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Showing papers in "Journal of Nuclear Science and Technology in 1979"


Journal ArticleDOI
TL;DR: In this paper, the hydrodynamic instabilities of two-phase flow are classified into at least eight types: the static or the Ledinegg instability, the dynamic or the density wave instability.
Abstract: 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 instability. Two typical types of instabilities are observed in our experiment, in each type different 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.

220 citations


Journal ArticleDOI
TL;DR: In this article, an experimental study was made in a cocurrent downflow for air-water system in tube on flow pattern, void fraction and pressure drop, where the same kinds of flow patterns as in up-flow were represented on the flow map of downflow with the same variables as those of upflow.
Abstract: An experimental study was made in a cocurrent downflow for air-water system in tube on flow pattern, void fraction and pressure drop. In addition to wetted wall flow which is a distinguished feature in downflow, the same kinds of flow patterns as in up-flow were observed. They were represented on the flow map of downflow with the same variables as those of upflow. The flow maps showed that gas phase is relatively hard to exist in the form of bubble in the cocurrent downflow. General correlations of the void fraction and the pressure drop in a cocurrent down-flow were obtained by applying the following equations which have been established in upflow, i.e. α/(1-α)(1-Kα)=β/(1-β) for void fraction and φl=(1.α)- z for pressure drop. The determined values of K and Z by using the experimental results in the present study and other experimental works in cocurrent downflow wereK=2.0–0.4/β for β≤0.2, K=-0.25+1.250 for β≥0.2 and Z=0.90. Comparisons between the predicted values by the presented correlations and exper...

45 citations


Journal ArticleDOI
TL;DR: In this article, an analysis on the hydrodynamic instability of two-phase flow in parallel multichannels is conducted by investigating into a characteristic equation, its roots and composing channel transfer functions.
Abstract: An analysis on the hydrodynamic instability of two-phase flow in parallel multichannels is conducted. Occurrence of instabilities and their modes of oscillations can be evaluated by investigating into a characteristic equation, its roots and composing channel transfer functions. It is also shown that a governing matrix is reduced to a diagonal one by using its eigenvalues, the oscillation modes being divided into N (number of channels) separate fundamental modes. Characteristics of each oscillation mode are given by examining corresponding characteristic equations. The derived equations are applied for the prediction of oscillation modes of systems composed of a few slightly different channels. The analysis successfully predicts the modes which have been experimentally observed.

43 citations


Journal ArticleDOI
TL;DR: In this article, the number of layers necessary to give a nearly perfect reflection (≥90%) at the main Bragg peak, for Ni-Mn multilayer monochromators, were found to be 7, 11, and 21 for layer thicknesses of 163, 112, and 83 A, respectively.
Abstract: Multilayer films for neutron mirror were made by vacuum depositing thin films of Ni and Mn or Ni and Ti on a glass plate alternately. Their neutron reflectivities were measured as a function of neutron wavelength by the time-of-flight technique. For Ni-Mn multilayer monochromators, the numbers of layers necessary to give a nearly perfect reflection (≥90%) at the main Bragg peak, were found to be 7, 11 and 21 for layer thicknesses of 163, 112 and 83 A, respectively. The reflectivities obtained experimentally were compared with those calculated with the method applying the conventional optics, and their agreements were quantitatively reasonable. Moreover, for supermirrors, the numbers of layers and the distributions of layer thicknesses were examined in order to get a reflectivity of near unity down to the wavelength much shorter than the critical wavelength of a totally reflecting mirror of Ni. The reflectivity of a supermirror consisting of 160 layers of Ni and Ti was observed to behave like that of a tot...

39 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed to add nitrite to nitric acid solution before denitration of highly radioactive liquid waste (HLW) from nuclear fuel reprocessing to suppress a vigorous chemical reaction.
Abstract: Denitration with organic reductant such as formic acid is exclusively used for controlling acidity of the highly radio-active liquid waste (HLW) from nuclear fuel reprocessing. This method, however, has a problem in suppressing a vigorous chemical reaction. The present study aimed at overcoming the disadvantage by the addition of nitrite to nitric acid solution before denitration. As a result, the nitrite addition in the denitration of simulated HLW could reduce the induction period to almost zero and the maximum gas evolution rate to less than 60% of that obtained in the absence of nitrite. Effectiveness of nitrite addition was enhanced especially for HNO3 concentration higher than 8 mol/l. The effective nitrite concentration was over 0.01 mol/l. in the reaction mixture.

