Radial Reflector Research Articles

Improved Pressurized Water Reactor Radial Reflector Modeling in Nodal Analysis

A one-dimensional method based on a combination of the “nodal equivalence theory” and response matrix homogenization methods was previously described for determining environment-insensitive equivalent few-group diffusion theory parameters for homogenized radial reflector nodes of a pressurized water reactor. This reflector model, called the NGET-RM model, yields equivalent nodal parameters that do not account for the two-dimensional structure of the baffle at core corners; this can lead to significant errors in computed two-dimensional core power distributions. A semi-empirical correction procedure is proposed for reducing the two-dimensional effects associated with this particular one-dimensional reflector model. Numerical two-group experiments are performed for a given reflector configuration (and soluble boron concentration) to determine optimal values for the two empirical factors defined by this model. It is shown that the resultant factors are rather insensitive to core configuration or core conditions and that their application yields improved two-group NGET-RM reflector parameters with which accurate nodal power distributions can be obtained. The results are also compared with those obtained with another one-dimensional environment-insensitive model that has an extra degree of freedom utilized here to reduce two-dimensional effects. Some practical aspects related to the application of the proposed correction procedure are briefly discussed.

Environment-Insensitive Equivalent Diffusion Theory Group Constants for Pressurized Water Reactor Radial Reflector Regions

A novel one-dimensional approach, which combines the nodal equivalence theory and response matrix homogenization methods, is developed for generating equivalent few-group nodal diffusion parameters for the radial reflector of a pressurized water reactor. This nodal reflector model has the advantage that it is much less sensitive to reactor core conditions than conventional nodal equivalence theory models. A special one-dimensional nodal equivalence theory reflector model is described and applied in numerical experiments to investigate the significance of the environment dependence of such models. Numerical results are presented to confirm the environment insensitivity of the new model and to illustrate its feasibility for application to multidimensional nodal rector analysis.

ANALYSIS AND DESIGN OF RADIAL RIB REFLECTOR ANTENNAS

ABSTRACT The radiation characteristics of radial rib reflector antennas are studied. This type of antenna can be used as a large deployable satellite antenna. The radiation patterns of a axi-symmetric reflector are computed using both an exact physical optics analysis and a simplified approximate analysis in order to understand the behaviour of the rib-related sidelobes which have a cyclic behaviour in the azimuthal direction. A parametric study is conducted. A shaped sub-reflector is designed using diffraction profile synthesis to compensate for some of the errors introduced by the main radial rib reflector.

Effectiveness of rotating control drums in the radial reflector of a reactor

Effectiveness of rotating control drums in the radial reflector of a reactor

Measurement of Migration Area and Multiplication Factor of UO2-H2O Lattice

The migration area, multiplication factor, and axial as well as radial reflector savings of a light water moderated critical assembly fueled with UO2 (enriched to 2.596 w/o in 235U) have been obtained through water height experiment applying the one group diffusion model. The water height was varied from 1,226 mm to 710 mm, while the core radius was changed from 183.3 mm to 196.8 mm in order to maintain the criticality. The linear relation obtained between the water height h and (∂p/∂h)-1/3 as well as between the radial buckling Br and the axial buckling B 2 γ indicate that the one group diffusion model is a good approximation for this core.

Tridimensional Theory of Heterogeneous Reactors

An extension of Galanin's heterogeneous theory to the tridimensional problems usually met in studies of small reactors is presented. 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. The codes used for the IBM-7090 computer lead to times of calculation that are reasonable for small reactors. They may also be used for much bigger reactors provided that they are used for bidimensional problems only. (auth)

Effectiveness of a system of rod absorbers in a reactor fitted with a reflector

The conditions of criticality and the distributions of the neutron flux for a homogeneous thermal-neutron reactor with a system of absorbing rods are obtained in the two-group approximation. The rods extend through the entire depth of the reactor and are situated around the circumference of the active zone or radial reflector at a uniform distance from one another. The results of the calculation are presented.