METHOD OF NUCLEAR FUEL FRAGMENTS DETECTING AND PARAMETERS DETERMINING IN THE STOPPED URANIUM GRAPHITE REACTOR STACK Russian patent published in 2018 - IPC G21C17/00 

FIELD: nucleonics; measurement equipment.

SUBSTANCE: invention relates to a method of the nuclear fuel fragments parameters detecting and determining in the stopped uranium-graphite reactor stack. Wells are searched by measuring the thermal neutron fluxes in the stopped uranium-graphite reactor graphite stack cells in a certain order at a distance of no more than 1.4 m between the cells and a pitch of 1 m by the graphite stack height. Investigation of the neutron field in the selected well is performed by scanning the epithermal neutron flux along the graphite stack height with a pitch of not more than 0.1 m directly in the cell with fuel fragments and adjacent cells. Scanned the cells with fuel fragments by a gamma-ray detector with a pitch by the graphite stack height of not more than 0.02 m. Then, determining the nuclear fuel fragments location by the graphite stack height by the gamma radiation intensity maxima analyzing. Obtained in a neighboring cell epithermal neutrons integral distribution is decomposed by the least squares method into its individual components using the Gaussian distribution. Fuel fragments fissures calibration measurements size, shape and location are determined from each distribution into the separate one obtained parameters values. After taking of the calibration factor into account, calculating the neutrons sources in the fuel fragments concentration and their mass. Calibration measurements are carried out directly in the uranium-graphite reactor stack.

EFFECT: technical result is the possibility of nuclear safety assessing and, if necessary, their local drilling out of graphite stack without dismantling the entire graphite column during the uranium-graphite reactor decommissioning.

1 cl, 7 dwg