Loading short duration, rapid

A break in a large reactor coolant pipe could cause several rapidly occurring internal and external transient loads to act upon the reactor vessel. In the event of a postulated LOCA at the vessel nozzle, asymmetric LOCA loading could result from forces induced on the reactor internals by transient differential pressures across the core barrel and by forces on the vessel due to transient differential pressures in the reactor cavity. Differential pressures, although of short duration, could place significant loads on the reactor vessel supports, thereby affecting their integrity. 

Many of the loads corresponding to external events described in subsequent sections, and particularly in Ref. [2], are loads of short duration and rapid rise time which are characterized by a finite energy or a defined momentum transfer. The loads are often localized, causing substantial local response of the individual target but with little effect on massive structures as a whole. Load-time functions can be derived by experimentation or analytical... 

It is worth noting that blast capacity of a polycarbonate pane is sensitive to the duration of the blast load. Because of this, the typical short overpressure duration testing of polycarbonate with small close-in charges with frame set-ups that permit a rapid pressure clearing time may give an unconservative estimate of blast capacity in many real world threat scenarios. 

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