NEUTRON-ACTIVATION METHOD OF MONITORING BURNING OF SPENT FUEL ASSEMBLIES OF THERMAL NEUTRON REACTORS AND APPARATUS THEREFOR Russian patent published in 2014 - IPC G21F9/00 

FIELD: physics, atomic power.

SUBSTANCE: present invention relates to means of measuring burn-up of spent fuel assemblies of thermal neutron reactors. A diagnostic container is placed at the bottom of a cooling pond under water. The wall of the housing has an annular cavity with a liquid tracer substance surrounded by polypropylene layers and steel layers, as well as a cadmium layer. The housing has a centre cavity in which spent fuel assemblies are placed. The container is closed with a cover. Water is removed from the centre cavity with the spent fuel assemblies. The tracer substance is activated, drained into a laboratory vessel and stirred. A sample is then collected. The average specific activity of the tracer substance is measured and the neutron radiation intensity of the spent fuel assemblies and the associated burn-up of the spent fuel assemblies is determined. The annular cavity with the liquid tracer substance can consist of multiple rings insulated from each other. Burn-up is then determined for each ring and a burn-up profile for the spent fuel assemblies is then constructed.

EFFECT: enabling all-round encircling of the core region of the spent fuel assemblies with the tracer substance, excluding the effect of water on measurement accuracy, eliminating background effect when measuring specific activity of the tracer substance and high accuracy of determining burn-up of spent fuel assemblies of thermal neutron reactors without retrieving spent fuel assemblies from the cooling pond.

9 cl, 3 dwg