摘要:

AbstractStability and burnout natural-circulation tests on an electrically heated 7-rod cluster were carried out to obtain data relevant to the Halden II reactor. The object of the tests was to measure the maximum channel powers obtainable without burnout at pressures up to 28 atm and various inlet subcoolings. The test-section heat flux was essentially uniform, but local heat-flux peaks were introduced at hot patches to probe burnout.It was found that at 28 atm and up to 6°C inlet subcooling, a channel power of nearly 600 kW could be reached without burnout or instability; increasing the subcooling further, reduced the burnout power. The instability channel power threshold was investigated and found to decrease with decreasing pressure. In addition, the natural-circulation inlet velocity was measured at various constant pressures and values of inlet-subcooler heat removal, as a function of channel power up to and in the hydraulic instability region. Flow oscillations of about 1-sec period were observed and recorded together with the burnout detector signal at trip under these conditions.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19756

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractA procedure, described previously, for the preparation of high purity beryllium hydroxide has been improved and demonstrated on a kilogram scale, and a systematic study of its chemistry has been carried out. The Be(OH)2·xH2O starting material is dissolved in acetylacetone (HX) as BeX2, scrubbed with aqueous EDTA to remove metallic impurities, stripped with nitric acid, and precipitated with ammonia. The dried Be(OH)2·0.3 H2O, a granular, free-flowing powder, was obtained in 85% yield. Detectable metallic impurities totalled<5 parts/106. The variation of BeX+and BeX2formation quotients with ionic strength as well as the variation of BeX2and HX distribution coefficients with both aqueous ionic strength and organic phase composition are summarized. Decontamination efficiencies for some 13 cations were estimated to be very high. Effective purification was demonstrated on a sample of Be(OH)2starting material which was contaminated with 1000 parts/106parts BeO of Na+, Mg2+, B(III), Cu2+, Al3+, Fe3+and Cr3+.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19757

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe epicadmium capture-to-fission cross-section ratio in U235is obtained from post-irradiation measurements on bare and cadmium-covered samples exposed in the beryllium reflector of the Materials Testing Reactor. Relative capture-to-fission rates are determined from measurements of the quantities of U236and of fission product Cs137produced. The bare experiment measurements are used in combination with the cadmium-covered measurements to eliminate the need to know the yield and half-life of Cs137. For the irradiation spectrum, the experiment gives a value of 0.51±0.03 for the U235epicadmiumα(above 0.51 eV).

ISSN:0029-5639    

DOI:10.13182/NSE65-A19758

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractMercury corrosion of Si-deoxidized, low-carbon steel was studied in 5000-h tests using four natural circulation loops with once-through boilers operating at 593°C and with 111°C of superheat. The relative effects of very small quantities of Ti or Zr additions to the Hg and the effectiveness of steel pretreatment (for 500 h at 590–620°C with a liquid Hg-Zr solution), prior to contact with boiling Hg, were determined. A fourth loop, which had no additives nor loop pretreatment, was run simultaneously.With the exception of the Hg-Zr pretreated loop, maximum depth of corrosion did not exceed 50µm and occurred near the superheater exit where the temperature was the highest. Boiler and condenser corrosion were less than 30µm in these latter loops. Corrosion 300–1000µm deep was found on the downstream side of the superheater of the Hg-Zr pretreated loop, and the severity of the attack was attributed to boiling instabilities, which caused liquid Hg to come into contact with the superheater walls.Adherent iron deposits were found in the boilers and cooler liquid regions of three of the loops, but no discernible iron deposits were found in the loop with Zr added. The total quantity of mass-transferred iron (deposits and particulate) was estimated to be approximately 0.2 gm in the Zr-added loop, 0.5 gm in the Ti-added loop, 1 gm in the loop with no additions and 2 gm in the loop pretreated with Hg-Zr solution.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19759

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractMeasurements of neutron fluxes have been performed in configurations depicting the regions extending radially and axially outwards from the core of a PHWR Reactor, in order to test the accuracy of the available methods in shield design on thin alternating laminae of Fe and D2O.The results are compared to fluxes calculated by the British 18-group removal-diffusion method and by the NRN method developed at AB Atomenergi. The results show that the values predicted may be expected to be within a factor of 2 from the true values in most cases. The predicted relative flux distributions follow the observed ones with fairly good accuracy in spite of the apparent misuse of diffusion theory for the thin regions in question.It is also shown that the predicted change in the fast spectrum while penetrating these setups should be confirmable with certain threshold detectors.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19760

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe neutron diffusion and integral scattering properties of graphite have been measured by the pulsed-neutron-source technique. Measurements were performed on assemblies with geometric bucklings from 0.0036 to 0.0151 cm−2. The time of attainment of asymptotic neutron-energy spectra was determined from transmission measurements. Results from these latter measurements indicated that the minimum thermalization time, for the assemblies investigated, was≍2 msec. Asymptotic‘average’neutron velocities, measured both internally and externally, were obtained as a function of assembly size. Results indicated that an asymptotic neutron spectrum did not exist for assemblies withB2≍0.015 cm−2at a time⪅2 msec after the neutron pulse. A value of the diffusion cooling coefficient,C= 45.6±4.7×105cm4/sec was derived from the measured‘thermal’neutron decay constants.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19761

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractA numerical procedure for the integration of the reactor kinetics equation is developed. It has the property of being numerically unconditionally stable for all values of the reactivity or integration-step size. The basic assumption of the method is that the neutron and precursor densities behave exponentially with a frequency characteristic of the asymptotic frequency corresponding to the reactivity. As a consequence of the assumption, and the factoring of the kinetics equation, it is then shown that for constant reactivity the asymptotic numerical eigensolution is exactly the asymptotic eigensolution of the differential kinetics equations. Thus, for constant reactivity, the asymptotic numerical solution can be shown to differ from the asymptotic analytic solution by at most a constant factor, proportional toht2, for all time.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19762

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractMaking use of the isotropic incident flux approximation, the disadvantage factorζfor a two-region unit cell can be written as a linear combination of two so-calledXfunctions, each of them depending on the properties of one region only. A general variational approach, based on Ritz-Galerkin’s method, is used to find a closed expression forXin terms of the‘weighted’collision probabilities,From this expression the properties ofXwill be deduced once more, but then in a general way. An analytical calculation ofXin slab geometry and a numerical one in cylindrical geometry are given. The results of the first have been used for a comparison with Theys’generalization of the Amouyal-Benoist-Horowitz theory; the results of the second example were compared with Leslie’s calculation of the sameXfunction by means of successive collision probabilities.It is furthermore shown that the same procedure that serves to calculateXfunctions gives, as an important by-product, the constant production and the isotropic abledo solutions of Peierl’s integral transport theory. From these solutions the flux distribution in the unit cell (of arbitrary geometry) can be constructed. Sauer’s simple recipe for calculating theXfunction is discussed and is shown to be inaccurate for weakly absorbing media.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19763

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThis paper gives a new and very simple method of calculating Dancoff factors in regular arrays of cylindrical fuel rods. This method is readily applicable to canned fuel, and comparisons with Monte Carlo calculations show that its accuracy is adequate for practical purposes. The paper also gives an extension of the standard equivalence theorem which, unlike the theorem itself, is accurate enough for practical work. This extension enables the resonance integrals of regular arrays to be calculated from the Dancoff factor and from calculations of the resonance integral in homogeneous mixtures. These methods have been compared with the very accurate Monte Carlo calculations of Levine; the result is most satisfactory.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19764

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor

摘要:

AbstractThe extrapolation distanceϵat the surface of a grey cylindrical control rod of given size is found in terms of the blacknessβof the rod and in terms of the extrapolation distanceϵbat the surface of a black rod of the same size.The formula iswhereλeis the transport mean free path in the region external to the rod. Tables are provided forβand an empirical expression forϵb/λeis given.

ISSN:0029-5639    

DOI:10.13182/NSE65-A19765

出版商:Taylor&Francis    

年代:1965

数据来源: Taylor