摘要:

A linear dynamic model, a quadratic performance index, and a Gaussian stochastic noise assumption (LQG-theory) have been used to design a feedback controller for a simulated current design 1100-MW(e) boiling water reactor. The total plant power control is studied in the range of 65 to 100% of rated power, with main emphasis on load-following control. An extended Kalman filter used in parallel with the compensator during normal operation is suggested for on-line parameter estimation. The algorithms are considered suitable for implementation in direct digital control.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26776

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

Systematic discrepancies between experimental and calculated neutron spectra in different fast-neutron media with high238U content were observed, allowing the uncertainties in certain238U neutron cross sections to be considered as the source of such discrepancies. Sensitivity studies, as well as the effect of the former uncertainties on such fast-neutron spectra showed that238U (n, n′) inelastic scattering is by far the main parameter determining the spectrum over a large energy range. Uranium-238 (n,γ) neutron capture is important only at low energies, below the238U (n, n′) threshold. The (n,γn′) reaction in238U using Fricke's data leads to an increase in the discrepancies in neutron spectra though this cross section could be considered negligible according to other arguments. A general least-squares adjustment of the238U total inelastic cross sections, on the neutron spectrum discrepancies, was carried out between 70 keV and 3.6 MeV, using two different inelastic probability matrices (those of ENDF/B-III and UKNDL-DFN 401), which were chosen among several evaluations of this reaction. The adjusted cross sections obtained in an energy mesh corresponding to lethargy intervals of 0.5 imply a systematic reduction of 20 to 30% relative to the initial values in both files, but they appear to be in good agreement with other recent (coarse-mesh) adjusted data, including the KFK-INR set.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26777

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

We describe a simple method for determining the neutron-absorption cross sections of radioactive nuclides and its application to22Na and126I. These nuclides are produced by fast-neutron reactions in cadmium-wrapped and unshielded samples simultaneously irradiated with cobalt flux wires. Values for the thermal cross section,σ0, the resonance integral,Σ′, and s0are calculated from the data using the Westcott convention. The results are as follows: for22Na,σ0= (5.11±0.31)×104b, s0= 2.3±0.1, andΣ′= (1.0±0.1)×105b; for126I,σ0= (9.0±5.0)×103b.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26778

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

Gamma-ray production cross sections were measured for the12C(n, xγ) and14N(n, xγ) reactions from 2.0- to 20.7-MeV neutron energy using the Intelcom Rad Tech Linac source. The carbon cross sections are presented for both high neutron resolution and ten broad neutron groups spanning the energy range. Cross sections for the discrete gamma-ray peaks from nitrogen are presented in 12 broad neutron groups, as are the“discrete plus continuum”cross sections obtained by unfolding the gamma-ray spectra. The measured cross sections generally agree with the evaluations and with previous measurements.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26779

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

Cross sections for the27Al(n, p)27Mg,46,47,48Ti(n, p)46,47,48,Sc.54,56Fe(n, p)54,56Mn,58Ni(n, p)58Co,59Co(n, p)59Fe, and64Zn(n, p)64Cu reactions were measured by activation methods for neutron energies from near threshold to 10 MeV. The cross sections were determined relative to235U and238U fission cross sections. The data are compared with values from the literature.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26780

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

The exact expressions for the first- and second-order moments of neutron density and the delayed-neutron precursor density are derived for a neutron multiplying system, with time-dependent stochastic perturbations in the reactivity and white noise source. The effect of finite correlation time of the reactivity on the stability of moments is discussed. For asymptotically long times, the moments are found to be stable. The exact expressions of the moments in the limiting case, when the reactivity correlation time becomes zero, are also derived. It is found that the expressions for this limiting case differ from the corresponding expressions of Williams.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26781

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractThe macroscopic representation of complicated moderating processes has been investigated to describe the collision integral in the Legendre polynomial expansion of the neutron transport equation in terms of the macroscopic moderating parameter, defined as the ratio of the l'th-order Legendre component of the slowing-down density to the corresponding collision integral. This approach is similar in form to the Wigner-type continuous slowing-down theory, but the present moderating parameter is a function of lethargy, space, and time. For practical applications a new Greuling-Goertzel approximation is proposed based on the factorization of the angular flux. The present parameter,γl(u), is defined so as to compensate the difference between the lethargy spectrum of the space- and time-independent flux and the exact spectrum.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26782

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractInteractions of neutrons with zinc have been studied by measuring gamma-ray-production cross sections. For a sample of natural zinc, spectra were obtained for incident-mean-neutron energies, En= 4.9, 5.4, and 5.9 MeV with gamma-ray detector systems utilizing coaxial Ge(Li) detectors. Nearly monoenergetic neutrons were obtained from the D(d, n) reaction using deuterons obtained from the (pulsed) Oak Ridge National Laboratory 5-MV Van de Graaff accelerator. Time-of-flight was used to discriminate against pulses due to neutrons and background radiation. Gamma-ray identification was aided by obtaining spectra for samples enriched in the isotopes64Zn and68Zn, and new information on the level structure of64Zn is reported. These cross sections have been compared, where possible, with previous comparable measurements with generally satisfactory results.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26783

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE75-A26784

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE75-A26785

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor