ISSN:0029-5450    

DOI:10.13182/NT87-A33946

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractA dynamic void quality perturbation model has been developed to improve the capabilities of the NUFREQ code with respect to local void perturbation calculations. The present model calculates the local void perturbation in terms of the local quality perturbation, the dynamic drift flux parameters, and the transient time. In addition, the model evaluates the void reactivity feedback and the boiling channel nuclear reactor feedback. Depending on the flow regime, this model can predict the local void fraction perturbation in horizontal (CANDU reactors) and vertical channels (light water reactors). Numerical results revealed that this model enhanced the capabilities of the NUFREQ code and improved its accuracy in predicting the lower natural frequency as well as the system frequency response at higher frequencies.

ISSN:0029-5450    

DOI:10.13182/NT87-A33947

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractFission product release tests and control tests recently conducted at Oak Ridge National Laboratory have provided new experimental data that help characterize the mechanism of fission product tellurium release behavior under severe light water reactor accident conditions. Release of tellurium from the fuel rod segments has been found to be dependent on the rate and extent of cladding oxidation. Tellurium was observed to be significantly retained by metallic Zircaloy cladding at test temperatures up to 2000°C. The results indicate that the tellurium was bound by the Zircaloy cladding as zirconium telluride, but once the available metallic zirconium was oxidized by the steam, tellurium was released in favor of continued zirconium oxide formation. The collection behavior of the released tellurium indicated that it was probably released from the fuel rods as tellurides of tin, cesium, and rubidium rather than as elemental tellurium.

ISSN:0029-5450    

DOI:10.13182/NT87-A33948

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractSimulation tests of a boiling water reactor (BWR) loss-of -coolant accident (LOCA) caused by a double-ended guillotine break of a recirculation pump suction line were carried out with the rig of safety assessment III (ROSA-III) test facility at the Japan Atomic Energy Research Institute. SAFER03 and TRAC-BD1 analyses with the ROSA-III test data have been performed to assess predictive capability for the large-break LOCA thermal-hydraulic response of a BWR. The analytical results indicate that SAFER03 and TRAC-BD1 predicted key phenomena very well. Furthermore, it was confirmed that SAFER03 predicted higher peak cladding surface temperature than the test data due to the conservative thermal-hydraulic model.

ISSN:0029-5450    

DOI:10.13182/NT87-A33949

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractAn electrochemical filter is used for efficient and fast removal of alumina particles suspended in heavy water circulating in a nuclear reactor. The process is based on electrostatic interactions between the charged colloids and an oppositely charged porous carbon electrode. A high degree of purification is achieved by this process.

ISSN:0029-5450    

DOI:10.13182/NT87-A33950

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractA computer graphics technique was used to measure cracks and other features of mixed-oxide fuel ceramographs to provide information useful for the modeling of fuel cracking and fragment movement. These measurements provided qualitative and quantitative information in several areas: crack formation and fuel-fragment movement, fuel-cladding gap size, crack size, crack orientation, radial distribution of crack porosity, and change in fuel volume (referred to as total fuel swelling) as a function of oxygen-to-metal ratio (O/M) and burnup. Examination of the ceramographs indicated that a crack starts on a free surface and propogates until it reaches another free surface. Thus, the first crack extends from one side of the fuel to the other, and succeeding cracks terminate on existing cracks or on the fuel surface. While crack formation was found to be independent of O/M, differences in crack healing at moderate power (19 kW/m) and high burnup (12 at.%) lead to a predominance of radial cracks for high O/M (∼1.96) fuel and both radial and circumferential cracks for low O/M (∼1.92) fuel. The different effects of circumferential and radial cracks on fuel behavior produce smaller postirradiation fuel-cladding gaps and larger cracks in the lower O/M fuel pins. Fuel swelling at intermediate burnup (∼8 at. %) is independent of O/M, but at high burnup (∼12 at. Vo) lower O/M fuel swells more. This swelling behavior may be related to a similar O/M dependence of retained fission gas.

ISSN:0029-5450    

DOI:10.13182/NT87-A33951

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractExposure buildup factors for plane normal sources have been calculated with an electron gamma shower Monte Carlo code, EGS4, for water, concrete, iron, and lead in the 10 to 100 MeV range. Electron reactions like multiple scattering, collision, and continuous energy loss are taken into account together with bremsstrahlung. The buildup factors in this energy region are affected very much by the energy loss mechanism of electrons and positrons in the medium. The energy of electrons or positrons in lead is mainly converted to photons via the bremsstrahlung reaction; therefore, buildup factors increase rapidly with the increase of the photon energy. In the case of water, the energy of electrons or positrons is mainly spent in ionization or excitation. Buildup factors for water decrease gradually to 40 MeV and increase gradually above that energy. The buildup factors in each medium are calculated for eight-source energy from 10 to 100 MeV for penetration depths as great as 10 mfp.

ISSN:0029-5450    

DOI:10.13182/NT87-A33952

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractAssemblies have been built for measuring gamma rays from coal following the capture of neutrons from252Cf. Sources of sizes to 60μg of calcium 1.4×108n/s were used. Paraffin moderated the fast neutrons, and beryllium metal was useful as a reflector. The gamma-ray spectrum from a Ge(Li) detector showed that the line intensities of a number of elements (e.g., hydrogen, iron, sulfur, and silicon) could be used to determine concentrations. The aim was to explore possible application in planned coal conversion plants.

ISSN:0029-5450    

DOI:10.13182/NT87-A33953

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractOur work was restricted to elementary models of condensation, coupling a laminar water film with an air-steam mixture boundary layer, under steady-state conditions, for some simple physical situations. We tested two categories of models. The models in the first category are merely the set of balance equations for which Sparrow’s numerical solutions have been replaced by Rose’s closed-form solutions. The models in the second category make use of correlations of mass transfer obtained by the Chilton-Colburn analogy and assumed closure laws concerning heat transfer across the film. The closed form of the solutions enabled us to propose numerical algorithms without integration, which we programmed in BASIC language. The differences we found between the results of the experiment and those of the models are systematic and positive, the calculated values being 50% less than the experimental results, on average. Comparing the abilities of the models, the situation of laminar-forced convection along a flat plate, whether the mixture is superheated or not, is the only situation where the model, using boundary layer theory, gives exact results. For the situation of turbulent free convection along a vertical wall, e.g., the containment wall of a pressurized water reactor system, the model, using the Chilton-Colburn analogy, gives only approximate results.

ISSN:0029-5450    

DOI:10.13182/NT87-A33954

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe fabrication of a miniature spark counter for public communication and education using naturally occurring radon as a radioactive source without involving any man-made radioactivity is described. The battery-powered miniature spark counter weighs 2.07 kg with a volume of 4.844×10−4m3. The circuitry consists of seven major components: timer, high-voltage power supply, attenuator, noninverting amplifier, low-pass filter, one-shot generator, and counter. Cellulose nitrate films irradiated with alpha particles from radon emanating from soil were etched and counted. The visible sparks during counting are rather heuristic, which can be used to demonstrate naturally occurring radioactivity in classrooms or showplaces.

ISSN:0029-5450    

DOI:10.13182/NT87-A33955

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor