摘要:

AbstractIn the worst hypothetical accident of a light water reactor (LWR), when all protection systems fail, the core could melt and be converted to a deep particulate bed as a result of molten-fuel-coolant interaction. The containment of such an accident depends on the coolability of the heat generating particulate bed.This paper summarizes published theoretical analyses that may predict bed dry out. In three of the analyses, the fluid flow in the heat generating particulate bed is considered to be laminar (Darcy's law), whereas in one study the fluid flow is solved for both the laminar and the turbulent flow regimes and is affected by capillary forces. The theoretical studies are compared with our recent data and with other recently published data covering a range of parameters that is expected in an LWR accident. An extension of the analysis and the experiments to a mixture of particle sizes is presented. The scaling of the dry out data to high pressures, which may be encountered during the course of an accident, is accomplished by multiplying the experimental bed dryout heat flux by the ratio of dry out flux at pressure to the dryout flux at atmospheric pressure.This ratio was calculated with the theoretical model, which agreed best with the experimental dryout data at atmospheric pressure. Based on the pressures and particle sizes expected in a pressurized water reactor core melt, it is concluded that stable (self-cooled) debris bed formation will occur if sufficient water is available.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21399

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe leaching behavior of a cement composite incorporating evaporator concentrates produced at a pressurized water reactor nuclear power plant has been studied for safety assessment of the final disposal of waste solids. Leaching tests were carried out in accordance with the method recommended by the International Atomic Energy Agency. Amounts leached were measured as functions of the waste-cement weight ratio (Wa/C), temperature of leachant, and curing time of specimens. The solidification of wastes containing boric acid with cement-vermiculite mixture was much improved by the alkalinization of the waste up to pH 12.The fraction of3H or90Sr leached increases with increasing Wa/C and leachant temperature, and with decreasing curing time. The amount of either137Cs,60Co, or144Ce leached does not depend much on Wa/C, but depends on the leachant temperature and curing time. The leaching fraction for these nuclides in de-ionized water as a leachant is higher than that in the synthetic seawater. The leachabilities of nuclides follow the order:3H>137Cs>90Sr>60Co>144Ce. The relationship between the fraction leached and the ratio of surface area and volume of a specimen has been examined in order to estimate the amounts leached from specimens of various geometries.On the basis of the results obtained, estimations were made of the amounts leached from a 200-ℓcomposite volume that is exposed to a water environment for extended periods.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21400

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractTransport of radioactive nuclides through a system of joints is discussed including a linear sorption isotherm. The expression for the effective retention factor is derived for (a) a single joint, (b) a system of identical joints separated by a given distance, and (c) a system of joints with arbitrary apertures and sorption characteristics. It is shown that the retention factors for cases a and b are the same. In the limit of dense fractures, the retention factor for the porous medium is recovered. Relevance to the one-dimensional geosphere transport problem in the heterogeneous geology is pointed out. An arbitrary number of joint sets can now be included in such a problem.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21401

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractA method to solve the incompressible Navier-Stokes equations for irregular three-dimensional geometries is developed. The method consists of two stages. The first stage involves a coordinate transformation that regularizes the awkwardly shaped surfaces into planar ones by suitably stretching or“ironing out”uneven surfaces. This change of coordinates converts the physical space into a transformed space, which forms, in general, a nonorthogonal curvilinear system. The resulting Navier-Stokes equations now involve a few additional nonlinear terms but the boundary conditions can now be applied very simply and accurately. The boundary layers near the surface are resolved through the second stage involving another coordinate transformation such that only the boundary layers are broadened without substantially affecting the interior region. This transformation from the transformed space of the first stage to the computational space is orthogonal and results in a concentration of grids near the boundaries only. All of the basic mathematical formulations are given in this paper.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21402

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe various sources and sinks for heat in the reactor fuel and in the containment atmosphere are followed as a function of time, and they are used to determine what combinations of failures would lead to fuel meltdown and to rupture of the containment. Heat transfer problems are discussed and it is shown that their rates are not generally limiting. In some cases, it is indicated that the Rasmussen study assumptions were highly conservative.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21403

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractA general approach to the application of neutron count moment analysis to passive assay is presented. The higher moments of the neutron count distribution are derived with the aid of the probability generating function and are used to formulate an analytic relation between the measurement uncertainty and the assay system parameters. The measurement uncertainty, expressed by the relative resolving power function, for the reduced variance method is developed and analyzed in detail. The study suggests an iterative approach for data processing where the interpretational models are chosen to yield the lowest possible resolving power.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21404

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe average beta-ray energy has been measured by a direct method for important fission products. For other nuclides, the average beta-ray energy has been determined using experimental data from a study of beta strength functions. In cases for which no experimental data exist, the average energy has been derived using extrapolated beta strength functions.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21405

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractA photoexcitation process by gamma rays from a60Co source has been studied for the nuclei of87Sr,111Cd,115In, and176Lu. The induced isomeric activity was measured with a Ge(Li) detector. The flux of photons scattered into the target has been estimated with the Monte Carlo method using the single-scattering approximation. From the observed induced activities and the calculated photon flux, the integral cross sections for isomer production by photoexcitation were obtained and compared with other experimental data.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21406

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe minimization of the functionals defined by the prior knowledge and integral data of a neutron spectrum can be the basis of many unfolding methods. The form of these functionals classifies the widely used methods: FERDOR, SPECTRA, RFSP, CRYSTAL BALL, SAND-II, STAYSL, and others. The methods are systematically derived and theoretically compared to each other. Their relations to the function expansion method are discussed, and several cases of estimated spectra are studied. Treatments of response-function errors are also mentioned.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21407

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor

摘要:

AbstractThe spatially dependent neutron temperature profile measured by flux perturbing activation probes is correlated with the actual one-dimensional profile via a new singular Fredholm integral equation of the second kind. In time-of-flight measurements, the integral equation reduces to a singular Volterra type. A distinct anomalous profile deformation effect is theoretically predicted to be associated with each of these two techniques. The analytical investigation of the anomalous effects for neutron rethermalization experiments established that their magnitude should be far less than the standard errors of the associated techniques of measurement.

ISSN:0029-5639    

DOI:10.13182/NSE82-A21408

出版商:Taylor&Francis    

年代:1982

数据来源: Taylor