Three-dimensional validation and analyses of the optimized CFETR HCCB blanket
Introduction
The breeding blanket, which is mainly responsible for tritium breeding, radiation shielding, energy extraction and transformation [12], is the critical component of the China Fusion Engineering Test Reactor (CFETR) [34]. Compared with other blanket concepts, the Helium Cooled Ceramic Breeder (HCCB) blanket has many advantages [12,56]: (1) helium coolant has good compatibility with both structural and functional materials; (2) helium coolant has no Magneto Hydro Dynamics (MHD) effect; (3) compared with water and liquid metal, using helium as the coolant has inherent security; (4) the outlet temperature of the HCCB blanket is much higher than the Water Cooled Ceramic Breeder (WCCB) blanket (as a result, its thermoelectric conversion efficiency is also relatively higher); (5) the water in the WCCB blanket serves as both coolant and neutron absorber, which is adverse to the tritium breeding (using helium as the coolant won’t cause this problem); (6) the tritium in water is difficult to be extracted. Besides, it will cause the tritium-water reaction; (7) compared with the liquid tritium breeding materials, the solid ones have many good qualities such as high thermal, chemical, mechanical and irradiation stability, good tritium release ability and compatibility with the structural material and Be pebble bed, etc. As a result, there have been a great number of research efforts conducted for improving the performance of the solid tritium breeding materials. Besides, their experimental performance parameters are relatively sufficient. In summary, the HCCB blanket is recognized as the most promising blanket concept in the future fusion demonstration (DEMO) reactor [2,7], and has been determined as one of the blanket candidates for CFETR [34].
The neutronics and thermal-hydraulic performance of the blanket is the foundation of the safe operation for CFETR [56], and they are strongly interacted with each other [6,8]. Up to now, there have been many neutronics and thermal-hydraulic analysis and optimization researches conducted for the CFETR HCCB blanket [[9], [10], [11], [12], [13], [14], [15], [16], [17]]. In the previous work [1112], considering that the radial structural layout of the internal functional zones has the largest impact on the blanket neutronics and thermal-hydraulic performance, NTCOC, a Neutronics/Thermal-hydraulic Coupling Optimization Code has been developed for calculating the radial structural layout scheme of the CFETR HCCB blanket with comprehensively optimized neutronics and thermal-hydraulic performance. However, for increasing the optimization calculation efficiency, the NTCOC employs the simplified 1D neutronics and 2D thermal-hydraulic models, the calculation results of which differ from the results of the 3D actual models [18]. Therefore, for verifying the reliability of adopting the simplified models in NTCOC, it’s essential to compare their calculation results with the corresponding 3D models.
In this paper, firstly, the 3D neutronics models corresponding to every point of the radial structural optimization processes of the CFETR HCCB blanket are established. On these bases, the 3D neutronics analyses of the blanket are conducted and the change tendencies between the tritium breeding rate (TBR) which are respectively calculated by NTCOC and the 3D models are compared. The comparison results show that they coincide with each other. Next, the 3D thermal-hydraulic model corresponding to the final optimized radial structural layout scheme which has been obtained through the previous integrated optimization method is established. On this basis, the 3D thermal-hydraulic analysis of the blanket is carried out and the radial temperature distributions which are respectively calculated by NTCOC and the 3D model are compared. However, the comparison results show that the 3D calculated temperature is generally higher than the NTCOC’s, which means that the direct application of the 2D thermal-hydraulic calculation model in NTCOC is not conservative. To solve this problem, a 3D thermal revision is added to the previous optimization method in the form of feedback. After revision, the radial coupling optimization design of the blanket is conducted again. The comparison results show that the 3D calculated temperature of the newly obtained radial structural layout scheme is generally lower than the NTCOC’s, which means that the previous problem of not conservative calculation model has been well solved after the thermal revision. Besides, as for the final optimized blanket scheme which is obtained after the 3D thermal revision, the maximum temperatures of all components are within the corresponding temperature limits.
This work comprehensively verifies the reliability of the NTCOC and the improved optimization method after the 3D thermal revision for application in the radial structural design and optimization of the CFETR HCCB blanket. It can provide some guidance for the further design and coupling optimization analyses of the CFETR HCCB blanket.
