摘要:

AbstractAn analytical method is developed for determining the energy dependent neutron flux in homogeneous and heterogeneous media. Using the heavy gas model scattering operator, neutron spectra in two-dimensional rod reactors of various types are calculated in the diffusion approximation. They show a strong spatial dependence even in the epithermal region, which fact is neglected in the numerical treatment of the problem by Honeck and Kaplan. It is just this epithermal part of the spectrum, which mainly influences the values of the thermal utilization and theη-factor. The value obtained for the latter quantity is too large if the correct neutron spectra in moderator and fuel are replaced by Maxwellian distributions at moderator-temperature or a suitably displaced temperature, for example.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26258

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractWe examine herein the decay constants,λkwhich appear in the modal expansion of the neutron density in a study of the time-dependent thermalization of neutrons. A study of the proton gas moderator indicates the existence of an infinite number of discreteλkin the range. The upper limit is a limit point for the eigenvalue sequence. Consideration of more general models indicates the existence of a discrete spectrum in the range 0min andmax and a continuous spectrum in.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26259

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractA simple technique is described for computing the interaction in groupings of fissionable units. The units may be slabs, cylinders, or spheres and may be surrounded by a reflector. The validity of the approximations employed is discussed. The technique is illustrated by applying it to the specific example of calculating the interaction in a reflected cubic array of eight spheres of uranium (93.5% U235). Comparisons are made with experiment and with other methods of calculation.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26260

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe present paper deals with the calculation of the thermal flux in the moderator of a supercell containing several fuel and control elements. It is assumed that the one group diffusion equation with a constant source holds in the moderator. It is further assumed that the absorption of thermal neutrons in fuel rods (or control rods) may be described as due to a cylindrically symmetric line sink. With these assumptions the diffusion equation is solved and a general expression for the thermal flux in the moderator is obtained. This expression is then used to calculate the thermal utilization in the supercell, and the ratios of absorption rates in the different elements of the lattice. General expression for the flux ratios and thermal utilization are obtained. By way of illustration, solutions of two typical cases of complex lattices are given.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26261

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractKnowledge of the Doppler coefficient associated with the nonuniform temperature distribution conditions obtained in a reactor runaway is of importance to reactor safety considerations of low-enrichment oxide cores. Measurement of this dynamic coefficient has been made at Spert in an investigation of the kinetic behavior of a water-moderated, UO2-fuel-rod reactor, by means of self-limiting power excursion tests covering a range of initial asymptotic reactor periods from 31 sec to 3.2 msec. In the long-period region, reactor shutdown was provided both by various heat-transfer-dependent mechanisms effecting loss of moderator from the core and by Doppler broadening. In the short-period region below 7 msec, where the reactor period is small compared to the thermal time constant of the UO2fuel rods and reactor shutdown is provided essentially by the Doppler reactivity alone, the data indicateRc(tm)=−6.2, whereRc(tm)andEmare, respectively, the compensated reactivity (¢) and energy (Mw-sec) at the time of peak power. An additional reactivity effect, positive in sign and resulting from systematic bowing of the fuel rods during the transient power burst, yielded a significant change in burst shape behavior. The fuel rod bowing effect was separated from other feedback effects by performing two series of tests, with and without mechanical constraints on the fuel rods. In the shortest period test, the maximum power was about 7500 Mw, the total energy released in the burst was about 110 Mw-sec, and the maximum pressure measured was less than 8 psi. No damage occurred as a consequence of this or any other test.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26262

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractTheoretical equations have been derived for calculating heat transfer coefficients for a fluid flowing through a concentric annulus for the following two cases: (A) constant and equal heat fluxes from both walls, and (B) constant, but unequal, heat fluxes from the walls, with equal wall temperatures at a given axial position along an annular channel. In the derivations, the conditions of fully-established velocity and temperature profiles, and independence of physical properties with temperature variation across the flow channel, were assumed.The only geometrical parameter in this general case is the radius ratio r2/r1, and in the study it was varied from 1.0 to 10.0.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26263

