.The Wing 9 hot cells in the CMR Facility were designed and constructed in 1960 to provide shielding and remote handling capabilities for work on highly radioactive materials. Commissioned in 1961 by President John F. Kennedy, the hot cells supported the Rover Project and the postmortem of irradiated fuels for breeder reactors. Even as the hot cells began decommissioning for closure in the late 1980s, they were used successfully to demonstrate the characterization and packaging of resident, remote-handled transuranic waste for eventual shipment to the Waste Isolation Pilot Plant (WIPP). This expertise continues to be a Wing 9 capability available to the industry and the DOE complex. Since 1989, a variety of projects have been identified that have extended the life of the facility and are discussed later in this article. Each of the 16 6'x6'x11' hot cells and the corridor that connects them are designed to provide adequate shielding to the worker from a 100,000 Ci source of 1-MeV gamma radiation (Figure 1). Also contained in the hot cells are in-cell remote machining and handling capabilities that allow operations on highly irradiated components. The inner-cell door design also provides a means of connecting two hot cells for installation of large pieces of equipment. The facility can handle all types of radioactive materials that are alpha, beta, gamma, and neutron emitters. An array of 364 heavily shielded storage wells and a crane capacity up to 25 tons support the hot cell capability. The current authorization basis allows a total inventory in the16 hot cells of up to 77 kg of 239Pu equivalent.
Figure 1. The hot cells in Wing 9 of the CMR Building can remotely handle and process all types of radioactive materials that are alpha, beta, or neutron emitters. Capabilities include characterization and packaging of WIPP waste as well as tasks that may require a room-sized, heavily shielded remote-handling facility for highly radioactive materials.
Technical and programmatic objectives require the Hot Cell Team in Group NMT-11 to work on programs that encompass state-of-the-art remote handling of highly irradiated materials, components, and systems. A key component of this program includes effective facility management practices to maintain remote handling operations that are compliant with DOE regulations. The Wing 9 staff expertise is the key to success with capabilities such as design engineering, process analysis, project management, welding, fabrication, robotic operations, and handing and shipping of high-activity components. Additionally, the staff has experience with the fabrication of parts made from special nuclear materials and disassembly and analysis of highly irradiated components and materials. Currently, the Wing 9 team is providing expertise to other laboratories and universities for a variety of special remote handling problems. Following are descriptions of some current Wing 9 projects.
The Molybdenum-99 Project
In response to the U.S. medical community's concern that the nation must
rely on a single, limited, foreign source for the radioisotope
molybdenum-99 (99Mo), Congress has tasked the DOE to develop a
domestic source of 99Mo, which is essential for conducting thousands of
life-saving medical diagnostic procedures each day. The 99Mo
program involves five primary activities: (1) target fabrication, (2)
target irradiation, (3) extraction and purification, (4) transportation,
and (5) waste management. The Isotope Production and Distribution branch
of the DOE conducted assessments that identified the best 99Mo
production option currently available: the fabrication of uranium targets
at Los Alamos National Laboratory and target irradiation, and extraction
and purification processing at Sandia National Laboratories.
A target fabrication demonstration program has successfully been completed in Wing 9. A target is a 304 stainless steel tube approximately 18 inches long and 1.25 inches in outer diameter. Inside the tubing, 235U is electroplated onto the steel surface to provide a very thin layer of uranium to interact with neutrons. The process takes 36 to 48 hours to deposit approximately 20 grams of uranium coating per target. The target tubes have caps welded at each end and are qualified as "reactor-ready" before transfer to Sandia for irradiation. The fabrication and electroplating process is shown in the glovebox enclosures in Figure 2.
Figure 2. The Wing 9 fabrication line produces uranium targets that will be used for production of 99Mo.
Neptunium Project
The NMT-11 staff of Wing 9 has been asked to fabricate a clad, solid ~7
kg 237Np metal sphere for criticality measurements at TA-18.
The 237Np first-daughter product, 233Pa, is highly
radioactive so the entire process must be performed within a shielded hot
cell.
The necessary equipment to melt and cast the 237Np metal
remotely will be installed in a hot cell "alpha box" to process the
alpha-emitting materials and to contain potentially high levels of
contamination. The alpha box will be purged with nitrogen gas, which
provides a low-oxygen-concentration atmosphere to allow work with the
neptunium metal, a pyrophoric material.
