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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.
Bojan G. Petrovic, Alireza Haghighat
Nuclear Science and Engineering | Volume 122 | Number 2 | February 1996 | Pages 167-193
Technical Paper | doi.org/10.13182/NSE96-3
Articles are hosted by Taylor and Francis Online.
An accurate prediction of the reactor pressure vessel (PV) fast neutron fluence (E> 1.0 MeV or E> 0.1 MeV) is necessary to ensure PV integrity over the design lifetime. The discrete ordinates method (SN method) is the method of choice to treat such problems, and the DORT SN code is widely used as a standard tool for PV fluence calculations. The SN numerics and the corresponding DORT numerical options and features offer alternative choices that increase flexibility but also impact results. The effects of SN numerics based on PV fluence calculations for two pressurized water reactors are examined. The differencing schemes [linear, zero-weighted (ZW), and θ-weighted (TW)] and their interactions with spatial and angular discretization are also examined. The linear and TW ( θ = 0.9) schemes introduce unphysical flux oscillations that for certain groups and positions may exceed 10%. The ZW scheme produces smooth results; however, its results differ from the other two schemes. A good compromise for PV fluence calculations is a TW scheme with a small θ value (i.e., θ = 0.3), which reduces the uncertainty to ∼3%. Angular discretization and spatial mesh size employed in typical calculations introduce another ∼3 and ∼2% uncertainty, respectively. The analysis further shows that the fixup is not necessary for the negative scattering source. The pointwise convergence criterion is also not a critical issue in the fast energy range because of a relatively fast convergence rate. Similarly, acceleration parameters impact mainly the execution time and only marginally the results. The root-mean-square combined uncertainty for standard PV fluence calculations due to the options analyzed is ∼5%.