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The National Aeronautics and Space Administration is considering nuclear power sources for space exploration. A series of critical mass experiments was designed to address the development, performance, and design of a space nuclear reactor being considered to support the Prometheus project. These experiments consisted of interlacing the refractory...
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Context 1
... NRPCT furnished Los Alamos National Labo- ratory ~LANL! with solid and annular molybdenum, rhenium, and tantalum plates for the critical mass ex- periments. c The dimensional specifications for the Mo plates are provided in Table I. Figure 4 shows photo- graphs for the refractory plates including the Mo plate. The differences between the nominal and measured diameters are judged to be negligible. ...
Context 2
... Re critical experiment plates were fabricated by stitch welding together three ;8-22-0.015-in. Re plates using a laser welder. d These stitch-welded plates were then electric discharged machined to their final di- mensions. 3 The dimensional specifications for the Re plates are provided in Table I. A photograph of a Re plate is also provided in Fig. 4. The Re plates have been fab- ricated from two lots of high-purity Re powder material: R-1478 and R-1481. The nominal thickness for the Re plates is 0.0150-in. ~Refs. 8 and 9!. BAPL performed high-accuracy density measurements using remnant sam- ples from the Re plates and found the average Re density to be 21.001 g0cm 3 . The chemical ...
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Citations
The neutron capture cross section of [Formula: see text]Ta is relevant to s-process of nuclear astrophysics, extraterrestrial samples analysis in planetary geology and new generation nuclear energy system design. The [Formula: see text]Ta([Formula: see text]) cross section had been measured between 1 eV and 800 keV at the back-streaming white neutron facility (Back-n) of China spallation neutron source(CSNS) using the time-of-flight (TOF) technique and [Formula: see text] liquid scintillator detectors. The experimental results are compared with the data of several evaluated libraries and previous experiments in the resolved and unresolved resonance region. Resonance parameters are extracted using the R-Matrix code SAMMY in the 1-700 eV region. The astrophysical Maxwell average cross section(MACS) from kT = 5 to 100 keV is calculated over a sufficiently wide range of neutron energies. For the characteristic thermal energy of an astrophysical site, at kT = 30keV the MACS value of [Formula: see text]Ta is 834 ± 75 mb, which shows an obvious discrepancy with the Karlsruhe Astrophysical Database of Nucleosynthesis in Stars (KADoNiS) recommended value 766 ± 15 mb. The new measurements strongly constrain the MACS of [Formula: see text]Ta([Formula: see text]) reaction in the stellar s-process temperatures.
A new array of four Deuterated Benzene (C6D6) detectors has been installed at the Gaerttner Linear Accelerator Center at Rensselaer Polytechnic Institute for the purpose of measuring neutron capture cross sections in the keV region. Measurements were performed on samples of Ta181 in the unresolved resonance region (URR) using a filtered-beam technique, by which a 30 cm iron filter was placed in a white-spectrum neutron beam to remove all time-dependent γ-ray background and all neutrons except those transmitted through resonance-potential interference “windows” in the iron. The resulting filtered beam was effectively a quasimonoenergetic neutron source, which was used for performing measurements on isotopes with narrow level spacings in the URR. The capture cross-section results obtained for two thicknesses of tantalum are in agreement with those documented in the JEFF-3.2 library, as are the average resonance parameters obtained via a fit to the data using the sammy-fitacs code.