Section snippets
3D neutronics model
In NTCOC, for increasing the neutronics modeling and calculation efficiency, the simplified 1D cylindrical neutronics model is adopted as Fig. 1(a) shows. During the whole coupling optimization processes, the radial structural layouts are solely adjusted in the simplified models, while both the toroidal and the poloidal parameters remain unchanged. The TBR of the 1D neutronics model is greater than the 3D actual model in general [18], only reflecting the change tendency of the tritium breeding
3D thermal-hydraulic model
In NTCOC, to increase the thermal-hydraulic modeling and calculation efficiency, the simplified 2D plane thermal-hydraulic model, which only focuses on the changes of the radial structural arrangement, is adopted as Fig. 4(a) shows. It is noticeable that the 2D thermal-hydraulic model only considers the radial heat conduction between the adjacent solid regions and the heat convection through the continuous coolant channel, while the top and bottom sidewalls of both the first wall (FW) and the
Coupling optimization design of the CFETR HCCB blanket after the 3D thermal revision
In this section, firstly, both the T3D CPinlet and the T2D CPinlet are monitored for the preliminarily optimized radial structural layout scheme, shown in Fig. 5. The calculation results indicate that the T3D CPinlet is approximately 52℃ higher than the T2D CPinlet. For making the calculation results more conservative, in the following calculations, we will increase both the FW inlet temperatures and the CP outlet temperature targets of all 2D thermal-hydraulic models by (T3D CPinlet-T2D CPinlet
Conclusion
In this paper, the detailed 3D neutronics and thermal-hydraulic analyses corresponding to the radial structural optimization processes of the CFETR HCCB blanket are performed, and the main conclusions are as follows:
- 1)
The change tendencies of TBR which are calculated by NTCOC and the corresponding 3D neutronics models coincide with each other. This indicates that adopting the simplified 1D neutronics model in NTCOC can reflect the change tendency of the tritium breeding performance during the
CRediT authorship contribution statement
Shijie Cui: Methodology, Software, Formal analysis, Visualization, Writing - original draft, Writing - review & editing. Yueheng Lang: Validation, Software, Writing - review & editing. Dalin Zhang: Investigation, Methodology, Conceptualization, Resources. Xinyu Jiang: Writing - review & editing. Haoyu Wan: Writing - review & editing. Wenxi Tian: Project administration, Supervision, Funding acquisition, Resources. G.H. Su: Supervision, Resources, Project administration. Xiang Gao: Funding
Declaration of Competing Interest
We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled.
Acknowledgements
This work was supported by the National Key R&D Program of China (No. 2017YFE0302100, No. 2017YFE0300503). Besides, the author would express his gratitude for the academic communication with Dr. Fengchao Zhao, Qixiang Cao, and Xinghua Wu from the Southwestern Institute of Physics.
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Cited by (2)
Neurtonics/Thermal-hydraulic analyses of the CFETR HCCB blanket for multiple operation modes under the poloidal nonuniform neutron wall loading condition
2021, Fusion Engineering and DesignCitation Excerpt :Based on the Computational Fluid Dynamics software CFX [50], the thermal-hydraulic models of both the No. 3 and the No. 4 blanket modules are established as Fig. 7 illustrates. In this paper, analogously, we have first built the simplified 2D plane thermal-hydraulic model of the blanket [26,50], and the detailed 3D thermal-hydraulic analyses will also be conducted in the future [12,36]. From Fig. 7 it can be noted that the whole thermal-hydraulic model is also divided into five identical parts along the poloidal direction for investigating the influence of the poloidal nonuniform NWL on blanket thermal-hydraulic performances.
Preliminary thermal-hydraulic influence of the poloidal nonuniform neutron wall loading on the CFETR HCCB blanket
2021, Fusion Engineering and DesignCitation Excerpt :Based on the Computational Fluid Dynamics software Fluent [29], the thermal-hydraulic model of the CFETR HCCB blanket is established as shown in Fig. 3. It should also be noted that in this paper, we have first built the simplified 2D plane thermal-hydraulic model of the blanket [15,29], and the detailed 3D thermal-hydraulic analyses will also be conducted in the future [21]. In the simplified thermal-hydraulic model, the top and bottom FW are not built either, while only the change of the radial structural arrangement is considered.