Resins and sludge treatment

Status: in progress
Duration: 2015 - 2024

The project involved the preparation, transport, treatment and conditioning at the Bohunice (Slovakia) plant of approximately 5.900 220-litre drums containing resins and radioactive sludge produced during the plant's operation.

The waste was treated by incineration and the ashes produced were conditioned by being placed in capsules and embedded in a cement matrix inside 440-litre stainless steel containers.

Treatment and conditioning activities were completed in the first half of 2023: a total of 794 tonnes of spent ion-exchange resins and 54 tonnes of radioactive sludge were treated, with the production of 100 final manufactured items suitable for transfer to the National Repository

Once the operating licence for the ERSBA2 facility has been obtained (see § Upgrading of temporary storage facilities, the conditioned manufactured items will return to Caorso and will be stored, as low-level waste, in the above-mentioned facility, pending their subsequent transfer to the National Repository.
Caorso - Preparatory activities for the transport of drums

The project performed was particularly complex due to difficulties in identifying suitable pre-treatment methods for resins and sludge, managing treatment operations abroad, and recovering the drums containing the medium-level resins from the ERSMA facility (Upgrading of temporary storage facilities).

Starting from 2015, a number of preliminary activities were carried out. In particular, a characterisation campaign was carried out in 2015-2016 on the resins stored in the ERSBA 1 and 2 (Low-Level Waste Buildings 1 and 2) storage facilities. Upgrading work was also carried out on the ERSMA storage facility so as to allow handling, packaging and characterising of drums extracted from the shielded cells to be sent abroad. These operations include the dismantling of the trans-elevator, used in the past to store drums in shielded cells and employed by Sogin to recover the first batches of drums. This equipment was replaced in 2018 with the Drum Recovery Machine (MRF), which allowed, by remote control, the extraction of 1,500 drums, which were quite difficult to recover due to their positioning.

In November 2017, the first drums of non-radioactive resins were sent to the Slovak plant for "cold testing" of the incinerator's pre-treatment system and feeding line, from which it emerged that, in order to comply with the required process qualification parameters for combustion residues, it was necessary to supplement the incinerator with a resin pre-treatment system and to change the feeding line to the combustion chamber.

Between 2018 and 2019, a plant modification was implemented, the "cold tests" were conducted and the transfers of the drums of radioactive resins and sludge began, with an initial series of 336 drums of resins and sludge for the "hot tests"; with these tests, the effectiveness of all process phases was verified, including the conditioning of the waste into final manufactured items with characteristics suitable for transfer to the National Repository; following the positive outcome of the "hot tests", approval was obtained for the Operating Plan for the treatment and conditioning of resins and sludge, and authorisation was obtained for the shipment and treatment of the remaining waste envisaged by the project.

Sogin thus started, on 29 January 2020, the second and final phase of the transfer programme (with 33 shipments) of the remaining drums, approximately 5,600.

On 21 April 2022, the programme to transfer all drums to the Slovakian plant in Bohunice, where the production of the final manufactured items is still ongoing, was concluded with a final shipment.

The transfer of all this waste, accounting for a volume equal to about 70% of the waste stored at the site, made it possible to empty the 3 temporary storage facilities in order to bring them up to current safety standards, without having to build additional storage facilities.

The planned duration for the transfer and treatment of the 5,600 radioactive drums and the return of the conditioned manufactured items is approximately 5 years in total (2020-2024).