Nuclear Weapons
Life Cycle

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Nuclear weapons are developed, produced, and maintained in the stockpile, and then retired and dismantled. This sequence of events is known as the nuclear weapons life cycle.

In the past, new weapons were developed in response to requirements for increased military capability as a result of changing geopolitical circumstances, for a nuclear weapon on a new delivery system, to attain greater military flexibility, and/or to incorporate newer and better safety and security features.

Since the end of the Cold War, the U.S. has not completed a new nuclear weapon through the full life-cycle phase process. New warheads are produced to replace legacy systems, those new weapons follow the Phase X process. Figure 7.1 depicts the traditional joint DoD-NNSA Nuclear Weapons Life-Cycle process and its associated phases.

Figure 7.1
Figure 7.1 Joint Nuclear Weapons Life-Cycle Phases (Phase X)

Nuclear Weapons Management

The responsibilities for nuclear weapons development and management were founded originally in the Atomic Energy Act of 1946, reflecting Congressional desire for civilian control over the uses of atomic (nuclear) energy and establishing the Atomic Energy Commission (AEC) to manage U.S. nuclear weapons programs. Basic departmental responsibilities and the development process were specified in the 1953 Agreement Between the AEC and the Department of Defense (DoD) for the Development, Production, and Standardization of Atomic Weapons, commonly known as the 1953 Agreement.

Figure 7.2 illustrates the respective departmental responsibilities of DoD and NNSA throughout the life-cycle process.

Figure 7.2
Figure 7.2 Joint Nuclear Weapons Life-Cycle Responsibilities

While the basic dual-agency division of responsibilities for nuclear weapons has not changed significantly, the 1953 Agreement was supplemented in 1977 (to change the AEC to the Energy Research & Development Administration (ERDA)), again in 1984 (to incorporate the details of the 1983 Memorandum of Understanding (MOU)), and in 1988 (to incorporate the newly established Nuclear Weapons Council (NWC)).

Phase 6.X Process

Since 1999, major stockpile sustainment activities have been guided by the Phase 6.X Process. The 6.X Process does not replace Phase 6 activities such as routine maintenance, stockpile evaluation, enhanced surveillance, and annual assessment. Rather, the 6.X Process was developed for non-routine nuclear weapon alterations (Alts) and modifications (Mods) at the system, subsystem, or component level; Life Extension Programs (LEPs); and other warhead modernization activities. For example, Phase 6.X does not apply to limited-life component exchanges (LLCEs) such as tritium gas bottle reservoir replacement, which is managed under normal weapon maintenance programs. Nuclear weapon Alts are assessed on a case-by-case basis to determine applicability of Phase 6.X. Depending on military requirements and the nuclear weapon delivery system, an existing warhead design may be modified through the Phase 6.X Process, or a warhead may be developed through the Phase X Process. For a specific stockpile sustainment activity, some portions of the 6.X Process may be merged, deferred, modified, or omitted, as approved by the NWC. Additionally, the NWC may authorize the weapon project officers group (POG) to coordinate Alts as routine weapon sustainment activities.

Since 1992, the NWC has concentrated its efforts on research related to the maintenance and sustainment of the existing weapons in the legacy stockpile and oversight of the stockpile sustainment activities in the absence of underground nuclear explosive testing. To manage and facilitate the stockpile sustainment process, the NWC approved the Procedural Guideline for the Phase 6.X Process in April 2000, with an update in December 2015. Figure 7.3 is an illustration of the Phase 6.X Process.

Figure 7.3
Figure 7.3 Phase 6.X Process

The Phase 6.X Process is based on the original joint DoD-DOE Nuclear Weapons Life-Cycle Process (Phase X), which includes Phases 1 through 7. The 6.X phases are a “mirror image” of Phases 1 through 6. There is no Phase 6.7, as any weapon slated for retirement, dismantlement, and disposition is covered by the traditional Phase 7 Process. The phased life-cycle process was used to develop a complete warhead, whereas the 6.X Process starts from an existing warhead design. Each Phase 6.X program is different, some involve the replacement of only one or two key components while others may involve the replacement of many key components. If a Phase 6.X program is adapting a warhead to a different delivery system or providing different military characteristics, the warhead design may be significantly modified. As a part of the Phase 6.X Process, the NWC reviews and approves proposed LEPs, Alts, and Mods. The NWC monitors progress throughout the 6.X Process to ensure the stockpile continues to be safe, secure, and reliable while meeting DoD and NNSA requirements. Figure 7.4 illustrates of the relationship of the 6.X Process to the Phase X Process.

