摘要:

Transient flow and freezing of molten core debris in coolant channels of the subassemblies of a liquid-metal fast breeder reactor has been an important consideration in postaccident heat removal. As a first step to study this phenomenon, transient freezing of a number of simulant materials in tube flow was investigated experimentally. Controlling parameters of the transient freezing process were determined from theoretical consideration. A parametric study of the effects of the controlling parameters on freezing was carried out, and an empirical correlation based on experimental measurements was obtained that is applicable over a wide range of Prandtl numbers. Results of the present study were compared to the existing analytical models.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26851

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

It was found that the results of the RELAP-3 code, which is one of the typical analytical codes for analysis of the loss-of-coolant accident (LOCA) of light water reactors, do not agree well with the results from the ROSA-I experiments under certain break conditions. It was determined that the discharge coefficient used in the code as a parameter can be correlated with the quality of the discharged fluid and that the calculated liquid mass transient does not always agree with the experimental one when a constant bubble escape velocity is assumed. These difficulties come from the possibility of shortcomings of the model dealing with the LOCA phenomena. An attempt was made to improve these aspects of the code by incorporating the correlation of the discharge coefficient with the quality and with Wilson's experimental interpretation of the bubble velocity and certain assumptions in its application. The results obtained by the modified code are in good agreement with both those from the ROSA-I experiment and experiments at Hitachi Ltd.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26852

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

Data presently available on photofission cross sections, photoneutron cross sections, and the angular distribution of photofission fragments of actinides near threshold are reviewed. Some suggestions for additional studies are made with an aim toward a better understanding of the threshold fission phenomenon in the framework of a double-humped barrier in fission.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26853

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

Proposed fusion reactor blanket designs bring into focus a large number of problems dealing with the interaction of 14-MeV neutrons with different materials. Carbon, oxygen, aluminum, titanium, and iron are among the materials used in the blanket. To have confidence in fusion reactor blanket calculations, a necessary prerequisite is that the transport code correctly describes the interaction of 14-MeV neutrons with the materials of the blanket. Spherical assemblies of the above materials ranging from 1 to 5 mean-free-paths in thickness have been bombarded with a centered nominal 14-MeV neutron source. The emitted neutron energy spectra were measured using time-of-flight techniques (3-nsec full-width-at-half-maximum system resolution) in a geometry where the flight path (7 to 10 m) is long compared to the dimensions of the spherical targets. The spectra have been calculated with the Monte Carlo neutron transport code TART using the ENDF/B-III and -IV neutron libraries and compared with measurements.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26854

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

Differential cross sections for the production of low-energy gamma rays (<240 keV) by neutron interactions in fluorine have been measured for neutron energies between 0.1 and 20 MeV. The Oak Ridge Electron Linear Accelerator was used as the neutron source; incident neutron energies were determined by time-of-flight techniques. Gamma rays were detected at 92 deg using an intrinsic high-resolution germanium detector. Results are presented for the production cross sections of three gamma rays having energies of 96, 110, and 197 keV. These data are compared with previous experimental data; the agreement varies between poor and good.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26855

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

The neutron-induced fission cross section of241Pu was measured at an 8-m-long flight path of the CBNM Linac from 50 to 0.01 eV, allowing a direct normalization to the 2200 m/sec reference cross section. The fission reaction rate and the neutron flux were determined simultaneously with surface barrier detectors placed on each side of back-to-back241Pu and10B layers. The fission cross section was calculated assuming a l/v behavior of the10B(n,α)7Li cross section. Several fission and resonance integrals were calculated from the normalizedσfversus energy curve and compared with other results. Also, the 20.44°C Westcott factor, gf, was calculated to be 1.046±0.006.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26856

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

Absolute neutron-capture cross-section measurements from 0.01 to 10 eV employing a Moxon-Rae detector and conventional time-of-flight techniques are described. For the calculation of multiple-scattering and gamma-ray attenuation effects in samples, new improved methods were developed. Cross-section curves were evaluated for the elements europium and lutetium as well as for the isotopes151Eu,153Eu,175Lu, and176Lu. The cross sections could be determined to an accuracy of better than 5%; however, for some resonance cross sections the total error increases up to 10%.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26857

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

The Army Pulse Radiation Facility Reactor has been pulsed to 17 cents above prompt criticality using external reflector control. This is a novel method of fast-pulse reactor operation. The purpose of this work is to provide a high neutron fluence uniform over a 106-mm-diam, 198-mm-high in-core irradiation cavity or“glory hole,”in both pulse and steady-state modes of operation. The 106-mm-diam glory hole is obtained by removing from the standard core a cylindrical center fuel element, the“safety block,”and replacing it functionally by three 50.8-mm-thick, 305-mm-high scramable copper reflectors positioned 5.3 mm from the reactor shroud. The cost of this modification was favorable since fabrication of new fuel pieces was unnecessary. To date this assembly has been successfully pulsed to yields as high as 1.83×1017fission/pulse. There is an∼38% increase in prompt neutron lifetime in the reflected core due to the central cavity and the reflectors. The prompt negative shutdown coefficient is decreased only slightly so that the reflected core can be pulsed with requisite safety and satisfactory reproducibility. At the routine pulse level of 1.5×1017(±2%) fissions, the pulse width is 66µsec, the neutron fluence in the glory hole is 5.0×1014n/cm2(>10 keV), where the peak neutron flux is 6.4×1018n/(cm2sec) and the gamma-ray dose is 1.6×105R. With a thermal-neutron flux trap, the peak thermal-neutron flux is 1×1018n/(cm2sec). With a neutron-to-gamma-ray converter, the peak gamma-ray emission rate is 3×109R/sec. Operation at 10 kW in a steady-state mode produces a neutron flux (>10 keV) of 1012n/(cm2sec). Experiments have been performed previously to evaluate the use of reflectors as control and pulse rods. The present method of operation extends the use of reflectors to provide the principal mechanical shutdown mechanism in superprompt critical pulse operation.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26858

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

The transport equation in toroidal geometry is derived in divergence form by the tensor method. This equation is then differenced by a method that is similar to the ordinary diamond scheme. A solution technique for the system of difference equations, which can be implemented in an existing SNcode, is presented.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26859

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

Some solutions of the differential equations, which describe an elementary model of the disposition of material carried by a fluid flowing in a pipe, are derived and investigated. The solutions pertain to a variety of assumptions made regarding the initial concentrations of the material in the fluid within the pipe and on the pipe interior surface, and the concentration of the material in the fluid entering the pipe. The means of obtaining some of the model parameters using the derived solutions and measured values of the concentrations of matter on the pipe surface and in the fluid are illustrated.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26860

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor