Weapons of Mass Destruction (WMD)

One of the safeguards which condition U.S. entry into a CTBT is:

DOE's existing capability to obtain diagnostic information was designed and implemented at a time when the agency could rely on direct observations of the results of underground nuclear tests to provide definitive answers to questions regarding nuclear weapons performance. Without the ability to verify weapons performance through nuclear tests, some remaining diagnostic tools are inadequate by themselves to provide sufficient information. Accordingly, as the Nation moves away from nuclear testing DOE must enhance its capability to use other tools to predict weapons safety, performance, and reliability. In particular, DOE must enhance its capability to perform hydrodynamic tests and dynamic experiments to assess the condition and behavior of nuclear weapons primaries.

Although the current U.S. stockpile is considered to be safe and reliable, the existing weapons are aging beyond their initial design lifetimes and, by the turn of the century, the average age of the stockpile will be older than at any time in the past. To ensure continued confidence in the safety and reliability of the U.S. nuclear weapons stockpile, DOE needs to improve its radiographic hydrodynamic testing capability as soon as possible. Uncertainty in the behavior of the aging weapons in the enduring stockpile will continue to increase with the passage of time because existing testing techniques, by themselves, are not adequate to assess the safety, performance, and reliability of the weapons primaries. Should DOE need to repair or replace any age-affected components, retrofit existing weapons, or apply new technologies to existing weapons, existing techniques are not adequate to assure weapons safety and reliability in an era without nuclear testing; DOE believes that it is probable that the existing weapons will require these types of repairs or retrofits in the foreseeable future. DOE has determined that no other currently available advanced techniques exist that could provide a level of information regarding nuclear weapons primaries comparable to that which could be obtained from enhanced radiographic hydrodynamic testing.

In addition to weapons work, DOE uses its radiographic testing facilities to support many other science missions and needs to maintain or improve its radiographic testing capability for this purpose. Hydrodynamic tests and dynamic experiments are important tools for evaluating conventional munitions; for studying hydrodynamics, materials physics, and high-speed impact phenomena; and for assessing and developing techniques for disabling weapons produced by outside interests.

Secretary of Energy O'Leary, in April, 1995, stated to the U.S. Senate Committee on Armed Services:

2.2 POLICY CONSIDERATIONS

The Nuclear Posture Review, completed by the Secretary of Defense in September 1994, reaffirmed that in today's security environment nuclear weapons remain essential even though nuclear weapons stockpiles will be reduced. The Review outlined:

In responding to the Nation's need to ensure safety, security, and reliability of the nuclear weapons stockpile, DOE must consider national policy regarding nuclear deterrence and stockpile stewardship.

2.2.1 Nuclear Deterrence

Nuclear deterrence remains a cornerstone of U.S. policy, and this Nation will continue to rely on DOE to maintain a safe, secure, and a reliable nuclear weapons stockpile. In the past, DOE has been able to accomplish that mission by retiring weapons before the end of their design life and by upgrading or redesigning weapons, if potential problems were detected, through nuclear testing and hydrodynamic tests and dynamic experiments (see figure 2-1). However, the President has discontinued underground nuclear testing and has decided that the United States will not build new nuclear weapons for the foreseeable future (even to replace those removed when past their useful life). Thus, under current U.S. policy, DOE would not produce new-design nuclear weapons.

Now DOE must rely more than ever on the data from hydrodynamic tests and dynamic experiments to ensure the safety and reliability of the weapons. The level of information received from underground nuclear testing cannot be fully replaced by current or upgraded hydrodynamic testing facilities. However, information that would be obtained from enhanced hydrodynamic capability would provide a higher level of confidence in maintaining the nuclear weapons stockpile in the absence of underground nuclear testing.

2.2.2 Stockpile Stewardship and Management

Since the 1940s, DOE and its predecessor agencies have been responsible for ensuring the safety, security, and reliability of the nuclear weapons in the stockpile. This stockpile stewardship assign-ment has always required hydro-dynamic testing and was included in the Atomic Energy Act [42 U.S.C. 2011 et seq.], along with the responsibility to design, manufacture, and certify nuclear weapons. DOE now intends to accomplish this mission through the SS&M Program. The SS&M Program is a single, highly integrated technical program for maintaining the safety and reliability of the U.S. nuclear stockpile in an era without nuclear testing and without new weapons development and produc-tion. This new approach must rely on scientific understanding and judge-ment, not on nuclear testing and the development of new weapons to pre-dict, identify, and correct prob-lems affecting the safety and relia-bility of the stockpile (DOE 1995).

Stockpile Stewardship & Management

Stockpile Stewardship – Includes activities required to maintain a high level of confidence in the safety, reliability, and performance of nuclear weapons in the absence of underground nuclear testing.

Stockpile Management – Includes activities required to dismantle, maintain, evaluate, and repair or replace nuclear weapons in the existing stockpile.

President Clinton, in the National Security Strategy, July 1994, stated:

President Clinton, in the Presidential Decision Directive of November 1993, stated:

DOE's three weapons laboratories [Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL), and Sandia National Laboratories (SNL)] perform the stockpile stewardship mission. These laboratories are asked to identify, develop, and implement selected tools – programs and facilities – needed to achieve their assigned responsibilities. Through the directors of the weapons laboratories, DOE must certify that nuclear weapons will not accidentally detonate during storage and handling (safety), that the weapons would thwart any attempts for unauthorized use (security), and that they would function as designed in the event of authorized use (performance and reliability).

For almost 50 years, nuclear tests were key to gathering data used for developing nuclear weapons and certifying their safety, reliability, and performance. Nuclear tests were also used to evaluate the effectiveness and certify performance of weapons that were redesigned. Since the 1992 moratorium on nuclear tests, DOE has recognized that a new approach, based on scientific understanding and expert judgment, is needed to ensure confidence in a nuclear deterrent and the U.S. stockpile. Given the moratorium on nuclear testing, the termination of new weapons development, and closure of weapons manufacturing and production facilities, this confidence will depend on the competence of the people who must make the scientific and technical judgments related to the safety and reliability of U.S. nuclear weapons. Those people must have a fundamental understanding of the basic scientific phenomena associated with nuclear weapons.

