摘要:

AbstractThe Dancoff correction to the surface term of a resonance integral has hitherto required tedious numerical evaluation of a double integral in cylindrical geometry. A recognition of the functional dependence of the correction on moderator mean free pathλallows a great simplification. If 1 -Cis the surface correction for two rods of radius,ρ, separated a distancedbetween centers, thenwhereis a function monotonically increasing withd/ρ, for which a graph is given. A simple formula is also given forCof a hollow rod’s interior.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25559

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

摘要:

AbstractUranium-molybdenum alloys have been shown to transform from the stable to the metastable phase due to neutron bombardment. This phenomenon has been explained on the basis of the smoothing out of concentration gradients due to the action of“displacement spikes”or“thermal pulses”generated within the sample. A kinetic study of this reaction in U-9 w/o Mo alloy specimens was performed in which the phase reversal was followed by electrical resistivity measurements on the samples while they were being irradiated and held at low temperatures in-pile. The special facility which was constructed to perform this work, as well as the results of the first in-pile experiment, are described. The results of this test are felt to verify the displacement spike model of radiation damage.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25560

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

摘要:

AbstractA common method used to determine reactivity is to measure the reactor period and then refer to the inhour equation which relates asymptotic period to reactivity. The implicit assumption in such a method is that the neutron population is varying exponentially with time. The conditions necessary for this assumption to be valid have been obtained by a quantitative examination of the time behavior of the neutron population. The results obtained show that under common experimental conditions, several minutes may be required following a positive step change in reactivity in order to achieve accuracy by means of a period determination. In addition, in the case of the reactor with a constant extraneous source, a significant increase in this waiting time can result even if the reactor is initially only very slightly subcritical. Whereas in principle both positive and negative reactivities may be obtained from period observations, it is pointed out that in practice serious objections exist for the case of negative reactivities.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25561

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

摘要:

AbstractA new spinning sample method has been used to measure the energies of beryllium-filtered neutrons scattered at 90°to the beam by samples of water, ethyl alcohol,n-amyl alcohol, benzene, paraffin, and zirconium hydride. The energy distributions from all samples show that an appreciable number of scattered neutrons gain energy. The zirconium hydride and water were measured to compare the spinning sample method with other methods of measuring inelastic scattering. The hydrogenous liquids were investigated to see if the scattering data could be correlated with known molecular properties and with proposed scattering theories.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25562

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

摘要:

AbstractThe economics and physics of plutonium recycle in the Calder Hall type reactor are considered. Three possible schemes of recycle are studied. In scheme A the plutonium produced in a run is blended with fresh natural uranium for a subsequent run; in scheme B the plutonium is alloyed with some diluent metal and fabricated into high heat-transfer elements more like MTR- or PWR-seed type elements and a subsequent load of fresh natural uranium elements is“spiked”with these plutonium elements; and in scheme C half the spent uranium is recycled as well as the plutonium. The conclusions are that scheme A will be the most economic means of recycle and will compete very favorably with the mode of operation where the plutonium is sold at the end of each run for $12 per gm. Viewed in another way, with natural uranium having its current value and lease charge, the fuel value of plutonium for recycling, with all costs considered, will be greater than $12 per gm. Schemes B and C do not look as attractive as A for the Calder Hall type reactor. The results are predicated on the assumption that the fuel elements will withstand exposure levels as high as 8800 Mwd/ton. This is beyond present experience, but it is believed that it is not unrealistic to assume that such exposures will be achieved in the future with improved fuel elements. A matrix-analytic solution to the differential equations governing isotopic concentrations as functions of flux-time is also developed.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25563

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

摘要:

AbstractThe Iowa State College subcritical assembly is a natural uranium-graphite pile constructed as a teaching tool to illustrate the principles of nuclear physics and engineering and as a facility for graduate thesis research in nuclear engineering. The determination of the basic operating characteristics of this assembly is described and discussed. The material buckling as determined from flux measurements was the parameter used in comparing the results. Tests were conducted for the 6 in.,in., and 12 in. lattice arrangements and for all uranium removed. Tests were made with air and water in the coolant annuli surrounding the uranium slugs. Bucklings were calculated using the elementary theory of Murray (in which all extraneous materials are treated as poisons) and the method of Volkoff and Rumsey (in which the moderating effect of the water and the shielding effects of the various materials are considered) for the three lattice arrangements, and they are compared with the experimental results. The position of the neutron sources in the source compartment and the presence of water around the sources were found to affect the measured value of material buckling.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25564

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

摘要:

AbstractThe space-independent pile kinetic equations are solved to give the excess reactivity explicitly in terms of the rate of change of power and an integral over the past history of the power, the precursor densities being eliminated algebraically from the equations. The need for digital computations for determining the reactivity from a given power trace is thereby reduced. The solution is applicable to arbitrary variations of power with time and is examined in detail for the case of small damped oscillations, where it leads to simple algebraic expressions for the gain and phase angle. The behavior of the reactivity as a function of time is also computed for the case of a power fluctuation occurring during a short time interval, for a power trace which increases exponentially and then stays constant, and for a rapidly decaying power burst.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25565

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

摘要:

AbstractReactor period-reactivity relations may be determined directly by numerical integration of“prompt-burst”neutron decay data without analysis into delayed neutron period and abundance values. Period-reactivity relations obtained by this method for six fissile species are compared with the corresponding relations calculated from the customary“inhour”equation. Application of this method to mixtures of fissile materials in various neutron energy spectra is discussed.

ISSN:0029-5639    

DOI:10.13182/NSE59-A25566

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE59-A25568

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE59-A25569

出版商:Taylor&Francis    

年代:1959

数据来源: Taylor