摘要:

AbstractA variational procedure for calculating fast energy few group constants is described. For a given medium, the method permits one to express the flux and current solutions of the Boltzmann equation, treated according toP−1 slowing down theory in each group of a few group scheme, as a linear combination of base flux spectra to obtain the group flux and as a linear combination of base current spectra to obtain the group current. The coefficients for combining the base spectra are provided by the theory and depend only on the concentrations of the component elements of the medium. Once the flux and current spectra in each group are calculated, the group constants for the medium can be easily calculated from base flux spectra weighted library microscopic cross sections. Group constants calculated in this manner agree well with those obtained from the MUFT V program.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26544

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractTransient-temperature behavior following a step change in internal heat generation has been analyzed to determine the power generation in the Battelle Shielding Facility fission plate. The fission plate is employed for shielding studies as a radiation source with a fission energy distribution. The plate is a 28-in. diam, 0.0199-in. thick uranium disk containing 3741 gm of uranium enriched to 93.14% in the uranium-235 isotope. It is plated with 0.0007 in. of nickel and clad with 0.025 in. of aluminum on each side and is in intimate contact with a 0.25-in. thick aluminum plate on one side. Ceramic spacers provide airgap insulation of the fission-aluminum plate combination from the surrounding media.Resistance thermometers were employed to observe the transient-temperature behavior following a step change in the internal heat generation in the plate for fission heating and for cooling tests. The cooling curve data were strictly exponential and rendered a decay constant of 0.0517 min−1which was utilized, along with the physical constants of the assembly, to render a solution to the transient-heating equation and an estimated power of 25.0±0.6 watts.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26545

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractSome problems of the theoretical interpretation of pulsed neutron experiments are investigated in this paper, on the basis of the energy dependent Boltzmann equation. The relation of the infinite medium theory to the finite medium experiments is discussed in details. We perform a calculation inP1L1approximation in order to determine the form of neutron flux and the extrapolation length. It is demonstrated that the existence of an asymptotic region is not required to apply the infinite medium theory to the finite medium experiments.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26546

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe applicability of the zero-neutron-lifetime approximation in describing the effects of neutron-level fluctuations is investigated for reactivities near and above prompt critical. It is concluded that meaningful statistical information can be obtained by the zero-lifetime model above prompt critical, and an approximate procedure for joining this model to a deterministic finite-lifetime model is suggested.Illustrative examples, comparing numerical results obtained by this approximation with more accurate finite-lifetime statistical calculations, are presented. In addition, application is made to Los Alamos and Livermore superprompt-critical burst experiments which fall outside of the practical computing range of the finite-lifetime model described in Part II. It is found that the agreement of calculation and experiment is as good as was found previously for a set of subprompt-critical burst experiments.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26547

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE63-A26548

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractIn general, the mono-acidic phosphates and phosphonates are dimeric and the di-acidic phosphates and phosphonic acids are polymeric in the diluents commonly employed in metal extraction studies. Therefore, they may be symbolized, respectively, as (HY)2and (H2Y)x.The extraction of tracer-level M(III) actinides and lanthanides from a dilute mineral acid by representatives of these two classes of extractants in toluene diluent may be represented, respectively, as:where the subscripts A and O refer to mutually equilibrated aqueous and organic phases. However, in an alcohol diluent the H2Y extractants appear to be monomeric, and they extract M+3cations with a third-power extractant dependency.In toluene diluent, the HY extractants function as dimers, the extractant dependencies for selected M+2and M+4cations being:(2-power); Ca+2, Sr+2, Ba+2(2.5-power, 3-power); Th+4(3-power). In certain systems, Th+4is extracted as a species containing one or two nitrate groups.Structures of the extracted species are postulated.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26549

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractFrom freezing-point and isopiestic studies, it has been found that the acidic organophosphorus extractants of the type (GO)2PO(OH) and GOG′PO(OH) (where G is aryl, alkyl, or a derivative thereof) are predominantly dimeric in nonpolar diluents, such as n-hexane, cyclohexane, benzene, and carbon tetrachloride. The dimers are very stable and appear to monomerize only in more polar solvents, such as acetone, chloroform, or ethanol. Infrared spectra of these acids have been made, and the positions of the phosphoryl absorption determined in terms of the electronegativity of the G group. It is concluded from these studies that for the acids (GO)2PO(OH) an ionic P+O−and a strong acid is the better extractant; while for the acids GOG′PO(OH) a phosphoryl group with high double bond character and a strong acid is a better extractant. For both acid types these criteria are provided whenever the G group is highly electronegative.Complexes of organophosphorus extractants with metallic nitrates have been studied by infrared methods and it has been concluded that the nitrate spectra is of lowered symmetry than is present in ionic nitrate spectra, indicating a higher degree of covalency in the metal to nitrate band. Examples of these complexes are RE(NO3)3·2TBP (where RE is a rare earth metal, TBP is trin-butyl phosphate) and M(NO3)(DEHP)3(where DEHP is bis-(2-ethylhexyl)phosphoric anion).Infrared investigations of the salts of the acidic organophosphorus extractants have indicated the appearance of 2-POO−absorptions (asymmetric and symmetric). The asymmetric absorption appears to vary (1200–1282 cm−1) with the nature of the G group (being at higher frequency where G is aryl), and with the ionic potential of the metal (being at higher frequency as the ionic potential increases).Recent ultraviolet and infrared studies of complexes of the type M/TTA/TBP have been made and certain structures for these compounds have been indicated.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26550

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe object of this paper is to review some recent Harwell work on the extraction of metals and acids from aqueous solution by alkylphosphoric acids and to discuss the basic equilibria involved.The solubility and distribution of mono- and di-n-butyl phosphoric acid (H2MBP and HDBP respectively) have been measured in various aqueous-organic solvent systems—in particular the TBP-kerosene-HNO3system. The data for HDBP can be interpreted in terms of a series of equations for the dissociation of the HDBP in the aqueous phase, the dimerization of the HDBP in the aqueous and organic phase, the association of HDBP with TBP and with nitric acid, and the distribution of the HDBP monomer and dimer, and the HDBP·HNO3complex, between the phases.Nitric acid and water are extracted by dialkylphosphoric acids and also by the commonly used diluents. Nitric acid is extracted by HDBP in toluene or kerosene largely as the HDBP·HNO3complex, which is in equilibrium with the hvdrated complexes HDBP·H2O and HDBP·HNO3·H2O.Metals are extracted from aqueous solution by dialkylphosphoric acids (HX) mainly in four forms containing as ligands:(i)X groups.(ii)X and HX groups.(iii)X and HX groups and also the anion, for example, NO3−, present in the initial aqueous solution.(iv)HX groups and the anion in the aqueous phase. The occurrence of one or more of these tvpes of complex is illustrated for U(VI), Zr(IV), and Be(II).

ISSN:0029-5639    

DOI:10.13182/NSE63-A26551

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractCombinations of dialkylphosphoric acids (HA) and neutral organophosphorus reagents (B) have for some time been known to produce enhanced (synergistic) extraction ofand otheractinide ions. This effect may be attributed to the formation of a mixed complex—either a substitution product MO2A3HB or an addition product MO2A4H2B resulting from the reaction of B with the extraction complex MO2A4H2normally formed with HA alone. Available extraction data, when analyzed in terms of the competing hydrogen-bonding interactions between HA and B, appear more consistent with an addition product MO2A4H2B. The stability of this mixed complex as a function of the neutral organophosphate used and as a function of the diluent used is consistent with hydrogen bonding or solvation of MO2A4H2by B. The much stronger and more general synergism found in systems wherein HA is replaced by theβ-diketone, Thenoyltrifluoroacetone (HY) may be attributed to the relatively weaker competing interaction between HY and B and to the less coordinatively saturated extraction complexes formed by HY alone.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26552

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThenoyl trifluoroacetone (HTTA) has been used by workers in England and the U. S. as the acid in combination with neutral organophosphates (S) to demonstrate a strong (synergistic) enhancement of extraction of metallic species. This enhancement using HTTA is exhibited by many metal species and is much larger (up to 108) than that obtained with the dialkyl phosphoric acids (up to 102). This effect is increased as S is changed from the neutral alkyl phosphates, through phosphonates, to the phosphine oxides. Examples of synergism with HTTA and S are also given where S, the neutral additive, contains no phosphorus and is an amide, alcohol, or ketone. Tracer work has established the composition of over 30 extracting species containing di, tri, and tetravalent metals of the general formula M(TTA)xSy, wherexis the valency of M, andyvaries between 1 and 3. Confirmation of these formulas has, in a number of instances, been obtained by ultraviolet spectrophotometry on tenth molar solutions and by analysis of anhydrous microcrystalline solids isolated from solution. Stability constants have also been ascertained for many of these synergistic species. Infrared work indicates the likelihood of some of the chelate Ugands becoming monodentate in the synergistic species with direct bonding of S to the metal.If an excess of neutral ester S is added to a synergistic system, antisynergism, that is the reverse of synergism, occurs and decreases of 108in extraction coefficient can occur. The degree of antisynergism depends on the quantity and nature of S. S could be an alcohol, amide, ketone, ether, ester (including organophosphorus esters) or, in fact, a so called“inert”diluent such as benzene or chloroform. The cause of these very large antisynergistic effects is bound up with the water content of the neutral additive S and of the diluent. There is ultraviolet spectral evidence that the anhydrous species is destroyed with formation of a hydrated TTA species.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26553

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor