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Abstract: A series of critical experiments containing PWR-type MOX fuels conducted at the TCA facility of Japan Atomic Energy Research Institute have been analyzed. The cores were composed of a central 4.91wt% plutonium enriched mixed-oxide (PuO2–UO2) 10×10 test lattice with water-to-fuel volume ratio of 2.40 or 2.96, surrounded by 2.6wt% enriched UO2 driver lattice with water-to-fuel volume ratio of 1.50 with a water gap in-between. The fissile plutonium content was 91.4wt%. The critical water level, the power distribution in the test region, and the neutron activation distribution of Au-wire were measured for six different cores of which two contain soluble boron of 309.4 and 554.0ppm, one contains four equidistant water holes in the central test lattice and one contains cross water gap at the core center. Calculation of corresponding effective multiplication factor, the fission reaction-rate distribution in the test region, and the capture reaction-rate distribution of Au have been performed using a continuous-energy Monte Carlo code MVP with two nuclear data sets based on JENDL-3.2 and JENDL-3.3. The calculated results agreed to the measurements within a maximum difference of 0.27% for the effective multiplication factors, 3.0% for the power distributions, 5.9% for the thermal activation distributions throughout the whole region, and 4.3% for the epithermal activation distributions in the core region. [Copyright &y& Elsevier]

Alkali–metal (K and Cs) promotion for sticking of nitrogen oxide molecule (NO) on Si(100) has been studied using a molecular beam method combined with an Auger electron spectroscopy (AES) and a laser ionization spectroscopy [resonance enhanced multiphoton ionization (REMPI)]. The observed sticking probability S shows a good correlation with alkali coverage, indicating that the alkali promotion is local in nature. The decay of S as a function of NO dose as observed with AES shows an anticorrelation with the evolution of the direct-inelastic scattering intensity as obtained with REMPI. This fact is understood as follows: since the direct-inelastic scattering occurs mostly in a single collision process with the surface, local alkali promotion is realized in a single collision of the incident NO molecule with the alkali–metal adsorbates. The decay of S as a function of NO dose is then analyzed with a reaction cross section. The evaluated reaction cross sections are close to the area of the 2×1 unit cell, and thus the estimated reaction radii are almost equal to but somewhat larger than the covalent radius of a K atom, with a increasing trend with alkali coverage. The alkali promotion is explained in terms of local electron charge transfer from the nonionized alkali adatoms to the affinity level of NO molecules based on the adatom density of state around EF. [ABSTRACT FROM AUTHOR]