IT is not often that the Department of Energy's Assistant Secretary of Defense Programs visits the Laboratory to deliver a pep talk on a newly announced national security program of paramount importance to the department and the country. But that's what happened last October when Vic Reis told a packed assembly of more than 350 employees that the "awesome responsibility" for decisions regarding the safety and reliability of the nation's nuclear weapon stockpile "has been put right back where it belongs--with the labs."|
Reis was referring to the DOE's far-reaching plan to make every effort possible to ensure that the nation's nuclear force remains safe, secure, and reliable without new weapon development or the use of underground testing. The plan, formally called the Stockpile Stewardship and Management Program (SSMP), is the result of close collaboration among the DOE and scientists from Livermore, Los Alamos, and Sandia National Laboratories. Indeed, in his address to employees, Reis credited LLNL Director Bruce Tarter and many top Livermore managers for their work to delineate for President Clinton, the Joint Chiefs of Staff, and the Congress the viability of the program, based on the projected capabilities and resources of the DOE weapon laboratories.
The SSMP will use enhanced computational and experimental capabilities to help predict, detect, evaluate, and correct problems affecting nuclear weapons in the national arsenal but without additional nuclear testing. For Lawrence Livermore, the program represents a fundamental change from its historic mission of nuclear weapon development, nuclear testing, and surveillance. Stewardship of the U.S. nuclear stockpile is now this laboratory's "foremost responsibility," according to Tarter.|
Specifically, the ambitious goals of the nation's SSMP are to:
This new program addresses the U.S. nuclear stockpile, which is shrinking dramatically from Cold War levels. In the desire to conclude the Comprehensive Test Ban Treaty (CTBT), the U.S. has unilaterally halted the development and deployment of new nuclear weapon systems, begun closing elements of the nuclear weapon production complex no longer needed for a much smaller stockpile, stopped underground nuclear testing, and been involved in unprecedented nuclear arms limitation agreements between the U.S. and the nations of the former Soviet Union.
The program received powerful support last fall when President Clinton said that his decision to pursue a CTBT was based on assurances that the DOE nuclear weapon labs can meet the challenge of maintaining the nuclear deterrent under a CTBT through a Stockpile Stewardship and Management Program that does not include nuclear testing. This April President Clinton reaffirmed his determination to achieve a worldwide CTBT in a joint declaration with Russian President Boris Yeltsin.
Urgency, Risk Underlie Program|
An urgency underlies the program that can best be understood by realizing that the average age of the weapons in the U.S. stockpile next year will be greater than at any time in the past and will continue to increase until it soon exceeds the base of experience of the nation's weapon scientists. This is because the U.S. has no new weapons planned or in production to replace the oldest stockpile weapons.
Also, it must be anticipated that the reliability of the stockpile may degrade as the weapons age beyond their designed lifetimes. Problems could be caused, for example, by radioactive decay, slow chemical changes, or incompatible materials. Serious consequences could arise from common-mode failures, ones that occur when similar materials or fabrication processes are used in several weapon systems. Because recently concluded arms control agreements have sharply reduced the number of weapons, such common-mode failures can affect a larger portion of the stockpile than in previous eras.
It seems likely that problems will arise over the next few years. Of the nuclear weapon systems introduced into the U.S. stockpile since 1970, nearly half have required post-development nuclear testing to verify whether a problem existed, or to resolve or fix ones relating to safety or reliability. Furthermore, all of the weapon systems that are candidates for the enduring stockpile (those weapons permitted as a result of the START II agreement with Russia) have already been retrofitted to some degree, including the replacement of major nuclear components in some cases.
Weapon scientists must be able to accurately evaluate the severity of problems and devise the right "fixes," whether they be a remanufactured component, modification to a component to extend its lifetime, or substitution of a more reliable or safer part. In the past, the extent of a problem or the effectiveness of a "fix" could be determined with an underground nuclear test at the Nevada Test Site. If the problem proved to be particularly severe, a new warhead or weapon system could be developed. With nuclear testing and new weapon development no longer options, stockpile stewardship must rely on an improved understanding of nuclear weapons based on greatly improved facilities and computational models.
In addition to urgency, some areas of risk were folded into the President's decision. It is known that in some cases there is no adequate substitute for nuclear testing. The weapon recertification process will take these risks into account.
The Human Factor: Preserving Key Skills and Assuring Sound Judgement
The Stockpile Stewardship and Management Program (SSMP) places a premium on skilled, experienced people. As Lawrence Livermore Director Bruce Tarter said in April, "Stewardship of an aging stockpile is a heck of a different job than innovative research and design. It will rely--even more than in the past--on people throughout the Laboratory, the universities, and industry."
