الفهرس 
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Abstract
Reactor control is one of the important problems in reactor design. In this work, the control of the reactors is investigated using several methods, such as control by adjuster rods, moderator cavities or changing reflector thickness.
~heoretical investigations show that: these methods of control have distinctive features but comparable effects on reactivity worth. It is -found that any of these methods of
reactivity control can be used with approximately equivalent
efficiences depending on the type of the technical facility in which they are used.
In this work, reactivity control by various combinations of the three methods is also investigated. The different
permutations of these combinations are studied to determine
the best for maximum worth of reactivity and minimum flux disturbance
A two dimensional computer code, Combination Control Method (ccM), has been developed to analytically calculate ~he effect of each control method on the reactivity and the flux distribution. In addition a three dimensional com-
puter code, Partially Inserted Control Blad (PICB), has been developed for digitally simulating the neutron flux dis-
tribution in the three cartesian coordinates. This code
utilizes the Finite Difference (F.D) technique with different
mesh size in the various regions of the reactor. Although
it has only been tested with two neutron energy groups (thermal and fast) the code is capable of predicting the flux for multiple energy groups. This, PICB, code has been verified by comparing its Benchmark problem calculations with those obtained from other codes, such as CITATION, and TRIBUNE.
Investigating the rusults of utilizing these methods of control one can draw the following conclusions:
Moderator cavities formation has a great effect on reactivity of the reactor, and they can be efficiently used for regulating both the bulk reactor power and the spacial power distribution.
The suggested methods of combination in this work is superior to absorber rod method in the sense that they provide more effec’tive worth with good neutron economy.
The degree of attenuation of the fast group in the rod is important in determining the effect of a control rod on reactivity.
The application of the coarse mesh calculations leads to aslightly higher value for keff compared by the fine mesh due to the ommission of the leakage term from the thermal group diffusion equation.