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractUsing a Lyon (3) type of analysis, theoretical Nusselt numbers have been calculated for liquid metals flowing in concentric annuli, under conditions of constant heat flux and fully-established turbulent flow. These have been expressed in the form of semiempirical equations for the case of heat transfer from the inner wall only and for the case of heat transfer from the outer wall only. Predictions on the basis of these equations are compared with those by other relationships and with experimental results. The proposed equations are consistent with those for turbulent flow of liquid metals inside circular tubes and between parallel plates; the former being the limit for an annulus asr2/r1approaches infinity, and the latter being the limit asr2/r1approaches unity.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26264

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe electrical resistances and Hall coefficients of polycrystalline graphite, neutron irradiated graphite, chemically doped graphite, and neutron irradiated chemically doped graphite have been measured over a range of magnetic fields at liquid nitrogen and liquid helium temperatures.The empirical equivalence of acceptor concentrations in irradiated graphite and in chemically doped graphite obtained by matching Hall coefficients has been found to be a function of the temperature of measurement. This observation may be explained in terms of temperature dependent trapping efficiencies of the electron traps introduced chemically or by neutron irradiation. This explanation affords some understanding of the electrical properties of the complicated neutron irradiated chemically doped graphite.The temperature variation of the resistances and Hall coefficients of the graphites studied may be reasonably well understood on the basis of the phenomenological theory of transport properties. Anomalous variations with magnetic field of resistances and Hall coefficients were observed at low temperature in some of the graphites studied; no satisfactory explanation has been found for these effects, although a recently introduced theory provides a plausible explanation for the observed magnetoresistance of polycrystalline graphite at liquid helium temperature.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26265

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractFast neutrons deposit energy in chemical systems by means of elastic scattering, inelastic scattering, and various charged particle reactions. For the particular case of 14.6 Mev neutrons and 1:1 solutions of liquid N2and O2,the proportions by which the three classes of reactions contribute are, respectively, about 1:1:4. The initial linear energy transfer (ILET) in the same system is of the order of 20 ev/Å.Dosimetry in fast neutron radiation chemistry experiments may combine a quantitative consideration of each nuclear reaction with a measurement of the neutron flux. This method of dosimetry has been applied to experiments on the production of NO2in 1:1 liquid N2and O2with the result thatGNO2,the number of NO2molecules formed per 100 ev deposited in the sample, was found equal to 0.5±0.1. This result is surprisingly close to that observed for irradiations by Co50gamma rays and by electrons whose ILET is three orders of magnitude less than that for 14.6 Mev neutrons.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26266

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe relative volatility or separation factor for deuterium enrichment in ammonia distillation was measured at pressures of 250, 375, 500, 600, and 760 mm Hg and at deuterium concentrations of 0.10, 0.24, 0.42, and 0.58 mole fraction deuterium. The measurements are summarized by the following equation:whereα= separation factorπ= system pressure mm Hgx= mole fraction deuterium.It is interesting to note that a dependence on the composition was observed. This is not predicted by the normal method of calculating the separation factor from the vapor pressure ratioHowever, the magnitude of the separation factor and its dependence on pressure are in good agreement with the vapor pressure ratio predictions (α= 1.042 at 1 atm).This information is helpful in predicting costs of heavy water production by ammonia distillation. It has been stated by Barr and Drews (3) that ammonia distillation would be competitive with other developed methods only if the actual separation factor was at least 1.062 at low deuterium concentration. Since the separation factor observed was only 1.042 at atmospheric pressure, ammonia distillation is not an economic method for producing heavy water.Deutero-ammonia was synthesized by isotopic exchange between natural ammonia and heavy water. Equilibrium determinations were made using an Othmer still modified for low temperature operation. The ammonia samples were analyzed for deuterium content by converting them to water by passage over hot copper oxide, followed by a differential density determination using the falling drop method.

ISSN:0029-5639    

DOI:10.13182/NSE63-A26267

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor