摘要:

AbstractThe spectrum of the multigroup-multipoint operator with delayed neutrons is studied under the assumption of a common fission spectrum. Using the fact that the fission operator is proportional to a projector, the Weinstein-Aronszajn technique for degenerate perturbation can be used. The general problem is first reduced to a problem without delayed neutrons. The high degeneracy of the spectrum is further examined and connected with the definition of“clusters.”

ISSN:0029-5639    

DOI:10.13182/NSE78-A15432

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe symmetric successive overrelaxation (SSOR) method and the symmetric strongly implicit procedure (SSIP) method are applied to a number of two-dimensional elliptic partial differential equations typical of those encountered in reactor engineering. The SSIP method is then incorporated in a program for multigroup diffusion calculation to compute the inner iterations. The results of applying the program to the solution of several reactor configurations are compared with the results from a version of the PDQ code. For cell problems (with Neumann boundary condition), the new methods outperform the SOR method.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15433

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe spatial distribution of the total neutron density from a252Cf source in pure water was measured to high statistical precision at distances ranging from 11 to 80 cm from the source. Assuming the adequacy of the ENDF/B-IV hydrogen cross sections and reasonable constraints on the fission spectrum mean energy, good agreement between experiment and a one-dimensional transport calculation was obtained for both ENDF/B-III and -IV oxygen cross sections, with Version III being slightly better. However, small residual differences remained that could not be removed by adjustment of the spectrum mean energy alone.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15434

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe total neutron cross section of58Fe has been determined in the energy range from 7 to 325 keV by a transmission measurement using samples enriched in the58Fe isotope. The data have been shape-fitted by means of an R matrix multilevel formalism to extract resonance parameters for s and l>0 wave resonances. The s-wave strength function was determined to S0= (4.3±1.9)×10-4.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15435

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractAn absolute scale for the differential cross sections of the reactions3H(p, n)3He,2H(d, n)3He, and3H(d, n)4He, measured for incident energies between 6 and 17 MeV, was established using a calibrated time-of-flight system. Accurate charged-particle reference cross sections were inter-compared so that a common scale with an uncertainty of±1.5% was obtained. By interchanging the target and beam nuclei, data were obtained at 180 deg in the original system for several cases. The new data were analyzed together with the previous data, and Legendre coefficients were extracted to permit presentation of the data between∼5 and 20 MeV, thus extending and partly revising previous evaluations. The typical shape error of the angular distributions, as given by the Legendre coefficients, is<3% over the entire angular range. In addition, data on the neutron production at zero degree by breakup are given for the p-T and d-D reactions.By correcting the previous counter telescope data for the1H(n, n)1H cross sections (according to more recent phase-shift analyses), scale ambiguities of∼3% were resolved, thus indirectly verifying these phase shifts up to neutron energies of∼16 MeV. However, at higher energies (above∼23 MeV) for3H(d, n)4He data, the corrected neutron counter telescope data deviate from the present analysis by∼5%. Whether or not this difference is caused by the1H(n, n)1H reference cross section used is open to further investigations.

ISSN:0029-5639    

DOI:10.13182/NSE67-190

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe Adler-Adler cross-section formalism with energy-dependent parameters is a practical approximation to the R-Matrix formalism, based on the smallness of the s-wave neutron width in fissile elements. Attempts have been made to represent experimental cross sections by the Adler-Adler formulas through an initial representation by the Reich-Moore approximation of R-Matrix and a subsequent conversion of the Reich-Moore formulas to the Adler-Adler formulas.Adler and Adler had foreseen difficulties in associating their formulas with approximate R-Matrix theories such as those of Reich-Moore. Indeed, it is shown that due to the nonunitarity of the Adler-Adler formalism on the one hand and the unitarity, by definition, of the Reich-Moore formalism on the other hand, the conversion from the latter to the former is ambiguous. Examples are shown to demonstrate that this ambiguity results in numerical inaccuracies, sometimes very large ones, for neutron widths that are not extremely small.Improved Adler-Adler-type formulas have been derived from the R-Matrix formalism. In these formulas, the multipliers of the Breit-Wigner resonance lines exhibit more explicit energy dependence than their original counterparts, mainly in the form of additional terms in the formula for the total cross section. The conversion from Reich-Moore cross sections to the improved resonance formulas is shown to be much less ambiguous and to produce very accurate cross sections. In particular, the inaccuracies encountered with the Reich-Moore-Adler-Adler conversion are eliminated.A computer code, PEDRA, was written to perform the conversion from a given set of Reich-Moore parameters to the parameters required in the improved formulas. The numerical algorithm of this code is based on an adaptation with modifications of the numerical approach of de Saussure-Perez in the POLLA code, which converts Reich-Moore parameters to Adler-Adler parameters.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15437

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThe kinetics of excitation in the laser enrichment process is sensitively dependent upon the density and temperature distribution in a freely expanding jet. In the present paper, the source flow expansion of the viscous heat-conducting low-density gas accompanied by a compression shock wave was studied by solving the unsteady Navier-Stokes equations. The basic equations were solved using the numerical scheme proposed by Sakurai. The numerical results presented are those of density and temperature profiles for uranium hexafluoride gas under various conditions. The effects of viscous dissipation and the rotational nonequilibrium were discussed. To examine the accuracy of the continuum source flow model, the prediction of the model is compared with the available experimental data. These numerical results will be useful in practical calculations for the design of laser enrichment apparatus.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15438

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractA calculation model was developed to predict the shutdown dose rate around the recirculation pipes and their components in boiling water reactors (BWRs) by simulating the corrosion product transport in primary cooling water. The model is characterized by separating cobalt species in the water into soluble and insoluble materials and then calculating each concentration using the following considerations:1.Insoluble cobalt (designated as crud cobalt) is deposited directly on the fuel surface, while soluble cobalt (designated as ionic cobalt) is adsorbed on iron oxide deposits on the fuel surface.2.Cobalt-60 activated on the fuel surface is dissolved in the water in an ionic form, and some is released with iron oxide as crud.The model can follow the reduction of60Co in the primary cooling water caused by the control of the iron feed rate into the reactor, which decreases the iron oxide deposits on the fuel surface and then reduces the cobalt adsorption rate. The calculated results agree satisfactorily with the measurements in several BWR plants.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15439

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractThis Note presents a concise version of the analogy between fusion (ignition) and fission (criticality) plus a new Tnτcriterion for evaluating fusion plasma quality with regard to ignition. A comparison with experimental data is also made.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15440

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor

摘要:

AbstractResults for our liquid-metal fast breeder reactor benchmark problem obtained by several diffusion computer programs for two- and three-dimensional reactor models showed unexplained behavior or discrepancies. With the help of additional calculations and comparisons, it was possible to improve some of the computer programs. Most of the original calculations have been repeated (and, in addition, some new calculations have been performed), and the revised results of the comparison are presented in this Note.

ISSN:0029-5639    

DOI:10.13182/NSE78-A15441

出版商:Taylor&Francis    

年代:1978

数据来源: Taylor