DOE's SS&M Program has been developed to meet three particular challenges (DOE 1995).

DOE identified five critical issues and strategies to address them (DOE 1995). Two of the strategies speak directly to DOE's continuing need for enhanced radiographic hydrodynamic testing capability.

DOE must be able to preserve the current high confidence in the safety and performance of the U.S. stockpile. Confidence is subjective; rests on the judgement of people; and is based on information, experience, and trust. In some cases, the Nation might be willing to forego the means to ensure a higher degree of confidence in the condition of its nuclear weapons in favor of some other value, as was the case when the Nation decided to accept a moratorium on underground nuclear testing. Preserving high confidence in the enduring stockpile without nuclear testing will require an improved, more complete, and more accurate understanding of the underlying physical principles involved in nuclear weapons and new or enhanced experimental capabilities (DOE 1995). DOE has determined that to ensure the continued confidence in the safety and reliability of the enduring stockpile, its hydrodynamic testing programs have increased in importance. They are an essential means to develop baseline experimental data, to determine the effects of aging, and to use as a tool for stockpile sampling; therefore, an enhanced radiographic hydrodynamic capability is needed as soon as possible.

Purpose of SS&M Program

Critical Issues and Strategies

2.3 NEED FOR ENHANCED RADIOGRAPHIC CAPABILITY

DOE has determined that it needs to obtain an enhanced capability to conduct radiographic hydrodynamic tests and dynamic experiments. The capability to obtain high-resolution, multiple-time, multiple-view information is needed to assess safety, performance, and reliability of weapons; evaluate aging weapons; obtain information about plutonium through dynamic experiments; and for other uses.

The DOE's determination has been independently confirmed by a panel of technical experts who studied the requirements for the DOE SS&M Program (JASON 1994). DOE has determined that aboveground, radiographic diagnostics are the best means – and for some parameters, the only known means – to obtain the needed information, and that linear induction accelerators (the technology proposed for DARHT) represent the best available technology to produce the high-speed, high-resolution, deeply penetrating radiographs that are needed. In addition, DOE has determined that no other advanced technology is currently available that could provide a comparable level of information. DOE's conclusions have been independently verified by panels of consultants convened to consider these issues (JASON 1994; HPAIC 1992; DFAIC 1992; and DOE 1993). The major points considered in these reviews included the ability of x-rays to penetrate ultra-dense materials at the late stages of an implosion, temporal resolution of the rapidly moving materials, spatial resolutions in the resulting image, and the need for an additional axis (or axes) to provide three-dimensional information. The capabilities and limitations of current facilities are described in section 2.4.

2.3.1 Assessing Weapons Safety, Performance, and Reliability

To ensure the continued viability of the smaller stockpile, DOE must improve its scientific understanding of the physics of a nuclear weapon beyond its design life, and develop a better understanding of how a nuclear weapon behaves during the complex interactions that occur in the brief interval between high-explosive detonation and nuclear explosion. This information is needed to assure the continued safety, performance, and reliability of existing weapons. Two examples of specific problems that involve both a fundamental understanding of weapons reliability and potential issues concerning stockpile aging are the process and efficiency with which boosting occurs (see figure 1-2), and the critical configurations required for materials at late stages of implosion. Both of these examples are best studied with the high-energy, high-dose, short-pulse capabilities planned for DARHT.

DOE has not yet determined how to predict with sufficient accuracy, from computer calculations alone, the rapidly changing shape of a weapons primary during the last stages of implosion. However, this information is essential to predict the safety, performance, and reliability of a nuclear weapon. At this time, the highest priority issues for stockpiled primaries are those that affect the successful ignition of the deuterium-tritium boost gas. DOE needs to be able to predict the implosion movement of the three-dimensional weapons assembly to provide an integral measure of the expected performance of the fission drive, to assess nuclear safety in accidents, and for render-safe and disablement effectiveness. Current diagnostic capabilities are insufficient to make all of the necessary types of measurements of an imploding primary or to make refined measurements at the high level of detail needed. Therefore, DOE needs to establish an enhanced diagnostic capability to make the necessary types of measurements at the desired level of detail. These kinds of technology issues would also arise in weapons design; but, under current U.S. policy, DOE does not develop or produce new-design weapons systems.

The safety aspect of DOE's stockpile mission arises from concerns about how a primary would behave if the high explosives were unexpectedly detonated in scenarios such as a transportation accident, damage from a projectile, or a nearby fire or explosion. In these instances, the high explosive would not be detonated in the manner required to trigger a nuclear explosion; but such an explosion could affect the primary. Even if nuclear yield did not result, an accidental detonation of the high explosives within a nuclear weapon could result in vaporizing or scattering plutonium metal or other hazardous materials. Assuring safety requires knowing how the primary materials might be affected by these explosion conditions.

Changes Can Affect Primaries

A nuclear weapons primary is part of the weapons' nuclear package (see figure 1-2). The primary is where the nuclear fission process starts. Many complex physical and chemical interactions occur during the split second that the primary operates. If the primary does not work properly, the secondary will not work properly. The interactions in a weapons primary are extremely complex. Changes as small as thousandths of an inch, or less than millionths of a second, can affect its margin of safety or performance.

High Explosives (HE). The primary contains HE which surrounds a metal pit. When a weapon is detonated a series of steps occur very rapidly in a controlled sequence. First the HE is detonated. After the detonators are triggered, a wave of detonation passes through the main HE charge. The HE burn and the detonation wave can be affected by the type of explosive and its chemistry, the grain size, impurities, manufacturing method, and gaps in the HE assembly, among other things. If the HE does not detonate as designed, the pit may not implode properly but may still blow apart, scattering plutonium metal or other materials.

Pit Implosion. The pressure caused by the detonating HE causes a shock wave to travel through the pit material. The pit responds in a complex set of interactions as it implodes radially to a compact shape. As the shock wave crosses the pit, small amounts of material may be ejected from each interface, which may or may not affect the implosion. The response of the pit _ how the metal moves, flows, or melts, for example _ is complex and depends on dynamic materials properties which can be affected by factors associated with component fabrication as well as by the intrinsic properties of specific materials (particularly plutonium). DOE has limited data on some aspects of the properties of plutonium and other pit materials, especially at the high strain rates associated with pit implosion. If the pit does not implode properly, the boosting process may be affected.

Boosting. The tritium-deuterium boost gas is heated by the pit implosion and the onset of the fissioning process. The heated boost gas undergoes nuclear fusion and generates large numbers of high-energy neutrons. These enter the fissile pit material and cause subsequent fissioning. These boost-induced nuclear interactions generate additional fission yield, "boosting" the nuclear yield of the primary. If boosting does not occur properly or is inadequate, weapons performance may be dramatically decreased.

Prior to the President's moratorium on nuclear testing, the United States used both hydrodynamic and nuclear testing to obtain information needed to assess nuclear weapons safety, performance, and reliability. Nuclear testing at appropriate nuclear yields allowed DOE to maintain the stockpile and its nuclear expertise with very high confidence; the performance and safety of the enduring stockpile was validated by such tests. Because of the moratorium on nuclear testing, DOE did not complete all of the underground nuclear tests that had been planned. Certain types of data gaps, which the design laboratories expected to be partially filled by analyzing the results of nuclear tests, remain unfilled.

Without nuclear testing, mathematical calculations based on experimental data would be the only way to obtain needed information on weapons performance and reliability. However, theoretical mathematical calculations alone cannot be relied on to predict the behavior of a nuclear weapons primary; the calculations must be verified against actual experimental data. DOE considers enhanced radiographic hydrodynamic testing to be the best (and in some areas, the only known) tool to obtain certain types of information regarding weapons primaries. These data are needed to verify and refine predictive analytical models.

In an era during which nuclear testing will not be performed, DOE will have to assess weapons safety, performance, and reliability in other ways. Enhanced radiographic hydrodynamic testing would provide a powerful tool for implementing the SS&M Program. Whether or not this approach will fully satisfy the need for stockpile assurance without nuclear testing is not completely known; and, it will not be known for several years after an enhanced hydrodynamic capability, among other tools, is put into place and test results are analyzed. The possibility exists that, without nuclear testing, the Nation cannot ensure the continued viability of a nuclear deterrent based on the existing weapons in the nuclear weapons stockpile. The sooner DOE can obtain better diagnostic information, the sooner the Nation can determine if its existing nuclear deterrent is sufficient. Conversely, the longer the Nation waits before an enhanced capability is achieved, the greater the chance that a problem will arise that cannot be addressed with the current capability, in a manner that is sufficient to ensure the necessary level of confidence in the nuclear weapons stockpile. Such circumstances could lead, pursuant to a Presidential announcement in August 1995, to U.S. withdrawal from a Comprehensive Test Ban Treaty (CTBT) under a "supreme national interest" clause to conduct necessary nuclear tests.

Baseline research is expected to take several years and will involve many different types of calculations, tests, and experiments performed at different DOE weapons facilities, primarily LANL, LLNL, and SNL. Baselining to document the correct physical status of the weapons systems will involve a broad range of observations, measurements, and tests. Hydrodynamic testing is one activity that would support baseline research and supply specific information needed to answer particular questions about the safety and performance of nuclear weapons. The extent and duration of these activities will depend on the nature of the results, but several years is the best early estimate.

2.3.2 Evaluating Aging Weapons

In August, 1995, an independent panel of experts, the JASONS, stated:

To maintain high confidence in the safety, reliability, and performance of the individual types of weapons in the enduring stockpile for several decades under a Comprehensive Test Ban Treaty (CTBT), the United States must provide continuing and steady support for a focused, multifaceted program to increase understanding of the enduring stockpile; to detect, anticipate and evaluate potential aging problems; and to plan for refurbishment and remanufacture, as required. In addition the U.S. must maintain a significant industrial infrastructure in the nuclear program to do the required replenishing, refurbishing, or remanufacturing, of age-affected components, and to evaluate the resulting product; for example, the high explosive, the boost gas system, the tritium loading, etc.

Stewardship of Nuclear Weapons Primaries

Confidence in the weapons in the enduring stockpile is based to a large extent on ensuring the safety and reliability of the weapons' primary. The boost, yield and implosion of the primary are key concerns regarding reliability. The primary contains the main high explosive (HE) charge and plutonium that would be the focus of safety concerns.

Age Related Changes

Material degradation and imperfections caused by aging can profoundly affect the performance of the primary. Every component in a nuclear weapon may exhibit changes as the weapon grows older. It is relatively easy to replace many of the weapons' electrical parts or other components. However, nuclear components can not be readily repaired or exchanged without taking the entire weapon apart, replacing the nuclear components with remanufactured or retrofitted parts, and reassembling the weapon. This could require that DOE recertify that the weapon is safe and reliable. Replacing nuclear components and recertifying a weapon is expensive.

Age-related changes that can affect a nuclear weapons primary include:

_ Structural or chemical degradation of the HE leading to a change in explosives performance, or migration of HE.

_ Changes in plutonium properties as impurities build up inside the material due to radioactive decay.

_ Corrosion along interfaces, joints and welds.

_ Chemical or physical degradation of other materials or components.

Weapons Safety and Reliability

The effects of aging on weapons components can affect their long-term safety and reliability. Safety may be affected by chemical or structural changes in the HE or detonators, which may lead to altered response to impact or fire. Corrosion or cracking may compromise fire-resistant layers in an accident. The reliability of the primary could be affected by changes that might perturb the primary implosion, and their effect on boosting.

If the effect of aging on the weapons' components is serious enough to require that the part be replaced, it is possible that the steps that would need to be taken to correct the problem could introduce additional changes that could affect the weapons' performance or safety. DOE must be able to ensure that the safety or reliability of the primary would not be compromised if the components were replaced. This requires the same special skills and expert judgment needed for a new design. Even very small changes in a weapons primary could dramatically affect the weapons performance, and remanufacturing or replacing the primary components could introduce these types of changes.

Although the U.S. nuclear weapons stockpile is presently safe and reliable, the nuclear weapons in today's U.S. stockpile are aging. Existing weapons, on the average, are about 15 years old, and in about 5 years, many weapons will begin exceeding their original design lifetime. In the past, individual weapons in the stockpile were replaced by new-design, upgraded, or replacement weapons before they approached the end of their design life. However, because the United States is not currently producing new nuclear weapons, DOE does not anticipate replacing the weapons now in the stockpile before the end of their original design life. This creates uncertainty about the safety and performance capability of the remaining weapons as they continue to age because DOE does not know how the weapons will behave over the long term.

DOE believes that inventorying or benchmarking the condition of weapons and their expected performance characteristics is needed as soon as possible. This would provide a baseline for comparing future surveillance observations and performance tests over the period of time that the weapons will eventually be called upon to serve in the stockpile. DOE would use many diagnostic tools at several of its sites to assist with benchmarking the inventory, which is expected to take several years. DOE would use enhanced radiographic hydrodynamic testing capability to accurately benchmark weapons primaries. The sooner that benchmarking takes place, the sooner DOE would have more reliable data and could be more certain about the condition of the weapons remaining in the stockpile. DOE would expect that aging or other types of problems would be discovered through surveillance activities, including "static" radiographs of weapons and components. These "static" radiographs can use long x-ray exposure times and, therefore, can be obtained without using DARHT facilities. Static radiographs, are also taken in preparation for dynamic experiment or hydrodynamic tests, before the high explosive charge is detonated and aligned. The static radiograph provides a picture of the initial condition of the test assembly and hence, defines the initial condition of an experiment.

Why Retrofit Existing Weapons?

A nuclear weapon may contain over 6,000 parts; the nuclear package, which contains the weapons primary and secondary assemblies, has about 300 parts (see figure 1-2). DOE continually monitors the condition of nuclear weapons through its surveillance program, where weapons are returned from the stockpile, taken apart, and examined. Some parts are tested and damaged or destroyed in the testing process. Through the surveillance program, DOE may find that any one of the thousands of parts in a weapon is defective. There may have been a miscalculation in the original design, a manufacturing error, or a part may have expanded, cracked, shifted, or deteriorated over time. In addition to observations through the surveillance program, new or improved computer codes may disclose that a weapon component may be defective or may not function as intended. Sometimes defective parts may be limited to a small number of warheads, and sometimes the defect may extend through an entire series of weapons ("common mode failure").

DOE must be able to replace parts that are destroyed through the surveillance process; and, if the examination reveals that a weapons part is defective or has changed, DOE must be able to decide whether to replace the part, redesign the part, or leave the part in place if the safety or performance of the weapon is still acceptable.

When the weapons were built, DOE manufactured some spare parts to replace those expected to be used up in surveillance testing. DOE did not manufacture spare parts for all components and could not foresee which components might need to be replaced.

Based on past experience, DOE expects that in the future some replacement parts will need to be manufactured, particularly as the existing weapons get older and the original parts degrade or change over time. In some cases, replacement parts will have to be redesigned or reengineered to solve defects or other problems uncovered by the surveillance program. In addition, DOE expects that as new technologies are developed, some parts will be replaced to take advantage of these improvements. DOE must be able to ensure that repaired, replaced, or newly developed parts will perform as expected and will not cause an unexpected problem within the entire weapons system. Hydrodynamic tests and dynamic experiments would continue to be one tool that DOE would use to ensure the safety, performance, and reliability of weapons in the enduring stockpile.

At first, it might seem that further testing of weapons systems would be unnecessary if DOE would remanufacture replacement parts to the original design specifications. However, this process would be impractical and would not avoid the need for future tests. Many weapons components were manufactured using machinery, such as large metal presses or milling equipment, that were cost-effective only for large production runs at facilities that now have been shut down, such as the DOE Rocky Flats Plant. In some cases the process lines, materials, tools, and equipment that were used for the original parts are no longer available. Manufacturing processes that were state-of-the-art when the original weapons were manufactured are now obsolete. Manufacturing specifications are never all-inclusive and some details of practice that were employed or manufacturing conditions (such as temperature or humidity) may not have been fully documented or would be difficult to reconstruct. DOE could not realistically expect the exact duplication of all production processes and practices and could not expect an exact replication of certain components. Therefore, the parts would still need to be tested.

Remanufacturing is, of course, only of interest for those cases when the original design specifications were correct. In those instances when the original design or manufacturing processes were faulty, there would be little incentive to duplicate them.

Based on these considerations, DOE has concluded that remanufacturing alone is not sufficient to maintain the enduring nuclear weapons stockpile and that remanufacturing would not offer an alternative approach to stockpile maintenance that would avoid future weapons testing.

As materials age, particularly those used in nuclear weapons, they tend to change. DOE weapons personnel can predict some types of changes that would be expected to occur over time in the materials that make up the weapons. However, other effects, which aging may bring about on the performance and reliability of these weapons and on their behavior under certain postulated accident conditions, are largely unknown. DOE needs to ensure that aging weapons remain safe and reliable. Should systems in aging weapons need to be reengineered or replaced, DOE needs a capability to validate that the replacement systems would not compromise weapons safety, reliability, or performance. Sophisti-cated manufacturing processes are not always easy to replicate once they have been dismantled. If weapons components are to be remanufactured, testing (nonnuclear) the products from this process is an important tool for reducing uncertainty about any significant differences from the original product. DOE also must be able to predict the physics behavior that would be expected from an aging weapon under abnormal conditions, such as those that might occur in an accident or those that might lead to changes in the material properties.

Many complex systems, including some weapons systems, experience a history of early problems, but their number and frequency decrease with time. This downward trend is a result of experience. Later, these same systems will show the effects of aging and the trend for problems may increase. Currently, most existing stockpile systems are believed to benefit from the experience factor, but are not yet suffering the increased problems due to aging. The potential for an eventual increase in problems is normal and expected.

DOE has considerable evidence to indicate that, as weapons age, problems related to the deterioration of weapons components can and do occur. Before the recent changes in policy, most weapons were replaced by newer systems before their design life had been exceeded. Therefore, most of the historical information on safety, reliability, or performance of stockpiled weapons was related to issues that arose unexpectedly before the end of their design lifetime. DOE has 50 years of experience in solving a wide diversity of issues (e.g., the large number of ways that materials can crack, corrode, or otherwise degrade) and in increasing its understanding of plausible accident scenarios. This experience helps prevent exact recurrences of past problems, but it does not prevent new issues from arising.

DOE operates direct surveillance programs that have been ongoing for more than 40 years. Under one of these programs, every system in the stockpile is examined each year; a given number of weapons for each system are taken as a representative sample and examined. The direct surveillance program may detect types of failures that could affect the dynamic performance of either the high explosives or other primary materials during the implosion process.

By itself, weapons surveillance is not adequate to predict and resolve performance or reliability problems. To certify a weapons system, prototype systems were tested extensively, using both nuclear testing and hydrodynamic tests, before any production of stockpile weapons was authorized. DOE relies on its stockpile surveillance program to observe post-production problems for weapons in the stockpile. Once a problem is discovered, DOE must determine the impact that the problem might have on weapons safety or performance and reliability. The probable impact of an observed change is calculated based on known computer codes and then corroborated with experimental testing.

Although certain limited-life components were designed to be replaced (such as batteries) or replenished (such as tritium gas reservoirs), other essential components of weapons were presumed to last the life of the weapon. High explosives, primaries, secondaries, and radiation cases were not designed to be replaced unless testing programs indicated that a problem existed with a given component. However, the metals, plastic explosives, and other materials that make up the weapons in the existing stockpile are known to have the possibility of becoming brittle, cracked, or otherwise show changes in their material properties over extended periods of time. The question faced by weapons personnel is whether these changes, if they occur, would affect the safe handling characteristics or performance reliability of the weapons.

The three weapons laboratories (LLNL, LANL, and SNL) conducted a study, Stockpile Surveillance: Past and Future (Johnson et al. 1995), to review the results of past surveillance and make recommendations for future actions needed to ensure the safety and reliability of the stockpile. The report notes that, in the past, significant problems have been found in the stockpile and that changes to stockpiled weapons have been made to assure safety, performance, and reliability; it also notes that problems have been found in each of the weapons types expected to be in the stockpile in the year 2000. The study concludes that it is reasonable to expect that problems will continue to arise in the stockpile at the rate of one or two defects per year that would require action as the stockpile ages beyond the original design expectations.

The nuclear weapons stockpile, projected for the year 2003 and beyond, would be smaller than the U.S. has had at any time since 1959. The newest weapons in the future stockpile would have been built in 1990, the average age of the stockpile in 2005 would be 20 years, and the oldest weapons would be about 28 years old. Under the present plans for continued downsizing, some weapons will remain in the stockpile for more than 40 years. Until the past few years, there has been no expectation that weapons would remain in the stockpile longer than they have in the past (about 20 years or less). Continuous modernization to improve the safety, reliability, and performance kept the stockpile relatively young as new weapons types replace old ones. With no new weapons entering the stockpile, the existing nuclear deterrent is steadily aging (Johnson et al. 1995).

The three weapons laboratories have updated their "Defects Database," which now contains more than 2,400 entries. Although specific details are classified, more than 370 cases have resulted in some kind of action due to safety or reliability concerns; 46 of the 50 weapons-types studied have had at least one problem; and problems not requiring actions to the nuclear components affected 39 weapons types (Johnson et al. 1995).

Until 1992, the U.S. used underground nuclear tests to test the full operation of a weapons system and to assure that the nuclear package would operate as intended. These tests contributed to a broad range of weapons research and design activities, from development of new weapons to stockpile confidence tests (tests to verify performance of already-manufactured weapons that have entered the stockpile). In the past, nuclear tests identified certain classes of problems not observed through the surveillance program, such as the lack of one-point safety for several weapons types previously deployed in the stockpile. In addition, nuclear tests were used to resolve issues raised by the surveillance program such as whether a particular corrosion problem would affect nuclear yield. They have been used to verify the efficiency of design changes, such as the adequacy of certain mechanical safing techniques. Nuclear testing also was used to prove that a potential problem that could have been expensive or difficult to fix did not exist (Johnson et al. 1995).

There have been 17 stockpile confidence tests since 1972, including a test of each of the weapons types expected to remain in the stockpile well into the next century. In addition, there have been at least 51 additional underground nuclear tests since 1972 involving nuclear components from the stockpile, weapons production lines, or specification builds. Five of these tests revealed or confirmed a problem that required corrective action. Six tests confirmed a fix to an identified problem; and five tests investigated safety concerns affecting three warhead types and confirmed that a problem did not exist (Johnson et al. 1995).

In a future without nuclear testing, DOE's ability to assess nuclear components will be more difficult and DOE must rely on other testing means to compensate for having set aside nuclear testing. This comes at the same time that the Nation has accepted reliance on a smaller, older, stockpile to serve as a nuclear deterrent for the foreseeable future. At this juncture of fewer diagnostic tools, and when confidence in the long-term capability of the stockpile becomes more uncertain, DOE needs to enhance its capability to make the best use of proven techniques.

DOE cannot predict with certainty when safety or reliability concerns will arise in the future, but DOE anticipates that problems will be discovered more frequently as weapons become older and exceed their original design lifetime. Because the weapons will become older than any weapons with which DOE has had experience, there will be a need to address and correct problems not previously encountered. Of the weapons types introduced since 1970, nearly one-half required nuclear testing following their development (either while they were deployed or still being produced) to verify, resolve, or certify that problems relating to safety or reliability were resolved. A majority of these problems involved the primary stage of the weapon. Since 1970, several thousand weapons have been removed from the active stockpile for major modification or have been accelerated on their path to retirement, to fully resolve such safety or performance reliability concerns.

