Evaluation on the heat removal capacity of the first wall for water cooled breeder blanket of CFETR

• Heat removal capacity of the FW is evaluated under BWR, PWR and He coolant inlet conditions.
• Heat transfer property of the gas–liquid two phase and the two boiling crises are analyzed.
• Heat removal capacity of water is larger than helium coolant.

The water cooled ceramic breeder blanket (WCCB) is being researched for Chinese Fusion Engineering Test Reactor (CFETR). As an important component of the blanket, the FW should satisfy with the thermal requirements in any case. In this paper, three parameters including the heat removal capacity, coolant pressure drop as well as the temperature rise of the FW were investigated under different coolant velocity and heat flux from the plasma. Using the same first wall structure, two main water cooled schemes including Boiling Water Reactor (BWR, 7 MPa pressure and 265 °C temperature inlet) and Pressurized Water Reactor (PWR, 15 MPa pressure and 285 °C temperature inlet) conditions are discussed in the thermal hydraulic calculation. For further research, the thermal hydraulic characteristics of using helium as coolant (8 MPa pressure, 300 °C temperature inlet) are also explored to provide CFETR blanket design with more useful data supports. Without regard to the outlet coolant condition requirements of the blanket, the results indicate that the ultimate heat flux that the FW can resist is 2.2 MW/m2 at velocity of 5 m/s for BWR, 2.0 MW/m2 at velocity of 5 m/s for PWR and 0.87 MW/m2 for helium at velocity 100 m/s under the chosen operation condition. The detrimental departure from nucleate boiling (DNB) crisis would occur at the velocity of 1 m/s under the heat flux of 3 MW/m2 and dry out crisis appears at the velocity of less than 0.2 m/s with the heat flux of more than 1 MW/m2 for BWR. The further blanket/FW optimization design is provided with more useful data references according to the abundant calculation results.