Plenum temperature

The heat release rate necessary for flashover was calculated, from the equation given by Quintiere et al. [31]. The series of equations is then solved, with the assumption that the temperature increase for flashover is 500 K (leading to an upper level temperature of TUL 795 K) and the plenum temperature for decomposition of the PVC products is 573 K. The results in Table III show that a much more intense fire is required, in all cases, to cause the PVC products to undergo dehydrochlorination than to take the room to flashover. Thus, the heat released by this fire at flashover is insufficient to dehydrochlorinate the PVC products in the plenum, for any of the scenarios. Therefore, the occupants of the room will succumb before there is an effect due to the plenum PVC products. 

Only those fires in category (i) cause sufficiently high plenum temperatures to allow decomposition of the PVC. PVC will start decomposing at ca. 473 K, and will decompose rapidly at temperatures above 523 K only. 

In all the cases studied with ten plenums, which represent a heating, ventilating and air conditioning system, the fire was of category (ii). Even in those cases were the upper level plenum temperature exceeded 523 K, this never occurred for a period of more than 2 min. 

A total of ca. 60 simulations were run and in the vast majority of them PVC decomposition plays a negligible, if any, role. In only two of the single plenum simulations was there a high enough plenum temperature for PVC decomposition to take place over a period of more than 1 min. Those worst cases, viz. 2, and 13, were analysed further, by considering various rates of PVC decomposition (HC1 generation), depending on upper level temperatures. 

Legends Timel period upper level plenum temperature exceeds 473 K Time2 idem for 523 K (maximum, in K) Depth max maximum smoke layer depth (time reached, in min) Rm CO max maximum room upper level [CO] (time reached, in min) Rm T max maximum room upper level temperature (time reached, in min). 

Find the minimum cost as a function of the plenum temperature T (in kelvin). 

Fig. 31. Effect of adding cooling air (simulated) to the bottom plenum chamber on plenum temperature.

To evaluate the effect of the secondary sodium surrounding the primary vessel, a preliminary analysis was made for a transient event of total blackout The temperature transient analysis of both the primary hot plenum and the secondary plenum indicate that the hot plenum temperature is lowered by the effect of heat transfer compared to that of the insulated case Therefore it should be noted that the large heat capacity of the cold secondary coolant works as a heat sink... 

One probable cause of the overpredicted core temperatures and underpredicted upper plenum temperatures are too large of values for the loss coefficients at the core/upper plenum junctions. This causes a flow restriction between the core and the upper plenum and results in a longer transit time through the... 

A list of 89 uncertainties was originally evaluated and considered in the setting of FI power limits. Several additional uncertainties have been recently included in the analysis. Most notable of these are an assembly effluent temperature basis and an inlet plenum temperature bias, which reduce FI power levels by 0.75 percent and 2.25 percent, respectively. As one would expect, most of the uncertainties have little effect on the FI power limit. Figure 6 illustrates the relative effect of the more important uncertainties. For restart, the uncertainty in fuel cylinder loading variation will be decreased from + 15 percent, as used in the analysis, to + 12 percent consistent with the actual fuel loading. This will reduce the 83 multiplier. 

The ratio of the gas plenum volume to the pellet volume is roughly the same as that in BWR fuel rods, 01. The gas plenum temperature is determined assuming it is placed at the top of the fuel rod and the temperature is equal to that of the outlet coolant. 

The TRACE Tgve was defined as the average between reactor inlet and outlet plenum temperatures. Once the TRACE model has been defined, the only constraints applied to the steady state run were the Tave (1024 1.5K), Brayton speed (4712.4 rad/s), and radiation heat transfer heat sink temperature (200 K). TRACE reactor power is allowed to float to a new state point. The TRACE fuel temperature rise is about 273K (1162 K - 889 K) at a reactor power level of almost 900 kWt. 

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