One example of unanticipated problems is the now-retired W68 warhead for a submarine-launched ballistic missile. Routine surveillance disclosed a premature degradation of the warhead's high explosive. Without modification, the problem ultimately would have rendered the weapon inoperable. Consequently, the weapons were disassembled and the high explosive replaced with a more chemically stable formulation. In addition, because some of the materials used in the original production were no longer available commercially, some additional changes were made in the rebuilt weapon. Nuclear test data were used to assure that the high explosive and other changes would not compromise adequate performance of the weapons. DOE performed a nuclear test to verify that the rebuilt weapons would perform as designed and was surprised to find that the weapon yield was degraded. However, DOE decided that the lower yield was acceptable. This example and others have been summarized in a 1987 unclassified report to Congress by Drs. George Miller, Carol Alonso, and Paul Brown (Miller et al. 1987).

The Miller report describes a number of weapons systems that have been in the Nations's stockpile. This report documents several examples of unanticipated problems that arose following deployment of a weapons system to the stockpile. This report is valuable because it provides historical examples of some problems with systems in the stockpile. However, the Miller report and several similar reports in the open literature have some important limitations. They cannot present classified information, which is especially important for the more recent systems in the enduring stockpile. As a result, these reports do not provide good bases for statistical conclusions about the rates or types of problems encountered. Still, the examples given will portray the existence of unanticipated problems in post-deployment systems.

Following publication of the Miller report, a one-point safety problem was identified in the W79 systems by way of nuclear testing. One-point safety implies that a device will not produce nuclear yield if its high explosive is detonated at any single place. This one-point safety greatly limits the impacts from a broad range of accident scenarios.

In the absence of nuclear testing, DOE must rely more heavily on hydrodynamic testing to provide the same assurance of safety, performance, and reliability – particularly to verify, resolve, or validate fixes to problems in existing systems. DOE considers enhanced radiographic hydrodynamic testing to be a crucial tool for producing information on the effects of aging within weapons primaries.

2.3.3 Dynamic Experiments with Plutonium

Some components of nuclear weapons contain plutonium, which is a material with unique behavioral characteristics. As part of its effort to better understand the materials science aspect of nuclear weapons aging and performance, DOE needs to develop a better understanding of the physical properties of plutonium. In metal form, plutonium is an extremely heavy, dense silvery metal; it is sometimes stored as an oxide or in solution. Any form of plutonium may react with water, plastics, metals, or other materials with which it comes into contact. It is important that the DOE weapons laboratories have the tools to study the various forms of plutonium and its physical properties and have an ability to evaluate and predict plutonium behavior under dynamic conditions (conditions involving very rapid motion).

Currently, the body of knowledge regarding the behavior of plutonium is inadequate for assuring weapons reliability and safety of weapons within the stockpile as they age beyond their design life. DOE needs:

Since radiographic dynamic experiments are the best tool to obtain this information, DOE must have the capability to conduct dynamic experiments with plutonium using enhanced high-resolution radiography. As a matter of policy, dynamic experiments involving plutonium, would always be conducted in double-walled containment vessels. Accordingly, DOE also needs the capability to stage, maintain, and clean out the plutonium containment vessels.

2.3.4 Other Needs

DOE also needs more information on other issues related to nuclear deterrence and nuclear weapons materials science.

In 1991, the President stated that the United States would not design new nuclear weapons in the foreseeable future. However, in the event that this Nation decides, as a matter of policy, that new nuclear weapons should again be developed, DOE would use all appropriate means at its disposal to accomplish this. Hydrodynamic testing, along with many other tools, could be used to assist in weapons development. However, any decision to develop new nuclear weapons would be made by the President and be subject to Congressional review and approval.

2.4 LIMITATIONS OF EXISTING FACILITIES

Along with other stockpile stewardship responsibilities, DOE has assigned a hydrodynamic testing mission to its two nuclear weapons physics laboratories, LANL and LLNL. The Pulsed High Energy Radiation Machine Emitting X-Rays (PHERMEX) is the existing radiographic hydrodynamic testing facility at LANL and the Flash X-Ray (FXR) is the existing radiographic hydrodynamic testing facility at site 300 at LLNL.

PHERMEX has been in continuous operation since 1963. In addition to major, full-scale hydrodynamic tests, PHERMEX is used for smaller types of experiments, such as high-explosive tests or tests requiring static radiographs. Although PHERMEX was state of the art in the 1950s when it was designed, it is no longer adequate. It cannot provide the degree of resolution, intensity, rapid time sequencing, or three-dimensional views that are needed to provide answers to current questions regarding weapons condition or performance. Even if this type of diagnostic information were not needed, PHERMEX might not remain a viable test facility over an extended time because of anticipated increasing difficulty in maintaining the facility.

A set of upgrades recently have been started at PHERMEX. These upgrades comprise a modification to safety systems in compliance with 10 CFR 835, Occupational Radiation Protection; a modification to the PHERMEX accelerator that required removal of large amounts of depleted uranium [176 lb (80 kg)] from shield; and a final modification, scheduled for completion in 1996, will provide for two reduced-intensity pulses and, hence, two radiographs, although at greatly reduced x-ray intensity. The removal of the uranium had an additional effect of reducing interference with the beam that increased the penetrating ability. These upgrades, still in progress, will have served to increase some of the capability of PHERMEX; however, enhanced radiographic capability, sufficient to meet DOE's purpose and need as described by the proposed action, is not attained. For example, the PHERMEX spot size and, therefore, degree of resolution will remain approximately the same as it has been.

FXR has been in continuous operation since 1983; it is DOE's most advanced radiographic hydrodynamic testing facility. Although FXR uses linear induction accelerator technology for high-speed radiography, it cannot provide the degree of resolution, intensity, or three-dimensional views needed to address current questions. Additionally, DOE does not perform dynamic experiments with plutonium at LLNL because the necessary infrastructure is not in place at site 300.

Nation's Commitment to Nonproliferation

"One of my Administration's highest priorities is to negotiate a Comprehensive Test Ban Treaty (CTBT) to reduce the danger posed by nuclear weapons proliferation. To advance that goal and secure the strongest possible treaty, I am announcing today my decision to seek a "zero" yield CTBT. A zero yield CTBT would ban any nuclear weapon test explosion or any other nuclear explosion immediately upon entry into force. I hope it will lead to an early consensus among all states at the negotiating table."

