U.S. NRC Experience with Undervoltage Trip Attachments on Reactor Trip Switchgear
An overview of the failures of reactor trip switchgear to trip soley on loss of voltage is presented. There are three types of switchgear in reactor protection systems in pressurized water reactors in the United States. The review of the failures to date and the corrective actions taken suggest that proper maintenance and surveillance testing of existing undervoltage trip attachments on reactor trip switchgear should reduce substantially the number of failures.
UNITED STATES NUCLEAR REGULATORY COMMISSION REGION II
Northern States Power Company, a Minnesota corporation, requests authorization for changes to Appendix A of the Monticello Operating License as shown on the attachments labeled Exhibits A, and B. Exhibit A describes the proposed changes, describes the reasons for the changes, and contains a significant hazards evaluation. Exhibit B is a copy of the Monticello Technical Specifications incorporating the proposed changes.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.