摘要:

AbstractTime-dependent neutron spectra in the center of an externally pulsed finite (7.16×25.02×25.4 cm3) H2O medium at 37.8°C were measured over an energy range 0.01 eV

ISSN:0029-5639    

DOI:10.13182/NSE70-A19493

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractA calculation of the one-phonon neutron scattering law for polycrystalline beryllium has been performed. This scattering law is an improvement over the results of the incoherent approximation and allows a more accurate computation of the total cross section below the Bragg cutoff.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19494

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractThe relative neutron capture and fission cross section in the neutron energy range 0.02 to 1.0 eV have been simultaneously measured. The data are normalized by means of the previously reported total cross section. The technique used consisted of passing a pulsed neutron beam through a233U fission chamber placed at the center of a large liquid scintillator. The prompt-neutron capture gamma rays were detected only in the liquid scintillator whereas a fission event was characterized by coincident signals from the liquid scintillator and fission chamber. This technique provides a new method of obtaining eta in this neutron energy range which is not subject to the same type of errors as are associated with a direct measurement. Comparisons with previously published data are given.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19495

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractAn extended series of exponential experiments was carried out utilizing233UO2-ThO2fuel elements in uniform arrays in light and heavy water. In this series the principal parameters measured were material buckling (), reflector savings (λ), dysprosium disadvantage factor (ζDy), ratio of epicadmium to subcadmium capture in thorium (), and ratio of232Th fission to233U fission (). A total of 29 clean and poisoned lattices was measured.

ISSN:0029-5639    

DOI:10.13182/NSE70-2

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractAdequate knowledge of the transmission probabilities of neutrons through control blades filled with round tubes containing absorbing material is required in reactor design. Starting from a strict formulation of the problem, some computational approximations are introduced which lead to compact expressions directly available to the designer. The accuracy of the proposed formulas is then investigated in conjunction with a theoretical and numerical analysis of the confidence limit of the most advanced method (P1 blackness theory) of accounting for control blades in diffusion calculations. Finally, comparisons with experimental integral data (Rossi-αmeasurements) confirm that the accuracy of the proposed formulas is consistent with the precision of the method.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19497

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractWe report here the complete eigenvalue structure and the corresponding eigenfunctions of the neutron transport operator for the neutron wave propagation through water and heavy water. The calculations have been performed in multigroup diffusion theory approximation using realistic scattering kernels. The results are found to be rather insensitive to the chemical binding effects. The bounds on the eigenvalues have also been discussed and the results corresponding to the fundamental mode eigenvalue have been compared with the experimental data for heavy water. Our results show that there exists only one resolvable mode for water and four resolvable modes for heavy water.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19498

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractThis paper discusses the statistical uncertainties of the self-shielded group cross section and its temperature derivative associated with the use of the biased selection technique where resonances are chosen to match the observed value of the unshielded cross section. Since the self-shielded group cross section can always be pictured as a superposition of an infinitely dilute term and a self-shielding term, the problem amounts to the estimation of the conditional variances of the self-shielding term and its temperature derivative for any given value of the infinitely dilute cross section. A semianalytical method based on the NR-approximation has been developed to estimate these conditional variances. Both qualitative and quantitative discussions are given for cases of239Pu and238U under various physical conditions.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19499

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractThe thermal fission yields of 43 mass chains for233U,235U,239Pu, and241Pu and the fast reactor fission yields of 45 mass chains for235U and239Pu have been measured with a relative standard deviation of 1 to 2%. The data were obtained mainly by measuring long-lived and stable fission products by the technique of isotope dilution mass spectrometry. This paper has two sections: the first reports the fission yields, the second describes the chemical analysis techniques for the fission products.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19500

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractBased on an examination of thermal and fast reactor fission yield data, specific fission products are recommended as burnup monitors for total fissions in various reactor fuel types and for fractional fissions in235U-239Pu and233U-235U reactor fuels. Emphasis is placed on long-lived and stable fission products determined by mass spectrometry. The types of monitors include a single fission product for total fissions and the ratio of two fission product isotopes of the same element both for total fissions and fractional fissions.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19501

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor

摘要:

AbstractAcoustic wave propagation in a gaseous core nuclear rocket is investigated by a theoretical model. Slab geometry in a long initially uniform cavity is assumed for simplicity and the reflector-heat sink is taken to be of infinite thickness. Blackness theory is used to determine the transmission of thermal neutrons (and thereby the generation of heat) in the fissionable gas of the cavity. Mutual feedback between neutron dynamics and gas dynamics occurs by means of the density-dependence of the blackness coefficients. Numerical results indicate that neutronic feedback can be a significant influence toward stabilization of acoustic oscillations. The critical wave length (which is twice the critical core length) without neutronic feedback is calculated to be 100 cm while critical wave lengths of 150 and 232 cm were obtained for carbon and beryllium reflectors, respectively. These results show that the critical core lengths are still comparable to or shorter than typical reference core lengths (300 cm). Thus, while neutronic feedback has an effect on acoustic instability, the effect is not strong enough to alter the general conclusion that acoustic instability is a potential problem area for gaseous reactor development.

ISSN:0029-5639    

DOI:10.13182/NSE70-A19502

出版商:Taylor&Francis    

年代:1970

数据来源: Taylor