Determination of reactivity effects and their compensation in a small-sized liquid-metal fast reactor of low power

The paper considers a possibility of using the rotating beryllium control drums with an absorbing sector made of boron carbide as the regulating bodies of the protection control system in the low-power nuclear plants. It assesses contribution of alteration in the efficient multiplication factor due to thermal expansion of the structural elements (reactivity thermomechanical effect) for a small-sized low-power fast nuclear plant with the liquid metal coolant. The paper shows that the reactivity thermomechanical effect greatly contributes to the reactivity integral power effect defined in this work as the sum of density, temperature (for fuel) and thermomechanical effects of the reactivity. It analyzes the structure thermal expansion on integral efficiency of the control drums in the considered nuclear power plant. The paper assesses the influence of a possible control drums distancing from the core center while maintaining the absorbing sector position relative to the drum axis associated with independent thermal expansion of the control drums supports and of the core.

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