Reactor History

A major problem in this design is the generation of convection cells due to the buoyancy of the gas heated by the pedestal. This results in very non-uniform depositions. To counter this, the gas flow can be greatly increased to dampen the buoyancy effets (again warm gas rises). One solution is to invert the reactor alternatively, the pedestal can be rotated at several hundred rpm to counter thermal convection and thereby form a rotating disk reactor (RDR) as described below. 

OMPVE has evolved into the most important compound semiconductor production technology, surpassing MBE and any of the other techniques reviewed in Sect. 4.2.1 OMVPE s ability to economically address the versatile needs of complex advanced devices and product demand has resulted in a drive to further scale production tools in order to match increased throughput needs. 

HIGH SPEED ROTRTING SUSCEPTOR, UERTICRL MOCUD GROUJTH RERCTOR 

The wafer temperature distribution in functioning reactors has been experimentally investigated much less frequently than the flow dynamics or static thermal distributions due to problems involved with experimental temperature measurements of moving components and in varying emissivities. Recently, a scanning pyrometer has been 

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Rosenthal, M.W., Kasten, P.R., and Briggs, R.B., Molten-salt reactors—history, status and potential, Nucl. Appl. Tech., 1970, 8, 107 117. 

The described experimental rig for the anionic polymerisation of dienes has been shown to behave as an ideal CSTR. The mathematical model developed allows the prediction of the MWD at future points in the reactor history, once suitable kinetic parameters have been estimated. 

Spent fuels vary in microstructure, and phase and elemental distribution depending on the in-core reactor operating conditions and reactor history. The chemical stability of spent U oxide fuel is described by local pH and Eh conditions, redox being the most important parameter. However, the redox system will also evolve with time as various radionuclides decay and the proportion of oxidants and reductants generated at the fuel/water interface changes with the altering a-, (J-, y-radiation field and with the generation of other corrosion products that can act as... 

E. J. Leshan, RBU—Calculation of reactor history including the details of isotopic concentration. Part I—The method, ASAE-34, December, 1958 (also ASAE-39, to be issued). 

Other reactors do not have this feature. The Russian developed reactor type RBMK-1000, for instance, is based on neutron moderation in graphite and heat transport by water. Under certain conditions of low power it has a positive temperature reactivity coefficient and this was - among many other reasons - also responsible for the largest accident in reactor history (Chernobyl, 1986). 

Russia has been experimenting with fast reactors since the 1950 s. Table 12.1 is a snapshot of all USSR and Russian civilian fast reactor history. 

Personnel Hazards The following case history illustrates how vacuum can be harmful and dangerous to personnel. A plant superintendent was checkiug an open nozzle on a glass-lined reactor on which there was a vacuum pump pulling vacuum, when suddenly his arm was sucked into the nozzle, up to his shoulder. He could not remove his arm until help arrived to release the vacuum on the vessel. He was injured painfully, though not seriously. The injury could have been veiy serious if help had not been nearby. Personnel hazards can also result from vacuum conveyor systems for solids handling. 

The tire analysis was assisted by SNL using methods described in NUREG/CR-4840 and the extensive operating history and fire experience. For 94 reactor-years from 1958 and 1987, 20 significant fire events were recorded. Hence, frequencies for the reactor building and the diesel generator buildings of 0.12 and 0.03 /y, respectively. A control room fire has never occurred at a SRS reactor. 

The reactor vessel can be rerated based on actual metal thickness and corrosion history at the new operating temperature. 

CFPs, especially the macroreticular ones, suffer of an appreciable fragility and require considerable attention to mechanical stress when employed in slurry reactors. A case history has been evaluated in this connection [29] and a considerable stability to friction in the case of some Pd / gel-type resin catalysts has been recorded (Figure 8). In any case, it has been observed that a shaken reactor is by far preferable to any rotationally stirred ones [29]. 

Influence of the mode of operation on process performance. The mode of operation of stirred-tank reactors can also significantly affect reactor performance. The history of concentrations will be changed by the time policy of reactant(s) addition to the reaction mixture. In view of our very limited possibility of controlling of temperature in stirred-tank reactors, the temperature-time dependencies for different policies of dosing will also be different. For example, the result of nitration depends upon the method of addition of nitric acid to aromatics, and the choice which phase is dispersed and which is continuous. Consequently, if the reaction is concentration- or temperature-sensitive the result will be dependent on the mode of operation (see Example 5.3.1.5). 

Summarizing, the output of the reactor is an integral over time and over the entire reaction space with all interconnections between different zones of the reactor. Mixing and heat- and mass-transfer conditions are usually different in various zones and the pattern of these differences as well as proportions between size of zones vary with scale. Obviously, the histories of concentrations and temperatures in the zones differ. Whether the integral outputs of laboratory and full-scale reactors differ from each other, depends on the sensitivity of the process to mixing and heat- and mass-transfer conditions. If the sensitivity is low only minor... 

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