23 citations


Journal ArticleDOI
TL;DR: In this article, isotope effect on dissociation behavior of uranium hydride has been studied and the equilibrium dissociation pressure of uranium protide(UH3), deuteride (UD3), and of equimolar mixture of both hydrides are measured.
Abstract: Isotope effect on dissociation behavior of uranium hydride has been studied. The equilibrium dissociation pressure of uranium protide(UH3), deuteride (UD3), and of equimolar mixture of both hydrides are measured. The dissociation pressure of deuteride is higher than that of the protide by a factor of about 2 at 400°C and mixed hydride of UH3 and UD3 has intermediate dissociation pressures. Enthalpy and entropy of formation as well as free energy of formation at 298 K obtained from the dissociation pressure are −29.9kcal/mol, −42.8 cal/K·mol and −17.7 kcal/mol for UH3, and −31.5 kcal/mol, −46.8 cal/K·mol and −17.5 kcal/mol for UD3, respectively, which are in good agreement with the values obtained from calorimetrie and heat capacity studies. Mole fractions of deuterium in the gas phase and the solid phase are determined when the mixed hydride is in dissociation equilibrium with gas mixture. In this case deuterium is found to be enriched in the gas phase and the separation factor defined by [D/H]g3S phase/[...

22 citations




Journal ArticleDOI
TL;DR: In this paper, the authors reported some irradiation effects and recovery behavior of neutron irradiated boron carbide pellets that were used as control rod elements in the Enrico Fermi Fast Breeder Reactor.
Abstract: This paper reports some irradiation effects and recovery behavior of neutron irradiated boron carbide pellets that were used as control rod elements in the Enrico Fermi Fast Breeder Reactor. Measurements were carried out on changes in lattice parameters, thermal expansion, helium release, elastic moduli and microstructure observations by annealing the irradiated pellets at elevated temperatures. The increase in unit cell volume of B4C upon irradiation was found to be 0.22%. The recovery in lattice parameter began at around 500°C and completed at 1,000°C. It was found that the pellet showed a sharp increase in a dimensional change at about 700 to 800°C with a large amount of helium release, and the pellet which showed larger swelling released smaller amount of helium.

16 citations


Journal ArticleDOI
TL;DR: In this article, a value function for multicomponent isotope separation is derived by utilizing the separation factors defined in each two component pair in multicomponents system, and the derivation is performed by extending the theory of separative power for binary separation system.
Abstract: A value function for multicomponent isotope separation is derived by utilizing the separation factors defined in each two component pair in multicomponent system. The derivation is performed by extending the theory of separative power for binary separation system. Since the value function for binary separation is constructed to cancel the difference between increases in value per unit flow of two components, the value function for multicomponent separation is expected to have a similar structure. In k components separating system, like binary separation, separative powers are introduced for all the pairs of j-k components (j = l, 2, ···, k — 1) between which separation factors are defined. These separative powers represent increases in value by separation. A multi-component value function is obtained by synthesizing the two-component value functions for all the pairs so that the differences among increases in value per unit flow of all components are counteracted.

15 citations


Journal ArticleDOI
TL;DR: In this article, the deuterium exchange reaction between hydrogen and water in the gas phase where the fed hydrogen gas is saturated with water vapor is studied experimentally by use of the proper hydrophobic catalysts supporting platinum.
Abstract: The deuterium exchange reaction between hydrogen and water in the gas phase where the fed hydrogen gas is saturated with water vapor is studied experimentally by use of the proper hydrophobic catalysts supporting platinum. It is found that the activities of those catalysts for this reaction system are very high compared with the other known ones for the systems in which gas and liquid should coexist on catalyst surfaces, and that the apparent catalytic activity becomes larger as the amount of platimun supported on a catalyst particle increases. By analyses of the data the following informations are obtained. The exchange reaction can be expressed by a first order reversible reaction kinetics. The pore diffusion in the catalyst particles has significant effect on the overall reaction mechanisms.

