Preliminary Study On The Thermal Hydraulic Design Criteria Of Supercritical Water Cooled Fusion Reactor Blanket

International Thermonuclear Experimental Reactor (ITER) is one ofthe largest international cooperation projects in which China participates.It is of great significance in promoting China’s development and progressin both fundamental science and engineered technology. Blanket is a keycomponent for energy transport and conversion in fusion reactor. As faras the blanket technology is concerned, how to ensure the blanket fullyand uniformly cooled, so as to maintain fusion reactor operating in anefficient, safe and reliable situation, remains the most important issue tobe resolved. Currently, the involved ITER partner countries haveproposed a variety of test blanket module (TBM) solutions, focusing onwater-cooled solid breeder blanket, helium-cooled solid breeder blanket,helium-cooled lithium lead breeder blanket, self-cooling liquid breederblanket and self-cooling molten blanket. In terms of the tritium breeder,all the parties involved in the program are spontaneously using solidbreeder blanket concept; and in terms of the blanket structure material,the low activation ferritic steel is chosen as the primary candidate. In1999, Japan first proposed the supercritical water-cooled solid breederblanket conceptual design, and actively embarked on fundamentalresearch in related technology applied in the concept. In fact, supercriticalwater-cooled blanket concept, which takes advantages of retainingengineering maturity and continuity of water cooling technique andpower generation experience (supercritical water-cooled fossil fuel powerplant, supercritical water-cooled fission reactors), and also, operating with a higher thermal efficiency, is considered as a rather good choice with thecomprehensive advantages for fusion reactor blanket.In this thesis, supercritical water-cooled solid breeder blanket isanalyzed in both thermal and hydraulic aspects, and relatedthermal-hydraulic design criteria for supercritical water-cooled solidbreeder blanket are preliminarily proposed. One of the important targetsof the SCW blanket steady-state thermal analysis of the supercriticalwater-cooled blanket (SCW blanket) is to favorablely cool the entireblanket system, providing a safe, reliable and economical heat transportsystem under static conditions. The first wall (FW) is a key part of theblanket, and in a sense, the integral safety of TBM depends on itsthermal-hydraulic aspect of safety performance. Therefore, in the thesis,steady-state thermal analysis is carried out for the FW structure of SCWsolid breeder blanket under rated condition. Firstly, a FW system model isestablished and various parameters of the system are determined undernormal operating conditions. Then, steady-state thermal analysis on thefirst wall under nominal operating condition is conducted using numericalcalculation software. The numerical study is performed and confirmedfollowing grid number and turbulence model selection based on gridsensitivity analysis and observations of turbulence model effect oncalculation results respectively. Sensitivity analysis for differentparametric effects on the temperature field and stress field within FWstructure is carried out through numerical simulation. Specificly,influences of the cooling pipe shapes, geometric parameters, and coolantflow direction on both temperature and stress distribution within the FWstructure as well as on heat transfer, are tentatively compared. All theseprovide basic thermal-stress coupled magnitude relationship for SCWsolid breeder blanket thermal design.Besides thermal and stress analysis, investigation of hydraulicswithin the SCW blanket are also presented in the thesis. Under pressureabove that of thermodynamic critical point, drastic changes of waterproperties as specific heat capacity, density, etc. are seen near thepseudo-critical point, and the blanket system might experience transitionsof flow instability due to the uneven volume variation of supercritical water. Therefore, instability study of coolant flow in the blanket systemseems very important. In this thesis, frequency domain analysis andMatlab programming are applied for flow instability in SCW blanketsystem.According to the structure of SCW solid breeder blanket coolingsystem, a geometric model is firstly constructed, and system parametersas well as nominal operating conditions are determined. Based right onthe geometric model, frequency domain analysis method is applied toinvestigate the coolant flow instability of SCW solid breeder blanket:starting off with the basic control equations of SCW coolant flow andheat transfer, corresponding characteristic equations are deduced throughLaplace Transformation and related eigen-roots are solved by numericalmethod. And flow instability feature of the system under certain operatingcondition is thus determined. Furtherly, related stability boundary andstability domain of the system flow under different inlet and exit localresistance conditions are dilievered.All the above work has provided beneficial reference for futureproposing of thermal design criteria and engineering design. And on thebasis of the present thermal hydraulic analysis, several thermal designcriteria for the supercritical water-cooled solid breeder blanket arepreliminarily proposed.