摘要:

AbstractThis paper summarizes similitude requirements for liquid-metal fast breeder reactor natural convection shutdown heat removal test facilities. It is generally not possible under natural circulation flow to reproduce both hydrodynamic and thermodynamic similarity when the thermal driving head is determined by structure-to-fluid heat transfer. This paper explores the source of the scaling difficulties and examines a number of possible solutions. Design and operating restrictions imposed on the test facility and the validity of extrapolating test facility data to the full-scale system are discussed.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19819

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractAttenuation of neutrons and photons transmitted through graphite, iron, water, and ordinary concrete assemblies were studied by spectral measurements using an NE-213 organic scintillation detector with an (n-γ) discrimination technique. Source neutrons and photons were produced by 52-MeV proton bombardment of a 21.4-mm-thick graphite target placed in front of the assembly. The distributions of the light output from the scintillator following activation by neutrons and photons were unfolded by the revised FERDO code. These experimental results were used as benchmark data on neutron and photon penetration by neutrons of energy above 15 MeV. Multigroup Monte Carlo and one-dimensional ANISN transport calculations were performed with the DLC-58/HELLO group cross sections to compare with the measurement and to evaluate the cross sections. The results of the ANISN calculation of neutrons in slab geometry and the three-dimensional Monte Carlo calculation agreed with the experimental values except for high energy neutrons transmitted through water and graphite. The agreement of both calculations was well within the accuracy of 7% in the measured attenuation coefficients for graphite, iron, and water, and20% over-estimation of the attenuation coefficients in the case of deep penetration through the medium for which the photon mean-free-path is shorter than that of neutrons, such as in iron and concrete. The secondary photons produced by the neutron-nucleus reactions are dominant compared with the primary photons, but otherwise the ANISN calculations gave good results.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19820

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractIn this paper, an attempt has been made to investigate the noise transmission characteristics of nonmultiplying media of liquid-metal fast breeder reactors (LMFBRs) and study its implications on the detection of malfunctions in LMFBR cores by using out-of-core detectors and noise analysis methods. Neutron wave propagation technique has been used to study the problem by employing different approximations such as infinite and finite medium, one- and two-group diffusion theory, and multiregion and multigroup diffusion theory approximations. It has been found that reactor core noise will be transmitted to the out-of-core detectors with equal attenuation for all frequencies,ω<(ωΣt)minwhereΥis the speed of neutrons andΣtis the total macroscopic removal cross section of the medium. For normal in-reactor vessel nonmultiplying media, (ΥΣt)minis of the order of 1 kHz. However, for materials like graphite if used as a moderator surrounding the out-of-core detectors, the limit (ΥΣt)mincan be as low as 10 Hz. Reactor noise of malfunctions due to thermal events inside the reactor core such as sodium boiling lies in the frequency range of 2 to 15 Hz for integral boiling and goes up to 1 kHz for local boiling. Noise due to mechanical events is also a high frequency phenomenon. Therefore for detecting the malfunctions due to thermal and mechanical events in LMFBR cores by out-of-core detectors and noise analysis methods, one has to keep in mind that for moderating materials like graphite used in the surroundings of detectors, a band limited noise in reactor may be transmitted to detector locations in a distorted way and since high frequency noise is likely to be attenuated more, it will pose a problem in detecting the malfunction in its incipient stage.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19821

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe results of a measurement of periods and yields of delayed neutrons from“fast”fission of237Np,238Pu,241Am,233U,240Pu, and241Pu are presented. For the first three nuclides, only a few incomplete experimental data have been published, while for the others, relatively great discrepancies exist among the data. The present results are given in Keepin’s six group representation. Since our instrumentation did not allow measurement of the yield in the sixth group, the values were calculated. The total yields obtained as the sum of the group yields areThe consistency with known systematics of the total yields of delayed neutrons was checked and found generally to be good. When possible, the results were compared with those recommended by Tuttle in a recent compilation. The total yields of240Pu and241Pu were in very good agreement, but not for233U. The agreement of the group yields was generally poor.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19822

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractFast neutron scattering cross sections have been measured for13C Angular distributions for elastic scattering over an angular range from 20 to 155 deg are presented for incident neutron energies of 9.97, 11.96, 13.94, 15.94, and 17.92 MeV. Inelastic scattering data were obtained at 9.97 MeV for states at excitation energy 3.09 MeV and for the unresolved states at 3.68 and 3.85 MeV. The data were corrected for finite sample and source effects using a Monte Carlo simulation. Legendre polynomial coefficients for angular distributions and optical model fits to the elastic scattering data are reported.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19823

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractWe have measured the fission cross-section ratio of237Np to235U as a function of neutron energy from 20 keV to 30 MeV using ionization fission chambers, the threshold cross-section method, and the time-of-flight technique at the Lawrence Livermore National Laboratory 100-MeV electron linear accelerator. The measured cross-section ratio, averaged over the neutron energy interval from 1.75 to 4.00 MeV, is 1.294±0.019.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19824

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractAn accurate background cross-section method for nuclear reactor cell homogenization is developed that is based on the very precise moment expansion approximation to the neutron escape probability that we recently suggested. The moment expansion approximation is so devised to properly generalize the equivalence relation that the background cross-section method attains a high accuracy to<1% error for each individual resonance, yet still preserves the very features of universality and simplicity of Bondarenko’s method.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19825

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractAn equation is derived to estimate the perturbing effects on the neutron spectrum caused by a spectrometer inserted in an experimental assembly. This equation is applied to estimate the spectrum perturbation by a miniature NE-213 fast neutron spectrometer in a graphite assembly. The results show that the perturbation effect is smaller than the experimental errors and uncertainties, and that the effect caused by the neutron-sensitive volume is smaller than that caused by the surrounding materials.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19826

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe angular flux for a semi-infinite medium with a specularly reflecting surface illuminated by a pulsed source is obtained via the multiple collision method of solution. Numerical results for the scalar flux are presented.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19827

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe fuel production capacity of a fission-fusion symbiotic system is investigated. On the basis of physical processes and under the assumption of discontinuous loading and off-loading conditions, maximum, minimum, and averaged trajectories for the fissile and fusile inventories have been derived and analyzed. From a comparative analysis, it is shown that this information leads to more accurate results for such reactor characteristics as doubling times and half-lives.

ISSN:0029-5639    

DOI:10.13182/NSE82-A19828

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor