Patent Number: 052672808
Section: summary

DESCRIPTION The present invention relates to a process for conditioning or recycling ion cartridges permitting the treatment of contaminated waters of storage pools or ponds for irradiated fuels from nuclear reactors. This invention more particularly applies to the nuclear field. Thus, nuclear reactor fuels are stored in pools, whose water must be kept chemically pure. This purity maintenance function is fulfilled by ion exchangers, which are also referred to as ion Nympheas. These Nympheas have two superimposed cylindrical cartridges, each cartridge having an ion exchange resin-filled metal structure. When these Nymphea cartridges (which will be called cartridges for short in the remainder of the description) have become used or spent, they are provisionally stored in a storage pool whilst awaiting their definitive conditioning. One possible conditioning of said cartridges performed in a specific room consists of injecting thermosetting resin in liquid form into the cartridge, the calender of the latter forming the final envelope for the waste. For economic reasons and the very high operating and investment costs, said process is difficult to put into effect. The present invention makes it possible to obviate this cost problem by proposing two processes respectively the conditioning and recycling processes in which the resins are extracted from the cartridge in order to permit the conditioning or recycling of the empty cartridge separately from the conditioning of the resins. Thus, once the resins have been extracted, the internal metal structure of the cartridge is rinsed and then, in the case of conditioning, the decontaminated empty cartridge is introduced into a metal container, which will be concreted prior to storage or, in the case of recycling, the decontaminated empty cartridge is filled with new ion exchange resins. More specifically, the present invention relates to a process for the treatment of used ion cartridges constituted by a hollow metal structure, sealed at its lower end by at least one filter screen and filled with ion exchange resins, said cartridges being stored in a cartridge storage pool. This process, in which use is made of a plurality of pools and a specific transfer casket or flask equipped with a cover and making it possible to transport a cartridge from a discharge pool to a treatment cell, is characterized in that it consists of performing the following operations: a) the transfer of the cartridge from the storage pool to a discharge pool, b) placing the cartridge to be conditioned in the transfer casket, c) emersion and decontamination of the transfer casket in a decontamination cell, d) transfer from the casket to the treatment cell and e) extraction by suction means of the resin contained in the cartridge. Advantageously, the operation a) consists of loading the cartridge to be conditioned into a transfer basket in an immersed medium for transferring it from the storage pool to the discharge pool. The latter is designed to receive several casket types containing fuel elements and permit their discharge. Operation d) of transferring the casket to the treatment cell comprises an engagement or berthing operation. More specifically, the latter consists of tightly positioning the casket respectively beneath the treatment cell, removing the cover from the casket and transferring said cover into said cell in order to ensure an opening between the casket and the cell. According to an embodiment of the invention, the suction means used for the extraction of the resins have a suction pipe introduced on the one hand into the cartridge and connected on the other to a pneumatic pump, which is itself connected to a spent resin storage unit. For the conditioning of the cartridges, the process also consists of carrying out, following the extraction of the resins, the following operations: f) removal of the cartridge from the casket and decontamination of the internal structure in the treatment cell, g) deposition of the contaminated cartridge in a conditioning case ensuring the confinement of said cartridge and h) deposition of the case in a storage container. The operation of depositing the cartridge in the case comprises an operation of engaging or berthing the case beneath the treatment cell and which consists of tightly positioning the case respectively beneath the treatment cell (the transfer casket having been previously disengaged), removing the cover from the case and transferring said cover into said cell in order to ensure an opening between the case and the cell. Advantageously, the process has a final operation i) consisting of filling the container with concrete for the storage thereof. According to an embodiment of the invention, following operation f), the process comprises the possibility of carrying out an operation of cutting up the cartridge in order to reduce its volume during the conditioning of said structure in the storage container. For the recycling of cartridges, the process also consists of carrying out, following the extraction of the resins, the following operations: j) removing the empty cartridge from the casket and transferring said cartridge into the treatment cell, k) disassembling the filter screen and washing the latter, l) decontamination and cleaning of the internal metal structure of the cartridge without its screen, m) reassembling the filter screen on the cartridge and putting into place again the said cartridge in the transfer casket and n) filling the metal structure of the cartridge with new ion exchange resins. More specifically, the washing of the filter screen consists of transferring the screen into an ultrasonic tank, where it is cleaned. According to the invention, the process involves a final operation o) of transferring the casket into the discharge pool permitting the transfer of the recycled cartridge to a storage pool.