Liquid releases event tree

Figure 2.3. Typical liquid release event tree.

Figure 5-4. Event Tree for Flammable Liquid Release...

Fig. 10.2 Event tree for an instantaneous or continuous release of a flammable liquid and pool...

In all of the SCB fire scenarios, the fire was assumed to envelop the liquid dissolution cocktail in the process containers during or following UO2 dissolution and release of radioactive material to the SCB and Zone 1 ventilation systems. While dilution of combustion products is expected to preclude damage to the ventilation system, an unmitigated release bounds the scenario where the filters or the ventilation system itself have been degraded or compromised as a consequence of a fire. The frequencies per year for such an accident developed in the event tree analysis shown in Appendix 3E.3 agree with the frequency for an extraction SCB fire as assessed in event CP-7 in the hazard evaluation (Appendix 3C). 

FIGURE 10.13 Example of a preincident event tree (for failure of a pressurized liquid storage vessel pressure control system resulting in release from a pressure safety valve). 

Estimate the source term (source term modeling), i.e., how much material in what form (gas/liquid/two-phase) is being released from containment as a function of time, and develop the release scenarios or possible hazard outcomes (toxic cloud, fire, explosion, etc.) following the release. (A powerful tool to develop and keep track of possible outcomes following a release is an event tree event trees are commonly used in quantifying the frequency of these various outcomes and were therefore described in Section 10.2.8.)... 

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