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LANL Eyes Requirements for Highly Enriched Uranium (HEU)

With the integration of TA-55 and CMR nuclear facilities, the scope of NMT's programmatic activities has increased and significantly expanded beyond plutonium. This article introduces one aspect of the uranium program, for example, carried out at CMR.

A significant part of maintaining the nation's enduring nuclear stockpile is the management of nuclear materials, including HEU. Issues involved when stockpile decisions are made include material disposition methods that ensure waste minimization and cost-effective, efficient operations. DOE evaluated alternatives for performing its nuclear weapons mission in 1995. The protocol for this evaluation, the Stockpile Stewardship and Management Programmatic Environmental Impact Statement (SSM PEIS), addressed alternatives for the various segments of the nuclear weapons mission. SSM PEIS criteria impact weapon fabrication, stockpile surveillance, remanufacturing of components, dismantlement of retired units, and the disposition and storage of weapons materials. Their impacts are felt in ongoing work at all sites in the nuclear weapons complex (NWC)(see figure below).

Concern for the management of HEU is shared among several members of the DOE nuclear weapons complex.

In order to meet these requirements, we must have the capability to understand the characteristics of HEU, the capacity for reworking the material, and reliable chemical processing that ensures a "steady-state" flow of material through the various processes to meet stockpile needs. Just what this steady state is will also be affected by changing nuclear weapon programmatic requirements and the push to channel material disposition efforts toward the fabrication of mixed oxide fuel for nuclear reactors. A balance in safety, operating costs, physical configuration, and technology will need to be defined for current and future HEU chemical processing operations.

The Oak Ridge Y-12 Plant, managed by Lockheed Martin Energy Systems, Inc., continues to support every weapon in the stockpile along with other related activities including the Stockpile Life Extension Program and the disposition and storage of weapons materials. As the DOE Lead Laboratory for Uranium, Lawrence Livermore National Laboratory supports the Y-12 mission. This assignment offers a link between the National Laboratories and the "plant," along with connections to DOE Headquarters and the various DOE area offices. Los Alamos National Laboratory works directly with Livermore in support of the goal to offer technology enhancements to the uranium-handling chemical processes. However, Livermore's technical capabilities are focused more on metal forming and shaping; Los Alamos plays a stronger support role for uranium process chemistry, including integrated manufacturing, material inventory management and disposition, and assistance with other DOE site issues including those at Rocky Flats.

Under the DOE integrated manufacturing initiative, future weapons manufacturing processes will be conducted in a drastically altered environment. Baseline requirements arising from the SSM PEIS include minimum floor space usage, maximum utilization of available equipment, and a significant reduction in total production expenses while using regulation-compliant systems that function effectively in flexible, batch-operating modes. Several aspects of the SSM PEIS baseline requirements match expertise we have already demonstrated at Los Alamos with our extensive capability in glove box operations. This expertise includes the use of batch-operating modes in which process throughput is scaled to chemical operations that can be completed in one day rather than continuous operations that require larger equipment and longer operating times.

The challenge is the maintenance of a robust and competitive manufacturing environment where science is integrated and matched to production requirements, and technology developments are focused on producing products. Thus, the interaction between Los Alamos and the Oak Ridge Y-12 Plant is moving towards a shared approach in technology development and demonstration. Initially, we are looking at chemical process enhancements that offer low risk and moderate payoff in terms of alternative processing capabilities. In the longer term, we are addressing SSM PEIS goals with technology developments that trade off high risk and high payoff for more cost-effective, smaller, and more flexible chemical process operations.

One of the major goals of our uranium chemistry activities is to develop state-of-the-art capabilities for uranium chemical processing and recovery in support of metal making and fabrication for both HEU and depleted uranium (DU). ULISSES, the Uranium Line for Special Separation Science, was first conceived as an attempt to recapture the uranium process technology that existed at Los Alamos until 1984. Now, it is apparent that there are new techniques, processes, equipment, and chemistry available that would be beneficial for processing HEU and DU in a more environmentally friendly and reliable manner. Thus, the ULISSES concept is now being developed as a "test-bed" capability to develop and demonstrate new chemical process technologies. A variety of new chemistries and techniques have been investigated including those for dissolution, separation, conversion, and metal making. The ULISSES Program's high-priority goals are to reduce the current inventory of HEU residues at Los Alamos and to introduce processes that will curtail waste and residue generation in support of future manufacturing operations.

To help the DOE meet various goals outlined in the SSM PEIS, as well as those of START I & II stockpile limits, Los Alamos will need to implement plans to address the NWC's approximately 3-metric-ton HEU inventory. Such plans involve the disposition and storage of a large portion of this inventory at the Oak Ridge Y-12 Plant. Thus, material transfer and storage issues between Y-12 and Los Alamos will need to be resolved. Work has already been initiated to address these issues through negotiations for Memoranda of Understanding and Memoranda of Agreement) between Los Alamos and Y-12. Preliminary estimates indicate that approximately two-thirds of LANL's HEU inventory will be available for transfer to Y-12 from Los Alamos. The remaining material will be used to support Los Alamos missions in the SSM program.

Other DOE sites, specifically Rocky Flats and Savannah River, will have similar issues to address concerning HEU materials and residues. It will also be important for them to transfer material to the Y-12 site to support the variety of ongoing HEU programs that are an integral part of the NWC. For example, HEU inventories at Rocky Flats comprise approximately 6 metric tons, and Savannah River has approximately 13 metric tons. We need to make sure the NWC has the capabilities necessary to transfer and store its HEU inventories at the Y-12 Site.

To address HEU site returns from Pantex, Y-12 has already implemented a new long-term storage system based on modular concrete pallets. These pallets can be stacked and are adaptable for various types of storage containers and facilities. This is one example of NWC technology-support activities from which Los Alamos would derive direct benefit. Material transfer between DOE sites will require continued support for fabrication and certification of shipping containers, storage facilities at Y-12, and a DOE-coordinated material transfer schedule to ensure that sufficient secure transport vehicles are available. In summary, Los Alamos plays a key role in the implementation of the SSM PEIS and DOE Office of Fissile Materials Disposition program thrusts to manage the DOE HEU inventory. An important aspect is our ability to transfer part of the Los Alamos HEU inventory to Y-12 for disposition and/or storage. In addition, we will work with Y-12 to implement various strategies that support Y-12's ability to dispose of waste materials at off-site locations. The need to help establish a DOE-wide discard limit for HEU is a high priority for both Y-12 and Los Alamos.

This article was contributed by D. Knobeloch (NMT-2), J. Fitzpatrick (CST-7), and K. Abney (CST-11).


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