Method for identifying 17-place casings with spent fuel assemblies of AMB reactors at the Beloyarskaya nuclear power plant

Abstract

A method is proposed for identifying a cylindrical case with a jacket containing 17 spent fuel assemblies from the AMB reactors at the Beloyarskaya nuclear power plant on the basis of measurements of the radiation characteristics in lateral surface of the jacket opposite the fuel assemblies in the outer and inner rows. Computational validation using the PRIZMA and MCNP computer codes is given for the method. It is shown that the collection of signals from detectors is specific to each jacket, and this makes it possible to use it as an identifying indicator.The No. 1 power-generating unit at the Beloyarskaya nuclear power plant was stopped in 1981 and the No. 2 unit in 1989. The spent fuel of the AMB reactor was partially removed and shipped to the Industrial Association Mayak, partially loaded into 17-and 35-place jackets and placed into storage in a holding pond near the reactors. The problem of further longterm storage of the fuel has become acute because it is impossible to repair the facing of the ponds without unloading them and because the jackets undergo substantial corrosion as a result of being submerged in water for a long time. In connection with the transition to dry storage, the spent fuel must be removed from the storage sites near the plant and transferred either to the Industrial Association Mayak for reprocessing or to the Integrated Mining and Chemical Plant in Krasnoyarsk for longterm storage and subsequent reprocessing.Each 17-place jacket consists of a set of 17 steel tubes (Fig. 1). A single spent fuel assembly, 13.5 m long, is placed inside each tube. The construction and composition of each tube are shown in Fig. 2 [1]. The relative arrangement of the tubes is fixed with the aid of several steel tubular separation boards.To place the jacket with the fuel into long-term storage, it is removed from the pond and placed into a steel cylindrical case whose wall is 1 cm thick. The cylindrical case must be equipped with an individual indicator so that it can be identified even after being in storage for several decades. The possible solutions where paint, engraving, securing plates with test or bar code, and so forth are used are simple, inexpensive, and certainly should be used, since they make it possible to identify a cylindrical case for at least the first 20-30 yr of storage. After this time, because of corrosion, these methods of identification can become less reliable and ultimately useless.In the present article, we propose a method for identifying the jackets on the basis of measurements of n and γ radiation from the spent fuel assemblies inside a jacket and we provide computational validation. For identification, n and γ radi-