Decommissioning & Waste Management

Technical Consulting and Custom Equipment Design: When processing radioactive waste, it is important to minimize the number of filters required and simplify filter changeouts to minimize downtime and worker exposure. Recently, during waste processing activities at a DOE site, rapid filter clogging and high frequency of filter changeouts were observed when using a traditional filtration system, and DEI was contracted to assist in restoring system performance. DEI technical support included:

• Replication of the rapid clogging issue in experimental testing using a simulant that closely represented the characteristics of the actual waste being processed
• Confirmation that DEI’s patented ultrasonic regeneration technology could be integrated to restore like-new filter performance periodically, as needed
• Development and fabrication of a custom filter module integrating DEI’s AMFM^TM regenerable filter technology to improve system performance, while minimizing redesign efforts

The modified system was helpful in maintaining favorable performance and providing a convenient and effective means for periodic regeneration of the filters, minimizing downtime and worker exposure by eliminating traditional filter changeouts.

Multi-physics Modeling and Experimental Validation: Deep geological repositories are designed to safely contain and isolate nuclear waste from the environment for significant durations (thousands to millions of years). Despite the robust engineering controls and stable geologic formations used for safe storage, the extended design isolation period requires rigorous engineering analysis and testing to justify. DEI performed numerous engineering analysis and testing activities in support of the Yucca Mountain nuclear waste repository in the US, including:

• Analysis of thermal profiles in the mountain following insertion of waste canisters
• Thermodynamic modeling to predict the chemistry of any groundwater concentrated in the vicinity of the canisters
• Probabilistic analysis of waste canister material and seal integrity over the design life of the repository
• Experimental testing to validate engineering analysis and modeling results

DEI also provides consulting services related to material integrity and in-service inspection of spent nuclear fuel storage canisters at independent spent fuel storage installation (ISFSI) facilities, as well as spent nuclear fuel transportation and containment systems.

EPRI Research Program: Decommissioning and dismantling of nuclear facilities involves a number of manual tasks with extended durations. Remote delivery and automation of these tasks can reduce the cost, risk, schedule and radiological exposure associated with these activities. DEI supported EPRI research program to automate reactor vessel internals segmentation and waste packaging activities during decommissioning. DEI technical support included:

• Evaluation of time/motion study of reactor vessel internals segmentation and waste packaging to identify time limiting steps with regard to overall schedule
• Development of automated processes to simplify reactor vessel segmentation and waste packaging activities by reducing tool/blade changes, performing segmentation and waste packaging activities in parallel, and minimizing manual intervention
• Design of robotic equipment with programmable controls for implementing automated reactor vessel segmentation and waste packaging activities

DEI has completed similar process automation and tooling design projects for fluidization and removal of hard heels and sediment from waste tanks and vessels, and remote delivery of concrete decontamination tooling.

Engineering Consulting for Material, Mechanical and Fluidic Issues: Nuclear waste processing facilities typically include a number of unique processes and equipment. Careful engineering and technical studies are required to properly design these facilities and ensure reliable operation. During recent startup of a radioactive waste treatment facility at a DOE site, DEI assisted the O&M contractor in evaluating and resolving a number of unique technical issues. DEI assistance and insights included:

• Forensic analysis of corrosion and mechanical degradation of processing equipment observed during pre-operational trials, including corrosion of Inconel 625 and FeCrAl-alloy components and subsequent degradation in waste processing efficiency
• Selection and evaluation of an alternate silicon carbide-based ceramic material to replace the affect components
• Computational fluid dynamics (CFD) using optimized mesh sizes to improve understanding of waste processing equipment and operations, while maintaining reasonable modeling run times and computing power

DEI analysis and supporting experimental investigations were beneficial for resolving technical issues identified during initial trials and startup of the waste treatment facility.