摘要:

AbstractThe void fraction at several locations in the EBWR has been measured. The technique used consisted in obtaining the cadmium ratios of cobalt wires, and then relating these to the local void content. This is possible because the thermal to epithermal flux ratio is approximately proportional to the local hydrogen density. Hydraulics calculations of this void fraction support these experimental results.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25977

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThe problem of space dependent thermalization of neutrons is solved for a slab lattice of heavy moderator and fuel. Fuel slabs are replaced by negative plane sources whose strength is computed by transport-theoretical arguments. The Fourier space-transform of the spectrum is obtained by iteration of an integral equation and the solution correct to the orderO(Δ2mod) is shown to reduce, in the absence of fuel, to the one found by Hurwitzet al. The influence of the hardening of the spectrum incident on the fuel slab is studied by means of the thermal utilization factor.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25978

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractStudies have been made for the application of liquid poisons in lieu of moving control rods for shim control of core reactivity. Liquid control is achieved by: (1) injection of neutron-absorbing poison into the system from a poison supply tank if lower core reactivity is desired; (2) removal of a certain percentage of neutron-absorbing poison from the system by ion exchange if higher core reactivity is required; (3) no poison is added to or subtracted from the system if no reactivity change is desired. There is a wide choice of absorbers which could absorb neutrons in the thermal and epithermal ranges because most of the nitrates of these absorbers are soluble. Nitrate or other salts of cadmium, europium, or gadolinium are suggested for absorbing thermal neutrons, while silver, indium, or hafnium salts are used for the removal of resonance neutrons. A mixed solution containing one or more of these salts in any desired ratio can be prepared according to the need of a particular reactor. Boric acid can also be used. The principal advantages of using chemical poisons are: (a) lower capital cost; (b) simpler maintenance; (c) ready control of large reactivities; and (d) elimination of rod hot-spot factors. The liquid control system under consideration was studied for its applicability to nuclear rocket reactor control, although it might also be feasible for the control of ordinary power reactors with certain modifications.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25979

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThis paper describes an extension of the method of Nordheim-Scalettar to the case of rods partially inserted in a bare reactor. In this study, the axial flux harmonics are introduced. It is assumed that the extrapolation distances of the rods for thermal neutrons still have the same value whatever their insertion length may be. This extrapolation distance can be calculated especially from data relative to rods of infinite length. Calculation methods for the determination of the efficiency of rod assemblies and the distribution of thermal neutron flux are described. It should be noted that the determination of the flux distribution may require the use of many more harmonics than the determination of rod efficiency, since the results converge more rapidly in the latter case. Significant examples are given.The calculation method has been programmed to be used with a BULL Gamma AET Computer.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25980

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThe influence of a non-uniform temperature distribution on the absorption of neutrons in a purely absorbing resonance of an isolated lump is studied. It is shown that in practical situations the absorption in the lump depends only on its average temperature and not on whether its temperature distribution is uniform or not.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25981

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractA multigroup diffusion theory is formulated for heterogeneous reactors having periodic arrays of line discontinuities. These discontinuities are idealized cylindrical internal boundaries of an otherwise homogeneous moderating medium, and appropriate mixed-group or multiplying boundary conditions at such boundaries allow Floquet solutions to be found for the neutron fluxes in the moderator. Real superpositions of such Floquet solutions can then give the physical fluxes in finite reactors.The requirement that a Floquet solution in the moderator have the proper thermal flux behavior at a cylindrical internal boundary, to match the thermal flux actually inside a fuel rod, leads to a“criticality”condition, the solutions of which give the spectrum of allowed Floquet solutions. For each of these a relation between material bucklingsBx2,By2, andBz2is obtained which is, in general, anisotropic.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25982

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractA comparative method has been developed for the determination of surface areas of UO2powder. The method depends on the sorption of phosphate ions from a solution containing P-32 labeled NaH2PO4on the powder surface. By comparison with samples of known surface area, measurements have been obtained in the range 1.0–14 meter2/gm. The internal consistency of the method is better than±2% and agreement with measurements by the BET method averages around±5%. The method is simple and fairly rapid, and can be adapted to irradiated material.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25983

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThe stability criteria are derived for a nuclear reactor with a power coefficient feedback. The power coefficient feedback is assumed to consist of two feedback paths, each with a single time constant. In reality, the system of the nuclear reactor is often well approximated by this model.The criteria are given in Table I and in Fig. 5, by which one can quickly determine the stability, when parameters are known. They also give an insight into the effects of various parameters on the stability of the nuclear reactor.The application of the criteria to a British-type gas-cooled reactor with a positive temperature coefficient of moderator is demonstrated. Comparisons are made with other works, of different approaches, on a fast reactor and a water-cooled reactor.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25984

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThis is a continuation of a previous article(1)wherein analysis of experimental data yielded a new procedure for the calculation ofk∞/ϵ. In this present paper corresponding values derived from conventional theoretical techniques are analyzed in a similar fashion. The results as presented amplify the discrepancy between cadmium ratio measurements and conventional resonance escape theory, thereby yielding a good illustration of the need for further theoretical as well as experimental work in this area. A suggestion for improving the accuracy of cadmium ratio measurements is also presented.It is shown that the previous general development can be utilized with slight modification to yield values for the resonance escape probability which are in essential agreement with values calculated by conventional techniques.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25985

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor

摘要:

AbstractThe total neutron cross section of Pu239has been measured at seventeen neutron energies between 0.00291 ev and 0.10 ev with a crystal spectrometer. The absorption cross section was obtained by subtracting the relatively small scattering cross section from the measured total cross section. The sample used was a plutonium-aluminum metallic foil containing 1% aluminum. The isotopic content of the plutonium was 99.82% Pu239, 0.15% Pu240, and 0.03% Pu241. The value obtained for the absorption cross section of Pu239at 2200 meters/sec wasσa= 1007±8 barns.

ISSN:0029-5639    

DOI:10.13182/NSE61-A25986

出版商:Taylor&Francis    

年代:1961

数据来源: Taylor