Journal of Nuclear Science and Technology
Online ISSN : 1881-1248
Print ISSN : 0022-3131
Volume 22, Issue 7
Displaying 1-9 of 9 articles from this issue
  • Criticality and Burnable-Poison Effect
    Seiji SHIROYA, Masatoshi HAYASHI, Keiji KANDA, Toshikazu SHIBATA
    1985 Volume 22 Issue 7 Pages 507-520
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    The critical experiments using medium-enriched-uranium (MEU) fuel in the Kyoto University Critical Assembly (KUCA), a light-water-moderated and heavy-water-reflected cylindrical core, were started in May 1981, as a part of the international Reduced Enrichment for Research and Test Reactors (RERTR) program.
    The following KUCA critical experiments were analyzed : (1) the criticality measurements for high-enriched-uranium (HEU) and MEU cores and (2) the reactivity effect measurements of boron burnable-poison (BP) for MEU cores. Five-group constants were generated using the EPRI-CELL code, and two-dimensional diffusion calculations were performed using a conventional finite-difference code DIF3D(2D), and a finite-element code 2D-FEM-KUR. Some of the results from the two diffusion codes were compared with each other. Advan-tage was taken of the finite-element method for the application of the 2D-FEM-KUR code to a detailed analysis of the BP effect measurements.
    Differences between the results of calculations and experiments were less than 1.8% in C/E ratios for eigenvalues. The agreement between the results obtained using the DIF3D(2D) code and the 2D-FEM-KUR code was excellent. The calculated results of the BP effects with use of the 2D-FEM-KUR code approximately agreed with the experiments.
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  • Daijiro TANAKA
    1985 Volume 22 Issue 7 Pages 521-528
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    A theoretical study based on time-dependent quasi-one-dimensional approximation has been carried out to estimate the interaction between combustor noise and working gas oscillations in a magnetohydrodynamic (MHD) generator, and also to gain information on the behavior of shock waves induced by fault affecting some of the DC-AC inverters. The MHD generator considered here is an open-cycle Faraday-type 25 MW-class generator fueled with heavy oil.
    The results of calculation indicate that relatively high frequency components of combustor noise (say above 10 kHz) would be conveniently attenuated through the MHD channel, but that low-frequency components would be transmitted along the channel, and this would, in turn, produce standing pressure waves of a frequency of around 2 kHz.
    Short-circuiting of a batch of inverters proves to induce a rapidly amplifying pressure wave, accompanied by a significant depression of gas velocity. The pressure wave and velocity depression fronts propagate upstream through the flowing gas at sonic velocity relative to the gas.
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  • Kimihiro IOKI, Masana NISHIKAWA, Ikuji TATSUMI, Takashi UCHIKAWA, Mako ...
    1985 Volume 22 Issue 7 Pages 529-537
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    A simple graphite limiter has been designed for high heat load in a tokamak device. The thermal contact conductance αc was measured as the function of contacting pressure p, because αc, is an important parameter for the graphite limiter design. Both experiments on small samples and full scale limiter assembly provided consistent data of αc=0.1 W/cm2•°C at p=1 kgf/cm2 (0.1 MPa). This value is considered to be sufficiently large from the viewpoint of the limiter thermal design.
    Heat load test was performed on the simple graphite limiter by using electron beam. Two kinds of materials employed in the test were POCO graphite and SIC-6 graphite which has thermal expansion coefficient similar to that of SiC. The test results showed that both graphite materials had enough thermal shock resistance to the heat load q=500 W/cm2, t=320 s, and SiC coating on SIC-6 graphite had better behavior against thermal shock, comparing with TiC coating on POCO graphite.
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  • Hajime AKIMOTO, Tadashi IGUCHI, Yoshio MURAO
    1985 Volume 22 Issue 7 Pages 538-550
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    In the reactor safety assessment during reflood phase of a PWR-LOCA, it is assumed implicitly that the core thermal hydraulic behavior is evaluated by the one-dimensional model with an average power rod. In order to assess the applicability of the one-dimensional treatment, integral tests were performed with various core radial power profiles using the Cylindrical Core Test Facility (CCTF) whose core includes about 2, 000 heater rods. The CCTF results confirm that the core radial power profile has weak effect on the thermal hydraulic behavior in the primary system except core. It is also confirmed that the core differential pressure in the axial direction is predicted by the one-dimensional core model with an average power rod even in the case with a steep radial power profile in the core. Even though the core heat transfer coefficient is dependent on the core radial power profile, it is found that the error of the peak clad surface temperature calculation is less than 15 K using the one-dimensional model in the CCTF tests. The CCTF results support the one-dimensional treatment assumed in the reactor safety assessment.
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  • Yukio SUDO, Hiroei ANDO, Hiromasa IKAWA, Nobuaki OHNISHI
    1985 Volume 22 Issue 7 Pages 551-564
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    This paper presents the outline of the core thermohydraulic design and analysis of the research reactor JRR-3, which is to be upgraded to a 20 MWt pool-type, light water-cooled reactor with 20% low enriched uranium (LEU) plate-type fuel. For the condition of normal operation, the upgraded JRR-3 core is planned to be cooled by two cooling modes of forced-convection at high power and natural-convection at low power. The major feature of core thermohydraulics is that at the forced-convection cooling mode the core flow is a downflow, under which fuel plates are exposed to a severer condition than an upflow in cases of operational transients and accidents. The core thermohydraulic design was, therefore, done for the condition of normal operation so that fuel plates may have enough safety margins both against the onset of nucleate boiling (ONB) not to allow the nucleate boiling anywhere in the core and against the departure from nucleate boiling (DNB). The safety margins against ONB and DNB were evaluated. The core velocity thus designed is at the optimum condition where fuel plates have the maximum margin against the ONB, and the minimum DNB ratio (ratio of DNB heat flux to the maximum heat flux) was evaluated to be about 2.1, which gives a sufficient margin against the DNB. The core thermohydraulic characteristics were also clarified for the natural-convection cooling mode.
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  • Masafumi ITAGAKI
    1985 Volume 22 Issue 7 Pages 565-583
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    The Boundary element method (BEM) has been applied to two-dimensional neutron diffusion problems. The boundary integral equation and its discretized form have been derived. Some numerical techniques have been developed, which can be applied to critical and fixed-source problems including multi-region ones. Two types of test programs have been developed according to whether the 'zero-determinant search' or the 'source iteration' technique is adopted for criticality search. Both programs require only the fluxes and currents on boundaries as the unknown variables. The former allows a reduction in computing time and memory in comparison with the finite element method (FEM). The latter is not always efficient in terms of computing time due to the domain integral related to the inhomogeneous source term; however, this domain integral can be replaced by the equivalent boundary integral for a region with a non-multiplying medium or with a uniform source, resulting in a significant reduction in computing time.
    The BEM, as well as the FEM, is well suited for solving irregular geometrical problems for which the finite difference method (FDM) is unsuited. The BEM also solves problems with infinite domains, which cannot be solved by the ordinary FEM and FDM. Some simple test calculations are made to compare the BEM with the FEM and FDM, and discussions are made concerning the relative merits of the BEM and problems requiring future solution.
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  • Masaki OZAWA, Shozo YASU, Osamu YAMAMURA, Kozo GONDA
    1985 Volume 22 Issue 7 Pages 584-586
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
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  • Katsumi UNE
    1985 Volume 22 Issue 7 Pages 586-588
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
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  • Yoichiro SHIMAZU
    1985 Volume 22 Issue 7 Pages 589-590
    Published: July 25, 1985
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
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