摘要:

AbstractA technique is described to account for effects of space- and time-dependent core source variations on pressure vessel surveillance dosimetry analysis. The procedure first defines an easily implemented geometry for a single adjoint transport calculation. The results from the adjoint calculation can then be combined with those from a single forward calculation, in conjunction with an adjoint scaling technique, to yield activities and pressure vessel fluxes simultaneously for a wide range of source distributions, dosimeter response functions, and detector locations. This method has been implemented in the LEPRICON code system for vessel fluence determination. An application to an R-θmodel of an operating power reactor shows that effects of source perturbations resulting in 20% changes in the core leakage can be predicted within∼3% at both downcomer and cavity dosimeter locations, for six different dosimeters, by choice of a single suitable adjoint response function.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18342

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA linear discontinuous finite difference formulation to solve the diffusion equations in coarse mesh and few groups is developed. The correction factors for heterogeneities, coarse mesh, and spectral effects are general interface flux discontinuity factors that can be explicitly calculated (synthetized) from detailed diffusion or transport solutions in fine mesh (heterogeneous) and multigroups, preserving the integrated fluxes and interface net currents. The stability is explicitly established for general synthetizations and for specific fine to coarse mesh and group reductions. Computing methods have been implemented for one-group (grey) synthetic diffusion acceleration, two-dimensional nodal/local solutions, and three-dimensional nodal simulation of pressurized water reactor cores. Results demonstrate the simplicity and stability of the formulation, a regular behavior of the correction factors, an outstanding acceleration performance, and high potential for parallel and vector computing.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18343

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAn analytic approach to calculate variance reduction under analog and biased Monte Carlo simulation of deep-penetration problems is presented. Within the framework of this formulation, the variance reduction characteristics of exponential biasing and a recently proposed scheme that couples exponential biasing to scattering angle biasing are studied. The advantages and disadvantages of the coupled scheme over exponential biasing on deep-penetration problems with varying scattering probability and anisotropy are clearly illustrated.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18344

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractVarious methods to measure independent yields are reviewed and discussed. A survey on actual measurements carried out after 1978 is given.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18345

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractComposite delayed neutron energy spectra from the thermal neutron fission of235U have been measured for eight delay-time intervals between 0.17 and 85.5 s. Our experimental technique combines a helium-jet and tape transfer system with a beta-neutron time-of-flight spectrometer. The neutron energy range of 0.01 to 2.0 MeV is spanned with6Li-glass, plastic, and liquid scintillators. Spectra are compared to ENDF/B-V as well as to individual precursors' data and average energies are tabulated for the present and previous compilations. An equilibrium spectrum is also calculated and compared to ENDF/B-V and individual precursor measurements.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18346

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA series of experiments was performed to measure the dependence on the incident neutron energy of the average number of prompt neutrons emitted per fission from233U,235U, and239Pu relative to the average number of prompt neutrons emitted in spontaneous fission of252Cf. The incident neutron energy range was 0.0005 to 10 MeV. A white neutron source was generated by the Oak Ridge Electron Linear Accelerator, and the energies of the neutrons incident on the fissile samples were determined by time-of-flight techniques. In each experiment the samples, including the252Cf standard, were contained in a fission chamber surrounded by a large volume (0.91 m3) of liquid scintillator loaded with gadolinium. The fission chamber detected the fission events, and the scintillator detected the accompanying prompt neutrons. The resulting data were analyzed to yield:p(E) =p(E) (fissile)/p(252Cf). For235U and239Pu our results overlap, within the experimental uncertainty, the results of the evaluation of Manero and Konshin (1972), and in the case of235U our data show the same general structure apparent in the evaluation up to 0.5 MeV. Ourp(E) for233U does not show the structure near 0.2 MeV obtained by Manero and Konshin.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18347

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractHigher order perturbation theory is developed in the form of a Taylor series expansion to third order to calculate the thermal utilization of a nonuniform cell. The development takes advantage of the self-adjoint property of the diffusion operator to provide a simple development of this illustration of generalized perturbation theory employing scalar perturbation parameters. The results show how a designer might employ a second-order theory to quantify proposed design improvements, together with the limitations of second- and third-order theory. The chosen example has an exact optimization solution and thus provides a clear understanding of the role of perturbation theory at its various orders. Convergence and the computational advantages and disadvantages of the method are discussed.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18348

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractA method for the calculation of the neutron flux in one-group P3approximation in a reactor polycell with multizone annular clusters is presented. The cluster central zone contains multizone fuel rods. The rod and cluster neutron fluxes are assumed to be azimuthally symmetrical. Four moments in the scattering function are taken into account. The CLUST code has been developed for computing the neutron fluxes in a reactor polycell. Its numerical results are compared with those of the other codes and appear to be in good agreement with them.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18349

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractAlgorithms for computing various eigenvalues of the transport equation can be classified as direct and indirect. The latter computes the eigenvalue by an iterative search on another, generalized, eigenvalue.Direct computation is shown to be a special case of indirect computation. As a result of this analysis, a new“modified direct”algorithm was defined. The new algorithm also works in cases when the direct algorithm fails and it shows generally fast convergence.The proposed algorithm is applicable even to nonfissionable systems where the classical indirect approach via the k eigenvalue is possible only after an artificial“juggling”of cross sections.

ISSN:0029-5639    

DOI:10.13182/NSE94-409

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe mass-yield distribution of fission products following degraded-fission-spectrum neutron-induced fission of232Th was measured by gamma spectrometry for 25 mass chains including mass 138 for the first time for fast fission. Cumulative yields for83gSe and130gSb were observed, the latter also for the first time for fast fission.In general, the yields for degraded-fission-spectrum neutron-induced fission of232Th were slightly higher in the inner portions of both the heavy and light mass wings than for those from reactor-neutron-induced fission of232Th. This was expected, since the average energy of degraded-fission-spectrum neutrons is slightly above that of reactor neutrons.

ISSN:0029-5639    

DOI:10.13182/NSE86-A18351

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor