Journal of Nuclear Science and Technology
Online ISSN : 1881-1248
Print ISSN : 0022-3131
Volume 16, Issue 2
Displaying 1-9 of 9 articles from this issue
  • S. BERGMAN, I. GUSTAVSSON
    1979 Volume 16 Issue 2 Pages 77-88
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    Spectral analysis as well as parametric identification techniques have been applied to data from boiling water reactor noise measurements to estimate the process dynamics. Three different parametric model structures were tried. Least squares and maximum likelihood methods were tried to estimate the parameters of the models. Low order models were obtained in most cases.
    The results show the difficulties to identify the dynamics and the static gain from normal operating data when strong feedback and correlation between the inputs exist.
    The results also show how sharp resonant peaks will be smoothed in long-time anal-ysis probably due to time-varying parameters. The resonance frequency in average power range monitor (APRM) and main circulation flow can be well predicted by rather simple models.
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  • Dick DUFFEY, W. L. BECK, G. I. GLEASON, P. F. WIGGINS
    1979 Volume 16 Issue 2 Pages 89-94
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    Photographic film was exposed to γ-rays from 226Ra and 60Co to levels of 5 mR to 5, 000 R. Measurements of the Ag in the developed films by both (a) activation with neutrons from 252Cf and counting 110Ag (half life 24.4 sec) and (b) X-ray fluorescence correlated with the known exposures. In the lower ranges conventional optical density measure-ments were made, and the correlation with the activation and X-ray methods was good.
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  • Kenji FUKUDA, Tetsuo KOBORI
    1979 Volume 16 Issue 2 Pages 95-108
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    An analysis shows that hydrodynamic instabilities of two-phase flow are classified into at least eight types. Three of them are roughly classified into the static or the Ledinegg instability, and other five of them into the dynamic or the density wave in-stability.
    Two typical types of instabilities are observed in our experiment, in each type dif-ferent pressure drop term : gravitational or frictional pressure drop of two-phase flow is found to be the governing term.
    Classification method of instabilities and its applications are presented.
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  • 1979 Volume 16 Issue 2 Pages 108
    Published: 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
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  • Hajime YAMAMOTO, Michio MURASE, Isao SUMIDA, Shigeru IZUMI, Norihiko S ...
    1979 Volume 16 Issue 2 Pages 109-116
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    In order to improve the measuring accuracy of plugging indicators, the relation be-tween the measured temperature and the impurity saturation temperature was investi-gated analytically for the oscillating plugging indicator. In the analysis, the differences between the true saturation temperature and the "plugging" or "unplugging" temperature were studied in view of the impurity precipitating mechanism.
    By this investigation, the difference of measured temperature from the saturation temperature can be evaluated by a function of the dimensionless numbers Re and St and the suitable operating conditions on which the measurement error becomes small are ob-tained.
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  • Kohtaro UEKI, P. N. STEVENS
    1979 Volume 16 Issue 2 Pages 117-131
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    The event value Wg (r, Ω) has been derived in a form which can be obtained directly from existing adjoint Monte Carlo computer codes. It is demonstrated that the event value and the point value functions obtained from the adjoint Monte Carlo calculation can be used as the path-length biasing and the angular biasing in the forward Monte Carlo calculation, respectively. The iterative forward-adjoint Monte Carlo method using the source biasings is employed to reduce the standard deviation in the shielding problem. In addition, the effectiveness of the source biasing schemes is investigated in the same problem. The results indicate a significant reduction in the standard deviation and a substantial improvement in the efficiency of the Monte Carlo shielding calculations.
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  • Molten Salt Extraction for Removing Hydrogen from Liquid Sodium
    Tadashi YANAGI, Thoru OHKUMA
    1979 Volume 16 Issue 2 Pages 132-136
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    Some fundamental studies for removing hydrogen from liquid sodium by a molten salt extraction were carried out. Alkali chloride eutectics LiCl-KCl and LiCl-KCl-NaCl (chlinak) were chosen because of their relatively low melting points, and the properties of these eutectics related to reactivities and mutual solubilities between the salts and liquid sodium were examined experimentally. From the comparison of the solubility of sodium in molten eutectics it was decided to employ chlinak for extracting hydrogen from sodium.
    The difference in hydrogen concentration in sodium before mixing of the two liquid phases and after equilibrium indicated that the molar distribution ratio of hydrogen be-tween molten chlinak and sodium was more than 10 at 400°C and decreased with increas-ing temperature.
    From these results, it was found that hydrogen was preferentially extracted into the molten salt phase, and deduced that molten salt extraction with molten chlinak was a feasible process for removing hydrogen from liquid sodium.
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  • Analysis of Cause of Cracks Found near Weld Joints Connecting Reactor Vessel Nozzle Safe-End to Pipe
    Yoshiaki FUTAMURA, Kinichi TORIKAI, Yutaka OGAWA
    1979 Volume 16 Issue 2 Pages 137-146
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
    Circumferential cracks detected in the JPDR (BWR) near welded joints connecting the nozzle safe-end to pipe (austenitic stainless steel) were studied in reference to the stresses applied in service, the conditions of welding, environment (O2 and Cl- concentra-tion, water flow, temperature etc.), metallurgical structure and operating records, to determine the cause of cracking. Fatigue tests were also undertaken with simulated welded pipe of size to examine possible contribution of fatigue to the cracking.
    The analysis indicated stress corrosion to be the principal cause of cracking, and that it had initiated in the heat-affected zone which had been sensitized by the excess heat input of welding. The factors contributing to the stress corrosion were the presence of oxygen in the fluid, which had at times attained a level exceeding 0.2 ppm, and which combined with stress, at times exceeding the yield strength. This had caused the cracks once initiated, to propagate along the grain boundary.
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  • Ichiro YAMAMOTO, Akira KANAGAWA
    1979 Volume 16 Issue 2 Pages 147-148
    Published: February 25, 1979
    Released on J-STAGE: April 18, 2008
    JOURNAL FREE ACCESS
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