Figure 7.4
Figure 7.4 Phase 6.X Process Relationship to the Phase Process

Phase 6.1 – Concept Assessment

DoD and NNSA are continuously engaged in assessments of nuclear weapons or components as part of normal operations. These activities result in a continuous exchange of information and provide potential concepts for sustainment of systems or components. DoD and NNSA conduct Phase 6.1 studies independently, except when they influence design and operation of the other Department’s components.

During Phase 6.1, concepts to meet DoD and NNSA needs are assessed. If the concept is assessed to be valid, the POG determines if a formal program study is warranted or whether the activity should be managed as a POG maintenance action outside the 6.X Process. A formal program study considers program execution, projected technologies, range of costs, and associated technological and programmatic risks.

Prior to commencing a Phase 6.1 study, the POG provides written notification to the Nuclear Weapons Council Standing and Safety Committee (NWCSSC). This notification includes, at a minimum, an overview of the study’s purpose, scope, objectives, and deliverables.

Key Tasks and Deliverables

At the completion of Phase 6.1, the POG provides:

  • a summary of study results to the NWCSSC, including a discussion of all potential concepts and a range of costs and technological risks based on technical boundaries that were considered in the study;
  • an initial assessment of supply chain protection considerations;
  • proposed potential changes to the military characteristics, stockpile-to-target sequence (STS), and any other requirements drivers; and
  • a recommendation to proceed to Phase 6.2, to terminate Phase 6.1 without further action, or to address any issues through normal POG activities.

The POG briefs the NWCSSC on the status of the Phase 6.1 study as requested. Phase 6.1 is complete when the POG submits its reports and deliverables to the NWCSSC.

Phase 6.2 – Feasibility Study and Design Options

Once the POG receives approval for entry into Phase 6.2, the POG is authorized to pursue a joint study to further refine potential concepts. During Phase 6.2, the POG develops design options and assesses the feasibility (e.g., cost, schedule, and technical maturity) of these options based on developed criteria, to include tradeoffs and courses of action depending on military characteristics, STS, timelines, and budgetary and resource constraints to meet the needs for a particular nuclear weapon.

Prior to entering a Phase 6.2 study, the POG acquires written authorization for entry from the NWC or NWCSSC, as appropriate, based on the scope of the effort. In arriving at a decision to authorize entry into Phase 6.2, the NWC considers the time available for completing activities when establishing the scope of a Phase 6.2 feasibility study of military performance requirements and design options.

Key Tasks and Deliverables

The POG develops a joint, integrated Phase 6.2 study plan outlining the approach, scope, and schedule for the Phase 6.2 analysis activities as early as possible. At a minimum, the Phase 6.2 analysis considers the following programmatic areas during system design:

  • range of design options, to include preliminary cost, technological risk, and schedule;
  • ability to meet system requirements, to include notional surveillance and logistics components overbuilds;
  • evaluation of options to enhance nuclear safety, security, and use control, to include supply chain protection considerations;
  • technology readiness levels and associated risk analysis;
  • research and development requirements and capabilities;
  • qualification and certification requirements;
  • production capabilities and capacities;
  • research and development, production, life-cycle maintenance, and logistics scope;
  • delivery vehicle and platform integration, to include platform nuclear certification considerations;
  • preliminary safety study, to include requirements to meet safety environments; and
  • rationale for component reuse, remanufacture, or replacement.

The POG updates existing or drafts new military characteristics to reflect DoD requirements. These military characteristics are validated within DoD and analyzed by NNSA to assess the ability to produce, qualify, and certify the design options. Additionally, the POG may evaluate and update existing STS and Interface Control Documents (ICDs). If updates are required, the POG coordinates any STS changes, while approval of ICD updates are controlled between NNSA and the appropriate Military Department.

NNSA prepares a Major Impact Report (MIR), identifying those aspects of the program that could significantly affect the schedule or pose a technical risk to the development or production of the nuclear weapon. The POG includes the MIR as an appendix to the Phase 6.2 study report.

