摘要:

This paper describes some general characteristics of the uncertainties in various fast-reactor parameters as a function of the corresponding uncertainties in nuclear data on the basis of statistical theory. By using the variational formalism, it is possible to relate the mean-square deviation of any reactivity coefficient (or reaction-rate ratio) to the covariance matrix of cross sections. The qualitative behavior of the uncertainties in fast-reactor parameters can be best illustrated geometrically in terms of the region of tolerance. The latter is the volume bound by a“hyper-ellipsoid”surface specified by the designer’s tolerance limit, the coefficients characteristic of the type of parameter in the system under consideration, and the correlation matrix. Exploratory studies and graphical illustrations are given for some cases of practical interest.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26651

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

The lambda-mode eigenvalue separation can potentially be evaluated in a power reactor using a static flux tilt method. The flux tilt, or offset, is measured per unit of perturbing reactivity, which is then related theoretically to the desired parameter. The use of higher order theory has explained a discrepancy in previous experimental correlations and has led to a procedure for more accurately estimating the parameter from the data.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26652

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

This paper investigates the application of two artificial intelligence techniques, heuristic programming and learning theory, to the problem of digital computer control of nuclear reactors. The purpose of using an artificial intelligence approach is to alleviate the requirement for a detailed mathematical model of the nuclear reactor system. A control system is developed which demonstrates the primary features of such an approach. Results are shown for several reactor and control problem variations using a computer simulated reactor.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26653

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

Two angular-dependent liquid-metal fast breeder reactor (LMFBR) disassembly models are derived in this paper. These models are based on the physical assumptions of the VENUS (r,z) computer codes (VENUS and VENUS-II). A two-dimensional (r,θ) model is derived to study disassembly in an infinitely long cylinder. The second model is an approximate three-dimensional model which employs the Galerkin method (a subset of the method of weighted residuals) to solve for the three-dimensional motions of materials during disassembly. An iterative technique which is employed to calculate trial and weighting functions for the Galerkin method is proposed and tested. The two angular-dependent disassembly models are used to study four configurations of a reference1000-MW(e) LMFBR. Most of the calculations performed employ the two-dimensional (r,θ) model to estimate the effects of angular dependence on three-dimensional calculations. In addition, a number of three-dimensional calculations are presented both to validate the model and to study the relative effect of angular motion on LMFBR disassemblies. The results indicate that angular motion is second order compared to radial and axial motions for the four configurations studied. These calculations also indicate that the models derived are relatively simple and inexpensive to use and can be employed to study other configurations which may be more dependent on angular motion during a disassembly accident than the four chosen for this study.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26654

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

Buildup factors for energy deposition in water and aluminum and for exposure in concrete are presented for monoenergetic, point isotropic gamma-ray sources. The buildup fac. tors were evaluated using the method of moments and are tabulated for energies from 0.03 to 10 MeV and distances out to 50 mean -free-paths from the source. Empirical representations of these buildup factors are developed using Berger’s formula. Fitting parameters are tabulated for each material as a function of source energy.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26655

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

The prompt- and delayed-neutron multiplicities for photofission of the eight isotopes,232Th,233U,234U,235U,236U,238U,237Np, and239Pu, have been measured using bremsstrahlung with end-point energies ranging from 8 to 13 MeV. The measured multiplicities are compared with those from the same compound nucleus formed in neutron-induced fission where such data exist.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26656

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

The formation of hot spots in fuel cladding due to the deposition of a low-conductivity heat-generating fuel or due to fission-gas-jet impingement is a very credible event and can significantly influence the probability for slow fuel-failure propagation in a subassembly of a liquid-metal fast breeder reactor. By assuming steady-state conditions, a general expression is obtained for the temperature distribution in these hot spots. As special cases, expressions are obtained for temperature distributions in hot spots caused by fission-gas-jet impingement and partial or total channel blockages by fuel debris. A partial verification of the model for thermal analysis is provided by comparing predictions for the temperature distribution in the gas-jet impingement region to the available experimental data.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26657

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

A simple boundary condition has been derived which allows prediction of the stability of an enclosed atmosphere above a heated liquid. The correctness of the condition has been shown by experiments with various vapor-gas systems. Application to nuclear reactor containments under hypothetical accident conditions demonstrates the presence of a stirred atmosphere for sodium-cooled reactors. In case of water-cooled reactors, the containment atmosphere will be stirred when large amounts of fission products are present in the sump water in the concrete cavities located in the lower part of the containment building.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26658

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractThe angular expansion of the induced scattering term in the linear transport equation is given, and some simple implications are discussed.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26659

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor

摘要:

AbstractBasic nuclear data libraries,such as ENDF/B-III, are used today for the generation of multigroup cross-section sets. Since the multigroup sets are determined by calculating the weighted averages of the cross-section curves, knowledge of the weighting function within each group is required. In principle, this function is not only dependent on the specific reactor, but is also a function of position in the reactor. With existing codes and methods the weighting function in the Bondarenko-type library is not iterated, since each time the weighting function is changed, a code that handles the basic data library and consumes much computer time must be run.A new method is presented that enables the user to obtain from a preprocessed library, in a few computer seconds, effective self-shielded multigroup cross-section sets averaged over any desired weighting function without reference to the basic data library. Specifications of the preprocessed library (only 2 to 3 times as large as a Bondarenko-type library) are given. The preprocessed library may be generated using existing codes.A family of functions with terms into which any weighting function can be expanded is used. Group averages of each cross section with respect to terms of the family and a set of shielding factors form the preprocessed library. Two families of functions, fn(E), are considered, and two methods are given for the expansion of W(E) into each series of fn(E). Nuclear parameters obtained by these methods are compared with the same parameters obtained using the exact weighting function (SNEAK flux) to check the methods. Very good agreement is found.A preprocessed compact library of ENDF/B-III materials is available, upon request, from the authors.

ISSN:0029-5639    

DOI:10.13182/NSE75-A26660

出版商:Taylor&Francis    

年代:1975

数据来源: Taylor