Journal ArticleDOI
TL;DR: In this article, the authors used DIDPA-DTPA systems to determine optimum conditions for applying DIDPA to the TALSPEAK type extraction process to separate transplutonides from lanthanoids in the partitioning of high level waste of nuclear fuel reprocessing.
Abstract: The distribution ratio Df and the separation factor β for Nd(III) to Am(III) were studied in DIDPA-DTPA systems to determine optimum conditions for applying DIDPA to the TALSPEAK type extraction process to separate transplutonides from lanthanoids in the partitioning of high-level waste of nuclear fuel reprocessing. Extraction of lanthanoids from 0.05–0.1 M DTPA-1 M lactic acid (pH 3.0) aqueous solution into 0.2–0.3 M DIDPA in DIPB gives the separation factor of 20 revealing practicability of this system in the partitioning. The nature of diluent affects greatly Df, and DIPB proved to be the most appropriate one for the separation of transplutonides from lanthanoids. The presence of lactic acid in the aqueous phase improved the extraction kinetics in DIDPA-DTPA system.

Journal ArticleDOI
TL;DR: In this paper, the density wave instability in a once-through boiling flow system is analyzed using a comprehensive distributed parameter model that is extended from the simplified lumped parameter model presented in a companion paper.
Abstract: The density wave instability in a once-through boiling flow system is analyzed using a comprehensive distributed parameter model that is extended from the simplified lumped parameter model presented in a companion paper A computer code DEW is developed for the calculations with an analytical approach in the time domain The proposed model is verified by comparison with published data obtained from experiments with a joule-heated system and a sodium-heated steam generator This comparison indicates that the proposed model can serve as a design tool for predicting the stability boundary Several features of oscillatory behavior, the existence of higher-mode oscillations and some analytical parameter effects on the flow instability are revealed in the present study

Journal ArticleDOI
TL;DR: In this article, a computer simulation method has been applied to the analysis of the NO and NO2 decomposition in the NO-N2 and NO 2 -N2 mixtures by electron beam irradiation.
Abstract: The computer simulation method has been applied to the analysis of the NO and NO2 decomposition in the NO-N2 and NO2-N2 mixtures by electron beam irradiation. The calculated results regarding the NO and NO2 decomposition were in good agreement with the experimental results in both mixtures. The NO and NO2 decomposition is mainly induced by the radical reactions and is hardly induced by the ion reactions. That is, the NO decomposition in the NO-N2 mixture is mainly induced by the attack of N formed by the radiolysis of N2. The NO2 decomposition in the NO-N2 mixture is induced not only by the attack of N, but also by the attack of O formed through the reaction of NO2 with N at low doses. At high doses, the decomposition of NO formed through the reactions of NO2 with N and with O is mainly induced by the attack of N, in contrast to the NO2 decomposition by the attacks of N and O at low doses. The G value of the formation of N(G(N)) by the computer simulation was 2.0.

Journal ArticleDOI
TL;DR: In this article, a new method for calculating the anisotropic neutron transport is proposed for the angular spectral analysis of D-T fusion reactor neutronics, which is based on the transport equation with new type of scattering kernels formulated by a single function Ii (μ′,μ) instead of polynomial expansion.
Abstract: A new method for calculating the anisotropic neutron transport is proposed for the angular spectral analysis of D-T fusion reactor neutronics. The method is based on the transport equation with new type of anisotropic scattering kernels formulated by a single function Ii (μ′,μ) instead of polynomial expansion, for instance, Legendre polynomials. In the calculation of angular flux spectra by using scattering kernels with the Legendre polynomial expansion, we often observe the oscillation with negative flux. But in principle this oscillation disappears by this new method. In this work, we discussed anisotropic scattering kernels of the elastic scattering and the inelastic scatterings which excite discrete energy levels. The other scatterings were included in isotropic scattering kernels. An approximation method, with use of the first collision source written by the Ii (μ′,μ) function, was introduced to attenuate the “oscillations” when we are obliged to use the scattering kernels with the Legendre polynomia...


Journal ArticleDOI
TL;DR: In this paper, the self-diffusion coefficient of oxygen in single crystal thoria was determined at 1,350°C in an 18O-enriched CO2 atmosphere of oxygen partial pressure 3×10−4 atm.
Abstract: The self-diffusion coefficient of oxygen in single crystal thoria was determined at 1,350°C in an 18O-enriched CO2 atmosphere of oxygen partial pressure 3×10−4 atm. The coefficient was close to the intrinsic self-diffusion coefficient determined in an oxygen atmosphere of 0.27 atm indicating the oxygen partial pressure independence. On the basis of the results, the mechanism was discussed for the conductivity data for thoria in the literature being due to the intrinsic diffusion and the extrinsic diffusion of oxygen ion and due to the intrinsic p-type electronic conduction predominant under high oxygen partial pressures.

Journal ArticleDOI
TL;DR: In this paper, the authors established the thermo-hydrodynamic model of the reactor core during reflood phase of LOCA and derived the quench time and quench temperature.
Abstract: The objective of this study is the establishment of the thermo-hydrodynamic model of the reactor core during reflood phase of LOCA. Based on the quench model proposed by the author, and assuming a reflood model including a flow model and a set of the thermo-hydrodynamic correlations, a reflood analysis code named “REFLA-1D” was developed. Considerably close agreement between PWR-FLECHT tests and the results calculated by REFLA-1D code for the critical Weber number Wec= 1 was obtained for fuel clad temperature histories and the quench time and the quench temperature except for the quenching from the top of the fuel rod. It was found that the errors of calculated quench time and temperature are within ±20% under the following conditions: (1) pressure 4.5–1.5 kg/cm2·a or core inlet velocity 15–4.8 cm/s, (2) inlet subcooling more than 30°C. In the transition flow region, the calculated tendency of the temperature histories is different from the measured. This reflood model appears to be reasonable but some mo...



Journal ArticleDOI
Katsumi Une1
TL;DR: In this paper, the relation between strain rate and iodine stress corrosion cracking (SCC) was studied on Zircaloy-2 subjected to uniaxial stress under constant extension rate in an iodine partial pressure of 4 T.
Abstract: The relation between strain rate and iodine stress corrosion cracking (SCC) was studied on Zircaloy-2 subjected to uniaxial stress under constant extension rate in an iodine partial pressure of 4 T

Journal ArticleDOI
TL;DR: In this paper, a Monte Carlo code was developed to examine response functions of a 2 in. dia. by 2. in. long NE-213 liquid scintillator for γ-ray.
Abstract: A Monte Carlo code was newly developed to examine response functions of a 2 in. dia. by 2 in. long NE-213 liquid scintillator for γ-ray. This code included the electron transport and the electron-photon cascade calculation to handle the wall and end effect induced by high energy electrons. Results of the Monte Carlo calculation were compared with measured values for standard sources, reaction γ-ray and thermal neutron capture γ-ray, and fairly good agreement was obtained. Response functions for monoenergetic γ-ray of energies 1~10 MeV were calculated at 1 MeV intervals. The calculations were made in parallel incident geometry without the peripheral material components surrounding the scintillator. The results are tabulated in this paper. A response matrix calculated from the above data was applied to the unfolding of NE-213 pulse height spectra using the FERDO code and fairly good results were obtained in absolute values.

Journal ArticleDOI
TL;DR: In this paper, the radiolytic effects upon the extraction of strontium, lanthanoids and transplutonium elements in partitioning were estimated to be sufficiently small, and the results were compared with the published data for the fuel reprocessing.
Abstract: Radiation dose absorbed in the organic extractant was estimated for the counter- current extraction with mixer-settler in the partitioning of the high-level liquid waste of fuel reprocessing The radiation dose due to the absorption of α and β-particles was calculated to be 10, 50 and 042 Wh/l for 150 days, 1 year and 10 years after fuel discharge from the reactor, respectively About 70–90% of the total dose was due to the absorption of β-particles These values were discussed in comparison with the published data for the fuel reprocessing On the basis of the calculated data, the radiolytic effects upon the extraction of strontium, lanthanoids and transplutonium elements in partitioning were estimated be sufficiently small

