Hulls and sludge retrieval project on HAO/South facility in La Hague - 13083

Full text of publication follows: The pond 907 clean up and dismantling within the HAO/South facility is a part of the La Hague UP2-400 plant dismantling project. During operations, this pond was used to receive hulls and end pieces from the shearing and dissolution cell. Those elements were placed in shuttle containers and transferred to the bulk storage silo using a hydraulic transfer system. At the end of operations 6 m3 of hulls and end pieces, 20 m³ of low and intermediate level waste are present mixed with 10 m³ of sludge. The sludge is mainly made of crushed ions exchange resins, zirconium fines, and other materials. This retrieval project was on the critical path of the waste retrieval programs of HAO/S facility. First off all, the clean-up project was based on using the existing equipment to transfer the legacy waste (hulls and sludge) to the storage silo. The first phase of the project has been to clear up, to dismantle and to remove the main equipments still present on the bottom of the pond, except the hydraulic transfer system which was still needed. The retrieval phase of the project started in February 2009 with the introduction of the articulated remote controlled mechanical arm in the pond. The first step was to clear up and pick-up the secondary waste (tools, poles, cables, ropes, etc). As operations were impaired by the lack of visibility due to the very light sludge, studies and implementation of an additional pumping and filtration system have been carried out during one year in order to be able to retrieve the sludge and then obtain better pond visibility. Between March and August 2010 a sluicing nozzle equipped with sludge suction ports was developed. The first concept of the clam shell hulls retrieval grapple had to be equipped with sludge suction ports and then avoid the spread of sludge. Finally, a new concept which combines hulls and sludge recovery has been deployed to cope with the collection of small amounts of wide spread hulls. In May 2011, the last canister of hulls was transferred to the silo. The project finally transferred 30 canisters of hulls for a total volume of 6 m³ and 15 m³ of sludge to the main storage silo. A specificity of this retrieval project is the need of continuous development for new tools during operations in order to answer of new technical stakes and/or improve performance to match the final time line with the other clean-up programs. In order of appearance: (1) an in-situ filtration system including an unclogging device was developed to be linked on the grapple in order to catch the powdery sludge during grappling operations, (2) gathering system to ensure a good filling of the grapple and accessibility to the hulls, (3) a combined retrieval device on a specific designed raft in the pond to draw up both hulls and sludge, with a direct separation of the two wastes in the canister.