On the basis of the analysis of the causes of traffic accidents,this paper gives the definition of safety margin and builds up the configuration of the accident model.

A grids method is adopted to analyse the deformation character, deformation path, deformation degree and safety margin in dangerous area which is determined by finite-element simulation and experiment.

Through analying the mechanical property and metallurgical structure of the visbreaking reactor; testing the temperature of the visbreaking reactor and stress; analying the Safety margin and Service life of the visbreaking reactor.

The values of margin of safety for all kinds .

The influence of switching off branch on system nodal voltages and line loads is analyzed and the concept of security margin and its calculation formula are given.

Based on the sensitivity of transient voltage security margin with respect to reactive power injection, a power system can be divided into control areas for preventive control of transient voltage security.

In order to enlarge the nuclear safety margin, ensure safe shutdown of nuclear reactors under loss of on-site and offsite power supply, and raise the unit availability through elongation of diesel fallback time under unavailability of emergency diesel generators, at present, nuclear power stations of most countries and zones in the world such as France, the U.