5. Some results from numerical simulation

## 5.1. Volumetric fission product inventory

The core inventory for typical 1000 MW PWR has been evaluated by ORIGEN 2.2 code which is used by our model as a subroutine. A 35% core damage has been considered and 20% (fx) as the puff release. While the rest of radioactive mass release along with coolant with mixing rate wx = 0.01 s<sup>1</sup> . The FP release inside the containment building as a function of time is depicted in Figure 5. The volumetric radioactive mass found to increase during first 300 s then starts decreasing with a constant rate. The cesium found to be dominant with 100 times higher than the other radioactive released masses. The Krypton gas is found to be 15% higher in magnitude with Xenon gas. However, the other isotopes show the similar

) as function of time (s) for various values of fx and wx = 0.01/s.

Numerical Simulation of Fission Product Behavior Inside the Reactor Containment Building Using MATLAB

http://dx.doi.org/10.5772/intechopen.70706

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The LOCA is due to the uncontrolled leakage from coolant piping (hot leg or cold leg). The coolant burst release generates the immediate escape of radioiodine into containment with the rapture. The volumetric activity of 137Xe inside the containment has been simulated for various values of instantaneous burst release (i.e., fx = 10–70%) of total activity inside the core. The simulation results are depicted in Figure 6. The results indicated that with the higher percentage of instantaneous release (fx = 50–70%), the activity in containment slightly increased and

However, a less fraction of burst release (fx = 10–30% of total activity), the activity inside the containment first increases and then starts decreasing after approaching to the maximum value. As the value of fx decreases, the peak shifts toward higher timescale. The peak becomes more prominent with small values of fx. This happens due to competition between fx term in the initial condition and (1-fx)(exp -wx) term in source term (Eq. (4)). The behavior of 137Xe for various values of instantaneous release (fx) with mixing rate wx = 0.01/s explains the clearer

behavior but with less in magnitude.

picture of airborne Xenon (Figure 6).

then decreased linearly.

Figure 6. 137Xe activity (g/cm3

5.2. Puff release (fx) effect on in-containment FPA

Figure 5. In-containment FP inventory during in-vessel release phase with mixing rate wx = 0.01 s<sup>1</sup> .

Numerical Simulation of Fission Product Behavior Inside the Reactor Containment Building Using MATLAB http://dx.doi.org/10.5772/intechopen.70706 55

Figure 6. 137Xe activity (g/cm3 ) as function of time (s) for various values of fx and wx = 0.01/s.

first 300 s then starts decreasing with a constant rate. The cesium found to be dominant with 100 times higher than the other radioactive released masses. The Krypton gas is found to be 15% higher in magnitude with Xenon gas. However, the other isotopes show the similar behavior but with less in magnitude.
