DEVICE FOR COMPENSATION OF NUCLEAR REACTOR REACTIVITY AND METHOD OF FLATTENING OF VOLUMETRIC ENERGY DISTRIBUTION AND OF FUEL BURN-UP Russian patent published in 1994 - IPC

FIELD: nuclear energy. SUBSTANCE: device for compensation of nuclear reactor reactivity is composed of two independently moved compensation elements: central compensating lattice which vertical axis matches axis of active section and outer compensating lattice. Both lattices include separate neutron-absorbing elements located between fuel elements. Outer compensating lattice is placed coaxially to central compensating lattice, it is made up of two steps with different compensating capability: lower step is low absorbing and upper step is high-absorbing. Outer diameter of upper step is equal to that of active section, lower step has diameter smaller than that of active section. Method of flattening of fuel-up over space of active section consists in the following: for hot and poisoned reactor at start of operating period with fresh fuel lower limit of outer compensating lattice coincides with lower limit of active section and for condition of sub-critical, cold and clean reactor with fresh fuel lower limit of outer compensating lattice is located beneath limit of active section and lower limit of upper step in this case is at such depth in active section that thermal effects of moderator and fuel are compensated as well as steady-state poisoning and initial sub-criticality is created. Central compensating lattice at start of operating period and in process of fuel burn-up is at lower limit of active section. Height of central compensating lattice is less than that of active section which keeps part of active section above it without absorbers limited by its upper step when outer lattice is lowered. EFFECT: improved efficiency and authenticity of compensation. 7 cl, 11 dwg