Problem 7-1. The solid fuel pellet of a PWR reactor has an outer radius of 4.7 mm, while the inner and outer radii of th

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Problem 7 1 The Solid Fuel Pellet Of A Pwr Reactor Has An Outer Radius Of 4 7 Mm While The Inner And Outer Radii Of Th 1 (71.77 KiB) Viewed 35 times

Problem 7-1. The solid fuel pellet of a PWR reactor has an outer radius of 4.7 mm, while the inner and outer radii of the cladding are 4.89 mm and 5.46 mm, respectively. The active length of the fuel element is 3.80 m, while the extrapolation distance, e below and above the core is 10 cm. You can assume that the axial power profile has a cosine shape. The fuel pins are assembled in a rectangular lattice with a pin pitch of 14 mm. a) Determine the heat up of the coolant within an average subchannel having the parameters given below if the coolant enters the core with a temperature of 270°C and has a velocity of 3.8 m/s. Calculate the mass flow rate in the average subchannel using the flow area, the coolant velocity, and the coolant density. b) Calculate the centerline and outer surface temperatures (Tcl,f and The) of the fuel, and the inner and outer cladding surface temperatures (Tci and Too) at the center core height (z = 0 m), where the linear heat rate is '= 20 kW/m, while the coolant temperature is the average of the inlet and outlet temperatures. For the heat conductivity of the fuel, use the Lyon-formula (T is in K, while kş is obtained in W/(mK)): ki 3824 + 6.1256.10-11.13 129.4 +T You can also use the Lyon-table for the calculations. The heat conductivity of the cladding (ke) is 18.69 W/(mK), while the heat conductivity of the gas gap (kg) is 0.277 W/(mK). Let's calculate the heat transfer coefficient between the moderator and the outer cladding surface (hm) based on the Dittus-Boelter correlation: Nu = 0.023 · Re0.3. Pr0.4. The thermal properties of water (1.5 bar, 285°C) are the followings: dynamic viscosity (u): 94.24x10-6 kg (ms); heat conductivity (km): 0.588 W/(mK); density (p): 754.65 kg/mº; heat capacity (cp): 5164.69 J/(kgK). Check out the above data in Steam Tables, e.g., here. Do not forget that the kinematic viscosity is the ratio of the dynamic viscosity and the density.