Journal of Nuclear Science and Technology
Online ISSN : 1881-1248
Print ISSN : 0022-3131
33 巻, 9 号
選択された号の論文の12件中1~12を表示しています
  • Hiroshi MATSUOKA, Misako ISHIGURO
    1996 年 33 巻 9 号 p. 675-685
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    "Package Flow Model" (PFM) is a simple simulation model for intuitive understanding of various types of system dynamics. In the previous papers, the PFM was proposed and its application to the dynamic analysis of nuclear reactor systems was presented. In the present paper, the same model and same application are considered but a new representation method of the PFMs by a neural network is introduced, so that the dynamic simulation of the reactor subsystem can be performed through the calculation of corresponding neural network. Furthermore, the quasi optimum parameter values of each PFM are easily obtained by applying appropriate learning algorithm to get weight-values of the neural network. Some case studies show that the learning process and the obtained optimum values can give us new useful information on approximate understanding of the dynamic behavior of actual processes in the system.
  • S. H. KIM
    1996 年 33 巻 9 号 p. 686-695
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    Time dependent flow and heat removal behavior up to incipient dryout in a porous medium are investi-gated numerically. The porous medium composed of coarse particles with volumetric heating is cooled by a countercurrent flow in a two-phase region with evaporation. A separated flow model, based on the two-phase extended Ergun equations with Ergun constants depending on Reynolds number and on the mass conserva-tion, is developed for a local thermodynamic equilibrium between each phase. Owing to the nonlinearity of the coefficients appearing in the governing equations, numerical computations are iteratively made. Numerical predictions are also compared with available data of dryout heat flux in the literature. For the cases of shallow porous media the predicted dryout heat generation rates lie in the experimental ranges. However, the cases of deeper porous media were overpredicted by this calculation. In addition, the transient heat removal process up to dryout is discussed qualitatively by means of the axial liquid volumetric fraction, phase pressure, liquid velocity and vapor velocity distributions.
  • Hideaki ASAKA, Yutaka KUKITA
    1996 年 33 巻 9 号 p. 696-702
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    A co-current, horizontally-stratified, two-phase flow would appear in the hot legs of a pressurized water reactor during a certain class of small-break loss-of-coolant accident. The liquid velocity in the hot leg may become so high that it exceeds the speed of interfacial waves. The condition for the onset of such a "supercritical" flow is studied in this paper by analyzing experimental data taken in the ROSA-IV Large Scale Test Facility. It is shown that the energy loss at the hot leg inlet needs to be taken into account to predict the above onset condition reasonably well.
  • Yasuteru SIBAMOTO, Taisuke YONOMOTO, Yutaka KUKITA, Yoshiyuki TSUJI, M ...
    1996 年 33 巻 9 号 p. 703-711
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    The operation of a PIUS-type reactor requires controlling the reactor pump speed to keep stationary the hot/cold liquid interfaces between the reactor coolant and cold borated water. The dynamic response of the interface location to pump speed perturbations is analyzed for an experimental loop simulating a PIUS-type reactor. The transfer function between the pump speed and the interface location is obtained by perturbing and Laplace-transforming the one-dimensional fluid momentum equations. The analytical results agree well with experimental data taken from the same facility. It is shown that the magnitude of the phase lag in the response of the interface location, which needs to be considered in designing a pump speed controller, primarily depends on the fluid inertia in the loop, the density lock flow area, and the density difference between the simulated reactor coolant and borated water.
  • Kazuhiro SAWA, Shusaku SHIOZAWA, Kazuo MINATO, Kousaku FUKUDA
    1996 年 33 巻 9 号 p. 712-720
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    In high temperature gas-cooled reactors (HTGRs), coated particles are used as fuels. For upgrading HTGR technologies, Japan Atomic Energy Research Institute has been developing high burnup Tri-isotropic (TRISO) coated fuel particles. The TRISO coatings consist of a low-density, porous pyrolytic carbon (PyC) buffer layer adjacent to the spherical fuel kernel, follwed by an isotropic PyC layer, a SiC layer and a final PyC layer. In safety design of HTGR fuels, it is important to retain fission products within the particles so that their release to primary coolant does not exceed an acceptable level. Therefore the basic design criteria for the fuel are to minimize the failure fraction of as-fabricated fuel coating layers and to prevent significant additional fuel failures during operation. In the high burnup coated fuel particle, stress due to fission gas pressure and irradiation-induced PyC shrinkage is introduced into the coating layers and consequently the stress could cause failure of coating layers under high burnup irradiation condition. Some models have been developed to evaluate failure fraction of coated fuel particles, however, they are regarded as a guideline for fuel particle design rather than as a predictive tool for coated fuel particle performance. Then the behavior of coated fuel particles has been examined only by many irradiation experiments and development of reliable model has been needed. A failure model is newly developed to predict failure fraction of TRISO-coated particle under high burnup irradiation. In the model, it is assumed that the failure fraction depends not only on failure of the SiC layer but also on that of the PyC layers. The failure fractions of through-coatings failed particles and the SiC-failed particles are calculated based on the failure probability of each coating layer. Based on the model developed here, parameter calculations for the first-loading-fuel of the High Temperature Engineering Test Reactor and for the high burnup fuel were carried out.
