Investigation of five factors affecting the aerosol generation in a glass frit bubbler system.

Quarterly report on activities related to the reactor safety program, analysis of safety-related critical assembly experiments, and reactor core thermal-hydraulic code development.

Three ''gassy'' irradiated uranium dioxide pins were run past failure in a 35-ms natural TREAT transient in TREAT loop Test E3 to guide in choosing between two modeling assumptions regarding energy conversion from sodium vaporization in an irradiated-oxide-fuel/coolant interaction (FCI): (1) The trapped fission gas enhances fuel fragmentation upon failure, accelerates fuel-coolant mixing, and thus promotes an energetic FCI, or, conversely, (2) the trapped fission gas blankets the fuel and reduces the rate of heat transfer to sodium, preventing an energetic FCI.

Cladding failure is one of the major considerations in analysis of fuel-pin behavior during hypothetical accident transients since time, location, and nature of failure govern the early post-failure material motion and reactivity feedback. Out-of-pile thermal transient tests of both irradiated and unirradiated fast-reactor cladding show that local plastic instability, or bulging, often precedes rupture and that the extent of local instability limits the initial rip length. To investigate the details of bulge formation and growth, a perturbation analysis of the equations governing large deformation of a cylindrical shell has been developed, resulting in a set of linear differential equations for the bulge geometry. These equations have been solved along with appropriate constitutive equations and various constraints on the ends of the cladding. Sources for bulge formation that have been considered include initial geometric imperfections and thermal perturbations due to either eccentric fuel pellets or non-symmetric cooling. Of these, only the first is relevant to out-of-pile burst tests. Here it has been found that the most likely imperfection that will grow unstably to failure leads to a bulge around half the circumference with an axial length 1.1 times the deformed diameter. This is in general agreement with burst-test results. For the …

The principal safety-related characteristics of current CANDU-PHW power plants are described, and a distinction between those characteristics which are intrinsic to the CANDU-PHW system and those that are not is presented. An outline is given of the main features of the Canadian safety and licensing approach. Differences between the U.S. and Canadian approach to safety and licensing are discussed. Some of the main results of the safety analyses, routinely performed for CANDU-PHW reactors, are presented. U.S.-NRC General Design Criteria are evaluated as regards their applicability to CANDU-PHW reactors; vice-versa the CANDU-PHW reactor is evaluated with respect to its conformance to the U.S.-NRC General Design Criteria. A number of design modifications are proposed to be incorporated into the CANDU-PHW reactor in order to facilitate its introduction into the U.S.

This report compares calculated reaction rates based on neutron-transport calculations in RZ and XY geometries with measured values from a low-power dosimetry test in EBR-II. Axial distributions of Uranium-235 and uranium-238 fission rates and uranium-238 capture rate are given for various radial locations along the length of the core and the axial reflectors, and along the length of the radial steel reflectors. Reaction rates, primarily at the reactor midplane, are given for a number of fission and capture reactions. The analytical RZ- and XY-geometry models used for the neutronics calculations are described.

Two-step explicit numerical procedures based on the method of characteristics are presented. These procedures use four bicharacteristics equally spaced on the Mach cone. The velocity components are first obtained for the entire field by use of known initial data. Pressure is calculated in the second step in which the advanced velocity data are used. Nowhere in these procedures is an iterative scheme required. A linearized set of hyperbolic differential equations describing two-dimensional transients in slightly compressible fluid is considered for numerical solution. Detailed schemes are described in which all integration paths (bicharacteristics) remain in the coordinate planes; hence, only simple linear interpolation is required. These schemes allow time steps as large as the entire Courant step. Further, a stable new scheme is discussed in which the allowable time step can actually exceed the Courant time step. The procedure recommended for such computations was chosen after an extensive numerical experimentation that demonstrated its simplicity, efficiency, and accuracy. Exact analytical solutions are constructed and compared with numerical results to demonstrate the accuracy of the recommended scheme. 13 figures. This report presents a two-step explicit numerical procedures based on the method of characteristics are presented. These procedures use four bicharacteristics equally spaced on …