摘要:

AbstractElectrical neutrality must be maintained in nuclear reactor fuels. The consequences of this requirement are illustrated for two fuel materials: solid UO2and dilute solutions of UF4in molten fluorides. In both systems, changes with time of the valencies of several fission product elements are sufficient to maintain the necessary electroneutrality. In the molten fluorides, however, the situation is more complex than in the oxide, due to the possibility that certain fission product species may react with the container. The importance of rare gas removal in this regard is demonstrated.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25527

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractA simple phenomenological theory is presented to describe the xenon poisoning of a molten fluoride fueled nuclear reactor which is sparged with a suitable inert gas. The extension of the theory to removal of other fission product species is indicated. The theory is illustrated by a parametric study. It is found that arbitrarily low levels of Xe135can be achieved by adequate sparging of the fuel. Such sparging also frees these reactors from the trouble-some rise of the xenon poisoning during shutdowns. No reactivity transients of a serious nature are likely to result from changes in the rates of the xenon removal processes.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25528

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractObservations are reported on the behavior of several fission product elements in molten NaF-ZrF4-UF4fuels, irradiated in capsule experiments, forced-convection in-pile loop experiments, and in the Aircraft Reactor Experiment (ARE). The rare gases have been observed to escape readily from the fuels in dynamic tests, although in static tests the rate of escape is very low. Ruthenium and niobium deposit on the Inconel walls of the fuel container, probably as metals. Other fission products studied (Sr, Zr, La, Ce) appear to remain in the fuel. The results obtained are entirely consistent with theoretical predictions. It is suggested that the observed noble metal deposit may serve to reduce corrosion of metals by molten fluoride fuels. The unsatisfactory nature of Cs137as a fission monitor in such fuels is reported and the use of Zr95as a substitute is discussed.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25529

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractThe PCTR is a seven-foot cube of graphite with a large cavity, 2×2×3 ft, located at its center. It is made critical by enriched uranium which is distributed on the boundary of the central cavity. One end of the assembly, 2×7×7 ft, is mounted on a movable cart, and can be moved away from the reactor proper allowing access to the central test region. The infinite medium, thermal neutron multiplication factor,k∞, of a multiplying material is obtained by determining the amount of thermal absorber, which, when inserted with the multiplying material into the central region of the PCTR, will change neither the reactivity of the assembly nor the energy distribution of neutrons in it. The design of the reactor and the method used for determining this absorber mass are discussed and results for two graphite-natural uranium lattices are presented.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25530

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractThe absorption area method allows rod absorptions to be considered without treating the rods as discrete boundaries. The source neutrons for a rod absorbing neutron energy group are reduced in proportion to the rod absorption area. This paper presents rod absorption factors based on absorption area calculations that may be applied in any reactor region penetrated by the rods. The factors derived are dependent on the core and rod composition, rod geometry, and include rod interaction effects.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25531

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractThe selection of appropriate epithermal group-averaged cross sections for use in a few-group criticality calculation is particularly difficult when resonance absorbers are present. However, by use of the SOFOCATE code for the calculation of thermal spectra in hydrogenous media, it is now practical to include low-lying resonances below 2 ev in the thermal group. Since the SOFOCATE code, which is based on the Wigner-Wilkins differential equation for monatomic hydrogen thermalization, has yielded good agreement with measured spectra in water, it is felt that use of this code and inclusion of low-lying resonances in the thermal group constitute a more accurate and convenient method of treating these resonances than other procedures. As an application of the method, a study has been made of some of the effects associated with the use of Eu as a means of reducing the temperature defect in water-moderated reactors. It is shown that the use of natural, unshielded Eu would reduce the temperature defect provided the spectral hardening introduced by the core absorption is sufficiently small. It is also shown that the strong dependence on spectral hardening is due to the presence of the Eu resonances at about 0.4 ev.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25532

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractThe effect of alloying on the amount of plutonium required in forming a critical mass of each alloy has been expressed in terms of an inventory requirement ratio,RI. This quantity was obtained for twenty-seven potential alloying elements at three compositional levels. The effectiveness of using Vegard’s law to estimate the density of the alloys was appraised by comparing the estimated densities andRIvalues of nine intermetallic compounds with their x-ray densities and theRIvalues computed from them. The parametric variation ofRIwithfT, the number of excess neutrons per collision was also studied.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25533

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractThe selection of materials for control of nuclear reactors employing a variety of coolants and working over a broad range of neutron spectra are considered from a qualitative standpoint. The materials discussed include hafnium, boron, cadmium, indium, silver, europium, gadolinium, and samarium. A basis for selection of materials is presented which should permit control of practically any reactor proposed today with a minimum of additional development. Materials are discussed from the standpoint of nuclear acceptability, metallurgical fabricability, corrosion resistance, radiation damage resistance, economics, and probable contributions to the over-all radioactivity problem.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25534

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractNuclear factors affecting the effectiveness of control rod materials for power reactors with a thermal or near thermal neutron spectrum are surveyed. The principal elements and isotopes which qualify as neutron absorbers are compared and physical requirements such as rod thickness, surface density, and weight ratios are stated. The importance of epithermal absorption and the nuclear effects of burnup due to long neutron exposure in power reactors are shown. The characteristics of absorption isotope chains such as europium are described and finally, the deleterious effects of cladding and scattering cross section of poison diluents on control effectiveness are shown.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25535

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor

摘要:

AbstractBoron alloys with titanium and zirconium have been examined as core materials for fixed poison components in the S3G reactor core without success. Subsequent work has demonstrated that round rods of 18% chromium, 15% nickel, 0.2% boron-10 stainless steel contained in an unbonded low cobalt stainless cladding will serve successfully in this application. Data on the irradiation and corrosion performance, mechanical properties, and thermal cycling resistance of the poison rods are presented. The elements are prepared by forging, rolling, and drawing the core alloy to final size, then cold drawing a tube of the cladding alloy onto its surface. Details of this fabrication procedure and methods for evaluating the end product are presented.

ISSN:0029-5639    

DOI:10.13182/NSE58-A25536

出版商:Taylor&Francis    

年代:1958

数据来源: Taylor