However, nuclear weapon science is a highly circumscribed field; there exists no broad industrial or university base from which to draw nuclear weapon expertise. U.S. weapon scientists have no true peers other than their colleagues at the three DOE weapon laboratories.
In the last few years, many of LLNL's most experienced weapon scientists and engineers have retired or left the Laboratory, and further retirements of experienced staff are expected in the next 10 years. To prepare for this situation, Livermore, Los Alamos, and Sandia are archiving their nuclear design data, knowledge, and skill bases. Lawrence Livermore, for example, is videotaping classified interviews of retired weapon designers explaining their craft and the steps leading to key design decisions. Scientists and engineers new to the weapon program will be able to draw upon archival data as well as their experienced colleagues as they acquire the expertise to maintain the enduring stockpile in a time of no nuclear testing or new weapon development.
The SSMP places a premium on expert judgment in another important way. Throughout the history of the U.S. nuclear weapon program, interlaboratory peer review has helped to compensate for incomplete knowledge about nuclear weapon physics. Without nuclear testing, an independent review process is even more important.
Livermore and Los Alamos continue to be responsible for the weapon systems each laboratory originally designed, while Sandia has responsibility for the non-nuclear components and integration of all systems. At the same time, under a process called dual revalidation, Livermore and Los Alamos (aided by Sandia) formally examine and assess the safety and reliability of each other's weapon systems under the auspices of the Project Officer Groups of the Departments of Defense and Energy. The program offers another layer of confidence in safety, security, and reliability provided by some of the best researchers in the nation.
Key Thrust Areas|
The national stockpile stewardship program has three main thrusts: laboratory experiments, computer simulations, and stockpile inspections. In each, Lawrence Livermore has particular responsibilities.
Upgrading Experimental Facilities and Capabilities
As a result, to provide needed data and simulations capability, a major thrust of the program is to upgrade existing experimental and computational capabilities at the three weapon laboratories and to design and construct several new facilities by providing insight into specific physics regimes. These strengthened capabilities will compensate, to the greatest degree possible, for the absence of nuclear testing. Together, the facilities will give the ability to investigate most phases of nuclear weapon operation. (See the box below for a list of key facilities.)|
Enhanced experimental facilities will provide the ability to evaluate safety and performance issues that could have significant stockpile consequences. The new data will be combined with past data from experiments and nuclear tests and used to validate new and evolving computational models. Also, enhanced experimental and computational capabilities will help the weapon laboratories maintain the knowledge and skill base that are essential for training new people and assuring continued support for stockpile stewardship.
It must be remembered that laboratory experiments cannot duplicate a nuclear test. Even the most advanced non-nuclear experiment can access only a small portion of the physics regimes or materials dynamics relevant to nuclear weapons. Scientists and engineers face the new challenge of interrelating and extrapolating data from many different experiments to provide an overall evaluation of weapon safety and performance.
Also important to the DOE and its laboratories is the planning under way now to develop and build the National Ignition Facility (NIF), which will provide more than ten times the power of the Nova laser at a greatly decreased unit cost. Site selection will occur after public review of a program-wide environmental impact statement and record of decision are completed later this year. The preferred site for NIF is Livermore, although wherever it is located, all of DOE's nuclear researchers will be using NIF to further understand nuclear weapons.
The need to obtain better data on the properties of plutonium and how it performs in an aging nuclear warhead is crucial. Experiments planned by Livermore and Los Alamos will reveal new information about the properties of plutonium at conditions close to those during weapon implosion. LLNL researchers also plan to conduct subcritical experiments on plutonium. Examples of this work include diamond-anvil-cell pressure measurements, equation-of-state studies, and metallurgical evaluations of aged plutonium.
Stockpile Stewardship: Advanced Experimental Facilities Needed by the program
A number of current and proposed experimental facilities are needed by the DOE-wide program to support assessments about weapon safety and reliability in the absence of nuclear testing. These include:
Nova Laser. The Nova laser, located at Livermore, is used for weapon physics and weapon effects experiments in addition to research on inertial confinement fusion (ICF). National Ignition Facility (NIF). NIF, a 192-beam laser facility planned for Livermore, will simulate on a small but diagnosable scale conditions of pressure, temperature, and energy density close to those that occur during a nuclear explosion. It will also serve ICF researchers.
