摘要:

AbstractAt least three distinct approaches have been employed for estimating the conditional probability of containment failure due to steam explosions within the pressure vessel of a water-cooled nuclear reactor. These approaches, which involve varying degrees of subjectivity and objectivity, are reviewed. It is concluded that, given the current state of knowledge, all approaches involve significant uncertainties; no method is currently capable of credibly defending any given value of failure probability or a narrow uncertainty range.

ISSN:0029-5639    

DOI:10.13182/NSE87-A16380

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractA rigorous method for representing the multilevel cross sections and its practical applications are described. It is a generalization of the rationale suggested by de Saussure and Perez for the s-wave resonances. The rationale can be interpreted as the natural consequences of the important physical condition that the collision matrices must be single valued and meromorphic in momentum space. Thus, the latter can be rigorously represented by rational functions with simple poles in√E domain for all states. Such representation is especially attractive when it is used in conjunction with the applications of the R-matrix parameters and the subsequent Doppler broadening using Solbrig’s kernel.A computer code WHOPPER has been developed to convert the Reich-Moore parameters into the pole and residue parameters in momentum space. Sample calculations have been carried out to illustrate that the proposed method preserves the rigor of the Reich-Moore cross sections exactly. An analytical method has been developed to evaluate the pertinent Doppler-broadened line shape functions. Since the principal parts of these functions are identical to the widely usedψandχfunctions when applied to the energy region above 1 eV, the method is readily amenable to many existing processing codes. A discussion is presented on how to minimize the number of pole parameters so that the existing reactor codes can be best utilized.

ISSN:0029-5639    

DOI:10.13182/NSE87-A16381

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractCapture cross sections and gamma-ray spectra for the neutron-induced reactions withmTa and197Au have been calculated using the level density parameters derived from a new low-lying level fitting method in which the constant temperature partial level density formula and the spin-selected level cumulation were used. The gamma-ray profile functions, of the Brink-Axel type with an anomalous bump, were employed for both nuclei. The capture cross sections, spectra, and gamma-ray strength functions obtained in the present calculation agree well with the experimental ones.

ISSN:0029-5639    

DOI:10.13182/NSE87-A16382

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe neutron noise was formulated based on a multidimensional, multiregion, multigroup diffusion model. To solve for the flux fluctuations, the model was generalized and clarified using the adjoint function approach, which included checking the reciprocity relation to assure the correctness of the established adjoint function, solving the adjoint function with a finite-volume detector, and increasing the rate of convergence of the series solutions by nonlinear transform.The model was applied to a coupled core reactor to recalculate detector responses to a unidirectional vibration of a neutron absorber. The lack of agreement between the calculated results and the measurements might be partly due to some simplifications and approximations. It is recommended that measurements should be made in cases where the model can be used more feasibly.

ISSN:0029-5639    

DOI:10.13182/NSE87-A16383

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe one-speed transport equation is solved for a ring reactor. A complete solution is obtained for the space-time relaxation of a pulse of neutrons in a multiplying medium in which delayed neutrons are neglected. The solution consists of a fundamental mode, a finite number of harmonics, and an integral transient. A condition is deduced, which gives the maximum number of harmonics that can exist for a given ring circumference. The limitations of diffusion theory are pointed out with particular reference to the shortcomings of that theory in dealing with the early stages of evolution of the pulse.Delayed neutrons are included and a complete solution is obtained by means of the prompt jump approximation. The results are illustrated by numerical calculations designed to show the onset of instabilities in the harmonics when the reactor is sufficiently large.

ISSN:0029-5639    

DOI:10.13182/NSE87-A16384

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractExposure and absorbed dose buildup factors for a photon point source in infinite beryllium have been calculated in the low-energy range of 0.03 to 0.3 MeV, for penetration depths up to 40 mfp, using two discrete ordinates codes, PALLAS-PL,SP-Br and ANISN. Comparisons of both result to values obtained by point Monte Carlo calculations using the electron gamma shower version 4 code showed reasonable agreement for two types of sources: normally incident and point isotropic sources.The fitting parameters of a geometric-progression method formula were determined for the resulting buildup factor data. These fitting parameters are in good agreement with the basic data within 5% over a great variation in magnitude.

ISSN:0029-5639    

DOI:10.13182/NSE87-A16385

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

摘要:

AbstractThe effect of a mixing vane was studied in a three-subchannel geometry for a 3.99-mm (0.157-in.) gap space, and for mass velocities of 339.0, 678.1, and 1356.2 kg/sṡm2(0.25, 0.50, and 1.0 Mlb/hṡft2, respectively). Mixing rates increased rapidly downstream of the vane and then decreased gradually as a function of downstream distance. The maximum increase in turbulent cross-flow for a mass velocity of 339.0 kg/sṡm2occurred∼10 hydraulic diameters from the end of the mixing vane and was 150% greater than the value observed at comparable conditions for the same test section without a mixing vane. The average increase in mixing due to the presence of the vane was∼58%.

ISSN:0029-5639    

DOI:10.13182/NSE87-A16386

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE87-A16387

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE87-A16389

出版商:Taylor&Francis    

年代:1987

数据来源: Taylor