Condensers valve, leak rate

It is important to know the leak rate of the valve D (Fig. 2.18.1) not only against the atmosphere, but also between the chamber and condenser for the pressure rise measurements for BTM and DR data. The leak rate can be measured as follows ... 

The decisive data during main drying (MD) is the temperature of the ice at the sublimation front, Tice, which can only be measured by barometric temperature measurement (BTM). Figure 1.77 shows the principle the valve between the chamber and condenser is closed for less than 3 s, to fill the chamber with water vapor of saturation pressure p., corresponding to Tke as shown in Table 1.11. The two conditions for the use of BTM a leak rate of the chamber below a certain limit and enough ice subliming during the time the valve is closed, are described in detail in Section 1.2.1. 

A valve between chamber and condenser which closes reproducibly and seals the condenser from the chamber with a leak rate that is small compared with LR of the total chamber. 

Anticipated operational occurrences are off-normal events, usually plant transients, which can be coped with by the plant protection systems and normal plant systems but which could have the potential to damage the reactor if some additional malfunction should happen. Their typical frequency of occurrence may be more than 10 year Some of the anticipated occurrences (PIEs - postulated initiating events) are due to the increase of reactor heat removal (as might occur for an inadvertent opening of a steam relief valve, malfunctions in control systems, etc.). Some are due to the decrease of reactor heat removal (such as for feed-water pumps tripping, loss of condenser vacuum and control systems malfunctions). Some are due to a decrease in reactor coolant system flow rate, as in the case of a trip of one or more coolant pumps. Some are connected with reactivity and power distribution anomalies, such as for an inadvertent control rod withdrawal or unwanted boron dilution due to a malfunction of the volume control system for a PWR. Events entailing the increase or decrease of the reactor coolant inventory may also happen, due to malfunctions of the volume control system or small leaks. Finally, releases of radioactive substances from components may occur. 

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