of data obtained from ASMM. In this computer are installed and weather patterns for preprocessing of weather elements. The software automates all possible processes of production, primary analysis, processing and presentation of finished results, as requirements for operator personnel in NPP suggest initial training in the field of meteorology. For this reason, for all the necessary knowledge are created algorithms and they are set out in this specialized software.
Designed and built ASMM of NPP "Kozloduy" meets all the requirements of existing national and international control regulations, certified in numerous national and international controls, namely:
1. Provides in real-time weather data during normal operation and mode of accident:
- Speed and direction of the wind at 10 m, averaged over 10 minutes;
- Intensity and amount of the precipitation;
- Dispersion of wind direction;
- Class of stability of the atmosphere in Pasquill;
- Temperature and relative humidity;
- Atmospheric pressure.
2. Provides in real-time in the event of an accident in the NPP data for:
- Height of mixing layer in the atmosphere over the area of the site;
- Speed and direction of the main transport in the atmosphere.
3. Archived and kept on a technical device all weather information from around the site of the NPP for the entire period of its operation;
4. Has reliably verified numerical dispersion model to calculate the distribution in the atmosphere of radioactive substances, concentrations, deposition and doses in the areas of responsibility of the NPP;
5. ASMM is protected, maintained, calibrated and with guaranteed service and provides at least 95% of the annual data.
