Book excerpt: When nuclear power plants reach the end of their nominal design life, they undergo a special safety review and an ageing assessment of their essential structures, systems and components for the purpose of validating or renewing their licence to operate for terms beyond the service period originally intended. Three different plant life management models have been used to qualify these nuclear power plants to operate beyond their original design life. This publication presents a collection of sample licensing practices for long term operation among IAEA Member States. The various plant life management models used to obtain long term operation authorizations are described and comparisons drawn against the standard periodic safety review model. Lessons learned and warnings about possible complications and pitfalls are also described to minimize the licensing risk during operation and future long term operation applications. The main intention of this publication is to support nuclear power plant owners and operators planning an extension of plant operation beyond its original design life, but it also serves as a useful guide for those interested in procuring, from the beginning, the necessary tools to implement ageing management in their future plant with long term operation in mind.