Analysis of several VERA benchmark problems with the photon transport capability of STREAM

STREAM - a lattice transport calculation code with method of characteristics for the purpose of light water reactor analysis - has been developed by the Computational Reactor Physics and Experiment laboratory (CORE) of the Ulsan National Institute of Science and Technology (UNIST). Recently, efforts have been taken to develop a photon module in STREAM to assess photon heating and the influence of gamma photon transport on power distributions, as only neutron transport was considered in previous STREAM versions. A multi-group photon library is produced for STREAM based on the ENDF/B-VII.1 library with the use of the library-processing code NJOY. The developed photon solver for the computation of 2D and 3D distributions of photon flux and energy deposition is based on the method of characteristics like the neutron solver. The photon library and photon module produced and implemented for STREAM are verified on VERA pin and assembly problems by comparison with the Monte Carlo code MCS - also developed at UNIST. A short analysis of the impact of photon transport during depletion and thermal hydraulics feedback is presented for a 2D core also from the VERA benchmark. (C) 2022 Korean Nuclear Society, Published by Elsevier Korea LLC

Analysis of Nociceptive Information Encoded in the Temporal Discharge Patterns of Cutaneous C-Fibers

The generation of pain signals from primary afferent neurons is explained by a labeled-line code. However, this notion cannot apply in a simple way to cutaneous C-fibers, which carry signals from a variety of receptors that respond to various stimuli including agonist chemicals. To represent the discharge patterns of C-fibers according to different agonist chemicals, we have developed a quantitative approach using three consecutive spikes. By using this method, the generation of pain in response to chemical stimuli is shown to be dependent on the temporal aspect of the spike trains. Furthermore, under pathological conditions, gamma-aminobutyric acid resulted in pain behavior without change of spike number but with an altered discharge pattern. Our results suggest that information about the agonist chemicals may be encoded in specific temporal patterns of signals in C-fibers, and nociceptive sensation may be influenced by the extent of temporal summation originating from the temporal patterns.open0

The isotopic and chemical compositions of the CO2-rich waters in Korea

Se investigó la composición química e isotópica de agua rica en CO2 que se encuentra principalmente en terrenos graníticos de Korea. Las aguas ricas en CO2 pueden dividirse en tres tipos dependiendo de su composición química: Na-HCO3, Ca-Na-HCO3 y Ca-HCO3. La química del agua indica que estas aguas evolucionaron a través de una reacción fuerte con las rocas huesped por una entrada de CO2 profundo durante la circulación profunda. El proceso de disolución del plagioclase es importante en las interacciones agua/granito y su cambios de solubilidad con la temperatura de reacción juegan un rol importante en la determinación de la composición química. Los calculos de equilibrio multicomponente mineral/agua indican que el agua rica en CO2 alcanza temperuras de 115-140 °C. Los datos de ä18O y äD indican que las aguas ricas en CO2 provienen de agua meteorítica y tienen una composición isotópica más ligera que otras aguas naturales. El contenido de tritio muestra un tiempo de residencia largo y la posibilidad de un flujo de CO2 en un acuífero a mayor profundidad. También existe una fuerte indicación de mezcla durante su ascenso hacia la superficie entre el agua profunda rica en CO2 y agua fresca más reciente. Los análisis de isótopos de carbono muestran que la composición del carbomo está asociada con CO2 proveniente del manto. Los datos preliminares de las relaciones de isótopos de helio tambien indican que el CO2 se originó en el manto. Las relaciones de isótops de estroncio indican que la química del agua rica en CO2 está determinada por la reacción con el granito local. doi: https://doi.org/10.22201/igeof.00167169p.2002.41.4.50

In Situ Control of the Eluted Ni Nanoparticles from Highly Doped Perovskite for Effective Methane Dry Reforming

To design metal nanoparticles (NPs) on a perovskite surface, the exsolution method has been extensively used for efficient catalytic reactions. However, there are still the challenges of finding a combination and optimization for the NPs’ control. Thus, we report in situ control of the exsolved Ni NPs from perovskite to apply as a catalyst for dry reforming of methane (DRM). The La0.8Ce0.1Ti0.6Ni0.4O3 (LCTN) is designed by Ce doping to incorporate high amounts of Ni in the perovskite lattice and also facilitate the exsolution phenomenon. By control of the eluted Ni NPs through exsolution, the morphological properties of exsolved Ni NPs are observed to have a size range of 10~49 nm, while the reduction temperatures are changed. At the same time, the chemical structure of the eluted Ni NPs is also changed by an increased reduction temperature to a highly metallic Ni phase with an increased oxygen vacancy at the perovskite oxide surface. The optimized composite nanomaterial displays outstanding catalytic performance of 85.5% CH4 conversion to produce H2 with a value of 15.5 × 1011 mol/s·gcat at 60.2% CO conversion, which shows the importance of the control of the exsolution mechanism for catalytic applications

Verification of Graphite Isotope Ratio Method Combined With Polynomial Regression for the Estimation of Cumulative Plutonium Production in a Graphite-Moderated Reactor

Graphite Isotope Ratio Method (GIRM) can be used to estimate plutonium production in a graphite-moderated reactor. This study presents verification results for the GIRM combined with a 3-D polynomial regression function to estimate cumulative plutonium production in a graphite-moderated reactor. Using the 3-D Monte-Carlo method, verification was done by comparing the cumulative plutonium production with the GIRM. The GIRM can estimate plutonium production for specific sampling points using a function that is based on an isotope ratio of impurity elements. In this study, the 10B/11B isotope ratio was chosen and calculated for sampling points. Then, 3-D polynomial regression was used to derive a function that represents a whole core cumulative plutonium production map. To verify the accuracy of the GIRM with polynomial regression, the reference value of plutonium production was calculated using a Monte-Carlo code, MCS, up to 4250 days of depletion. Moreover, the amount of plutonium produced in certain axial layers and fuel pins at 1250, 2250, and 3250 days of depletion was obtained and used for additional verification. As a result, the difference in the total cumulative plutonium production based on the MCS and GIRM results was found below 3.1% with regard to the root mean square (RMS) error