The following proposal is focused on the developing, verification and validation of a new version of RELAP5 code capable to consider the global effects generated into a high-intensity magnetic field on the pressure drops and heat transfer capabilities for liquid metals. These effects are important to reach an optimized design for a liquid fusion reactor blanket, namely the Water Coolant Lithium Lead (WCLL) concept, currently being developed for implementation in ITER (as a Test Blanket Module) and DEMO. This is based on a Lithium Lead Eutectic blanket and to realize a reliable and solid design is necessary to analyze all its peculiar aspects with a unique code, usable both in design and during the safety analysis.
The RELAP5 code, the main and more widespread two-phase system code developed by Idaho National Laboratory (USA) has been selected as base for our version.
The correlations planned to be implemented in the code to evaluate the magnetohydrodynamic (MHD) pressure drop cover both basic geometry elements (round and rectangular straight pipes) and more complex ones (i.e. cross-section variation, bends, etc). which are present within the LiPb hydraulic circuit.
This activity will lead to a significant improvement in the baseline RELAP5 code presently used to aid the WCLL design by including basic MHD modeling capability. Since very few system codes presently include these features, and none include hat transfer, there is potential for our modified version to become the reference in the field.
This know-how could be used to attract potential funding from European and international projects correlated to the ITER WCLL TBM development, other liquid metal blanket concepts, and the Divertor Tokamak Test(DTT). In particular, the DTT machine, that will be realized in the next years in Frascati and will be the main experimental facility developed in Italy in this field, with worldwide importance, could be a fundamental application for our modified version of the code.
The proposed activities are focused on the developing, verification and validation of a new version of RELAP5 code capable to consider many correlations for MHD pressure drops evaluation in fusion reactor blanket. The correlations that will be included in the code cover all the basic straight geometries, the cross-sectional variations and the standard curves. This is first the possibility to become a reference point, in comparison with the other the state-of-the-art code. The Italian version of the RELAP5 code, developed by Sapienza team and used by ENEA-lead international team for the WCLL design and safety analysis, will be improved to reach the capability to simulate all the significative pressure drops into the BB and relative collectors. This innovation is a remarkable contribution to speed up the BB design phase with a unified tool for the verification of the hydraulic design of the water loop and the LiPb loop. In the LiPb pressure drop evaluations, using an ad hoc developed database and our competence in the MHD CFD analysis, we solve the problem of the pressure drop analysis building a validated tool for this kind of analysis. Thanks to this innovation, will be possible to design iteratively the LiPb loop, considering all terms and selecting the appropriate pump to reach the nominal mass flow rate in all conditions. Another additional advantage, is the preliminary prediction of the mass flow rate distributions in each parallel channel, verifying the active contribution of all the LiPb present into the BB for the tritium generation.
This approach is obviously simplified in comparison to an MHD CDF simulation but is able to reach a global evaluation with enough accuracy, reducing by at least one order of magnitude the simulation time.
An area not covered by the existing version of system codes is the convective heat transfer coefficient (HTC) modification caused by the magnetic field. This aspect could be easily improved into the source code, but, actually, it is not possible to cover all heat transfer geometries for the absence of specific reference. Despite this, recently, some correlations are developed and the implementation of a model for the heat transfer only for straight tubes is included in this project. Thanks to this addition, the code could predict an approximation of the temperature distributions along the tubes, verifying the right outlet conditions. Future work foreseen includes the addition of more correlations for complex geometrical elements and implementation of simplified relations to model MHD effects on heat transfer coefficient.
Resuming, this activity leads the upgrade of the RELAP5 version used in the WCLL design including the best capabilities in the MHD pressure drop evaluation, filling this gap with other similar codes and becoming the reference in this field.
This know-how could be used to attract new potential works correlated to the ITER WCLL TBM development, and the Divertor Tokamak Test (DTT). In particular, the DTT machine (budget 626 M€), that will be realized in the next years in Frascati and will be the main experimental facility developed in Italy in this field, with worldwide importance, could be a fundamental application for our modified version of the code.