摘要:

A model for the analysis of pressure pulse generation due to sudden gas release from failed pins in a liquid-metal fast breeder reactor is presented. The predictions of the model are compared to experimental data on sudden gas release in the ducts of the Experimental Breeder Reactor II. The predicted magnitudes of pressure pulses are in good agreement with the experimental observations. The predicted pressure pulse, however, seems to decay at a faster rate than the experimentally observed rate. The effects of the pin internal pressure upon rupture, the rupture area, and the amount of compressed gas are studied parametrically. The pressure pulse magnitude is found to be more sensitive to the internal pin pressure upon rupture than to either the rupture area or the compressed gas volume.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26803

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

The neutron capture cross section of stable93Nb was measured by time-of-flight methodology at the Oak Ridge Linear Electron Accelerator. Individual resonances were parameterized to 7.4 keV with energy resolution≤0.14% full-width-at-half-maximum. The average cross section was deduced from 3 to 700 keV with an accuracy estimated at 3 to 5% SD. The average data to 100 keV are well fitted by strength functions, but the fluctuations about the fit are not consistent with an energy-independent level density proportional to 2J + 1 beyond 20 keV.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26804

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

Critical-experiment data are presented on a heterogeneous lattice of fuel rods comprised of uranium and plutonium oxides, clad with stainless steel, and moderated with (U + Pu) nitrate solution, a condition not unlike that encountered in a fuel-element dissolver operation. The effect of a soluble neutron absorber (gadolinium nitrate) on the criticality of this type of system was also examined for its possible use as a method of criticality prevention and control during the dissolution step. The results provide data for code validation, an essential requirement on complex systems such as this, if the calculations are to be utilized to prescribe subsequent control limits under similar or related conditions in fuel processing. Experiments indicate (for the very limited data presented) that a heterogeneous system composed of these fuel rods in water can have a larger buckling than the fuel in the dissolved state. The question is, whether a fuel rod of a size different from that used in these experiments, immersed in fissile-bearing solutions, might have a still higher buckling (and smaller critical size) than the highest achievable buckling for fuel rods of optimum diameter and spacing in water. This important consideration regarding the criticality safety aspects of dissolvers must be examined in each case. The results of calculations of these systems with the KENO Monte Carlo code utilizing ENDF/B-III cross sections are presented.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26805

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

The coefficients of a truncated Legendre series are usually used in multigroup cross-section sets to describe the angular distribution for a group-to-group scattering event. Discrete ordinates codes use the truncated Legendre series because this representation of the scattering angle can be used with the addition theorem to conveniently treat the scattering source term. However, the truncated Legendre series has inherent disadvantages for Monte Carlo calculations. In this paper, we examine the truncated Legendre series representation, a discrete angle representation, a step function representation, and an exact representation that is applicable for isotropic scattering in the center-of-mass system. The three approximate representations use the coefficients of a truncated Legendre series as a working base. We show in a sample problem that the step function representation has advantages for multigroup Monte Carlo calculations, and we recommend its inclusion as an option in multigroup codes.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26806

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractA new evaluation of basic neutron data for238Pu has been performed. In the present report the resolved resonance parameters, the radiative capture, and the fission cross sections, as well as the average number of neutrons per fission, are discussed. A comparison is made with the corresponding ENDF/B-IV file.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26807

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractThe fission cross sections for233U,235U,239Pu, and241Pu reported in 1958 have been revised using the very precise, recently published, specific activities 21 405±20 dpm/µg233U, 4798.1±3.3 dpm/mg235U, and 746.19±0.41 dpm/mg238U. Revised ratios of fission cross sections at 2200 m/sec are:233U/235U = 0.9142±0.0012,239Pu/235U = 1.2876±0.0034,239Pu/233U = 1.4084±0.0036, and241Pu/239Pu = 1.3506±0.007. Revised fission cross sections at 2200 m/sec in barns relative toσc(197Au) = 98.7±0.2 are:σf(233U) = 527.4±3.1σf(235U) = 576.9±3.4,σf(239Pu) = 742.8±4.4, andσf(241Pu) = 1003.3±5.2. The errors do not include g-factor errors of±0.2% for233U,±0.155% for235U,±0.285% for239Pu, and±0.7% for241Pu.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26808

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractThe discrete eigenvalue problem associated with the one-speed azimuthal Fourier harmonics in plane geometry is discussed. An explicit expression, well-suited to numerical evaluation, is given for the dispersion function, and the reality and maximum number of discrete eigenvalues are demonstrated. From numerical examples, it is found that quite often there are no discrete eigenvalues, particularly for the higher harmonics.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26809

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractWe consider a nonlinear neutron transport problem in a finite homogeneous body with temperature feedback. By using some techniques of the theory of evolution equations, we prove existence and uniqueness of a mild solution u(t). Finally, we calculate an upper bound for‖u(t)‖.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26810

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractNonleakage probabilities calculated in multigroup transport and diffusion theory are compared with experimental data. The results are used as a criterion for choosing energy group structures as well as the actual number of groups. In addition, the importance of using the correct type of computer code for generating groups constants is shown.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26811

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor

摘要:

AbstractGeneralized perturbation methods relevant to quantities linear with the neutron flux in time-dependent problems are discussed. In addition, it is shown how the well-known generalized perturbation formulations relevant to the static case under critical conditions can be simply derived. The time-dependent formulations in the neutron field may as well he applied to that of the nuclides in burnup and buildup problems by considering the buildup and decay matrix in place of the Boltzmann operator.

ISSN:0029-5639    

DOI:10.13182/NSE76-A26812

出版商:Taylor&Francis    

年代:1976

数据来源: Taylor