Immobilization Of Irradiated Heu Graphite Fuel In Kazakhstan

Year
2020
Author(s)
Igor Bolshinsky - Idaho National Laboratory
Ken Bateman - Idaho National Laboratory
Erlan Baterbekov - National Nuclear Center of Kazakhstan
Erbol Koyanbayev - National Nuclear Center of Kazakhstan
Yulia Baklanova - National Nuclear Center of Kazakhstan
Abstract

The National Nuclear Center of Kazakhstan (NNC) poses an Impulse Graphite Reactor (IGR) with homogeneous uranium-graphite core. Graphite blocks of the reactor core are impregnated with water solution of uranyl nitrite with concentration of ~3.1 gr of uranium per one kilogram of graphite. Enrichment of uranium by isotope U-235 is 90%. The reactor core consists of immovable and movable parts surrounded by graphite reflectors. The Physical start-up of the IGR reactor took place in June 1960, and energy start-up - in August 1961. The irradiated first HEU core from IGR reactor was discharged in 1967 and is currently stored in a dry storage at the reactor site. The total core weight is about 2,600 kg, total mass of uranium (including uranium 235U and 238U) is about 7.46 kg, radionuclide composition is as following: 137Cs, 90Sr, 151Sm, 99Tc, 155Eu, 93Zr, 135 Cs. Since this material was irradiated in a reactor its down-blending at the UMP is not allowed under the current UMP license. Recently the government of Kazakhstan made a decision to down-blend and immobilize irradiated HEU graphite fuel from IGR reactor at the territory of the Semipalatinsk test site. In 2018-2019 NNC conducted a feasibility study for down-blending and final disposition of the irradiated IGR graphite fuel. Based on preliminary results of the feasibility study the dry mixing technology using natural uranium has been proposed as a prospective method for down-blending of the irradiated HEU graphite fuel with the following cementation of the down-blended material.