Journal ArticleDOI
TL;DR: In this article, the average capture cross sections of europium isotopes 151Eu and 153Eu were measured in the neutron energy range of 3~100keV with the time-of-flight facility at the 52 m station of the JAERI Electron Linear Accelerator.
Abstract: Neutron capture cross sections of europium isotopes 151Eu and 153Eu were measured in the neutron energy range of 3~100keV. Experiments were carried out with the time-of-flight facility at the 52 m station of the JAERI Electron Linear Accelerator. Prompt capture γ-rays were detected by a large liquid scintillation detector and the neutron flux shape was determined with a 6Li glass scintillation detector. The average capture cross sections were examined in terms of energy independent strength functions for 151Eu and 153Eu.

Journal ArticleDOI
TL;DR: In this article, a violent pressure oscillation was observed in a vertical tube under a temperature gradient, and it was determined that the pressure was due to the existence of a large temperature gradient in the system, and that it occurred in the low temperature region of the system.
Abstract: In the subcooled decompression experiments of water in a vertical tube under a temperature gradient, a violent pressure oscillation was observed. By varying the gradient conditions it was ascertained that this pressure oscillation was due to the existence of the large temperature gradient in the system, and that it occurred in the low temperature region of the system. The generation of the pressure oscillation could be explained by assuming a reflection surface for the pressure wave caused by the blowdown. Two positions of the reflection surface were experimentally obtained from the structure of oscillatory pressure behavior and by computing the autocorrelation function of the pres- sure curve. In the system of a linearly descending temperature distribution, a flashing occurred partially and those two values were in good agreement with the position of the phase boundary generated just after the passage of the decompression wave. The conventional thermal equilibrium model could not completely explain this ...

Journal ArticleDOI
TL;DR: The fracture strength of two kinds of UO2 specimens possessing pores of different maximum sizes (60 and 140 μm) was measured in the range of room temperature − 1,300°C by means of diametral compression testing as mentioned in this paper.
Abstract: The fracture strength of two kinds of UO2 specimens possessing pores of different maximum sizes (60 and 140 μm) was measured in the range of room temperature − 1,300°C by means of diametral compression testing. The fracture strength thus obtained proved to be smaller than any of the values reported by previous authors who mainly used bending tests. Finite element analysis showed that the method used in the present study should logically yield results close to the true tensile fracture strength. The descrepancies noted with the results reported from the other studies were attributable to the differences in the methods used for the measurements. The fracture strength was found to remain almost constant in the relatively low temperature region (R.T.–800°C) beyond which the value increased with temperature (intermediate temperature region of 1,000–1,300°C). Electron-microscopic observations of the fractured surface indicated that the brittle-to-ductile transition temperature (Tc ) was situated between 800 and...

Journal ArticleDOI
Abstract: A computer code MIRA-PB for predicting the iodine removal by containment spray in LOCA was prepared on the basis of MIRA-P/MIRA-B code developed in Battelle Columbus Laboratories. MIRA-PB considers behavior of inorganic iodine, organic iodide, and iodic aerosol and simultaneous removal by natural deposition, liquid-film absorption, spray washout, filtration and leakage to the environment. The iodine removal by the containment spray systems in LOCA of PWR and BWR is calculated with the MIRA-PB.



Journal ArticleDOI
TL;DR: In this paper, the authors describe the dynamical correction for light nuclei liquids in the case of the Time-of-Flight neutron diffraction method, which consists of two seperative treatments in the high and low Q regions.
Abstract: It is necessary to correct the dynamical effect for obtaining the structure factor of liquids by the neutron diffraction method. The dynamical correction is so difficult for light nuclei that the neutron diffraction method has been prevented to be applied to various hydrogeneous liquids. The present paper describes the dynamical correction for light nuclei liquids in the case of the Time-of-Flight neutron diffraction method. The formulae of the correction consist of two seperative treatments in the high and low Q regions. The former is based on the Wick's short time approximation, whilist the latter is derived by the Placzek's inverse mass expansion method.