Reactivity ramp change

It might be expected that the next most difficult case arises when the initial input of reactivity is linear, of the form a + bt, frequently called a ramp change of reactivity. The truth of the matter is that a periodic input of reactivity gives rise to a much simpler problem (see Garabedian [5]), but interest will be focused for the present on problems associated with ramp insertions of reactivity. 

A recent literature report has shown that changes in the stability of the different stable oxidation states of copper can be produced upon interaction with CO-Oj mixtures [12]. Thus, in order to examine the changes produced in the copper species characteristics upon interaction of the calcined samples with a CO-O2 mixture, the evolution of carbonyl bands has been monitored for CuA and CulOCA, as shown in Figure 6. Two different temperatures were selected for these experiments at 373 and 573 K. The samples were heated using a 10 K min ramp until the corresponding temperature is reached, and subsequently cooled to RT, in a stoichiometric flow similar to that used for the catalytic reactivity tests shown above. Then, after prolonged outgassing at RT, a known CO pressure is admitted in the cell. 

The external reactivity is inserted at a ramp rate of 0.1 0/s, which is ten times larger than the ramp rate required to change the reactor power by 1%/min. The peak coolant temperature at the hottest nominal fuel element reaches 970°C up to 1 insertion, while the hottest fuel temperature is below the melting point. The inserted reactivity is almost cancelled by the Doppler reactivity. The calculated reactor power rises to 1.31 of the rated value. 

The reactivity of surface nitrates with NO is demonstrated by a transient experiment where we first adsorbed NO2 (1,000 ppm, concentration step change, in a stream of water (3 % v/v) and Helium) on the Cu-zeolite at 2(X) °C, then we added 1,000 ppm of NO to the water/Helium feed stream, and eventually performed a T-ramp where the catalyst temperature was linearly increased from 200 to 550 °C at 20 °C/min. 

An overview of a measurement protocol is depicted in Fig. 5.17a, showing the temperature, as well as the gas flows He, O2 and CO) as a function of time the corresponding text file can be found in the appendix. Over the course of the measurement area measurements (Fig. 5.17b, flat temperature signals) take turns with reactivity measurements (Fig. 5.17c, temperature ramps). This allows for monitoring possible changes in surface area along with reactivity measurements at different temperatures. The maximum temperature of513Khas been measured only for some samples and is also not shown in the overview the different area measurements are numbered consecutively. 

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