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Commercial nuclear innovation "new space" age
In early 2006, a start-up company launched a small rocket from a tiny island in the Pacific. It exploded, showering the island with debris. A year later, a second launch attempt sent a rocket to space but failed to make orbit, burning up in the atmosphere. Another year brought a third attempt—and a third failure. The following month, in September 2008, the company used the last of its funds to launch a fourth rocket. It reached orbit, making history as the first privately funded liquid-fueled rocket to do so.
Donald Bogart
Nuclear Science and Engineering | Volume 123 | Number 2 | June 1996 | Pages 228-237
Technical Paper | doi.org/10.13182/NSE96-A24185
Articles are hosted by Taylor and Francis Online.
Although resonance neutron captures for 238U in water-moderated lattices are known to occur near moderator-fuel interfaces, the sharply attenuated spatial captures here have not been calculated by multigroup transport or Monte Carlo methods. Advances in computer speed and capacity have restored interest in applying Monte Carlo methods to evaluate spatial resonance captures in fueled lattices. Recently published studies have placed complete reliance on the ostensible precision of the Monte Carlo approach without auxiliary confirmation that resonance processes were followed adequately or that the Monte Carlo method was applied appropriately. Other methods of analysis that have evolved from early resonance integral theory have provided a basis for an alternative approach to determine radial resonance captures in fuel rods. A generalized method has been formulated and confirmed by comparison with published experiments of high spatial resolution for radial resonance captures in metallic uranium rods. The same analytical method has been applied to uranium-oxide fuels. The generalized method defined a spatial effective resonance cross section that is a continuous function of distance from the moderator-fuel interface and enables direct calculation of precise radial resonance capture distributions in fuel rods. This generalized method is used as a reference for comparison with two recent independent studies that have employed different Monte Carlo codes and cross-section libraries. The Monte Carlo studies have been found to undercount reference radial resonance captures in the moderator-fuel interface region. The steep radial capture gradients within 0.50 mm of the interface account for the majority of resonance captures and take place where Monte Carlo spatial resolution is poor and the effects of resonance peaks on neutron flux are large. Inconsistencies in the Monte Carlo application or in howpointwise cross-section libraries are sampled may exist. It is shown that refined Monte Carlo solutions with improved spatial resolution would not asymptotically approach the reference spatial capture distributions. It is suspected that the resolved resonance peak and off peak cross sections may not be represented or accounted for appropriately in the Monte Carlo calculations and should be reviewed. If these inconsistencies were cleared up, use of the generalized method might very well challenge the need to perform further Monte Carlo studies of radial resonance captures for isolated uranium-oxide fuel rods.