The Military Department may decide to conduct a preliminary Pre-Operational Safety Study to begin the process of identifying specific weapon system safety rules. During Phase 6.2 and continuing through to Phase 6.5, the Nuclear Weapon System Safety Group (NWSSG) examines system design features, hardware, procedures, and aspects of the concept of operations that affect safety to determine if DoD nuclear weapon system safety standards can be met. The NWSSG identifies safety-related concerns and deficiencies so corrections may be made in a timely and cost-efficient manner.

The POG briefs the NWCSSC on the status of the Phase 6.2 study at least every six months and delivers a final Phase 6.2 study report to the NWCSSC at the conclusion of the study.

The Phase 6.2 study report summarizes the considered options and associated analyses. It documents criteria used to down select from the options considered (e.g., the extent to which each concept meets DoD and NNSA requirements) as well as operational risk management plans to ensure U.S. operational commitments are not affected by the stockpile sustainment activity. Draft military characteristics1 and STS2 documents are also included in the Phase 6.2 study report.

The POG down selects design options to be analyzed for cost in Phase 6.2A (design definition and cost study). Frequently, the POG makes these down selects early and throughout Phase 6.2 in order to manage costs. These down select options are presented to the NWC for approval during Phase 6.2 and prior to commencing Phase 6.2A. Section 3141 of the National Defense Authorization Act for Fiscal Year 2013 (Pub.L.112-239) requires the NWC to submit a report to Congress assessing the design options considered and the advantages and disadvantages of each option before proceeding beyond Phase 6.2.

Phase 6.2A – Design Definition and Cost Study

Phase 6.2A continues upon successful completion of Phase 6.2 activities. During Phase 6.2A, the POG refines the down select options by updating the down select criteria developed in Phase 6.2, developing design and qualification plans, identifying production needs, and creating a preliminary life-cycle plan. The life-cycle plan includes costs to address system stockpile evaluation program requirements and rebuilds, maintenance and logistics, trainer procurement, and handling gear for the protected period (the design lifetime). This phase culminates with the release of the Joint Integrated Project Plan (JIPP) from the POG and the Weapons Development Cost Report (WDCR) from NNSA.

Key Tasks and Deliverables

The POG creates the JIPP based on DoD and NNSA input to implement the proposed down selected set of options. The JIPP serves as the baseline control document for the stockpile sustainment activity. It discusses, as applicable:

  • scope (e.g., Mod, Alt, or LEP);
  • design definition;
  • project schedule (including joint DoD-NNSA milestones, planned management briefings and reviews, first production unit (FPU) milestone, and certification schedules);
  • cost analysis;
  • configuration management plan;
  • qualification and certification plans;
  • supply chain protection program plan;
  • military test and evaluation plans;
  • military characteristics, STS, and ICD changes;
  • system memoranda of understanding between DoD and NNSA;
  • stockpile evaluation planning;
  • operational safety implications (integrated safety process);
  • proposed changes to technical publications;
  • trainers and weapon-type requirements;
  • spares, handling gear, use-control equipment, tools, gauges, and field testers;
  • development testing and modeling support requirements;
  • process development and product qualification;
  • archiving and lessons learned;
  • component and material characterization for disposition;
  • product delivery (components and documents);
  • risk management plan; and
  • classification management review.

NNSA develops the WDCR to reflect preliminary cost estimates for design, qualification, production, and life-cycle activities. The JIPP and WDCR are primary inputs to the Phase 6.2A study report.

The POG briefs the NWCSSC on the status of the Phase 6.2A study, as requested. At the conclusion of the study, the POG delivers a final Phase 6.2A study report to the NWCSSC that serves as the basis for a Phase 6.3 entry request, if recommended. The report describes Phase 6.2A activities and includes a recommendation on the design option to carry forward into Phase 6.3, including the applicable Military Department costs. The JIPP and WDCR are included as appendices to the report.

The major deliverables for Phase 6.2A are draft military characteristics, draft STS, MIR, JIPP, WDCR, and the Phase 6.2A report.

Upon completion of Phase 6.2A, the POG presents a summary of the Phase 6.2A study report to the NWCSSC. At a minimum, this summary includes the following program information:

  • scope of stockpile sustainment activity;
  • design definition, to include preliminary component reuse forecast;
  • preliminary project schedule with major milestones (including FPU);
  • military requirements, to include any changes;
  • supply chain protection program plan;
  • qualification and certification plans, to include updated platform nuclear certification considerations;
  • trainer and ancillary equipment forecast;
  • proposed Stockpile Evaluation Program plan;
  • platform requirements, to include any changes;
  • risk management strategy;
  • requirements management process;
  • configuration management process; and
  • cost analysis, to include trade-off decisions.

Phase 6.3 – Development Engineering

During Phase 6.3, NNSA, in coordination with DoD, conducts experiments, tests, and analyses to develop and validate the selected design option. The national security laboratories initiate process development activities and produce test hardware, as required.

The POG submits a recommendation to the NWC to proceed to Phase 6.3 with a down select option. The recommendation for Phase 6.3 entry includes JIPP, MIR, WDCR, and updated military characteristics and STS documents, as appropriate. Prior to executing Phase 6.3 activities, the POG receives written authorization from the NWC to proceed.

Key Tasks and Deliverables

Following authorization to enter Phase 6.3, the NWC prepares a letter requesting Military Department and NNSA participation in Phase 6.3. The appropriate Military Department would generate and approve interagency agreements, as required, to cover technical and financial responsibilities for product-specific or joint activities. DoD and NNSA forward acceptance letters to the NWC confirming their participation in Phase 6.3. These letters also include comments on the military characteristics and STS as well as any exceptions or concerns regarding study execution or schedule.

As required, the NWSSG provides a preliminary Pre-Operational Safety Study briefing to the NWCSSC and appropriate Military Departments that includes draft weapon system safety rules.

NNSA formally updates the WDCR and reissues it as the Baseline Cost Report (BCR). NNSA provides the BCR to the NWCSSC to establish a program cost baseline. In coordination with the Defense Threat Reduction Agency (DTRA) and the Military Department, NNSA also prepares a product change proposal identifying stockpile sustainment activity scope, schedule, and specific DoD and NNSA roles and responsibilities.

The national security laboratories prepare a draft addendum to the Final Weapon Development Report (FWDR) or create a new FWDR draft. This draft includes a status of the design as well as an initial discussion of design objectives, descriptions, proposed qualification activities, ancillary equipment requirements, and project schedules.

The Military Department convenes a Design Review and Acceptance Group (DRAAG) to review the draft FWDR. Once the review is complete, the Military Department informs the NWC of the preliminary DRAAG report findings and recommendations.

The POG updates the JIPP based on Military Department and NNSA input. The POG also updates the military characteristics and STS documents, as appropriate, and ensures stakeholder requirements are fully considered.

The POG briefs the NWCSSC on the status of Phase 6.3 at least every six months.

The major deliverables for Phase 6.3 are BCR, draft addendum to the FWDR (or new FWDR draft), preliminary DRAAG report, updated JIPP, and approved military characteristics and STS documents.

Once the national security laboratories finalize the design definition and conduct the Baseline Design Review, NNSA authorizes the national security laboratories and production plants to enter into Phase 6.4.

Phase 6.4 – Production Engineering

During Phase 6.4, NNSA refines the developmental design into a producible design and prepares the production agencies for production. During this phase, the acquisition of capital equipment is completed; tooling, gauges, handling gear, and testers are defined and qualified; process development and process prove-in (PPI) are accomplished; materials are purchased; processes are qualified through production efforts; and trainer components are fabricated.

NNSA updates production cost estimates based on experience gained in PPI and product qualification. Finally, DoD and NNSA define procedures to conduct stockpile sustainment, including supply chain protection considerations and the necessary logistics supporting weapon movements.

Key Tasks and Deliverables

During Phase 6.4, NNSA performs a number of activities to transition to a producible design, including:

  • testing developmental prototypes, conducted with the Military Department to ensure operational validation, as appropriate;
  • conducting PPI activities leading to qualified production processes;
  • releasing engineering authorizations to support product and process development; and
  • updating production cost estimates.

DoD and NNSA also accomplish a number of joint activities, including:

  • provisioning for spare components;
  • conducting a laboratory task group and joint task group review to validate proposed procedures;
  • updating and finalizing technical publications through a manual files conference; and
  • updating the Stockpile Evaluation Plan (SEP).

The POG briefs the NWCSSC on the status of Phase 6.4 at least every six months.

