Translated Abstract
Chinese Fusion Engineering Test Reactor (CFETR) is a transitional fusion experiment device between International Thermonuclear Experimental Reactor (ITER) and future fusion demonstration (DEMO) reactor. The main objectives of CFETR are to achieve steady-state operation with 50-200 MW fusion power and 0.3-0.5 duty time factor, to demonstrate the tritium self-sufficiency of fusion reaction, to conduct experimental research on the key components of the tokamak under actual fusion environment, and to lay a foundation for the design and construction of future fusion DEMO and fusion power plant (FPP). As one of the critical components of CFETR, blanket is required to achieve the function of tritium self-sufficiency, fusion energy transformation and radiation shield. The helium cooled solid breeder blanket has some remarkable advantages in stable structure, easily realization and good compatibility, etc. Therefore, the present thesis performs the coupled neutronic/ thermal-hydraulic/mechanical analyses of the typical outboard equatorial helium cooled solid breeder blanket module (No. 12) for CFETR.
First, three dimensional coupled neutronic/photonic model of the typical blanket module was performed using the Monte Carlo N-Particle transport code MCNP with IAEA general purpose neutron sublibrary FENDL-3.0 and ENDF-B-VII.0/n. The neutronic calculation results and the subsequent thermal calculation results were iterated, which made it possible for the coupling of the neutronics and thermal-hydraulics. Then the tritium breeding capability of the proposed blanket was assessed and the adopted three radially arranged U-shaped breeding zones were optimized for higher Tritium Breeding Ratio (TBR). Based on the preliminarily optimized blanket structure, the influences of different factors such as the option of tritium breeder, the enrichment of Li6, the packing factor of lithium ceramic pebbles and beryllium pebbles on TBR and nuclear heating rate were all investigated for the best scheme. On that basis, nuclear heating analysis was carried out for later thermal-hydraulic and structural analyses.
Then thermal and fluid dynamic analyses were performed under both normal and critical conditions, based on thermal-hydraulic calculation model of the best scheme established by CFX. The results showed that the temperature on the blanket module could be effectively cooled below allowable temperature limits of the materials under normal condition. But when the FW was suffering the maximum surface heat flux, the maximum temperature of FW would exceed the structural material temperature limit while the temperature of other components showed little differences. Under both two conditions, the minimum temperatures of lithium ceramic pebbles and beryllium pebbles were all above the temperature limits for the release of tritium, and the pressure drop of helium coolant were all relatively small.
With thermal-hydraulic boundary conditions, the coupled thermo-mechanical analyses of the structure materials under both normal and critical operating conditions and over-pressurization of blanket box were all carried out using finite element method software ANSYS Workbench. The results showed that the maximum Von Mises stress under normal condition satisfied the performance requirement of the structural material according to 3Sm
rule，but it wolud exceed the corresponding stress limit under critical condition. When the over-pressurization of blanket box occurred, the maximum Von Mises stress and total deformation would increase sharply and exceed the corresponding limits greatly, which would explode the structure directly. As a result, this serious accident must be avoided during the operation.
In addition, several parametric sensitivity studies were conducted to investigate the influences of the main parameters (e.g. surface roughness, coolant mass flow rate, inlet temperature, lithium ceramic pebble bed thermal conductivity, beryllium pebble bed thermal conductivity and fusion power, etc.) on the temperature distributions of the blanket components. The results had an important significance for the understanding of the failure mechanism under accident conditions.
This paper verify the reasonability of the optimized conceptual design and is meaningful for the following coupled neutronic/thermal-hydraulic/mechanical analyses for the CFETR helium cooled solid breeder blanket. Besides, it can also provide an important reference for the following optimization design and safety analysis.
Translated Keyword
[CFETR, Helium cooled solid breeder blanket, Neutronic characteristics, Sentivity analysis, Thermo-mechanical characteristics]
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