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Unformatted text preview: the water moderator/coolant. .have a large number of control rods to adjust the reactivity over a wide range. 16. A thermal nuclear rocket using hydrogen as the propulsive gas operates for one hour at a thermal power of 4000 MW and a temperature of 2700 K. Estimate (a) the amount (in grams) of fissile material consumed, (b) the specific impulse of the engine. Solution: (a) The fission energy released is Eth = Pth x ~t = 4000 (MW) x (1/24) (d) = 166.7 MWd. Since 1 MWd of fission energy requires the consumption of 1.24 g of 235U (see p 150), the mass of 235U consumed by the rocket is M(235U) = Eth X 1.24 g/MWd = 206.7 g 235U consumed. (b) At an exhaust temperature of 2700 K, the hydrogen is in the form of a diatomic molecule H2. The mass of an exhaust hydrogen molecule is Me = 2 x M(lH) = 2(1.0078 u)(1.661 X 10-27 kgfu) = 3.347 X 10-27 kg. From page 342, the specific impulse is Isp =v~ = ~ = 5326 m/s = 5.3 km/s. July 24, 2002...
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- Spring '06