Contained Firing Facility (CFF). The CFF, an addition to the Flash X-Ray (FXR) facility at Livermore, will provide for well-diagnosed, fully contained high-explosives testing of up to 60 kilograms of energetic explosives. Dual-Axis Radiographic Hydrodynamic Test (DARHT) Facility. The DARHT Facility at Los Alamos will provide enhanced radiography of the high-explosive implosion, including data on implosion symmetry as a function of time. Sub-Critical Experimental Facility (SCSS). This facility at the Nevada Test Site will provide capability to gather data on fissile materials in explosive-driven experimental geometries. Advanced Hydrotest Facility (AHF). An AHF would provide three-dimensional time-radiography of high-explosive implosions. Its location is not yet determined.
Accelerator and Pulsed-Power Facilities
Los Alamos Neutron Science Center (LANSCE). LANSCE provides an accelerator-based neutron science capability for materials science studies of weapon components and for development of the technology for accelerator production of tritium. Atlas Facility. The Atlas pulsed-power facility at Los Alamos will provide implosions of cylindrical assemblies to obtain physics information that apply to weapons. High-Explosive Pulsed-Power Facility (HEPPF). HEPPF will be used to study weapon physics issues of shock pressures and velocities close to actual weapon conditions. Advanced Radiation Source (ARS). An ARS facility would provide high-energy, high-temperature, x-ray pulses for experiments in weapon physics, radiation effects, ICF, and pulsed power technology.
Simulating Nuclear Testing|
In the absence of nuclear testing, computer simulation is the only way to assess the performance of a complete nuclear weapon system. Numerical simulation also provides an essential tie to data from past nuclear tests and is an important means of predicting the performance and changes that might occur in the stockpile due to aging, environmental exposure, materials incompatibilities, or other reasons.
However, even today's most advanced supercomputers are not adequate to do the job. Increases of up to 10,000 times in computational speed, network speed, and data storage capacity are needed to provide simulations of weapon safety and performance of the required complexity and detail when testing is not an option. New generations of supercomputers, especially those employing many parallel processors, will greatly increase the accuracy, completeness, and resolution of computer calculations as they simulate nuclear weapon phenomena in three dimensions.
The objective of DOE's Accelerated Strategic Computing Initiative (ASCI) is to vastly improve the weapon simulation capability at the national security laboratories to the level required for stockpile stewardship. The goals are to develop advanced computational models and to work with industrial partners to develop the requisite technologies, including processors, software, and data storage to implement them.
Enhancing Stockpile Surveillance and Maintenance
The Challenges for LLNL|
For LLNL, says Associate Director for Defense and Nuclear Technologies Michael Anastasio, the job of stockpile stewardship will be "as challenging as anything we have done." The work at Lawrence Livermore centers on seven major efforts: extension of weapon lifetimes, enhanced stockpile surveillance, revalidation of existing weapon systems, flexible manufacturing, high-explosives experiments, the NIF, and supercomputers (including ASCI).
Extending Weapon Lifetimes
Enhancing Stockpile Surveillance
Assessing with Dual Revalidation
Flexible, Affordable Manufacturing
Lawrence Livermore experts are developing precision casting, spinforming, and machining techniques to replace the current methods of rebuilding uranium parts destroyed in the surveillance program. For example, a project is under way to demonstrate the feasibility of using lasers to cut uranium parts with very little waste and almost no damage to the remaining material. The process uses laser expertise developed in LLNL's Inertial Confinement Fusion program and Atomic Vapor Laser Isotope Separation program.|
Remanufacturing of critical parts requires a process of recertification, based on detailed tracking of the remanufacturing process as well as experimental and computational tools. Even more important, recertification requires expert judgment to provide confidence that the remanufactured component or weapon will perform as designed. Such judgment is essential because it is impossible to exactly duplicate past processes and practices. Researchers must reconsider how to remanufacture many of the old components and weapons because they are considered unacceptable today for environmental, safety, and health reasons.
High-Explosives Tests Critical
NIF for Critical Physics Data
Moving to New Supercomputers
At the same time, Livermore computational experts are incorporating improved data from non-nuclear tests, developing a secure high-speed network to interconnect Livermore and Los Alamos supercomputer resources, and collaborating with universities and supercomputer companies to hasten the arrival of new generations of machines.|
"Sustaining confidence in the stockpile in the post-Cold War world will be extremely difficult," says Associate Director Anastasio. "It's going to require us to adapt our skills to different approaches and different teaming across the Laboratory and throughout the DOE complex. That's the changing culture we face. There is plenty for everyone to do. We need the whole Laboratory working together to help pull it off. But this is something the Laboratory is very good at."
Key Words: Accelerated Strategic Computing Initiative (ASCI), Advanced Design and Production Technologies (ADaPT), Advanced Hydrotest Facility (AHF), Comprehensive Test Ban Treaty, (CTBT), flash x-ray (FXR), National Ignition Facility (NIF), Nova, Stockpile Stewardship and Management Program (SSMP), stockpile surveillance.