  • Tamaki SHIBAYAMA, Akihiko KIMURA, Hideo KAYANO
    1996 年 33 巻 9 号 p. 721-727
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    In order to study the effects of small additional elements on precipitation behavior in reduced-activation ferritic steels under neutron irradiation, analytical transmission electron microscopy was used to examine the microstructure and the precipitation of the extraction replica of several reduced activation ferritic/martensitic steels which have different contents of small additional elements after 60 displacements per atom (dpa) irradi-ation at 693, 698 and 733 K in the Fast Flux Test Facility (FFTF)/Materials Open Test Assembly (MOTA). All of reduced-activation ferritic/martensitic steels were found to have a good phase stability after irradiation. Micro-voids were observed in both materials of Fe-9Cr-2W with or without boron, the density of micro-voids in the steel with boron is larger than that without boron, and the mean size of micro-voids is smaller than that without boron. However void swelling was less than 1%. Most of the precipitates in the irradiated specimens were found to be M23C6 which consists of mainly Cr. The remainder of the precipitates were found to be Ta-rich M6C. Laves phase was observed only at 733K. Several precipitates which were Ti-rich including Si and W were also observed at grain boundary in Ti addition steels at 733 K irradiation. Several Y2O3 particles were observed in an yttrium containing alloy. No precipitation including Al was observed in an Al containing alloy. Ti addition decreased precipitation of Ta-rich M6C in 9Cr and 12Cr steels in this irradiation condition.
  • Tadahiro HOSHIKAWA, Akira SASAHIRA, Tetsuo FUKASAWA, Fumio KAWAMURA, Y ...
    1996 年 33 巻 9 号 p. 728-730
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    Volatilization behavior of technetium was investigated in order to evaluate the decontamination efficiency of an evaporator for reprocessing waste solutions. The gaseous species of technetium volatilized over HTcO4 solutions had been considered as the mixture of Tc2O7 and HTcO4. Estimation of the decontamination efficiency needs to determine whether the dominant gaseous species is Tc2O7 or HTcO4. The continuous dis-tillation of dilute HTcO4 solution was carried out and we obtained the purification factor (PF) defined as the concentration ratio of technetium in the concentrate and distillate. The PF was normalized by total pressure, HTcO4 molarity and mole number in 11 solution. The normalized PF was reciprocal to the second power of HTcO4 molarity and was proportional to the activity of water. These findings suggested the dominant gaseous species were Tc2O7 and volatilization was the dehydration of HTcO4 forming gaseous Tc2O7. The vapor pressure of Tc2O7 was obtained from PF and the equilibrium constant of volatilization reaction was calculated considering that the gaseous species was dominantly Tc2O7. The thermodynamic functions con-trolling the volatilization reaction were obtained from the dependence of equilibrium constant on temperature as, ΔH=82.3 kJ•mo;-1 and ΔS=205.4 J•mo;-1K-1, respectively.
  • Christine GOJON, Bernard DUREAULT
    1996 年 33 巻 9 号 p. 731-735
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    In order to realize an optical fibre chemical sensor for hydrazine in the Purex process, the reaction between hydrazine and p.dimethylaminobenzaldehyde (p.DMAB) in nitric acid medium was studied by spectropho-tometry and 1H.NMR. The effect of temperature and acidity were determined. The equilibrium constant is of 7, 800l/mol at 15°C and decreases to 600 at 55°C. The reaction is fully reversible. In order to keep p.DMAB out of damage, the acidity working range has to be within 0.1 to 1.0 M in nitric acid medium. This reaction is suitable for the application of optical fibre chemical sensors because direct reversibility or regeneration by temperature or acidity may be possible.
  • Deng LI, Cai SHAOHUI, Huang ZHENGFENG, Huang JIE
    1996 年 33 巻 9 号 p. 736-740
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
    This report introduces the Monte Carlo simulating processes for gamma-ray Klein-Nishina scattering probabilities to finite detectors and a few modifications for producing photon mode and gamma production data from the neutron collision. Those approaches have been used in MCNP code. The calculation results are given according to the primary continuous photons, the line photons and the Compton photons, respectively. The results are compared with that of MCNP code. It indicates that the approach is valid and efficient for deep-penetration problems.
  • Mohammad Dhandhang PURWADI, Masashi TSUJI, Masakuni NARITA
    1996 年 33 巻 9 号 p. 741-743
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
  • Hiroyuki MIYAMARU, Keiji FUJII, Toshiyuki IIDA, Akito TAKAHASHI
    1996 年 33 巻 9 号 p. 744-746
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
  • Katsuhiro SAKAI
    1996 年 33 巻 9 号 p. 747-749
    発行日: 1996/09/25
    公開日: 2008/04/18
    ジャーナル フリー
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