摘要:

AbstractThe oxidative decladding of UO2fuels has been demonstrated on three-foot sections of unirradiated fuel rods and on eight-inch sections of fuel rods irradiated to 21,000 MWd/MTU.Decladding rates were unaffected by the extent of irradiation. Uranium dioxide which was unirradiated, irradiated, and with fissia added to simulate 100,000 MWd/MTU irradiation was declad at similar rates. The effect of pressure and temperature on decladding rates was determined. Puncturing the cladding greatly enhanced the rate and gave a coarser product. This product was not completely converted to U3O8during oxidative decladding.Greater than 99.9% of the UO2fuel was removed from the cladding. There was no detectable contamination of the product by the cladding material. Little or no fission-product or plutonium decontamination was observed. Dissolution rates for the declad product, in 50% nitric acid, were 20 times as fast as for the“as received”UO2fuel.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19784

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractTo evaluate the potential health hazard of beryllium under certain circumstances, a study was made of the interaction of metallic beryllium with oxidizing environments. This study consisted of two parts. Beryllium was subjected to the action of hydrocarbon/hydrogen/oxygen flames at temperatures below and above the melting point, A determination was made of the amount of contamination by the oxide of the downstream flue gases. The experiments indicated that the oxidation rates and the contamination are relatively low below the melting point of beryllium (1283 C). Above this temperature, however, it was found that the molten metal burned rapidly when unprotected by an oxide layer. This caused a sharp increase in both rate of oxidation and in downstream contamination.The second part of this study was concerned with the behavior of beryllium when surrounded by water substance. The experimental work was divided into two phases involving reaction in liquid water and in steam. In general, it was found that the oxide layer formed was at first tightly adherent and later became thick and porous. The time between these two conditions depended on temperature, decreasing sharply as the melting point was approached. Upon melting, the oxide layer tended to act as a crucible containing the liquid metal. Under suitable conditions, the liquid would break out of its cage and oxidize very rapidly. When this occurred, the surrounding steam was slightly contaminated with the oxide.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19785

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe effects of neutron irradiation, post-irradiation annealing and re-irradiation on the Charpy V-notch impact transition temperature of pressure-vessel steels were investigated. Specimens representing several heats of pressure-vessel steels were irradiated at elevated temperatures to fast (>1 MeV) neutron exposures up to 2×1020nvt. The general observation was that irradiation caused an increase in the transition temperature; however, it was discovered that specimens representing various heats of a given material composition could show a vastly different increase in transition temperature due to irradiation. These results have led to the arbitrary classification of these steels as“sensitive”or“insensitive”heats. Possible correlation of heat to heat sensitivity with microstructure is discussed. Post-irradiation annealing in the temperature range of 650–800 F was found to reduce the effects of irradiation on the transition temperature significantly. However, subsequent re-irradiation of specimens that were post-irradiation annealed at 650 F increased the transition temperature to a level that could not be distinguished from that of specimens that were not annealed prior to re-irradiation. Re-irradiation studies were not conducted on specimens that were post-irradiation annealed at the higher temperatures. No explanation of the re-irradiation behavior after annealing is available.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19786

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractA semi-empirical equation is used to predict excess reactivity in the ETR as a function of power-time in terms of reactivity parameters which are routinely measured in a mockup of each ETR core in the ETR Critical Facility. Constants in the equation were evaluated by fitting the equation to plots of excess reactivity as a function of power-time obtained for several cores in the ETR. The equation and reactivity measurements fulfill the need for frequent and reliable predictions of core charge life as well as control-rod positions during reactor operation.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19787

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractNusselt numbers have been calculated for bilateral heat transfer to fluids flowing in annuli. The following four cases have been treated: (A) uniform and equal heat fluxes from both walls, under the condition of slug flow; (B) equal wall temperatures at the same axial location and uniform but unequal heat fluxes from the walls, under the condition of slug flow; (C) same as case (A), except flow is laminar; and (D) same as (B), except flow is laminar. In the calculations, the following assumptions were made: (a) the conditions of fully-established velocity and temperature profiles, and (b) the independence of physical properties with temperature variation across the flow channel.The Nusselt numbers, independent of Reynolds and Peclet numbers, are given as functions of the geometrical parameter,r1/r2, which varied from zero to unity, the former limit representing the case of a round pipe and the latter that of parallel plates.For case (A), the heat-transfer coefficient for the heat transferred from the inner wall becomes infinite atr1/r2= 0.214 because the inner wall surface temperature and the bulk temperature of the flowing fluid are equal under these conditions. For case (C), this happens atr1/r2= 0.1685.The differences in Nusselt numbers between cases (A) and (B), and between cases (C) and (D), are appreciable, attaining maxima aroundr1/r2= 0.20. Atr1/r2= 1, cases (A) and (B), of course, become identical, as do cases (C) and (D).Finally, equations are given for calculating heat-transfer coefficients for each wall, for the general case where the heat fluxes from the annulus walls are uniform but not necessarily equal.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19788

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThis article is devoted to an extension of Galanin’s heterogeneous theory to the tridimensional problems usually met in studies of small reactors. Clearly, this method is also applicable to bidimensional problems. Here also, it brings in several improvements compared with the parent theory, especially concerning the radial reflector, which can here be of finite dimensions. Significant numerical examples are given in the final section. The codes used—for the IBM 7090 computer—lead to times of calculation which are reasonable for small reactors. They may also be used for much bigger reactors provided that they are used to treat bidimensional problems only.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19789

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe thermal-neutron diffusion constant was measured in a plexiglas system with empty channels, using the pulsed-neutron-source technique. From separate sets of measurements on rectangular blocks, the diffusion constants parallel and perpendicular to channels were determined, whereas the measurements on cubes give the average diffusion constant. The results are compared with existing theoretical estimations. It is found that the average diffusion constant is well below the theoretical predictions of Behrens. On the other hand, the difference between the parallel and the perpendicular diffusion constant is almost as large as predicted theoretically.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19790

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractWe discuss the behaviour of the asymptotic thermal flux in the“pulsed”and“exponential”experiments. In particular, we give a pair of theorems which bear upon the possibility of measuringλ0andLin certain cases. One shows that allλi(B2) disappear at sufficiently largeB2, the other that all space decay constants disappear at sufficiently large concentration of absorber.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19791

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractIn a previous paper1some general properties of the Boltzmann equation governing the transient behaviour of neutron distributions have been developed. The experimental consequences of these considerations are examined and some reported experimental results are discussed. It is found that in some cases theoretical restrictions on time-decay constants and diffusion lengths are apparently violated.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19792

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractWe have studied the thermal-neutron flux near the boundary of a semi-infinite non-absorbing gas which scatters neutrons isotropically. The THERMOS code was used to obtain numerical solutions to the integral transport equation. The properties of the flux, integrated over all energies, at the surface of the semi-infinite medium were found to be very insensitive to variations in the scattering properties of the medium.

ISSN:0029-5639    

DOI:10.13182/NSE64-A19793

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor