Comprehensive Analysis Of Electromagnetic-thermo-Mechanical Effects On HCSB Under Plasma Transient Events For CFETR

The blanket system is the fundamental component of the fusion reactor with the functions of containing plasma,energy conversion,tritium breeding and radiation shielding.However,the blanket is subject to large thermo-mechanical loads and electromagnetic loads due to the environment of strong magnetic field,high heat flow and irradiation,especially in plasma transient events.Plasma transient events will cause significant damage on the blanket due to its induced high energy density in a short time and large electromagnetic loads.In this paper,based on the CFETR helium cooled solid blanket design scheme,the electromagnetic-thermo-mechanical coupling method and the comprehensive analysis of the blanket under plasma transient event are studied.Plasma events include main disruption(MD)event and vertical displacement event(VDE)and the induced consequences.The MD event refers to a phenomena in which the plasma discharge is abruptly terminated while the plasma thermal energy and the plasma current are completely lost.Due to the rapid release of plasma thermal energy,there will be a potential local melting or sublimation risk of the blanket module.At the same time,due to the loss of current,the magnetic field changes rapidly,and additional Lorentz force and moment are introduced,resulting in the distortion and deformation of the blanket structure.Under the VDE event,the balance of the plasma in the pole direction will be out of control and drift up and down,accompanied by a MD event.The electromagnetic force and moment of the blanket under the VDE event will be affected by the drift and disruption of the plasma,which threatens the safety of the blanket structure.Firstly,the electromagnetic-thermo-mechanical comprehensive analysis under MD event for HCSB is conducted in the establishment of electromagnetic analysis,thermal analysis and stress analysis models,among which the electromagnetic analysis model includes magnet system,vacuum chamber and blanket system.The typical blanket module on the equatorial port uses a detailed structure model,and the simplified blanket modules around it are also created taking into account the influence of surrounding ferromagnetic material on the magnetic field.In the electromagnetic analysis,the distribution and variation of the typical blanket magnetic field strength,induced current,electromagnetic force and electromagnetic moment in the plasma linear quenching mode are calculated.The temperature field obtained by the transient thermal analysis shows the maximum temperature of W armor reaches and exceeds the recrystallization temperature and that the maximum temperature of the FW is higher than the safety limits,while temperatures of the rest components remain almost unchanged under the MD event.The stress analysis of the blanket under different load conditions at the end of the event are carried out,and the stress field distribution of the blanket is obtained.Referred to the SDC-IC and RCC-MX evaluation criteria,the structural assessment of the HCSB under the MD shows that the HCSB meets the structural design criteria for the primary stresses and the secondary stresses are within the allowable stress.In addition,the electromagnetic-thermo-mechanical comprehensive analysis for HCSB under vertical displacement event(VDE)is conducted.A more accurate model where the plasma described by 69 filaments is adopted to simulate the vertical movement of the plasma.In the electromagnetic analysis,the distribution and variation of the typical blanket magnetic field strength,induced current,electromagnetic force and electromagnetic moment in the plasma linear quenching mode are calculated.The temperature field under the intervention of the disrution mitigation system obtained by the transient thermal analysis shows the maximum temperatures of W armor and FW are higher than the safety limits while temperatures of the rest components remain almost unchanged.The stress analysis of the blanket under different load conditions at the end of event are carried out,and the stress field distribution of the blanket is obtained.The structural assessment of the HCSB under the MD shows that the HCSB will maintain structural integrity,but the FW has a small safety margin.In this paper,with reference to the design scheme of CFETR magnet system and helium cooled solid blanket system,the electromagnetic,thermal and mechanical coupling effects of blanket are comprehensively analyzed.The electromagnetic-thermo-mechanical coupling methods and the approach to assessing the safety of blanket structure under plasma transient events comprehensively are studied,which provides an analytical method and important references for the design optimization of the blanket system.