In the design phase of any plant, measures are taken and design features are incorporated to ensure that the plant can satisfy stringent safety, reli­ability and economic criteria. The designs are subjected to rigorous analysis and, where feasible, testing to verify performance claims. Subsequently they will be further analysed by the prospective owner operators and by regula­tory authorities. The process of evaluating the designs is very demanding and time consuming and necessarily so.

It follows therefore that it is equally important that all the components are manufactured and assembled in accordance with the design intent. Throughout the manufacturing and construction phase of any plant, meas­ures must be taken to ensure that the plant and equipment complies fully with the licensed design requirements. The owner or operating organisation must be in a position to ensure that is the case before acceptance of the plant. This will require the operating organisation to establish programmes for evaluation of quality of components throughout the manufacturing and construction phases of the plant.

Throughout the operating lifetime of the plant, the operators have an obligation to ensure that the plant remains compliant with the licensed design. Maintenance inspection and testing programmes will be developed for this purpose.

Over time, the cumulative evolution of changes in plant performance and the condition of the plant due to in-service aging will need to be assessed. Periodic safety reviews are a common feature of regulation in many coun­tries where comprehensive reappraisal of the plant status against the design and licensing criteria are undertaken. The periodicity will vary from regula­tor to regulator and the terms of reference and scope will vary.

Modifications or changes to operating procedures to address identified issues must be subjected to an approval process. The scope and criteria for approval of changes are usually related to the nuclear safety significance of the change in question.

These responsibilities will be placed on the operating organisation for the full lifecycle of the plant, which will be for several decades. It is vital, therefore, that every operating organisation establishes the knowledge base and capability to fulfil these functions at an early stage in the plant’s lifecycle.

Typically, the body of personnel assembled to fulfil such a function is known as the ‘Design authority’ for the operating organisation. The IAEA has published two documents in the INSAG series that address the concept of a design authority:

• INSAG-14 (1999), Safe management of the operating lifetimes of nuclear power plants

• INSAG-19 (2003), Maintaining the design integrity of nuclear installa­tions throughout their operating life

As the lifecycle of the plant will probably span the working lives of more than one generation of personnel, programmes must be established to retain the knowledge and capability to fulfil that function over several decades.