Journal of Nuclear Science and Technology
Online ISSN : 1881-1248
Print ISSN : 0022-3131
21 巻, 3 号
選択された号の論文の8件中1~8を表示しています
  • Hiroshi MIZUTA, Munenari YAMAMOTO
    1984 年 21 巻 3 号 p. 161-171
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
    An improvement of the IR (Intermediate Resonance) approximation is proposed. The effective resonance integrals of the infinite cylindrical fuel lattices are calculated by the analytical method, efficiently and with reasonably good accuracy. The fuel escape probability Pf (E) is based on the two-term rational approximation with an accurate Bell factor ?? The IR parameters λ, κ and μ are determined taking into account the interference between the resonance and potential scatterings, and the effect of the fuel temperature.
    The effective resonance integrals of the main resonance levels of 238U were calculated using the improved IR approximations, and the accuracy of the method was ascertained by comparing the results with those obtained by the RICM code, which solves the neutron slowing-down equations numerically. Simple approximate expressions for J(ζ, β) and J(ζ, δ, β) functions, which are useful in the IR approximations, are also given together with a table of J(ζ, β) and the errors of the simple approximation.
  • Takamichi OGINO, Hiroshi INUJIMA, Kazuo HAGA
    1984 年 21 巻 3 号 p. 172-186
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
    A series of experiments on LMFBR local core accidents were carried out in an out-of-pile sodium test loop. In the experiments were used 37- and 61-pin bundle test sections which simulated fuel subassemblies. Throughout these experiments temperature and flow fluctua-tion signals were measured by thermocouples and by an eddy-current type flowmeter that serve to develop an anomaly detection method with high sensitivity.
    The experimental results indicate that flow fluctuation at the outlet could be more effectively used for the detection of a large local boiling than temperature fluctuation and that a burst type single cladding failure could be detected by use of the flow fluctuation.
    We proposed a real time anomaly detection algorithm based on the whiteness test for the residual random process. A study was made on the relation between the algorithm and the spectral error measure and its performance. It shows the applicability of the method to a real time system and the effective features of the algorithm.
  • Okitsugu SAKO
    1984 年 21 巻 3 号 p. 187-204
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
    The exactly solvable stochastic point reactor model systems are analyzed through the stochastic Liouville equation. Three kinds of model systems are treated : (1) linear system without delayed neutrons, (2) linear system with one-group of delayed neutrons, and (3) nonlinear system with direct power feedback. The exact expressions for the fluctuations of neutron density, such as the moments, autocorrelation function and power spectral density, are derived in the case where the colored reactivity noise is described by the dichotomic, or two state, Markov process with arbitrary correlation time and intensity, and the effects of the finite correlation time and intensity of the noise on the neutron density fluctuations are investigated. The influence of presence of delayed neutrons and the effect of nonlinearity of system on the neutron density fluctuations are also elucidated.
    When the reactivity correlation time is very short, the correlation time has almost no effect on the power spectral density, and the relative fluctuation of neutron density in the stationary state is not affected very much by the presence of delayed neutrons and also by the nonlinearity of system. On the other hand, if the reactivity correlation time is very long, the effect of the reactivity noise on the power spectral density appears at very low frequency, and the presence of delayed neutrons has an effect of reducing the neutron density fluctuations.
  • Yoshitaka GOTOFP, Osami OKADA
    1984 年 21 巻 3 号 p. 205-214
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
    As a basic study of plasma-wall interactions, chemical state of graphite basal face after deuterium bombardment are studied by means of X-ray photoelectron spectroscopy. As the fluence of deuterium ions with energy of 1 or 4 keV is increased from 1014 to 1018 ions/cm2, the C is line is observed to shift towards the lower binding energy at first, down to the minimum by about 0.2 eV and then towards the higher energy up to an asymptotic value of about 0.2 eV higher than the initial position. The first negative shift is due to lattice dis-placement at the target surface, and the subsequent positive shift is due to the deuterium trapping at the graphite surface. The fluence dependence of the observed C is shift is ex-plained by a simple saturation model.
  • Nelson VEISSID, Shigueo WATANABE, Georgi LUCKI
    1984 年 21 巻 3 号 p. 215-223
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
    Sample of FeNi, FeNi: Cr, FeNi: Mo, and FeNi: Si alloys were irradiated by neutron beams in the vicinity of a 2 MW reactor core and their magnetic hysteresis curves, magnetic after effects as well as variations of magnetic permeability with temperature were determined. From these curves Curie temperature shift, spectrum width k, and activation energy for self-diffusion of Fe and Ni atoms were obtained.
    The presence of Si impurities in the FeNi alloy produces a considerable attenuation in the vacancy supersaturation and the analysis of the spectrum width in this sample indicates that the defect structure due to neutron irradiations is more complex than that due to thermal effect.
  • Keiji ODA, Hiroshi KOYAMA, Takayoshi YAMAMOTO, Masaharu KAWANISHI
    1984 年 21 巻 3 号 p. 224-232
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
    In order to ascertain the accuracy and applicability of the method which was developed in the previous paper for evaluating the dose equivalent in a single-burst and mixed radiation field, a comparison with two other ones has been carried out. One is based on the measure-ment of the neutron energy spectrum with TOF system and the separate measurement of the absorbed doses with twin chambers. In the other, a tissue-equivalent proportional counter is used for measuring the LET distribution of the absorbed dose. The average quality factor has been evaluated in a pulsed and mixed field generated by an electron linear accelerator. A good agreement has been found among these methods.
    A problem about the experimental determination of the dose equivalent index has also been discussed. It was pointed out that the average quality factor as a function of the depth in tissue could be regarded as characteristic of the mixed radiation field.
  • Teruo KIKUCHI, Tsutomu TOBITA, Katsuichi IKAWA
    1984 年 21 巻 3 号 p. 233-242
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
    A study was made of uranium contamination in (a) the coating layers of TRISO particles (a-1) before compacting and (a-2) separated from once-compacted fuel heat-treated at 1, 400 or 1, 800°C, and (b) in the matrix material of the same compacts. The contamination in the pyrocarbon layers of the coating was determined, after mechanically separating the coating layers, by a procedure of neutron activation, burn-off and 133Xe trapping. For the silicon carbide coating layer, the fragments of coating left from the above procedure were fused into alkaline melt, and the 133Xe released at each heating step was trapped. For the matrix material, the fuel compacts were deconsolidated electrolytically or mechanically, followed by activation analysis. The results of the foregoing measurements proved the uranium con- tamination in pyrocarbon and silicon carbide coating to be at most of the order of 10-4 in reference to uranium content in kernel, while the corresponding value for particles sampled from fuel compacts heat-treated at 1, 800°C were appreciably higher. The corresponding values found for the matrix material were of the order of 10-5.
  • Masafumi NAKATSUKA
    1984 年 21 巻 3 号 p. 243-244
    発行日: 1984/03/25
    公開日: 2008/04/18
    ジャーナル フリー
feedback
Top