摘要:

AbstractThe fission cross sections of244Cm,246Cm, and248Cm have been measured from 0.1 eV to 80 keV using the Rensselaer Intense Neutron Spectrometer. The cross sections were normalized to the235U ENDF/B-V broad-bin-averaged fission cross section. Fission areas and widths were determined for the resolved low-energy resonances. In general, the ENDF/B-V fission cross sections for the curium isotopes are in poor agreement with the measured cross sections and a new evaluation of these curium cross sections is recommended. The observation of structure in the measured cross sections in the unresolved region is suggestive of intermediate structure in the even curium isotopes.

ISSN:0029-5639    

DOI:10.13182/NSE85-A18621

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractSplitting techniques are among the most common and successful variance reduction techniques used in Monte Carlo calculations. The simplest type of splitting occurs when the splitting ratio, v, is an integer. In this case, one particle of weight w is replaced by v particles of weight wv−1.Often, v is specified as a ratio of two numbers. In these cases, v need not be an integer. Two alternative splitting techniques for noninteger v, sampled splitting and expected-value splitting, are compared. Formulas are reported that indicate when each type of splitting is preferred.

ISSN:0029-5639    

DOI:10.13182/NSE85-A18622

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractSome recent results pertinent to condensation as it affects the course of light water reactor transients are reviewed. These include interfacial shear stress, local condensation heat transfer coefficients, and stability of stratified countercurrent steam/water flow. Cold-leg and combined cold- and hot-leg oscillations are also discussed. Some avenues for further research are pointed out.

ISSN:0029-5639    

DOI:10.13182/NSE85-A18623

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractSome qualitative results of neutron noise in a boiling water reactor (BWR) are reported. By using one-group theory, it has been shown that the neutron flux fluctuations caused by a distributed source in space, representative of the coolant boiling noise in BWRs, can be considered as made up of two components: The first one, having a global character, is a quickly varying function of frequency and follows the fundamental mode solution in space; the second, called nonglobal (local), follows the spatial variation of noise-source intensity distribution and is independent of frequency forω

ISSN:0029-5639    

DOI:10.13182/NSE85-A18624

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractDependencies of radiolytic aspects on geometric and operational conditions of boiling water reactor (BWR) primary systems were studied for normal operation or for hydrogen alternate water chemistry (HAWC) by using a computer simulation code AQUARY. Statistical regression analyses were applied to those calculated results and a great many close correlations were found among radiolytic concentrations.In the course of the study, it was discovered that residence time and energy deposition rate in the downcomer had a critical effect on HAWC. A set of simple estimation formulas for radiolytic conditions was proposed for normal BWR operation, and the following prediction formulas were proposed for the oxygen gas release rate and oxygen concentration in the recirculation line under HAWC:

ISSN:0029-5639    

DOI:10.13182/NSE85-A18625

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractUsing the single-channel resonating group method, in which a central nucleon-nucleon potential containing a soft repulsive core (SRC) is adopted, the (d + d) scattering phase shifts, differential scattering cross sections, and total reaction cross sections at a series of energies<20 MeV with and without imaginary potentials are calculated. The agreement between the theoretical and experimental results is quite good. The main conclusions are: The (d + d) nonlocal kernel function KS(R, R’) deduced is correct; hence, the discrepancy between the kernels in other similar work is clarified. The SRC causes a decrease in the total strength of the (d−d) direct potential VNs(R) and, in particular, the strength of VNsfor short range and small channel spin s decreases much more. The SRC causes a decrease in the phase shiftsδls(E) (toward the negative direction); the decrease is especially large when E is at or near a resonating energy. The SRC reduces the total reaction cross sectionsσRappreciably and causes a distinct increase in the differential scattering cross sections dσ/dΩ(θ) at the forward and backward angles; however, it does not greatly influence the differential cross sections at other angles.

ISSN:0029-5639    

DOI:10.13182/NSE85-A18626

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractRadiation widthsΓγof (310±20), (312±12), and (340±130) meV were found for55Mn(n,γ) resonances at 337, 1099, and 2327 eV, respectively. A fourth resonance was found at 1658 eV, with gΓnΓγ/Γ= (7.6±0.3) meV.

ISSN:0029-5639    

DOI:10.13182/NSE85-A18627

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractThe statistics of neutron slowing down are studied with a‘small jump model,’which is shown to be still surprisingly accurate when applied to slowing down by light nuclei. The same model is used to elucidate the consequences of a traditional carelessness in reactor physics textbooks about the number of collisions necessary to slow down, as recently pointed out by Ruby.

ISSN:0029-5639    

DOI:10.13182/NSE85-A18628

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

摘要:

AbstractUsing diffusion theory and the eigenfunction expansion method, a detailed time-dependent study of fast neutrons has been made for three iron assemblies: infinite, 1 m3, and 0.5 m3. Various results have been obtained by taking two different source energies, namely, 14.47 and 1.0076 MeV. All the calculations have been carried out using the 50-group cross-section set of Ahmed et al.For the 1.0076-MeV source, (a) the time-dependent spectra exhibit two distinct peaks up to∼50 ns, (b) energy variation of the mean slowing down timeshows“anomalous”behavior similar to that observed by Beynon et al., and (c) the most probable timehas two different values for some energy groups below∼240 keV, in conformity with the results of White et al. The double values of(except for the 40th and 41st groups) and the“anomalous”behavior observed incease when we take the source energy to be 14.47 MeV. Further, for all values of energy Ei, the values of bothanddecrease as the size of the assembly is reduced. It has been shown that in the two larger assemblies, pseudoasymptotic conditions are established in certain time intervals. It was determined that some energy groups tend to cluster and decay with the same decay constant after a certain time.

ISSN:0029-5639    

DOI:10.13182/NSE85-A18629

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor

ISSN:0029-5639    

DOI:10.13182/NSE85-A18630

出版商:Taylor&Francis    

年代:1985

数据来源: Taylor