scope:

(a) This Case provides Class 2 and Class 3 overpressure protection rules for those pressure-boundary structures which, having been designated by the Owner (NCA-1140 and NCA-3230) as a group of items requiring such protection, are not covered by NC-7000 or ND-7000 rules because some of the structures are expecting service temperatures above those currently allowed under the rules of Subsection NC and Subsection ND.

(b) Whereas the rules of NC-7000 and ND-7000 are oriented toward water and steam-cooled reactor systems, the rules of this Case envision a wider variety of coolant fluids.

(c) The rules of NC-7000 or ND-7000 shall govern unless paragraphs are specifically altered by the rules of this Case. All references to other NC-7000 and ND-7000 paragraphs are to be interpreted as referring to the NC-7000 and ND-7000 paragraphs as modified by this Case.

(d) As with NC-7000 and ND-7000, the rules of this Case presume that all system conditions, including transients, are accurately described in the Design Specifications for the components being protected.

(e) In the evaluation of the effects of overpressure events, structural loadings shall include, but not be limited to, the types of events listed below.

(1) System overpressure due to a closed valve, a blocking object, or a solid core of metal coolant.

(2) Overpressure due to the addition of heat to an isolated portion of the system.

(3) Overpressure due to nuclear transient effects.

(4) Overpressure due to failure of a system component, including the effects of leaks from adjacent systems and possible resulting chemical reactions.

(5) Overpressure resulting from operator error.

(6) Overpressure due to constant pressure in combination with a rising over-temperature condition.

(7) Overpressure due to pump overspeed.

(f) Add to NC-7111(b) and ND-7111(b) the following:

Some examples of events whose overpressure transients are not considered in detail by the rules of this Case are:

(1) Rapid closure of a check valve leading to fluid shock conditions in a local region.

(2) Earthquake motions inducing sloshing of fluids contained in large tanks.

(3) Nuclear incidents inducing a severe pressure spike in a local region.

(4) Rapid closure of a valve during high flow rate conditions introducing pressure shocks.

Note that each of the above events may lead to loss of coolant in systems utilizing nonreclosing overpressure relief devices.