AUTOMATED RADIATION MONITORING AND EARLY W ARNING SYSTEMS NETW ORK (RESA)
Necati KUCUKARSLAN. Adem ERDOGAN, Ahmet GUVEN
TAEK, Qekmece Nuclear Research and Training Center
www.taek.gov.tr nel@nukleer.gov.tr
In recent years, especially after the Chernobyl Accident, radiation detection and evaluation of the obtained results are subjects with increasing importance. To implement a solution, some countries develop and install widespread radiation-monitoring systems on their lands. For the same purpose, in Turkey, Turkish Atomic Energy Authority, £ekmece Nuclear Research and Training Center initiated the RESA Project.
THE SERVER SOFTWARE
The server software, one of the main two components of the RESA project, manages the probes and the data obtained from measurements, thus, minimizes human interaction to the system. The software has been developed with the PASCAL programming language to run under the Microsoft Windows operating system and has been designed to present the output in graphical format for user convenience. The server software communicates to the probes over the serial ports of the computer by modems or direct lines. Alarm conditions raised by radiation levels rising to specified threshold values are reported to the user or authorised personal over telephone lines by audio and visual warning. The user is provided with an additional software, which communicates with the server over the Internet to supervise the system remotely. When provided, the server may make use of extra telephone lines as many as the number of serial ports of the computer. This enables the server to communicate with more than one probes simultaneously. To achieve this, the software has been developed with multi-threaded routines. The server software has been designed to be multi-lingual for international usage. Current version includes support for Turkish and English.
The main window of the program has been illustrated in
l * w I I - h r J M u l l s £ $ A S e r v e r IL k " >#-... .1 --■ t i l l i i r b m M M i k Mb' :l — ' — ■U-— ^ _____ J : ■ — i . —i . . * — Figure 1.
Data accumulated in the databases of the server may be displayed in tabular form as in Figure 2 or in graphic form as in Figure 3.
Figure 2: Data in tabular form Figure 3: Data in graphic form
To compare data of more than one probes one may display overlayed graphics. Each probe is presented with a different colour. To display unscaled graphics with respect to time the user may choose the Bar Graph option.
For unattended and automated operation a task module has been implemented and inserted. The user may define tasks by means of the form shown in Figure 4 and run them periodically or for a single time.
Figure 4: Task description form Figure 5: Probe map
All the operations that can be conducted on the probes may be activated through maps, which help the user to locate them easily. A sample map is illustrated in Figure 5. The user may define new maps as long as he/she has the graphics file for it (Bitmap or Windows Metafile format).
Figure 6: Probe parameters Figure 7: User definition form
A security system has been implemented to protect sensitive data. The user is expected to provide a user name and password for specific operations. The user rights that may be specified for a user is listed on the user definition form shown in Figure 7.
The server databases may be queried remotely by the RESA Client software. This program and the server communicate via the TCP/IP networking protocol. The user may access the server system over the Internet as long as he or she provides the IP number of the server and a pair of valid user name and password.
THE REMOTE STATION Remote Station Equipment
The station consists of a “smart probe” incorporating the detectors and measuring circuits and of an external modem and an uninterrupted power supply unit. The probes, operating in open air are sealed against atmospheric conditions.
The Probe
In the probe there are 2 Geiger Muller (GM) detectors sensitive to gamma and X-Rays and the electronic circuit.
The Electronic Circuit
Each GM detector owns its high voltage and preamplifier circuits separately. The microcontroller 87C51FA from the MCS-51 family is used for the evaluation of the counts of the detectors and data transfer. A nonvolatile memory for storing data, a real time clock for timing and dating the data are the main components. Data rate in the telephone lines is determined by the modems according to the condition of the lines.
The Algorithm of the Probe Operation
It was necessary to use 2 separate Geiger Muller detectors, because of the large measuring range of radiation dose rate 0-400 R/h. At the end of every minute it is tested whether the end of the measurement is reached, so it is possible to change the operating mode during operation. The measurement is terminated depending on the operating modes described below. At the end of the measurement the alarm condition and the status of the probe are tested and it is decided whether the center will be informed or not. The measured value and all the measurement parameters are written in the probe memory along with the real time as a "record", and a new measurement starts. If it is decided to inform the center it is done simultaneously during the measurement period. It is tested continuously if each of both detectors is operating.
The Operating Modes:
There are two operating modes that can be selected from the center: a. The Fixed Precision Mode
Measurement in this mode continues uninterruptedly until the measurement reaches %95 statistical accuracy. The measuring period is proportional to the radiation dose rate.
b. The Average Mode
The measurement in this mode is terminated at the end of the time interval determined by the center. In this mode measurement accuracy is proportional to the radiation level and the accuracy at 2a confidence level is calculated at the end of this time interval and sent with the measurement result to the center. Measuring time interval can be selected from 1 to 240 minutes.
The Measurement Result
At the end of the measurement, the measurement result and the information detailed below are written as a “record” in the probe’s memory.
The record consists of the following information: 1. Date and time of the measurement.
4. Measurement duration. 5. Alarm condition. 6. Alarm level. 7. Precision (in %).
8. Confirmation of the result with both detectors (in case of alarm state). 9. Record memory %70 full.
10. Battery condition. 11. GM1 detector defect. 12. GM2 detector defect.
13. Occurrence of the power-off.
14. Occurrence of the program restart (watchdog occurrence). The Evaluation of the Alarm
For every minute’s count the consequent measured radiation is compared with the selected alarm level. If the alarm level is exceeded the probe changes its operation mode to the alarm mode and continues operation in this mode. The alarm mode can be selected like the main measurement modes as “fixed precision” or “average” mode. At the termination of alarm mode if the measurement result does not exceed the alarm level the probe returns to its normal operating mode, but if the measured value exceeds the alarm level a “record” is written and the center is informed with the alarm condition.
Probe’s Calling Selections:
а. Calling when the Condition Changes
The conditions listed below are controlled continuously. If minimum one of these conditions happens the probe calls the center and informs it with its the actual condition. As long as this condition remains probe does not call the center again.
Conditions of the probe’s searching the center: 1. The alarm condition.
2. GM1 defect. 3. GM2 defect. 4. Low battery.
5. Record memory at least %70 full. б. Power-off occurrence.
b. Calling at the End of Every Measurement
After the measurement is complete and the “record” is written in the memory the probe calls the center and the last measurement is sent. This procedure is repeated at the completion of each measurement.
c. Canceling the Call Completely
If the conditions causing the calling change very frequently the operator can cancel the calling of the center completely to prevent the occupation of the telephone lines unnecessarily.
Probe’s Nonvolatile Memory
2032 measurement results can be written in the probe’s nonvolatile memory. It means that data accumulated during approximately 6 months when measuring at normal conditions (background) can be saved, that is if there is no communication with the station for any reason and data cannot be received, radiation data of the last six months remain stored.
Probe’s identification number, password, telephone number of the center, calibration parameters, alarm level, operations settings are stored in the nonvolatile memory.
