The Phase 6.x Process is based on the original Joint Nuclear Weapons Life Cycle Process, which includes Phases 1 through 7 and covers all phases of a weapon’s life from initial feasibility studies and design through development, production, maintenance, deployment, retirement, and dismantlement. These traditional phases were established by the Department of Defense and the Department of Energy who share responsibility for all U.S nuclear weapons.
Since all stockpile weapons are currently in Phase 6, Quantity Production and Stockpile Maintenance and Evaluation, an expanded process is necessary to extend the life of weapons in the stockpile. Therefore, the Phase 6.X process is actually an expanded subset of the Quantity Production and Stockpile phase (Phase 6) of the Joint Nuclear Weapons Life Cycle Process. The Phase 6.X process provides a framework to conduct and manage the life extension activities for existing weapons. It makes the maximum use of the established structure, flow, and practices from the traditional phase process.
For purposes of the Phase 6.X process, the enduring stockpile phase is designated Phase 6.0, and is the beginning and end point of the Phase 6.X process. The individual phases (6.1 through 6.6) follow the sequence of the traditional acquisition process. Each phase ends with a major project decision to go forward into the next phase, to remain in the present phase, or to return to an earlier phase (including a return to Phase 6.0, which is to not modify the weapon).
The 6.X phases are as follows:
Phase 6.0 - Quantity Production and Stockpile Maintenance (note: same name as Phase 6 and indicates presence in the stockpile before and after the life extension project)
Phase 6.1 - Concept Assessment
Phase 6.2 - Feasibility Study and Option Down-select
Phase 6.2A - Design Definition and Cost Study
Phase 6.3 - Development Engineering
Phase 6.4 - Production Engineering
Phase 6.5 - First Production
Phase 6.6 - Full-Scale Production
In the pure sense, the Phase 1-7 process is applicable to the fielding of new weapons whereas the Phase 6.X process is used when life extension activity is planned for a weapon already in the stockpile. Other weapon changes, such as those to improve the capability of an existing weapon, will be assessed by Defense Programs to determine which process (Phase 1-7 or 6.X) will be applied.