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Device Assembly Facility (DAF)

Construction began on the Device Assembly Facility (DAF) in the mid-1980s to support underground nuclear testing. The DAF was designed and built to consolidate all nuclear explosive assembly functions, to provide safe structures for high explosive and nuclear explosive assembly operations, and to provide a state-of-the-art safeguards and security environment. Now that the United States is under a continuing nuclear testing moratorium, the DAF now supports diverse users such as Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), and external entities.

For 41 years, nuclear weapons testing was the primary mission at the NNSS, during which nuclear testing operations occurred in a safe, remote, and secure environment. These operations included assembly, disassembly, modification, staging, transportation, maintenance, repair, retrofit, and testing of nuclear devices. The mission of the DAF continues to evolve due to the nuclear weapons testing moratorium, which began in October 1992. Current missions are an integral part of the NNSA Stockpile Stewardship Program, which includes work to support subcritical and criticality experiments.

Facility Design
The DAF is a collection of individual steel-reinforced concrete buildings connected by a rectangular common corridor. The entire complex, covered by compacted earth, spans an area of 100,000 square feet.

Safety systems include fire detection and suppression, electrical grounding, independent heating, ventilation and air-conditioning systems with high-efficiency particulate air filters, alarm systems, and warning lights. In operational areas, pairs of blast doors, designed to mitigate the effects of an explosion, are interlocked so that only one door may open at a time.

The operational buildings in the DAF include assembly cells, high bays, assembly bays (one of which houses a glove box and another which houses a down draft table), and radiography bays. Staging bunkers provide space for staging nuclear components and high explosives. All materials packages arrive or depart the DAF through one of two shipping and receiving bays. The support buildings include vaults for staging explosives or special nuclear material, decontamination areas, and an administration area with office space, a conference area, personnel changing and shower rooms, and a machine shop. In addition, two buildings provide laboratory space – one for conducting instrumentation and environmental testing and the other for observing operations in an adjacent assembly cell.

The DAF includes assembly bays for activities involving uncased conventional high explosives and special nuclear material.

Assembly Cells (Gravel Gerties)
The assembly cells were named Gravel Gerties after a 1950s Dick Tracy comic-strip character. Modeled after the structure at the Pantex Plant, these are where hands-on assembly and disassembly of U.S. nuclear weapons and devices would take place. They provide the maximum environmental and personnel protection in the event of an inadvertent high-explosive detonation. Should a detonation occur, the Gravel Gertie would minimize release of nuclear material and its spread to other areas of the facility and to outside areas.

A National Resource
The DAF is a national asset. The design of the facility and its safety features makes the DAF well-suited to address new national challenges – such as the addition of the National Criticality Experiments Research Center to the NNSS – in support of maintaining the Nation's nuclear stockpile. Additionally, the DAF is used to prepare subcritical experiments and target chambers for the Joint Actinide Shock Physics Experimental Research (JASPER) Facility experiments.

Currently, the United States is not conducting nuclear tests. However, the President pledged to maintain an underground test readiness program in the event that nuclear testing resumes. The DAF plays a crucial role in achieving test readiness capability.

The DAF is located in the interior of the NNSS, its remoteness providing a substantial safety zone for the general public and adds to the security of the facility. In addition, activities at the DAF comply with the National Environmental Policy Act and all applicable federal, state, and local regulations.