In the R&D programme for the MYRRHA ADS, research effort is devoted to support the development and to demonstrate the feasibility of innovative components that are specific for a heavy liquid metal (HLM) cooled sub-critical system.
Pool type experiments
The reactor vessel will have a pool configuration of which the design is supported by numerical simulations. To understand the thermal-hydraulic pool behaviour, to validate computational tools and to qualify the design and safety, experiments using scaled-down models are needed. The required similarity of the scale model for specific phenomena puts constraints on the modelling fluid and geometrical scale factors to be used. Currently an R&D programme defining all relevant parameters with the purpose to design, build, instrument and operate an experimental installation is being set up.
The primary heat exchangers of the ADS have been designed and sized, based on existing literature data. The main uncertainties arise from the validation of heat transfer correlations in the liquid metal and the assessment of the thermal resistance of the tubes due to oxide layer build-up. Both aspects are being investigated in the EUROTRANS project. When new results become available, the HX design will be re-evaluated and a mock-up will be constructed to verify its design by experiments.
Lead-Bismuth Eutectic (LBE) pumps
For HLM pumping, both MHD and centrifugal pumps are in use under relevant conditions in several European experimental loops. This demonstrates the feasibility of HLM pumping and provides feedback on possible optimisations for application in a real nuclear system. On the basis of requirement analyses for both primary system and the spallation loop, the most appropriate pumping options will be selected. These will be investigated in a tested LBE loop at SCK•CEN for their operational performance and endurance.
LIDAR: LIght Detection And Ranging
In the spallation target the position of the free surface will be monitored using a LIDAR system. Experiments have shown that a commercial LIDAR can measure the distance to the target free surface with an accuracy and repetition rate close to those required in the ADS although a test in a real life-size mock-up is still required. This will prove the feasibility of the measurement system and give extra information on the reflection properties of the target that is needed for a detailed design of the final LIDAR system. The effect of radiation in the basic building blocks of the LIDAR system will be studied to yield a final LIDAR design that can withstand the radiation environment of MYRRHA.
Because of the opacity of the liquid metal coolant, an ultra-sound based imaging system is envisaged. The development of the single element transducers to be used here is reaching completion. The full ultrasonic camera development is ongoing and no show stoppers have been identified. Future actions focus mainly on qualification of single element transducers (thermal cycling, irradiation) and a further development of an ultrasonic visualisation strategy with the final goal of constructing an operational ultrasound camera and its testing in a real LBE environment.
The final innovative component in the MYRRHA ADS is the full remote handling option. Although it has been employed in a gas atmosphere at elevated temperatures and in radioactive conditions for fusion research, liquid metal submerged remote handling is still to be demonstrated. A remote handling validation experiment set-up has been designed and the preparation of the experimental test programme has not revealed any show-stoppers. The next step is the construction of the remote handling test facility followed by the execution of the test programme addressing the critical handling components. The final step is the validation of a full scale robotic joint and actuator in LBE at 300 °C.