摘要:

Measurements were made of the diffusion losses of lanthanide and actinide elements from graphite at temperatures from 1600 to 2600°C. In the lanthanide series, a close correlation was observed between the diffusion rates from graphite and the boiling points of the metals. Where boiling point measurements permit comparison, a similar correlation was also noted for the actinides. The most volatile of these elements are the ones for which lower oxidation states can be attained chemically [Sm(II), Eu(II), Yb(II), and possibly Am(II)]. Conversely, those elements which exhibit oxidation states higher than (III) show high-temperature stability in graphite. Although the diffusion loss of uranium is not negligible above 2100°C, no loss was detected from a small graphite pin heated for four hours at 2050°C; under the same conditions, about 50% of the plutonium was lost. The possible significance of these measurements to high-temperature reactor design is discussed briefly.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25905

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

The relative U238resonance capture integrals of 0.387-in. diameter UO2and uranium metal fuel rods have been measured as well as the spatial distributions of the captures in each type of rod. The effective resonance integral of the UO2rod was found to be 1.30±0.02 times that of the uranium metal rod. This difference is due to the lower density of uranium atoms and the presence of oxygen moderation in the UO2fuel rod.The relative importance of each of these two effects was determined by means of U-Zr and U-Al alloy fuel rods. Of the 0.30 excess of the UO2resonance capture integral over that of the uranium metal, 0.15±0.02 was contributed by the lower U238atom density of the UO2rod, and the remaining 0.15 was attributed to oxygen moderation.Work done by Hellstrand (5) gives a value of 1.41±0.03 for the U238resonance capture integral for the UO2rod relative to that of the uranium metal rod. Furthermore, by evaluating his expression for the resonance integral of a metal rod at a value ofS/Mcorresponding to a“low-density”uranium metal rod (U238atom density equal to that of the UO2rod) of 0.387-in. diameter, one obtains a density effect of 1.32.These discrepancies can be attributed, at least partially, to a differing flux spectrum at energies above 30 kev in the present experiment as compared with Hellstrand’s experiment. Whereas the high-energy flux is depleted in his experiment, there was an appreciable flux peak present in the TRX measurements.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25906

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

The principal result of the work reported in this paper is a first-order differential equation for the neutron spectrum in an energy region where the effects of chemical binding are significant but not dominant. Solutions of the differential equation provide accurate results for the spectrum in the cases of moderation by hydrogen, as well as by the heavier moderators, such as beryllium and graphite. In the derivation of the results, no restrictions are made concerning the nature of the motions of the moderator atoms. Interference effects in the neutron scattering are, however, neglected. The integral properties of the scattering kernel, which are found to influence the spectrum significantly, are calculated by means of the short-collision-time approximation, first introduced by Wick to compute the effects of chemical binding on slow neutron-scattering cross sections.Finally, for heavy moderators the representation of the energy-transfer properties of the moderator in terms of a first-order differential operator are combined with theP1approximation to give a useful description of the spatially dependent spectrum.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25907

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThe method presented can be used to determine fluid flow and coolant pump speed transients in a nuclear reactor system. Included are transients due to power failure, starting pumps in idle loops, and the opening of an active pump’s discharge valve. Parallel pumps in the system may be analysed independently of each other. Typical cases are presented for the N. S. Savannah (NMSR) and the Consolidated Edison Thorium Reactor (CETR).Partial failure of pumping power results in an unbalanced change in primary flow, i.e., flow in the active loops accelerates while flow in the failed loops decelerates rapidly. Maximum deceleration occurs when all pumps are operating and only one fails. The maximum rate of cold water is pumped into the reactor when the pumps in an idle loop are started while the discharge valve is open.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25908

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThe feasibility of purifying irradiation-degraded Purex-type solvent by distillation was indicated by laboratory scale studies. Direct fractional distillation does not appear to be feasible; however, flash distillation of the mixture into separate TBP and Amsco components and subsequent fractional distillation of each component can be performed in a trouble-free manner. The results of this work indicate that a washing operation and several flash distillations should suffice for purification of solvent irradiated up to 120 w-hr/liter.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25909

