SAM, a mobile measurement system of high level disposal cell casings for ANDRA
ANDRA is the French Agency responsible for granting the safe management and disposal of the radioactive waste to protect the present and future generations from the risks inherent in such substances. ANDRA oversees the Cigèo project (Industrial Centre for Geological Disposal) consisting of a deep geological facility aimed for disposing of the highly radioactive long-lived waste. Within this frame, the Underground Laboratory of Bure was built as an exceptional tool to perform the research activities required to implement Cigèo.
SAM (Systèm d’Auscultation Mobile por l’alvéole AHA) is a high-precision robot that performs different types of measurements inside High Level (HL) disposal cell casings. The HL disposal cells are “micro-tunnels” of at least 80m long and internal diameter of approx. 0.7m in which the waste packages will be placed. SAM is to be used in a set of underground experiments to produce a cell demonstrator and study its behavior.
SAM moves through the pipe and checks the consistency of values from the “outer casing” measuring devices. These activities will be repeated in several campaigns to monitor how the parameters change over time.
SAM can measure with high accuracy its own position in the disposal cell, longitudinally as well as when pitching and rolling; casing geometry by analyzing the out-of-roundness of the inner part of the pipe and the environmental atmospheric conditions. It is also adjustable so it can host additional measurement systems.
SAM exploring a pipeline. Copyright: ANDRA (Agence Nationale pour la gestion des déchet radioactifs)
ANDRA was looking of for an autonomous system with high precision in the measurements and low maintenance needs. The following elements were critical to ensure the success of the project:
- Repeatability and resolution (<10 µm) of the pipe deformation measurements
- Repeatability and accuracy (< 0.5 cm) of longitudinal positioning of SAM
- Flexibility to embark new measurement systems and transmit its gathered data
- Reliability, effectiveness and retrievability
- High degree of automatization
- Fast and easy programming of the moving/measurement sequence
- Fast development and testing.
SAM has been designed to obtain high precision data from deformation measurements within up to 150m long and from 610 to 710mm diameter tubes in horizontal position (±1o). Some of the aspects to highlight are the following:
- SAM incorporates a rotation plate with three high-accuracy distance sensors installed in a spinning platform to measure the distance between the rotor and the inner surface of the pipe. The distance information is gathered and sent via coaxial cable or Wi-Fi to the control unit where the geometry of the pipe is calculated.
- Using SAM with the spinning platform blocked allows it to perform measurements of three generatrix at the same time.
- A laser set installed at the cell entry that points to a target placed at the back of the robot control the longitudinal location of SAM.
- Equipped with illumination LEDs and on-board video camera, humidity, pressure and temperature sensors.
- A support tray can accommodate up to 20kg load to carry other instruments on board.
- Capability of measuring in manual or autonomous mode and in static and in motion modes. The manual mode allows the user to operate it with almost full control while the automatic mode allows the robot to execute tasks with no need of supervision.
- Control Station with a Graphical User Interface that communicates with SAM. This interface allows the user to verify the status, modify parameters and settings and collect the acquired data and actions performed by the robot to save them in log files. It also storages the rest of sensors: atmospheric measurement, tilt and roll, speed control and several control modes. This interface also displays a section graph showing the operator where the sensors are positioned in real time and the reconstructed section shapes.
Every subcomponent of the system has been tested and validated by ANDRA at the final inspection stage prior delivery.
One test has been performed so far at the underground laboratory of Bure on July 2019. SAM successfully responded within the specifications of the experiment, aiming to determine de baseline of an HL cell. Further campaigns will be performed shortly by ANDRA to monitor the parameters’ evolution at the same cell.
SAM will be used as standard basis for the measurement and monitoring of AHA cells to be built at the Underground Laboratory of Bure from 0 to 150m long but can be easily upgraded to longer distances. SAM demonstrated how a high level of customization can be obtained using standard mobile platforms with short development times. The resulting system is designed targeting a cost affordable future production of several units and with short lead times.
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