Safe operation of nuclear power installations depends on the maintenance of effective control, cooling and containment of the reactor core and its contents at all times. Designers provided systems and safeguards to satisfy these requirements. It is the role of the operator to ensure that these systems and safeguards remain available and functional through all phases of start-up, steady-state operation, transients, shutdowns and maintenance activities. The operator is also required to ensure that the plant operates within design limits and conditions that are determined in the design phase safety analysis.

Suitably qualified and experienced personnel are charged with these responsibilities; the numbers and qualifications of such people so charged are also part of the safety analysis and feature as limits and conditions to be observed in regulations.

Engineered safeguards are designed to maintain core control, cooling and containment of the reactor core. To ensure the availability and functionality of equipment, the operators conduct surveillance tests, preventative main­tenance activities, inventory management and configuration management activities. These requirements feature in the form of rules and regulations for operator compliance.

From time to time, equipment will become unavailable or inoperable, operational limits will be encroached upon and transients will occur. In such

circumstances it is important that the operator makes decisions in a control­led and logical manner that are consistent with the plant design limits and conditions. Technical specifications provide the operator with the basis for such decision-making.

The IAEA Safety Guide on limits and conditions (IAEA, 2000) describes the basis for the development of operating limits and conditions or techni­cal specifications.

The US, Nuclear Regulatory Commission were the pioneers in the devel­opment and use of technical specifications. In the US, Standard Technical Specifications (STS) are published for each of the five reactor types as a NUREG-series publication. Plants are required to operate within those specifications. The regulations describe the limits and conditions to be observed in a whole range of reactor parameters.