ISSN:0029-5639    

DOI:10.13182/NSE63-A18439

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe mechanism and kinetics of nitrogen release from UO2pellets containing high nitrogen impurities have been investigated at elevated temperatures. A combination of metallographic and x-ray analyses showed that nitrogen present in the UO2exists as a second phase in the form of uranium nitrides. The kinetics of nitrogen release were measured at temperatures of 1000, 1200, 1400, and 1600°C and the mechanism of release was determined to be controlled by the diffusion of nitrogen through the UO2lattice.The variation in nitrogen pressure upon heating a UO2fuel element to elevated temperatures was studied. The data showed that a reversible equilibrium pressure-temperature relationship did not exist between the nitrides in the UO2and the nitrogen gas above it as occurs with pure uranium nitrides. The quantity of nitrogen which will be released in a UO2fuel element is determined by the kinetics of diffusion of nitrogen through the UO2lattice and may be computed for any given fuel element design utilizing a diffusion model similar to one used for computing release of fission gases.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18440

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractIn the experiment to be described the 28 Mev electron linac at Harwell was used as a neutron source to produce 1µsec bursts of 1011electrons 160 times per second. A natural uranium target was placed centrally against one face of a 60 cm x 62.2 cm x 71.1 cm graphite block, and a neutron beam extracted from a channel running into the center of the block. This beam was interrupted by a slow chopper running in synchronism with the pulses from the accelerator. In this way 100µsec“time samples”of the neutrons in the block were taken and their spectrum determined by the time-of-the-flight method. The instant of the“time sample”relative to the fast neutron pulse could be varied by an electronic delay circuit. Neutron spectra are presented for the time varying between 300µsec and 1000µsec after the pulse. These spectra differ from the Maxwellian shape but approach asymptotically to a“cooled Maxwellian”from which they are indistinguishable after 1000µsec. Detailed calculations of the spectra have been made using an IBM 7090 computer to obtain a numerical solution of the time and energy dependent diffusion equation; using a scattering kernel based on the scattering measurements made at Chalk River. The experimental results are also compared with spectra using a scattering kernel based on the heavy gas model with a fictitious mass of 33.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18441

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractDetails are provided on the construction and operation of a two-stage diaphragm pump successfully used for the first time in liquid metal service. From the results of a 5376 hr test of the pump it was concluded that it is well suited to the pumping of liquid metals at low flow rates where pulsating flow can be tolerated and also where remote operation is required. Operating temperatures and pressures are limited only by the availability of suitable materials of construction.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18442

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractMeasurements of the spatial dependence of the zero power transfer function of the reactor NORA have been performed, using a local reactivity perturbation. Spatial effects were observed for frequencies higher than the break frequencyβ/l, and the wave nature of the flux space-time variation has been recognized. A theoretical interpretation based on two-group diffusion theory is given by solution of the equations by the finite difference method on an analogue computer. The qualitative agreement between theory and experiment is good.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18443

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractIn the treatment of integral equations one frequently employs such analytic approximation techniques as a variational principle or a method of successive approximations. The mathematical relationship of these approximations is investigated and the conditions under which they should give equivalent results are revealed.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18444

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe distribution of fissions within one fuel pin of a cluster is asymmetrical because of self-shielding and neutron streaming phenomena. An implicit solution of the integral form of the Boltzmann equation indicates that, for a given neutron spectrum, this distribution is primarily a function of three dimensionless parameters: (1) pin radius/neutron mean free path in pin material; (2) pin circle radius/pin radius; and (3) pin radius/fuel element radius.The actual distribution was determined experimentally by detector foils and autoradiographic techniques for various seven-pin, cluster type, gas-cooled fuel elements. The experimental fuel pins were fabricated by winding alternate 0.001 in. thick layers of pure aluminum and enriched uranium (93% U235) on a solid core until the desired pin diameter was reached. Seven of these pins, assembled into a fuel element, were irradiated in the thermal column of a research reactor. The layers of uranium and the uranium detector foils (which had been exposed concurrently) were subsequently autoradiographed and the resulting x-ray film optical density measured on a microdensitometer. The detector foils were also counted in a gamma detector, thus providing a key between relative radioactivity and optical density.It was found that the fission distribution within the center pin of the cluster was symmetrical and could be represented byThe fission distribution in the outer pins of the cluster was asymmetrical with respect to the pin center but could be represented byValues of the constants in the above equations are correlated by the first two dimensionless parameters given above but appear to be independent of the third.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18445

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractTwo methods of calculating Doppler-broadened resonance cross sections are described. Both methods use series expansions suitable for use in a digital computer. Tables of the single-level and interference functions are given which cover the range of arguments normally found in reactor calculations.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18446

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractThe asymptotic energy spectrum of thermal neutrons in an infinite medium of beryllium has been calculated for three temperatures: 300°K, 200°K, 100°K, for a constant plane source of neutrons at the midplane. The techniques of multigroup diffusion theory were applied, using Nelkin's first order scattering kernel for Be, and the energy-dependent transport mean free path,λtr(E), calculated by Bhandari. Because of the violent variation ofλtrin the vicinity of the Bragg cutoff energy, for the lower moderator temperatures the calculated flux spectrum is quite different from the Maxwellian. At 300°K the deviation from the Maxwellian is small.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18447

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor

摘要:

AbstractTrilaurylamine nitrate diluted in dodecane is considered as an extracting agent for plutonium. The use of this solvent is proposed for a tail-end plutonium recovery from irradiated uranium solutions which have already been purified by one or more TBP cycles. Mention is made of general properties of the solvent. The study of the stripping of plutonium is emphasized. The first choice stripping solution is a mixture of sulfuric and nitric acid which gives a final concentrated and purified Pu4+solution. Some alternative purification flowsheets are given. They show that a decontamination factor of 104can be attained for Zr-Nb and uranium. Kinetics of the extraction and radiolytic degradation of the solvent are briefly discussed.

ISSN:0029-5639    

DOI:10.13182/NSE63-A18448

出版商:Taylor&Francis    

年代:1963

数据来源: Taylor