Atomistic Dynamics of the Richtmyer-Meshkov Instability in Cylindrical and Planar Geometries

We apply molecular dynamics (MD) simulations to study the evolution of the shock-driven Richtmyer-Meshkov instability (RMI) in the cylindrical and planar geometries. Compared to traditional hydrodynamic simulations, MD has a number of fundamental advantages: it accounts for strong gradients of the pressure and temperature, and captures accurately the heat and mass transfers at the early stage (shock passage) as well as the late stage (perturbation growth) of the instability evolution. MD has no hydrodynamic limitations for spatial resolution and thermodynamic quasi-equilibrium at atomic scale. We study the instability evolution for different perturbation modes and analyze the role of the vorticity production for RMI dynamics

Specific-heat study for ferromagnetic and antiferromagnetic phases in SrRu_{1-x}Mn_xO3

Low-temperature electronic states in SrRu_{1-x}Mn_xO_3 for x <= 0.6 have been investigated by means of specific-heat C_p measurements. We have found that a jump anomaly observed in C_p at the ferromagnetic (FM) transition temperature for SrRuO_3 changes into a broad peak by only 5% substitution of Mn for Ru. With further doping Mn, the low-temperature electronic specific-heat coefficient gamma is markedly reduced from the value at x=0 (33 mJ/K^2 mol), in connection with the suppression of the FM phase as well as the enhancement of the resistivity. For x >= 0.4, gamma approaches to ~ 5 mJ/K^2 mol or less, where the antiferromagnetic order with an insulating feature in resistivity is generated. We suggest from these results that both disorder and reconstruction of the electronic states induced by doping Mn are coupled with the magnetic ground states and transport properties.Comment: 4 pages, 2 figures, submitted to the proceedings of ICM2009 (Karlsruhe

<Advanced Energy Conversion Division> Nano Optical Science Research Section

3-1. Research Activities in 202

Design Study of Full Scale Accelerator Driven System (ADS), for Transmuting High Level Waste of MA/Pu

The ADS system used in this study consisting of a high intensity proton linear accelerator, a spallation target, and a sub-critical reactor core. The Pb-Bi spallation target is bombarded by high intensity protons coming from the accelerator. The fast neutrons generated from the spallation reaction were used to drive the sub-critical reactor core. In this ADS system, the neutron source is in the center of reactor core region, so that the neutron distribution was concentrated in the center of core region. In this case, the B/T of MA/Pu could be performed effectively in the center of core region. The neutron energy in the outer region of reactor core was decreased due to the moderation of fuel and coolant materials. Such condition gives a chance to perform Burning and/or Transmutation of LLFPs.The basic parameters of this system are shown in the form of neutronic design, neutron spectrum and B/T rate, including other aspects related to the safety operation system. Furthermore, the analysis of the ADS system was accomplished using ATRAS computer code of the Japan Atomic Energy Research Institute, JAERI[1]. Due to the complexity of the reactor calculation codes, the author has carried out only those calculations needed for analyzing the neutronics system and some parameters related to the safety system. Design study of the transmutation system was a full-scale power level system of 657.53 MWt sub-critical reactor for an accelerator-driven transmutation system. The liquid Pb-Bi was used together as the spallation target materials and coolant of the system, because of some advantages of Pb-Bi in the system concerning the comparison with the sodium coolant. Moreover, they have a possibility to achieve a hard neutron energy spectrum, avoid a positive void reactivity coefficient, allow much lower system operating temperatures, and are favorable for safety in the event of coolant leakage. The multiplication factor of sub-critical core design was adjusted exclusively through the high intensity protons beam accelerator at the spallation target. The fuel was assumed to have homogeneous compositions in the form of (MA-Pu) ZrN mixture with 15N enriched. The compositions of Pu and MA were the same with the compositions of UO2 fuel from 33-GWd/t burn-up in PWRs spent fuel after 5 year cooling. The results have been compared with the spent fuel composition from 45 and 60 GWd/t burn-up in PWRs at the same cooling time. The calculation of the burn-up step was 730 days per one batch reloading by using 4-regions core calculation model. The specific parameters of ADS system used in the calculation are described in Table1

Accelerator-Driven System Analysis by Using Different Nuclear Data Libraries

An accelerator-driven system (ADS) has been investigated to transmute minor actinide (MA) included in high-level waste. In the neutronic design of the ADS, the accuracy of nuclear data for MA and lead bismuth (LBE) which is the candidate material for coolant and spallation target, is important. To know the current accuracy of nuclear data libraries, this study aims to compare representative nuclear data libraries, JENDL-4.0, 3.3, ENDF/B-VII.1 and VII.0 through the neutronic calculation of the ADS geometry proposed as the IAEA benchmark problem. The calculation results showed that about 1.1%dk, 0.7%dk and 2.7%dk differences were observed between JENDL-4.0 and ENDF/B-VII.1, ENDF/B-VII.0 and JENDL-3.3 at the beginning of cycle, respectively. These results mean that the current nuclear data libraries are still insufficient for the neutronic design of the ADS. The enhancement of nuclear data libraries by cross section measurement is required and, moreover, integral experiments with MA and LBE isotopes are essential. Received: 29 June 2012; Revised: 22 August 2012; Accepted: 30 August 201

Design Study of Full Scale Accelerator Driven System (ADS), for Transmuting High Level Waste of MA/Pu

The ADS system used in this study consisting of a high intensity proton linear accelerator, a spallation target, and a sub-critical reactor core. The Pb-Bi spallation target is bombarded by high intensity protons coming from the accelerator. The fast neutrons generated from the spallation reaction were used to drive the sub-critical reactor core. In this ADS system, the neutron source is in the center of reactor core region, so that the neutron distribution was concentrated in the center of core region. In this case, the B/T of MA/Pu could be performed effectively in the center of core region. The neutron energy in the outer region of reactor core was decreased due to the moderation of fuel and coolant materials. Such condition gives a chance to perform Burning and/or Transmutation of LLFPs.The basic parameters of this system are shown in the form of neutronic design, neutron spectrum and B/T rate, including other aspects related to the safety operation system. Furthermore, the analysis of the ADS system was accomplished using ATRAS computer code of the Japan Atomic Energy Research Institute, JAERI[1]. Due to the complexity of the reactor calculation codes, the author has carried out only those calculations needed for analyzing the neutronics system and some parameters related to the safety system. Design study of the transmutation system was a full-scale power level system of 657.53 MWt sub-critical reactor for an accelerator-driven transmutation system. The liquid Pb-Bi was used together as the spallation target materials and coolant of the system, because of some advantages of Pb-Bi in the system concerning the comparison with the sodium coolant. Moreover, they have a possibility to achieve a hard neutron energy spectrum, avoid a positive void reactivity coefficient, allow much lower system operating temperatures, and are favorable for safety in the event of coolant leakage. The multiplication factor of sub-critical core design was adjusted exclusively through the high intensity protons beam accelerator at the spallation target. The fuel was assumed to have homogeneous compositions in the form of (MA-Pu) ZrN mixture with 15N enriched. The compositions of Pu and MA were the same with the compositions of UO2 fuel from 33-GWd/t burn-up in PWRs spent fuel after 5 year cooling. The results have been compared with the spent fuel composition from 45 and 60 GWd/t burn-up in PWRs at the same cooling time. The calculation of the burn-up step was 730 days per one batch reloading by using 4-regions core calculation model. The specific parameters of ADS system used in the calculation are described in Table1