equipment, of 2000 kg for a 100-150000 kg/annum facility. No estimates were available for beneficiation, but some kind of mechanical separation using shaking tables and/or magnetic or electrostatic separation was felt to be feasible. An estimate of 2000 kg for the beneficiation plant was made. This is believed to be conservative, as a scaled estimate from ilmenite processing [1] was only 704 kg. Furthermore a large scale power plant and radiator will be associated with a lunar oxygen plant which has a very large beneficiation facility. The incremental cost to produce the required fractions for a lunar radiator could be small or zero. The pipe radiator can take advantage of the good emissivity of the lunar soil by radiating to it from the underside of the pipe. A separation of 2-3 times the pipe diameter was believed to be optimal. The optimal diameter was 1-1.5 in. (2.5-4 cm). Selecting 1.5 in. (4 cm) allowed standardization with the condensate return lines. The wider separation for larger pipe gives easier access for pipe assembly, but increases the condensate return line water inventory. The problem of micrometeorites was considered and a double tube design was evaluated and compared to a single tube or flat plate. The manufacturing problems of a double tube are considerable and clear silica glass needed for the outer tube is not readily available because of iron contamination. Furthermore, the major advantages of a double tube are a reduction in weight—which is not particularly relevant for lunar derived construction materials. A thicker reinforced single tube design with automatic leak detection and section isolation capability may be preferable. Water inventory was calculated for various layouts and the final choice for the flat plate panels was four separate radiators of 6000 m2 each. Each radiator consisted of four panels of 300 m X 5 m with the collection gutter centrally located. Loss of one of the four sections would mean raising the radiating temperature to 330 K. Loss of one panel would mean an increase to 313 K. The panels are somewhat larger for the pipes because of the pipe separation and consequent reduction in W/m2 of panel. For a separation of 2 pipe diameters (3 in.) there would be 8740 pipes in 666 m. For 3 pipe diameters it would be 7288 pipes and 833 m. If the dimensions were broader rather than longer the water inventory in the radiator would increase while that in the condensate line would be reduced. The slope of the radiators to the central gutter could be increased from its current 5° thus reducing inventory but this would mean increasing the tube length to compensate for the loss in radiating area. The steam header lines are 12 in. (30 cm) diameter to minimize pressure drop as are the isolation valves. The condensate return lines are only 1| in. diameter and operate at 20 GPM. This yields a 12 psi pressure drop for the 400 m transfer. This corresponds to 152 ft or 50 m of head in th gravity. Gravity flow is easily possible for 2 in. diameter pipe where the head requirement is only 21 ft or 7 m. It is suggested that the reactor be located where gravity feed is possible. Gravity flow is desirable for ease of operation and reliability. The ability to completely drain a radiator by gravity would also protect against freezing in a shut down condition. Radiation protection afforded by a lava tube roof would also enable the radiators to be located closer to the reactor thus cutting water inventory should the reactor be located in a lava tube or other roofed structure. Freezing is always a concern when using water as a heat transfer medium, but many remedies are available. The simplest is insulation and the condensate return pipes would be well insulated by their covering of lunar soil. A second solution is to keep the water moving as moving water freezes at a lower temperature. This requires avoiding dead legs in the detailed design. A third solution is to completely drain the
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