摘要:

Self-shielding and edge corrections were investigated for varying thicknesses of 1 cm dia. gold foils. Test foils were irradiated in the hohlraum or air chamber of the Cornell University TRIGA Mark II reactor. The self-shielding effect was determined from the activation of a series of foils of different thicknesses and the edge correction from the activities of successively smaller concentric rings punched from the parent foil. Edge effects were found in the 2.5 mil and thicker foils and were statistically significant only in the outer millimeter of the foil radius. After cutting off the outer millimeter of the foils, the activity was found to follow the law for infinite foils.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26528

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

A new method of utilizing pulsed neutron source measurements for the determination of the subcriticality of an assembly directly in terms of dollars is proposed. Essentially, the method determines the parameter (kβ/l) using the complete response curve of a repetitively pulsed assembly after the quasi-equilibrium state has been attained. This value of (kβ/l) coupled with the usualα-measurement, assuming the prompt decay constant to be dominant, yields the reactivity directly. The analytical model is based on a bare one-group diffusion theory system withm-delayed precursors. The application of these results to experiment shows that their applicability is much broader than the simple analytical model would indicate.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26529

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

Resonance integrals computed by the method of Chernick and Vernon are compared with precise results from a series of Monte Carlo calculations with very large numbers of histories. The range of applicability of the method of Chernick and Vernon is exhibited by this comparison. Some simplifications are made in the method of presentation of the resonance integral results so that the correlation among single lumps and lattices of various compositions is improved.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26530

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE63-A26531

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

The time-dependent behavior of the neutron population in an unreflected, unmoderated cylindrical assembly of 90 wt.% uranium (93.2 wt.% U235), 10 wt.% molybdenum alloy following a rapid establishment of superprompt critical conditions with negligible initial neutron population has been studied. Reactivity increases up to 11 cents above prompt critical resulted in bursts yielding as many as 1.8×1017fissions and peak power up to 100,000 Mw with periods as short as 16µsec and temperature increases as large as 400°C. For bursts greater than about 6×1016fissions the safety block—a piece of the core held in place by an electromagnet—is driven out by pressure waves about 225µsec after the peak of the burst.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26532

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

Fission cross section ratios of U233, U235, and Pu239and capture rates in Mn55and In115have been measured in an NRX type uranium metal rod irradiated in a heavy water moderated reactor. The results have been compared to the values obtained using a model designed for NRX burnup calculations. Agreement was obtained using an“incurrent”spectrum composed of a Maxwellian thermal component and an epithermal component of the form obtained from neutron spectrometer measurements. Changes in spectrum caused by the light water coolant were also studied.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26533

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

Four irradiated UO2samples were ground to break them along grain boundaries, then dissolved in a series of successive leaches with 3NHNO3. The successive acid extractions were then analyzed for Cs138, Ce144, Zr95, Sr90, and Eu155, as well as total uranium. Very considerable variation in the specific activities of the fission fragments was found between one acid extraction and another of the same sample. The fission products were concentrated in the first and last portions of the material to dissolve. In one sample, which underwent irradiation for a very short time, the increase in concentration in the last portion to dissolve was not observed. It is speculated, on this and other evidence, that fission fragments do not remain in solid solution in uranium dioxide, but instead migrate to grain boundaries and other lattice defect sites.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26534

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

The rational approximation to the escape probability is generalized to contain a geometry dependent parameter. In this way, approximate expressions that are both simple and remarkably accurate are obtained for the escape probability from solid and hollow fuel rods, and for the Dancoff correction in regular rod lattices. These approximations are derived from suitably chosen one-parametric chord distribution functions that have the same general character as the exact chord distributions of the fuel and moderator regions. It is shown that it is reasonable to determine the parameter belonging to each geometry—the geometric index—from the condition that the logarithmic moment of the exact and the approximate chord distribution functions be equal. The geometric indices are given for solid and hollow fuel rods, and for square and hexagonal lattice configurations. For solid or hollow fuel rods the error in the approximation is less than 1 %. The Dancoff correction for rod lattices is obtained with comparable accuracy.

ISSN:0029-5639    

DOI:10.13182/NSE16-03-329

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE63-A26536

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE63-A26538

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor