.	Safe operation (What?)
•	Introduction
•	Prevention
•	Monitoring
•	Means of action
•	Summary
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At each stage in the life of a plant, the same approach is used as in applying the defense in-depth principle. First, the requirements are announced to the parties responsible for the design, to the vendor or the operators organization. These organizations have to follow and to be absolutly in accordance with the requirements.

A system is then organized to monitor the discrepancies between requirements and performance. Means of action are implemented to correct the differences.

This material is intended for operators, therefore two whole chapters are devoted to safety during operation. The first chapter, Chapter 4: Safe Operation (What?), describes in detail the main requirements relating to safety during operation concerning prevention, monitoring and action.

The second chapter devoted to safety during operation, Chapter 5: Safe operation (How?) shows how nuclear power plants meet the safety requirements and prove that safety is guaranteed (compliance of operating methods and the installations with safety requirements).

Control of safety during operation

Control of safety during operation is a matter of "actually obtaining, and proving it to the general public and the Safety Authority, true compliance of the operating methods and installations with the safety requirements, while maintaining the competitiveness of the electric production". This definition is derived from Nuclear Power Plant Operations Safety Policy documents.

Safety requirements

The safety requirements are both regulatory and associated with the design and operating feedback from the plants. The latter are specified in the General Operating Rules, the On-Site Emergency Plan, and the In-service Inspection Rules for Mechanical Components of PWR Nuclear Island.

The General Operating Rules is an interface document between design and operation. A series of rules is established specific to the operation the unit which must comply with the requirements to stay within the scope of the safety elements presented in the Safety Analysis Report.

Evolution of safety requirements

Following startup, equipment and procedures of units undergo a permanent process of modification.

This continuous process has the disadvantage of making the safety level of the unit difficult to assess. The level of safety depends naturally on the state of progress of modification work. A rapid rate of change in the installations could increase the operating errors. Applicable safety requirements must be clearly defined and must not undergo constant revisions in order to efficiently manage the safety of the units. The practice of grouping modifications satisfies this requirement.

The process of safety reexamination, introduced in the French regulations (Decree dated 11 December 1963 and modified on 19 January 1990), offers the opportunity of clarifying the relationship between the implementation status and safety requirements.

This reexamination essentially consists of:

• Clarification of the frame of reference of the safety requirements consisting of the various rules, criteria, and specifications applicable to a standardized series
• Appraisals of the conformance of the units to these requirements by reevaluating safety studies, when the proof in the initial Safety Analysis Report appears to be inadequate, as well as reviews to check the condition of the equipment, systems and barriers
• An assessment of the frame of reference in the light of new studies or occurrences and more recent reference material; this may lead to a change in the frame of reference when safety considerations clearly outweigh any negative effects of the modifications

Any modifications resulting from the reexamination will be implemented in batches during ten-year inspections. This is a general rule.

Therefore:

• Changes in safety requirements resulting in updating the Safety Analysis Report and the General Operating Rules
• And corresponding changes in the installations by incorporating batches of modifications

should occur every 10 years (barring major safety problems).