> Diversion of nuclear materials frcm fission reactors for use as weapons. • Perceived inadvertent acute exposure of a large population to SPS microwave radiation. • Crash of an SPS heavy-lift launch vehicle or a low earth orbit vehicle into an urban area. Environmental Welfare Effects Effects not related to health and safety are classified here as environmental welfare effects, e.g., weather modification by carbon dioxide (CO2)t materials degradation, electromagnetic interference with communications, ' aesthetics, and noise. In the side-by-side comparison, only qualitative evaluations of the effects were made. For some issues, definitive work has been done, e.g., SPS electromagnetic interference. Although the C02 problem is much discussed, there is certainly no consensus on the risks involved. Resources Resource comparisons in this assessment were limited to net energy, materials, and land. The net energy analysis showed that all the technologies are net energy producers if the thermal fuel value of non-renewable fuels is not considered. The SPS and TPV become more efficient producers as the energy efficiency of all production improves (e.g., SPS could go frcm a 6-year to a 1.5 year payback period for a silicon system). An SPS system utilizing gallium aluminum arsenide was compared to the silicon system and looks premising, but very little information is available to support this ccmparison. Each technology (with the exception of the LMFBR) has material requirements that could be considered critical because of environmental control requirements or limited production capability. Hcwever, none of these materials appears to be limiting, but a thorough materials assessment based on materials demand and supply, including world demand forecasting, has not been done for all technologies. Water use by the SPS and TPV is minimal in ccmparison to that by coal and nuclear systems. Even coal and nuclear systems do not have overall water limitations, but siting is constrained by the availability of water. Land use was compared on the basis of quantity, duration, and location, and the comparisons were broken down by the different phases of the fuel cycle. The total amount of land required for the complete fuel cycle is roughly the same for all technologies (for SPS and TPV, a little larger) . However, the SPS and TPV require large blocks of continuous land and may involve additional long distance transmission because of remote siting, which could cause additional difficulties*. * However, societal assessment studies to be reported at this program review may show little necessity for SPS transmission lines over 300 Km.
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