Neither PHERMEX nor FXR is adequate to provide the enhanced radiographic hydrodynamic testing capability that DOE now needs in the absence of nuclear weapons testing. At present, both PHERMEX and FXR can take only one image at a time. If planned upgrades are completed, PHERMEX and FXR may soon have the capability to make sequential radiographs up to 100 –s apart (referred to as double-pulse capability), but without improvement in x-ray dose or spot size. In fact, in producing the sequential radiograph, there is a noticeable reduction in x-ray dose, thus reducing the degree of penetration of the x-ray beam. While this capability allows DOE to obtain more information than the original PHERMEX or FXR design, the level of information obtained from these radiographs does not satisfy DOE's need for enhanced radiography. These machines are not capable of producing a high x-ray dose coupled with a small beam spot size to provide the diagnostic capability that DOE now needs. Neither machine is capable of taking very high-resolution radiographs, which is dependent on the accelerator beam spot size, nor are they capable of producing x-ray beams with the intensity required, which is principally dependent on x-ray dose strength. They do not have the capability to obtain three-dimensional information for one test event, which requires the ability to take pictures from more than one point of view. To obtain three-dimensional data at PHERMEX or FXR, laboratory personnel must make up more than one test assembly, explode them one at a time, and rotate each subsequent device to obtain an additional point of view. Besides increasing cost – a full-scale hydrodynamic test costs $1.5 to $2 million, with the cost multiplied by the number of views tested – it is difficult to reproduce precise dimensions and alignments (within hundredths of an inch) to replicate test results for components in a series of tests. The confidence in the resulting data is also limited because of the uncertainties of using sequential tests. DOE's observations regarding the limitations of PHERMEX and FXR, even after planned upgrades have been incorporated, have also been reflected by independent researchers (JASON 1994).

2.5 NONPROLIFERATION

DOE has determined that enhanced hydrodynamic testing capability in support of its SS&M Program would be consistent with the U.S. policy on nonproliferation.

The President is committed to curbing the proliferation of nuclear weapons. The DOE SS&M Program is a key component of the U.S. nonproliferation strategy. This Nation's commitment to nonproliferation is evident by our support for an indefinite extension of the Nonproliferation Treaty in force since 1970; [21 UST 483] (see box). In support of these goals, the SS&M Program provides a means to assure the safety and reliability of the Nation's remaining stockpile of nuclear weapons under a continuing testing moratorium and a future comprehensive test ban.

On August 11, 1995 the President announced his commitment to seek a "zero-yield" CTBT (see box). The President also established several safeguards that condition the United States entry into a CTBT. One of these safeguards is the conduct of a science-based Stockpile Stewardship and Management Program, including the conduct of experimental programs. This safeguard enables the Nation to enter into such a treaty while maintaining a safe and reliable nuclear stockpile consistent with National security strategy (see box section 2.2).

One global benefit of science-based stockpile stewardship is to demonstrate the U.S. commitment to Nonproliferation Treaty goals; however, the U.S. nuclear posture is not the only factor that might affect whether or not other nations might develop nuclear weapons of their own. Some nations that are not declared nuclear states have the ability to develop nuclear weapons. Many of these nations rely on the U.S. nuclear deterrent for security assurance. The loss of confidence in the safety or reliability of the weapons in the U.S. stockpile could result in a corresponding loss of credibility of the Nation's ability to provide a nuclear deterrent and could provide an incentive to other nations to develop their own nuclear weapons program.

The United States has halted the development of new nuclear weapons systems. The Nuclear Posture Review commits the United States to maintaining a safe and reliable nuclear deterrent. The hydrodynamic testing program, when used to assess the safety and reliability of the nuclear weapons primaries in the remaining stockpile, does not constitute proliferation. The results of such testing are classified and could not lead to proliferation without a breach of security. Nonproliferation verification would not be affected by a choice to perform hydrodynamic testing in open-air shots or containment. The levels of energy release from high explosives in hydrodynamic testing is far from adequate for clandestine nuclear testing of weapons, even very-low-yield nuclear testing. Because the United States is already a nuclear weapons state and has had a hydrodynamic testing program for several decades, continuing to maintain a hydrodynamic testing capability does not change our Nation's status regarding proliferation. Lack of hydrodynamic testing capability, while seriously impacting our ability to ensure the continued safety and reliability of the stockpile, also would not change the status of the United States in terms of proliferation – we would remain a nuclear weapons state. Proliferation drivers for other states, such as international competition or the desire to deter conventional armed forces, would remain unchanged regardless of whether DOE implemented the proposed action analyzed in this EIS.

Most of the component technology used for hydrodynamic testing is unclassified and is available in the open literature; many other nations have developed a considerable accelerator technology capability. Accelerator-based radiographic technology is currently used by other weapons states for many of the same reasons it is used by the United States. In the NPT the parties agree to not transfer nuclear weapons, other devices, or control over them, and to not assist, encourage, or induce nonnuclear states to acquire them. However, the treaty does not invoke stockpile reductions by nuclear states, and it does not address actions of nuclear states in maintaining their stockpiles. Article VI obligates each of the parties to negotiate in good faith on the "cessation of the nuclear arms race at an early date and to nuclear disarmament..." The concept of hydrodynamic testing is known to all the signatories, and the capability exists with several of the nuclear states. Such capability is said to have been an important factor for the nuclear states to have entered into the treaty and to agree to further negotiate for a CTBT.

Note: Dates are subject to change.

2.6 RELATIONSHIP OF THE DARHT EIS

TO OTHER DOE EISs

DOE plans two other National Environmental Policy Act (NEPA) reviews regarding proposed actions at LANL related to the Dual Axis Radiographic Hydrodynamic Test (DARHT) Facility Environmental Impact Statement (EIS) – the LANL Sitewide Environ-mental Impact Statement (SWEIS) and the Stockpile Stewardship and Management Program-matic Environmental Impact Statement (PEIS).