The POG provides an updated JIPP to the NWCSSC and NNSA updates the BCR. Prior to entry into Phase 6.5, the POG provides written notification to the NWC that NNSA is prepared to transition to Phase 6.5.

Phase 6.5 – First Production

During Phase 6.5, NNSA production agencies produce the first warheads. The POG determines if these warheads meet design and military requirements.

Key Tasks and Deliverables

NNSA makes a final weapon evaluation of the design and production processes. The national security laboratories, in coordination with NNSA, prepare the final draft addendum to the FWDR, and then submit it and the draft Major Assembly Release (MAR) to the DRAAG for final review.

The Military Department convenes the DRAAG to review the final draft addendum to the FWDR. Once the review is complete, the Military Department informs the NWC of the final DRAAG report findings and recommendations. The DRAAG, in coordination with the Military Department, informs NNSA whether the weapon meets military characteristics, STS, and other applicable requirements. DoD acceptance is conveyed in a letter from the Military Department and/or the NWC chair to the NNSA Administrator.

The national security laboratories finalize and release the addendum to the FWDR upon receipt of DRAAG comments, findings, and recommendations and attach a nuclear system certification letter, which serves as the formal recertification for the nuclear system and re-qualification for system deployment.

The FPU milestone occurs when the Military Department and/or the NWC accepts the design and NNSA verifies the first produced weapon(s) meets the design.

The national security laboratories also finalize and transmit the MAR to NNSA following evaluation of production activities and completion of DoD reviews; NNSA formally issues the MAR. The first weapons are released to DoD when the NWC accepts the final DRAAG report and the MAR is issued.

The POG briefs the NWC on readiness to proceed to initial operational capability (IOC) and full deployment. The POG also coordinates specific weapon requirements for test or training purposes.

The Military Department conducts a final Pre-Operational Safety Study that ensures specific weapon system safety rules can be coordinated, approved, promulgated, and implemented, at least 60 days before IOC or first weapon delivery. During this study, the NWSSG examines and finalizes system design features, hardware, procedures, and aspects of the concept of operations that affect safety. The NWSSG also validates that the system meets DoD nuclear weapon system safety standards. The NWSSG recommends final weapon system safety rules to the appropriate Military Departments.

The POG briefs the NWCSSC on the status of Phase 6.5 at least every six months. The POG requests approval from the NWC to proceed into Phase 6.6.

Phase 6.6 – Full-Scale Production

NNSA must have written authorization from the NWC prior to beginning full-scale production and delivery of refurbished weapons for the stockpile.

Key Tasks and Deliverables

NNSA provides a briefing to the NWCSSC outlining the plans and schedule to complete full-scale production.

The POG prepares an End-of-Project Report that serves as the final JIPP and documents the details of each phase of the 6.X Process. This report also includes an analysis of lessons learned for the NWC to use when documenting the activities carried out in the 6.X Process.

NNSA delivers and releases refurbished weapons into DoD custody on a schedule agreeable to both DoD and NNSA.

Phase 6.6 ends when all planned activities, certifications, and reports are complete.

Phase 7 – Retirement, Dismantlement, and Disposition

Phase 7 begins with the first warhead retirement of a particular warhead-type. At the national level, retirement is the reduction of the quantity of that warhead-type prescribed in the Nuclear Weapon Stockpile Plan (NWSP) for any reason other than to support quality assurance. This phase initiates a process that continues until all warheads of that type are retired and dismantled. From the DoD perspective, a warhead-type just beginning retirement activities may still be retained in the active and/or inactive stockpiles for a period of years.

In the past, when the retirement of a warhead-type began, a portion of the operational stockpile was retired each year until all the warheads were retired, because at that time, most of the warhead-types were replaced with “follow-on” programs. Currently, Phase 7 is organized into three sub-phases:

  • Phase 7A, Weapon Retirement;
  • Phase 7B, Weapon Dismantlement; and
  • Phase 7C, Component and Material Disposal.

While NNSA is dismantling and disposing of the warheads, if appropriate, DoD is engaged in the retirement, dismantlement, and disposal of associated nuclear weapons delivery systems.

1 The military characteristics define the operational characteristics of the weapons.

2 The STS defines the normal peacetime, war employment, and abnormal environments to which the warhead may be exposed during its life cycle.