The 237Np sphere will be cast in a vacuum within a graphite
mold designed by MST-6 to eliminate voids in the sphere volume. The mold
design (shown in Figure 3) has been successfully tested by MST-6 using
depleted uranium to cast a sphere to within about 0.010" on the diameter
and very near theoretical density. MST-7 personnel encapsulate the
237Np sphere first within tungsten hemispheres and then within
two pure, welded Ni spheres for cladding. This project provides a tool to
the Los Alamos Critical Experiments Facility staff for experiments for
fundamental research.
Figure 3. Mold design test casting using depleted uranium. Eventually a clad 237Np sphere will be used for criticality measurements.
Sanitization Project
Plans are being formulated to initiate a sanitization project at Los
Alamos to remove classified aspects from actinide-contaminated,
nonnuclear weapon components generated from disassembly of nuclear
weapons and other weapons-related activities. The system designed for
accomplishing this activity consists of an induction furnace for melting
metallic components and a jaw crusher for pulverizing brittle,
nonmetallic items. This system is tentatively planned for installation in
Wing 9 of the CMR Building and consists of several glove boxes containing
the processing equipment and a HEPA-filtered environmental housing
surrounding the glove box system. Discussions with DOE sponsors are
currently underway to establish the funding and scope of the operation.
ULISSES Program
To achieve the next generation of uranium processing technology, Los
Alamos has developed the Uranium Line for Special Separation Science
(ULISSES), a modular test-bed for chemical process optimization. This new
processing line will include state-of-the-art dissolution chemistry and
separation science, on-line sensors coupled to automated instrumentation,
and recycling with waste minimization based on environmentally benign
chemicals. This technology base will be used to develop, design, and
demonstrate advanced chemical processing technology that minimizes
hazardous wastes.
Figure 4. Drum-loading, canister-handling system for loading, welding, packaging, and transportation of waste destined for WIPP.
Remote-Handled Transuranic Waste (RH-TRU)
The RH-TRU Program involved characterizing and packaging remote-handled
TRU waste for ultimate WIPP disposal. Because many of the waste cans
packaged thus far have typical radiation readings between 400 and 1000
R/hr at contact, a unique drum-loading and canister-handling system was
designed and constructed for loading, welding, packaging, and
transportation of the RH-TRU Waste (see Figure 4). To date, sixteen
WIPP-approved canisters have been characterized, packaged, and placed
into retrievable underground storage at Los Alamos (Area G) awaiting
shipment to WIPP. This capability in the hot cell facility is operational
to support the eventual disposition of RH-TRU waste at WIPP. The
technology will also serve to resolve RH-TRU packaging problems at other
sites within the DOE complex.
Magnetic Isotope Separation (MIS) Program
The MIS process is designed to separate isotopes for medical applications
and the stockpile stewardship program. The process is performed in a
separator system with the potential to process many different elements.
The isotopes being separated are radioactive and have an activity of up
to approximately 20 Ci. Radioisotopes of interest to be separated are
82Sr/85Sr, 32P/33P,
184Re/186Re, 168Tm,
170Tm/171Tm,
173Lu/174mLu/174gLu,
88Zr/93Zr/95Zr,
190Ir/192Ir, and possibly others. These
radioisotopes are limited to nonactinide materials.
Accelerator Production of Tritium (APT) Program
This Wing 9 capability has been developed to support the APT Program by
evaluating and testing candidate materials that have been irradiated
(Alloy 718, 316L and 304L stainless steel, modified Fe9Cr1Mo(T91),
Al6061-T6, Al5052-0) for use in the APT target and blanket. The specimens
have been irradiated for fewer than 3,600 hours to a maximum proton
fluence of 4 x 1021 p/cm2 in the center of the
proton beam. Specimens are then carefully removed from the packages in
the hot cells in Wing 9 to begin mechanical testing, which includes
tensile, bend and compact tension tests, metallographic examination, and
transmission electron microscopy. Specimens will yield data on the
effects of proton irradiation under a number of test conditions.
Actinide Source-Term Waste Test Program (STTP)
The Actinide STTP is designed to measure time-dependent concentrations of
actinide elements from actual, contact-handled TRU waste immersed in
brines that are chemically similar to those typically found in the
underground formations of WIPP. The STTP will determine the effect of TRU
waste matrices and brine chemistry on the concentrations and behavior of
actinides under WIPP bounding conditions.
Several actual TRU waste types typical of DOE waste inventories have been characterized and loaded into specially designed test containers filled with brine containing additives to enhance the action of each influencing variable. The test containers are then placed in environmental chambers in Wing 9 to simulate in-situ conditions found at WIPP. Analysis is then performed on the brine leachate and headspace gas in the test containers.
This article was contributed by Stan Bodenstein, Suzanne Helfinstine, Robert Romero, and Jim Ledbetter, all of NMT-11.
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