Reactor period stable

The only gross mode that is normally observed is the rotational n = 2 instability. The observed stable period before the mode onset is consistent with the FRC increasing in angular velocity until it crosses a threshold for instability predicted by a Vlasov fluid code. The angular acceleration could be due to an external torque perhaps applied by plasma outside the separatrix through viscosity.Another cause of acceleration could be net angular momentum carried by particles diffusing across the separatrix. This particle loss model predicts that the onset of the instability should occur when about half the particles are lost. This prediction is consistent with the experiment. Since the external torque or other sources of rotation are also possible, better correlation between experiment and theory is needed to properly understand this issue. However, if the FRC stable period Xg (time before mode onset) continues to scale with the time required to lose half the particles, then particle transport, not the rotational mode, will limit the reactor potential of the FRC. 

In-Hour - (ih or IK) - A measure of reactivity. If zero reactivity is defined as that reactivity which causes the reactor to operate with constant power (infinite period) a reactivity of one inhour will result in a stable period of one hour. For a reactor which is very nearly critical (long period), the reactivity in inhours is the reciprocal of the period in hours. For wider departures from critical (shorter periods) the Inverse period does not hold because of the delayed neutron groups. Since the delayed neutron makeup of a production reactor is exposure dependent, the "inhour" is a somewhat elastic unit. 

Why does the neutron flux increase rapidly and then settle into a stable period when positive reactivity is added to make the reactor supercritical ... 

The relationship between the reactivity and the stable period for a fueled reactor is shown in Fig. 3.11 for a range of neutron lifetimes for convenience the reactivity is expressed as a function of the total delayed neutron fraction, j = X i . This is equivalent to the introduction of a new unit, called the dollar, for measuring reactivity. One dollar is an amount of reactivity equal to the delayed neutron fraction the reactivity in dollars is then obtained by dividing p, as defined by equation (3.60), by the delayed neutron fraction for the particular fuel in the reactor. The specification of reactivity values in terms of the delayed neutron fraction is convenient in that a given reactivity in dollars will produce essentially the same rate of flux rise for reactors containing or Pu fuel. 

The fine control rod of the AGN-201 reactor will be calibrated in this experiment. The technique used to measure reactivity changes at different rod positions in the core will be measurements of positive asymptotic periods. The reactivity of the assembly corresponding to a measured stable period will be determined from the basic inhour equation, which is derived below. 

The quantity odq is the reciprocal of the stable asymptotic period T. If a measurement of this stable period is made when a reactor is supercritical, the reactivity corresponding to the period can be determined from Eq. (10). Substituting CJO = i/t into the basic inhour equation gives... 

Knowledge of the thermal-neutron lifetime and the delayed-neutron parameters of the reactor in question will enable a plot of reactivity versus stable period to be made. This plot for the AGN-201 reactor is made in... 

The reactivity changes that occur in the reactor when an absorber is placed at its center will be measured in terms of asymptotic positive periods. The stable period of a supercritical reactor is related to the reactivity through the basic inhour equation. This expression involves the prompt neutron lifetime and the delayed neutron parameters (see Appendix B). 

The exact stable period of the reactor is determined by the external BF3 counting system. The BF3 counter is placed at a desired location in access port number four. The counts per fraction of a minute are then taken periodically, A plot of the counting rate versus time is made on semilog paper. The plotting should commence when the first count is taken, this will enable the participant to determine whether or not the reactor is rising on a stable period. The stable reactor period will be determined from the semilog plot and recorded along with the control rod position and temperature on the data sheet. 

A Lucite blank is then placed at the center of the glory hole in place of the boron sample A. Caution is again stressed in this operation, since positive reactivity is being inserted. The coarse control rod is then raised to its previously recorded position. Once the reactor has reached its stable period, a period measurement should be made with the external BF3 counter as described above. The reactor period should, of course, be shorter since the boron absorber has been removed from the core. Record control rod settings, period and temperatures. 

As well as being active, the immobilised enzyme also needs to be stable (active for a long period) and the support must promote this. The support must also have appropriate mechanical characteristics it should not disintegrate if used in a stirred tank reactor it should produce even flow (without channelling) in a packed bed reactor. Hie cost of the support is also important. 

Example 14.1 shows how an isothermal CSTR with first-order reaction responds to an abrupt change in inlet concentration. The outlet concentration moves from an initial steady state to a final steady state in a gradual fashion. If the inlet concentration is returned to its original value, the outlet concentration returns to its original value. If the time period for an input disturbance is small, the outlet response is small. The magnitude of the outlet disturbance will never be larger than the magnitude of the inlet disturbance. The system is stable. Indeed, it is open-loop stable, which means that steady-state operation can be achieved without resort to a feedback control system. This is the usual but not inevitable case for isothermal reactors. 

The same samples, after a pretreatment in flowing oxygen (10%) at 625 K, were used as catalysts for the oxidative dehydrogenation of ethanol and methanol in the same reactor. The reaction mixture consisted of O2 (3 or 5%), methanol vapor (3%) or ethanol vapor (5%) and He (balance), all delivered by Tylan mass flow controllers or vaporizer flow controllers. Products were analyzed by gas chromatography. The catalysts exhibited no induction period and their activities were stable over many days and over repeated temperature cycles. 

An important problem in emulsified organic-aqueous systems is that of scale-up, which is concerned with the realization of stable emulsions and the separation of phases after the reaction. The use of biphasic membrane systems that contain the enzyme and keep the two phases separated is likely to solve this problem. In the case of 5-naproxen an ee of 92% has been demonstrated without any decay in activity over a period of two weeks of continuous operation. A number of examples of biocatalytic membrane reactors have been provided by Giorno and Drioli (2000) and include the conversion of fumaric acid to L-aspartic acid, L-aspartic acid to L-alanine, and cortexolone to hydrocortisone and prednisolone. 

The determination of rate change of the logarithm of the neutron level, as in the source range, is accomplished by the differentiator. The differentiator measures reactor period or startup rate. Startup rate in the intermediate range is more stable because the neutron level signal is subject to less sudden large variations. For this reason, intermediate-range startup rate is often used as an input to the reactor protection system. 

The composition of the dispersion agents, which are produced in dedicated reactors, is the same for all recipes. The batch sizes may be one or two polymerization batch units for Dl and one, two, three or four polymerization batch units for D2. The processing times are ten hours for Dl and two hours for D2, and they do not depend on the batch sizes. The dispersion agents in their final states are unstable in the reactors and stable for limited periods of time in the storage... 

In this section we develop a scheme implemented in a continuous polymerization reactor to regulate polydispersity by tracking periodic conversion profiles and maintaining stable temperature conditions. Oscillatory conversion is tracked by manipulating the initiator feedrate while the heat exchange rate is used to regulate reactor temperature. 

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