1INTERNATIONAL ATOMIC ENERGY AGENCY, Design of the Reactor Coolant System and Associated Systems in Nuclear Power Plants, IAEA Safety Standards Series No. NS-G-1.9, IAEA, Vienna (2004).

2‘Well defined and accepted’ generally means either widely accepted by Member State regulatory bodies or proposed by international organizations.

3The categories of service condition are defined as follows:

• Normal service conditions: Loading conditions to which the equipment might be subjected during normal operation including normal operating transients and startup and shutdown conditions.
• Upset conditions: Loading conditions to which the equipment might be subjected during transients resulting from the occurrence of a postulated initiating event categorized as an anticipated operational occurrence.
• Emergency conditions: Loading conditions to which the equipment might be subjected during transients resulting from the occurrence of a postulated initiating event categorized as an accident of low frequency.
• Faulted conditions: Loading conditions to which the equipment might be subjected during transients resulting from the occurrence of a postulated initiating event categorized as an accident of very low frequency.

4Meeting the stress limit given by codes for emergency conditions or faulted conditions is generally not considered adequate by the regulatory body.

5In some States, the quantity of water that is immediately available (including water stored at the site in tanks or reservoirs) is thirty days, unless a shorter time period can be justified by conservative analysis.

6In some States, this quantity of water is designed to ensure heat removal capability for three days.

7If the heat produced by the operation of some components is also removed and transported by those systems, the corresponding additional heat loads should be included.