In-vessel remote handling in heavy liquid metal cooled reactor types (PhD)

In liquid metal cooled innovative reactors in general and in the liquid lead-bismuth cooled Accelerator driven system (ADS) MYRRHA in particular, in-vessel remote handling has been identified as one of the critical issues. Remote handling is an essential part of MYRRHA operation as four robotic in-vessel manipulators are planned to be constructed : two for manipulation (one fuel handler and a recovery manipulator) and two for visualization (periscope viewer and snake-type viewer).

Although remote handling in a nuclear environment is not new with applications in installations like the experimental torus for fusion research : JET, the technological issues that are related to the liquid metal environment pose a very different challenge. There has been very little research concerning the use of mechanical components submerged in liquid lead-bismuth eutectic (LBE). Issues like tribology and lubrication, the behaviour of materials and coatings under Hertzian or impact stresses or the use of complex components like bearings and gears, is currently unknown. In addition, the integrated operation of a robotic manipulator constructed with suited components is yet to be demonstrated.

This PhD is set up to address the issues mentioned above and in this way investigate the necessary technological challenges to make a robotic arm able to operate in the lead bismuth eutectic (LBE) at an operation temperature between  200°C and  300°C,  without visibility and this for the complete life span of the reactor. At the end a working scale model on example of an in-vessel robotic manipulator namely the fuel handler will be constructed and evaluated. In MYRRHA two in-vessel fuel handlers are foreseen to move the fuel assemblies between core, storage and ex vessel fuel transfer machine positions. In this work, the focus will be placed on the mechatronic design and not on the interface with a human operator.

This challenging project to build a robot manipulator working in liquid Pb-Bi nuclear reactor vessel is divided in a number of workpackages. They will be performed in a collaboration between SCK•CEN and the Robotics & Multibody Mechanics research group (R&MM, VUB), which has experience in robotics, manipulators and multibody mechanics.

In the first workpackage “Analyses of the components in Proof Of Principle (POP) test setup” a test setup will be built that will be used to potential components such as bearings, axes, gears, crank-rod mechanisms and cables in a POP LBE bath. On top of the POP test setup an input motor and a load motor with a control and measurement unit is placed. The input and output torque, position, speed, temperature and number of cycles in the test will be stored. From that data, parameters such as power, efficiency, stiffness, backlash and wear can be derived. After failure or end of test the test module will be dismantled, cleaned and inspected after which the analysis is performed. An initial assessment of the remote handling operating conditions will be performed to determine typical use scenarios remote handling manipulator. A first estimation will determine kinematic and dynamic requirements in order to make a first component selection and to determine the relevant test conditions. Relevant items in this context are the test duration, number and speed of movements, specifications for the different performance parameters (precision, stiffness, friction, wear,) at the end of testing and at intermediate points. Also procedures to determine the these parameters

When a rigid body moves in a fluid, hydrodynamical forces will work on the body. These forces are unknown for Pb-Bi. In the second workpackage “Study of fluid-structure interaction” this will be investigated.

In the third part : “Multibody analysis”, a simulator tool will be developed based on the previous obtained mathematical model of LBE in order to calculate the necessary forces/torques in the joints and to select the required motors. Validation of this model will be done using existing or purpose-built modules in the SCK remote handling test rig.

Subsequently, the different components of the robot arm need to be designed in the workpackage “Strength analysis”. Here, the simulator tool will be used to calculate the forces on the separate components of the remote handling manipulators in various use scenarios.

The final workpackage “Realisation and validation of a scale model” will be devoted to the design and validation of a scale model of the fuel handler. For this purpose the information from the four previous workpackages is combined to accurately select suitable components for the construction of the different RH manipulators. This information will be used to design a scaled-down version of a manipulator for testing in a pool-type experiment.