Passive lead compensation

The central tubes of fuel assemblies located in the middle of the core accommodate hydraulically driven absorber rods made of WB2 sinking in lead. These rods serve the purpose of reactivity compensation and also perform the function of the reactor safety system, which operates passively in the event of coolant flow interruption or increase of its temperature at the core outlet. 

Natural circulation cooling leads to low cost power generation. The core outlet temperature of 345°C and the pressure of 15.5 MPa have been selected for the core cooling system to obtain higher thermal efficiency. The coolant system does not use chemical shim for reactivity control. To compensate for bum-up reactivity swing, a perfectly passive reactivity control system is under study, based on burnable poisons in fuel and using moderator void feedback. 

XPS measurements of passivated Fe and Ni electrodes that have been exposed to aggressive anions (Ni and Fe to F Fe to Cl , Br, and I ) but have not already formed corrosion pits support this mechanism. The quantitative evaluation of the data clearly shows a decrease of the oxide thickness with time of exposure [22,48], Not only F but also the other halides cause thinning of the passive layer (Fig. 8) [48], The catalytically enhanced transfer of cations from the oxide to the electrolyte leads to a new stationary state of the passive layer. Its smaller thickness yields an increased electrical field strength for the same potentiostatically fixed potential drop, which in turn causes faster migration of the cations through the layer to compensate for the faster passive corrosion reaction (1) at the oxide-electrolyte interface (Fig. 2a). Statistical local changes... 

The assumption of traveler passivity biases conventional benefit-cost studies towards positive net benefits. The reason for the bias in favor of safety equipment is that reasonable substitutions (risk compensation) can lead to more accidents and more violent accidents. The consequences are that the decrease in occupant fatalities will be less than expected based on technological effectiveness and that there will be an increase in nonoccupant injuries. 

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