Qualification: A tool for determining critical components

Generally speaking, qualification programmes aim to demonstrate that mechanical and electrical equipment important for safety can perform its function in accident situations if necessary even at the end of plant lifetime. In the first place, therefore, qualification programmes include a period in which the equipment is aged before the stresses associated with accidental situations are applied. It is obvious that the lifetime of some equipment may be shorter than the assumed lifetime of the power plant. In this case, when the qualification programme is drawn up, the ageing process takes into account only the estimated lifetime of the equipment, which will, at the end of the tests, become its 'qualified lifetime'. Thus, the operator undertakes to replace the equipment at the end of its qualified lifetime. To a great extent, therefore, the accelerated ageing stage makes it possible to evaluate the critical components in terms of the lifetime of the equipment. Since in some cases the overall nature of artificial ageing methods as opposed to natural ageing in a power plant has not been fully established, it is necessary to determine in advance a policy of in-service monitoring of this equipment. This monitoring would be designed to ensure that real ageing corresponded to the assumptions made during qualification of the material. (author). 1 fig., 1 tab