PNNL

Abstract

This document provides an overview of the remote retrieval equipment and strategy for the retrieval of waste from Silos 1 and 2 at the Department of Energy's Fernald site in southwestern Ohio. The scope of this paper is limited to general descriptions of remote equipment specifically related in-silo retrieval. The retrieval strategy describes how the contractor team is planning to utilize the various remote subsystems to efficiently remove the waste from the silos from a philosophical standpoint as opposed to a procedural and operational standpoint. The retrieval strategy and approach is based upon the successful tank retrieval operations conducted at DOE's Oak Ridge and Hanford Sites. Lessons learned from these previous operations have been utilized in planning an approach for the Fernald Silo Retrieval Project. The equipment overview includes discussion of the retrieval system configurations together with descriptions of the robotic arm and retrieval end effectors, the conditioning and transfer pumping system, the sluicer and sluicing pump, as well as the debris retrieval system. A unique challenge being addressed as part of this project is the waste contents. Silos 1 and 2 contain two distinct layers of material that need to be retrieved. The first layer is a Bentonite (trade name BentogroutTM) cap that was placed in the silos to prevent radon migration into the dome space and out of the silos. The Bentonite layer varies, but in general it is approximately six inches deep in the center of the silo and thirty-six inches near the silo walls. The material may have dried out on the surface, and may still be wetted near the bottom of the bentonite layer. The K-65 ore tailings, which were slurried into the silos, are the remainder of the waste that is over 20' in depth. This paper provides an overview of the retrieval strategies, technologies, and techniques that will be used to safely and efficiently retrieve the waste from the Fernald Silos.