Fuel power density

Fuel material Natural UO2 Fuel inventory (tons of heavy metal) 531 of U Average core power density (kW/litre) 12.8 kW/L Average fuel power density (kW/kgU) 25.4 kW/kgU Maximum linear power (W/m). 54 kW/m of fiiel rod Average discharge bumup (MWd/t) 6167 MWd/t of U Initial enrichment (wt%) 0.711 wt%... 

Cladding of fuel elements (under continuous integrity control) at low fuel power density. 

Fuel inventory (tones of heavy metal) - 32 Average core power density (kW/liter) - 38.5 Average fuel power density (kW/kgU)... 

Average fuel power density - the amount of energy produced by a specific mass of fuel. It can be calculated as a quotient of the thermal reactor power and the total fuel weight. Data providers should enter the actual value in kW/kgU. 

The heat transfer coefficients for liquids are considerably better than those for gases. Figure 4 shows the temperature profile from the coolant at 1000°C to the center of the fuel compact for molten salt coolant at two different fuel power densities as well as a profile for helium. The temperature increase at the surface of the coolant channel is less for the liquid coolant consequently, the fuel in the AHTR operates at lower temperatures for the same coolant exit temperatures as in a comparable gas-cooled reactor. Also shown is the temperature jump from the graphite matrix to the fuel compact. 

The preconceptual AHTR designs have assumed fuel power densities (8.3 watts/em ) similar to those of traditional helium-cooled reactors. However, the heat transfer capabilities of the molten salt coolant are superior to those of helium. As a consequence, the peak fuel temperatures during normal operation are 100 to 200 C lower than for a comparable gas-cooled reactor. Economic incentives to reduce the reactor core size and thus lower plant capital cost and refueling times are substantial. As such, there are strong economic incentives to increase fuel power densities, which will, in turn, increase the thermal gradient between the centerline fuel temperature and the coolant channel. 

Core average power density (structures and fluids) 13.38 MW/m Core maximum fuel power density (fuel pellet) 70.83 MW/m ... 

Fuel type/ Case cladding number material Fuel power density (maximum) (MW/m ) Core power density (MW/m3) Mass flow per channel (kg/sec) Coolant oudet temperature (K) Cladding surface temperature (K) Maximum fuel temperature (K) Reactor power (MW) Equivalent core diameter (m) Elevation between heat exchanger and core (m)... 

The core power density would be 22.5 MW/m, the coolant outlet temperature would be 393 K, and the maximum fuel temperature would be 474 K (assuming a 2.4 peak-to-average fuel power density ratio). The core flow velocity associated with the 0.0448 kg/s-per-fuel rod mass flow rate is 0.539 m/s. 

Case 2 evaluated the increased fuel centerline temperature that would result if aluminum cladding is replaced with stainless steel. The results indicate that using stainless steel cladding will only cause the fuel centerline temperature to increase by 10 K above that obtained with aluminum cladding. Thus, at these low fuel power densities it makes little difference from a thermal-hydraulic viewpoint what cladding material is used for the fuel pin. 

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