DOE is in the process of preparing the SWEIS for LANL [Notice of Intent, 60 FR 25697]; the public comment period on the scope of the SWEIS ended on June 30, 1995. The purpose of the SWEIS is to provide DOE and its stakeholders a comprehensive look at the cumulative environmental impacts of ongoing and reasonably foreseeable future operations at LANL. The SWEIS will focus on impacts of current LANL activities and activities proposed or anticipated to occur 5 to 10 years into the future. It will replace the prior SWEIS that was completed in 1979. The SWEIS will include all activities at LANL and will incorporate the results of any related environmental impact analyses in any current NEPA documents, which will be combined with impact analyses performed specifically for the SWEIS. Under current schedules, the DOE plans to issue the Record of Decision (ROD) on the DARHT EIS prior to issuing the draft SWEIS. Information on the environmental impacts of the course of action selected in the DARHT ROD will be included in the analysis of cumulative impacts for the SWEIS.

DOE gave preliminary notice of its intent to prepare the Stockpile Stewardship and Management PEIS in October 1994 [59 FR 54175]. DOE's report, The Stockpile Stewardship and Management Program: Maintaining Confidence in the Safety and Reliability of the Enduring U.S. Nuclear Weapons Stockpile, (DOE 1995), provides a framework for the issues to be considered in the PEIS. DOE started the PEIS in June 1995 [Notice of Intent, 60 FR 31291]; the public comment period on the scope of the PEIS ended August 11, 1995. The PEIS will assess the environmental impacts of alternatives for conducting the SS&M Program, will assist with decisions to identify specific capabilities and facilities for conducting the program, and will help determine the configuration (sites for facilities) of the nuclear weapons complex that would most efficiently implement the SS&M Program. The environmental impact analysis of the course of action selected in the DARHT ROD will be incorporated into the PEIS.

Proceeding with the DARHT EIS in advance of the completion of either the SWEIS or the PEIS is necessary because a decision on whether to proceed with the DOE's preferred alternative to implement DARHT, or pursue another alternative course of action, is needed as soon as possible to help ensure the continued safety and reliability of the nuclear weapons stockpile. As a matter of policy and in response to Presidential and Congressional direction, DOE will continue to maintain and improve its hydrodynamic testing capability regardless of the outcome of either the SWEIS or the PEIS. Thus, the alternatives analyzed in this DARHT EIS are not dependent on the decisions expected to flow from either the SWEIS or PEIS.

Under NEPA regulations, while work on a required program environmental impact statement is in progress, a Federal agency may not undertake in the interim any major action covered by the program unless the action:

DOE believes that any course of action selected after completion of the DARHT EIS would meet this standard. Chapter 2 of the EIS provides the technical justification for providing enhanced hydrodynamic testing capability. This conclusion has been supported by the President and Congress who have directed DOE to rely on hydrodynamic testing to ensure the safety, performance, and reliability of the stockpile in the absence of underground nuclear testing. This determination is unrelated to, and would not depend on, any other stockpile stewardship actions which may be proposed as part of the SS&M program. Under any course of action to be analyzed in the SS&M PEIS, DOE would still need to continue hydrodynamic testing and would still need to acquire enhanced radiographic capability.

Similarly, because enhanced hydrodynamic capability is needed in the near term regardless of the alternatives to be analyzed in the SS&M PEIS or the decisions that will result from the SS&M ROD, DOE believes that a decision to implement any of the alternatives analyzed in this DARHT EIS would not prejudice any ultimate decisions regarding the SS&M program. Hydrodynamic testing and dynamic experiments at LANL as an ongoing mission will continue in support of stockpile stewardship, and this fact will be one of the baseline assumptions for the SS&M PEIS. The proposal contained in the DARHT EIS would not render more or less reasonable any of the alternative courses of action to be considered in the SS&M PEIS, nor would it affect any decisions expected from the SS&M ROD. DOE believes that the DARHT EIS adequately identifies and analyzes the proposed action and the reasonable alternative means to achieve it. Therefore, DOE believes that its proposal to acquire enhanced radiographic capability meets the regulatory requirements for interim actions, and that any actions decided upon in the DARHT ROD would not be limited pending completion of the SS&M PEIS.

The DARHT project is likewise a permissible interim action pending completion of the LANL Sitewide EIS. DOE's need for enhanced radiographic capability to conduct science-based stockpile stewardship as directed by the President and Congress provides the independent justification for the project. That capability can be provided by implementing any of the alternatives analyzed in the DARHT EIS without requiring additional new facilities or changes in operation for existing facilities at LANL, since radiographic hydrotesting is an ongoing mission for LANL. Thus, deciding whether and how to provide enhanced radiographic capability will not prejudice any decisions resulting from the LANL Sitewide EIS.

2.7 REFERENCES CITED IN CHAPTER  2

DFAIC (DARHT Feasibility Assessment Independent Consultants), 1992, DARHT Feasibility Assessment Independent Consultants DFAIC Panel, Final Report, SAND92-2060, September, Sandia National Laboratories, Albuquerque, New Mexico.

DOE (U.S. Department of Energy), 1993, Report of Independent Consultants Reviewing Integrated Test Stands (ITS) Performance and Readiness of DARHT for Construction Start, DOE/DP-0119, August, Washington, D.C.

DOE (U.S. Department of Energy), 1995, The Stockpile Stewardship and Management Program: Maintaining Confidence in the Safety and Reliability of the Enduring U.S. Nuclear Weapon Stockpile, May, Washington, D.C.

Drell et al., 1995, Nuclear Testing: Summary and Conclusions, Report Number JSR-95-320, August, JASON/Mitre Corporation, McLean, Virginia.

HPAIC (Hydrotest Program Assessment Independent Consultants), 1992, Hydrotest Program Assessment, PSR Report 2320, October, Arlington, Virginia.

JASON/Mitre Corporation, 1994, Science-Based Stockpile Stewardship, Report Number JSR-94-375, November, Washington, D.C.

Johnson, K., et al., 1995, Stockpile Surveillance: Past and Future, August, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Sandia National Laboratory.

LLNL (Lawrence Livermore National Laboratory), 1994, "NIF and National Security," Energy and Technology Review, December, National Technical Information Service, Springfield, Virginia.

Miller, G.H., et al., 1987, Report to Congress on Stockpile Reliability, Weapon Remanufacture, and the Role of Nuclear Testing, UCRL-53822, October, Lawrence Livermore National Laboratory, Livermore, California.