CAISE provides continuous environmental surveillance around nuclear facilities using measured meteorological and radiological data. It complies with the REI (guidelines for monitoring emissions and exposures at nuclear facilities). CAISE not only assists you with the routine work of environmental monitoring and radiation protection, but it also serves as a real-time decision support system in case of unexpected incidents, such as increased emission levels. CAISE is also an effective training instrument and serves as simulator for exercises.
With CAISE you obtain a clearly improved quality of work in daily operations – with simultaneous reduction of cost and difficulties. CAISE is easy to use and provides you with reliable and effective support.
During normal operation CAISE keeps the surroundings of a nuclear facility under surveillance. To do this, the system uses both, online meteorological and radiological data and some offline radiological data. The release values for noble gases, iodine and aerosols are recorded online. In addition, filter samples are evaluated. You enter the resulting release values for iodine and aerosols and their nuclide compositions manually. The data are stored, filed, backed up and used in the evaluation. The meteorological and radiological data are stored in relational databases over a period of several years and are always available for later evaluations.
For evaluation of meteorological data mean values are derived from the online values from the measuring instruments. In accordance with Rule 1508 of the Commission on Nuclear Technology (KTA – Kerntechnischer Ausschuß) CAISE prepares a four-dimensional set of weather statistics which is based on: four precipitation levels, six diffusion classes, ten levels of wind speed and twelve directions. These statistics are used primarily for the long-term dispersion calculations. You can select any value for the period for the multidimensional weather statistics, and for the wind rose and vertical wind profile.
During normal operation CAISE continuously compares the calculated release values with the activity thresholds. If a threshold is exceeded, CAISE sets off an alarm and starts the emergency calculation automatically. The dispersion and dose calculations for daily operation are performed in accordance with the General Administrative Regulations (AVV), pursuant to § 45 of the Decree on Radiation Protection. CAISE calculates both permanent short-term dispersions factors, based on the automatically recorded mean values over time, and short-term and long-term dispersion factors for freely selectable periods. Based on the dispersion calculations dose distributions around the facility are defined. CAISE calculates the doses at the points of a defined reference grid for the following five exposure paths:
- Exposure due to beta radiation within the plume (beta submersion)
- Exposure due to gamma radiation from the plume (gamma submersion)
- Exposure due to gamma radiation from the radioactive substances deposited on the ground (ground radiation)
- Exposure due to inhaling radioactive substances (inhalation)
- Exposure due to intake of radioactive substances with food (ingestion) for several exposure paths.
In compliance with the AVV regulations the results for all of the reference points are listed in tables.
In the case of increased emission levels (emergencies), the dispersion calculations are carried out with a Gaussian puff model. This model calculates the current level of radiation exposure at intervals of ten minutes. For each ten-minute interval CAISE uses the released volume, the nuclide composition and the meteorological values as input data. Following the calculation of the current level of radiation exposure you can also make a forecast of the dose which can be expected over a freely selectable period. This forecast can be made at any time during an emergency. For forecast calculations CAISE always uses the nuclide composition of the last emission sample measurements fed into the system. Not all of the required data are always available online for the real-time calculations. For this reason, in order to be able to calculate the dose for the various exposure paths with a greater degree of accuracy, CAISE also allows as follows for measurements of emission samples obtained at irregular intervals:
- Every ten minutes CAISE automatically initiates a dose calculation using the current meteorological data and the online noble gas release volumes. The release rates for iodine and aerosols are at first set to zero unless online values are available. CAISE uses the last nuclide composition distribution fed into the system.
- When the specific nuclide activity concentrations from the first emission sample measurements are known, they are fed into the system manually.
- The calculation is automatically reset to the beginning of the emergency, and all of the previous dose calculations are repeated taking into account the emission sample measurements for iodine and aerosols.
- If the nuclide composition from the first emission sample measurement for the noble gases is available, CAISE proceeds as in step 3.
- With the results from the next emission sample measurements, for iodine and aerosols or for noble gases, the dose calculation is reset to the end of the previous corresponding emission measurement and repeated. This step is repeated until the emergency calculation is halted manually.
With CAISE you can perform simulations of emergencies in order to obtain the practice necessary for a safe response. The course of the simulated event corresponds closely to that of a real emergency. For the calculation CAISE uses the online meteorological data, but the online activity release data are simulated. During a practice simulation you can also feed fictitious emission sample measurements into the system. CAISE uses six emergency scenarios for the simulation calculations. The cumulative fission product releases from Phase B of the German Risk Study are multiplied by the nuclear inventory and transformed into a distribution over time of the activity releases in accordance with Phase A of the German Risk Study. The default release rates can be adjusted individually at the beginning of an emergency simulation.
The results of the evaluations are presented or output as tables or as graphics on site-specific maps. CAISE includes a special module for the routine compilation of reports for the authorities. This module produces tables and reports as specified by the authorities.
The CAISE system runs on commercially available PCs under the WINDOWS NT operating system. The currently standard PC configuration is all that is required. The CAISE system configuration comprises the evaluation computer and a number of workstation PCs. All of the computers are interconnected via a LAN.