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WIPP’s SSCVS: A breath of fresh air
This spring, the Department of Energy’s Office of Environmental Management announced that it had achieved a major milestone by completing commissioning of the Safety Significant Confinement Ventilation System (SSCVS) facility—a new, state-of-the-art, large-scale ventilation system at the Waste Isolation Pilot Plant, the DOE’s geologic repository for defense-related transuranic (TRU) waste in New Mexico.
A. Tsechanski, M. Segev, G. Shani
Nuclear Science and Engineering | Volume 84 | Number 3 | July 1983 | Pages 226-233
Technical Paper | doi.org/10.13182/NSE83-A17791
Articles are hosted by Taylor and Francis Online.
Integral experiments with a large graphite stack and fast neutron spectra calculations are described. A well-collimated beam of (14.75 ± 0.05) MeV (D,T) neutrons from a generator incident on the graphite resulted in a neutron spectrum that strongly correlated with the fine structure of the carbon nuclei, including anisotropy of elastic and inelastic scattering to first levels. This experimental approach is easier and more straightforward from the calculational point of view than one with a neutron source inside of a stack. The neutron spectrum measurement was performed by an NE-213 liquid scintillator using a pulse-shape discrimination technique to reject gamma-ray counts. The unfolding of the proton recoil spectrum was done by the FORIST code. The calculations were performed using the DOT 3.5 two-dimensional discrete ordinates neutron transport code incorporating the ENDF/B-IV cross-section library with the ETOG III group cross-section generating code. Comparison between measured and calculated spectra showed a reasonable agreement in the 1- to 8-MeV energy range. On the other hand, great discrepancies (up to an order of magnitude) are revealed in the range from 8 to 10.5 MeV. It was found that these discrepancies are due to the fact that the ETOG III program does not take into consideration the angle/energy correlation in inelastic scattering. Including the angle/energy correlation in inelastic scattering drastically improved the agreement between measurements and calculations in the inelastic scattering range to the first level of the carbon. The calculated spectrum in the 7- to 10.5-MeV range, i.e., in the inelastic scattering range, was found to be very sensitive to the anisotropy distribution of inelastic scattering to the first level. Therefore, these kinds of integral experiments (with a monoenergetic collimated neutron beam introduced from outside) supply direct data on the anisotropy of both inelastic and elastic scattering.