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractAn experimental investigation into the effects on Inconel of the application of relatively high-frequency thermal oscillations under conditions such as to generate significant transient stress in the surface fibers is described. Thermal instabilities of this nature may be generated in the operation of certain types of nuclear reactors. Fatigue-type cracking was observed in 214 hr at 1.0 cps for a surface temperature amplitude of±64°F (17,800 psi maximum elastic surface stress); incipient cracking occurred in 23 hr at 0.4 cps for an amplitude of±104°F (31,300 psi). Application of±46°F surface temperature oscillations (12,800 psi) at 1.0 cps for 612 hr produced accelerated intergranular corrosion in a fused salt environment. The results are correlated in terms of the maximum calculated elastic surface stress.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25910

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractAmong recent accomplishments in the field of the transuranium elements have been the discoveries of elements 99–102. The fact that these elements are members of the actinide transition series and have chemical homologues in the lanthanide or rare-earth series of elements has provided a basis for their initial identification. Special techniques have also been required, however, for their discovery. In the case of element 101, when only one or two atoms per bombardment were synthesized, a new method, the recoil technique, was used to separate the product from the target material by purely physical means. Element 102 is the first element to be discovered as a product of heavy-ion bombardment. This element, which has a half-life of approximately three seconds, was identified chemically by means of its daughter Fm250. The element 102 and Fm250atoms were isolated by an ingenious adaptation of the recoil technique which was used in the discovery of element 101.Indications are that new transuranium elements will be discovered, but research along this line is extremely complex and difficult. One of the problems to be solved is concerned with the availability of target materials of high atomic number. These are synthesized by the long-term neutron irradiation of plutonium. One such irradiation program has supplied us with californium and berkelium in macroscopic amount. As an interesting result of this program the first pure californium compounds have been prepared, and studies of their properties are in progress. A national program for the production of heavy isotopes is expected to yield milligram amounts of californium by 1965.The use of heavy-ion bombardments offers the most promise for the synthesis of new elements, and work on the preparation of element 103 and heavier elements by this means is in progress. Fission predominates in such nuclear reactions, and thus only extremely small yields of elements of high atomic number can be obtained. Another difficulty lies in the fact that the elements beyond element 102 are expected to have very short half lives. These difficulties indicate that new methods for their identification need to be used. Although the position of these new elements in the periodic table can be predicted so that their chemical nature can be anticipated, the first identifications will probably not be made by traditional chemical methods.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25911

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractProcesses for dissolving uranium-zirconium and uranium-zirconium-niobium alloy fuels in ammonium fluoride solutions (Modified Zirflex processes) were developed in the laboratory. A non-aqueous process (Zircex process), in which high-zirconium alloys are hydrochlorinated at about 600°C, offers the possibility of zirconium separation prior to solvent extraction. Dissolvents consisting of mixtures of hydrofluoric acid and hydrogen peroxide or hydrofluoric acid, nitric acid, and aluminum nitrate are also attractive, but corrosion rates with common construction materials have proven excessively high at over 20 mils per month.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25912

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThe equal charge displacement rule has been used for estimating yields of some important fission products. The results are not appreciably different from previous estimates but the present method increases the reliability of the values. Using recent yield values, thermal and resonance effects of gross fission products have been calculated and compared with measured effects in an irradiation experiment by Gunst, McGarry, and Scoville as well as with previously calculated values.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25913

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractYttrium metal rods of commercial purity (3300 ppm O2) were heated to 1230–1370°C for 200 hr in static argon by passage of direct current. Chemical and metallographic examination indicated that oxygen and several metallic impurities (Fe, Mn, Ni, B, Ti, Co) had migrated extensively to the anode with the oxygen content near the cathode being reduced by 80%. The metal near the cathode was ductile and could be cold rolled to 65% reduction without edge cracking. These experiments are the first successful attempt to utilize electrolysis of a solid metal as a purification technique. The results indicate a marked potential for the method, and confirm the belief that pure yttrium is a ductile metal.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25914

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor