CONSIDERATIONS ON CONTACTLESS MEASUREMENTS IN HYDROGEOLOGY USING VERY LOW FREQUENCY ELECTROMAGNETIC TECHNIQUES

Studies of groundwater consist in data acquisition, their processing and interpretation. In areas of interest hydrogeological is assumed that there is a network of wells drilled. This network provides a first in the hydrogeological information. Electromagnetic (EM) mapping through the use of such areas, using data obtained from existing network of wells drilled, calibration and confirmation. Measurements using the EM can highlight the existence of several layers with different characteristics: clay, limestone, sand, etc. Studies of groundwater interpretation are used for developing a regional hydrogeologic model. The application of electromagnetic techniques for measuring soil resistivity or conductivity has been known for a long time. Conductivity is preferable in inductive techniques, as instrumentation readings are generally directly proportional to conductivity and inversely proportional to resistivity. The operating principle of this method is: a Tx coil transmitter, supplied with alternating current at an audio frequency, is placed on the ground. An Rx coil receiver is located at a short distance, s, away from the Tx coil. The magnetic field varies in time and the Tx coil induces very small currents in the ground. These currents generate a secondary magnetic field, Hs, which is sensed by the Rx receiver coil, together, with primary magnetic field Hp. The ratio of the secondary field, Hs, to the primary magnetic field, Hp, (Hs/Hp) is directly proportional to terrain conductivity. Measuring this ratio, it is possible to construct a device which measures the terrain conductivity by contactless, direct-reading electromagnetic technique (linear meter). This technique for measuring conductivity by electromagnetic induction, using Very Low Frequency (VLF), is a non-intrusive, non-destructive sampling method. The measurements can be done quickly and are not expensive. The Electromagnetic induction technology was originally developed for the mining industry, and has been used in mineral, oil, and gas exploration, and archaeology. In these applications, differences in conductivity of subsurface layers of rock or soil may indicate stratified layers or voids that could be of interest

CONSIDERATIONS ON CONTACTLESS ELECTROMAGNETIC MEASUREMENT OF HUMIDITY IN PEDOLOGY

To put into practice the conventional determination of resistivity by the galvanic method, requires a relatively large amount of labor and is, therefore, expensive. At the basis of any interpretation are the lateral or vertical variations of re sistivity. The high cost of resistivity maps execution generally means that fewer measurements are made than desirable, with the result that, either (i) the explored area is not large enough to establish a reasonable background, against which the anomaly areas are to be delineated, or (ii) the anomaly areas are obscure and lack definition. The application of electromagnetic techniques (EM) for measuring soil resistivity or conductivity has been known for a long time. Conductivity is preferable in inductive techniques, as instrumentation readings are generally directly proportional to conductivity and inversely proportional to resistivity. The operating principle of this method is: a Tx coil transmitter, supplied with alternating current at an audio frequency, is placed on the ground. An Rx coil receiver is located at a short distance, s, away from the Tx coil. The magnetic field varies in time and the Tx coil induces very small currents in the ground. These currents generate a secondary magnetic field, Hs, which is sensed by the Rx receiver coil, together with primary magnetic field Hp. The ratio of the secondary field, Hs, to the primary magnetic field, Hp, (Hs/Hp) is directly proportional to terrain conductivity. Measuring this ratio, it is possible to construct a device which measures the terrain conductivity by contactless, direct-reading electromagnetic technique. (linear meter.) This latest technique for measuring conductivity by electromagnetic induction, using Very Low Frequency (VLF), is a non-invasive, non-destructive sampling method. The measurements can be done quickly and are not expensive. The Electromagnetic induction technology was originally developed for the mining industry, and has been used in mineral, oil, and gas exploration, hydrogeology studies, and archaeology. In these applications, differences in conductivity of subsurface layers of rock or soil may indicate stratified layers or voids that could be of interest

PARTICULARITIES REGARDING THE OPERATING PROCESS OF THE CUTTING AND EXTRACTION DEVICE IN THE CANDU HORIZONTAL FUEL CHANNELS PRESSURE TUBE DECOMMISSIONING PART I: MOVEMENT AND FIXING DEVICE INSIDE THE PRESSURE TUBE

This paper presents some details of operation process for a Cutting and Extraction Device (CED) in order to achieve the decommissioning of the horizontal fuel channels pressure tube in the CANDU 6 nuclear reactor. The most important characteristic of the Cutting and Extraction Device (CED) is his capability of totally operator’s protection against the nuclear radiation during pressure tube decommissioning. The movement and fixing processes present few particularities due to special adopted technical solutions: train guiding-fixing modules equipped with elastic guiding rollers and fixing claws, traction modules with elastic rollers and variable pitch, also with propriety to adapt the system according to various dimensions of the tube. The Cutting and Extraction Device (CED) is a train of modules equipped with special systems to be fully automated, connected with a Programmable Logic Controller (PLC) and controlled by an operator panel type Human Machine Interface (HMI). All processes are monitored by video cameras. In case of error, the process is automatically stopped, the operator receiving an error message and the last sequence could be reinitialized or aborted due to safety reason

PARTICULARITIES REGARDING THE OPERATING PROCESS OF THE CUTTING AND EXTRACTION DEVICE IN THE CANDU HORIZONTAL FUEL CHANNELS PRESSURE TUBE DECOMMISSIONING PART II: CUTTING AND EXTRACTING PRESSURE TUBE PROCESS

This paper presents some details of operation process for a Cutting and Extraction Device (CED) in order to achieve the decommissioning of the horizontal fuel channels pressure tube in the CANDU 6 nuclear reactor. The most important characteristic of the Cutting and Extraction Device (CED) is his capability of totally operator’s protection against the nuclear radiation during pressure tube decommissioning. The cutting and extracting pressure tube processes present few particularities due to special adopted technical solutions: a special module with three cutting rollers (system driven by an actuator), a guiding-extracting and connecting module (three fixing claws which are piloted by an actuator and block the device in the connecting position with extracting plugs). The Cutting and Extraction Device (CED) is a train of modules equipped with special systems to be fully automated, connected with a Programmable Logic Controller (PLC) and controlled by an operator panel type Human Machine Interface (HMI). All processes are monitored by video cameras. In case of error, the process is automatically stopped, the operator receiving an error message and the last sequence could be reinitialized or aborted due to safety reasons