The remote New Mexico laboratory has designed the majority of weapons in the past and present nuclear stockpile.
Los Alamos National Laboratory, which unfolds from the base of New Mexico’s Jemez Mountains eastward across narrow mesas and rugged canyons to the Rio Grande, is one of the largest national laboratories in the United States, both in terms of number of employees and physical footprint. More than 16,000 people work across its sprawling 40-square-mile campus, in satellite offices in nearby Santa Fe, or remotely (approximately 11 percent of the workforce is part of the telework program that launched during the COVID-19 pandemic).
Although the Laboratory excels at all types of science, technology, and engineering research and development, Los Alamos is at its core a nuclear weapons laboratory; its primary mission, backed by an unprecedented $4.6 billion budget in fiscal year 2023, is to help the United States maintain a robust and credible nuclear deterrent.
“That’s our responsibility to the nation,” explains Bob Webster, deputy Laboratory director for Weapons at Los Alamos. “The United States relies on nuclear deterrence to provide defense of our homeland and our allies. Our job as a national nuclear security laboratory is to make sure the nuclear deterrent is safe, secure, and effective—now and into the future.”
The Early Days
Los Alamos was founded in January 1943 as “Project Y” of the Manhattan Project—the U.S. government’s top-secret effort to build the world’s first atomic bombs to help end World War II.
A top-secret effort requires a top-secret location, so a remote mesa in northern New Mexico was deemed appropriate by the few government officials who knew about the project. Scientists, engineers, and their families came from across the world to the hastily erected “secret city,” which was enclosed by a barbed-wire fence and guarded by Army soldiers. The new residents endured shoddy government housing, censored mail, and unpaved roads but also enjoyed raucous parties, adventures in the surrounding mountains, and day trips to Santa Fe (where P.O. Box 1663 was their official mailing address).
Twenty-eight months later, they had designed and built the Gadget—the world’s first nuclear device, which was detonated at the Trinity site in southern New Mexico on July 16, 1945. Just a few weeks later, they provided the Little Boy and Fat Man bombs to the military. The weapons were dropped on Hiroshima and Nagasaki, respectively, in August 1945. World War II came to an end, but the Atomic Age had just begun.
The Cold War Years
On the heels of World War II came the Cold War, which saw both the United States and the Soviet Union designing, testing, and producing nuclear weapons at an increasingly rapid pace. At its height in 1967, the U.S. stockpile contained 26 types of weapons for a total of 31,255 weapons. “At this time, most Americans feared the Soviet Union and supported having a big stockpile with a diverse array of nuclear weapons,” says Los Alamos senior historian Alan Carr. “People realized how valuable these weapons were in deterring Soviet aggression.”
Carr notes that the Cold War solidified the Laboratory’s future as a nuclear weapons laboratory. “Project Y was now Los Alamos Scientific Laboratory, and its mission was to refine the weapons developed during World War II, as well as develop entirely new weapons designs,” he explains. Those designs ranged from the W54, the 1950s-era warhead that could be carried by an individual, to the W53 thermonuclear warhead, which weighed more than four tons and topped Titan II missiles from 1962 to 1987.
Of course, not every Los Alamos weapons design made it into the stockpile. Many nuclear devices were tested (106 in the Pacific Marshall Islands, 928 at the Nevada Test Site, and 20 in other locations) to gauge their potential. These tests, which occurred in the atmosphere, underwater, or underground, provided data on the many complex aspects of a nuclear detonation that occur simultaneously on a nanosecond time scale. These data allowed scientists to better understand nuclear explosion characteristics and evolve their designs accordingly.
Los Alamos Today
The United States has not fielded a newly designed nuclear weapon since 1991 and has not conducted a full-scale test of a nuclear weapon since 1992. These decisions are influenced by national policy and reinforced by treaties, such as New START, which caps the number of nuclear weapons in the U.S. stockpile, and the Comprehensive Nuclear-Test-Ban Treaty, which prohibits all nuclear testing.
Over many decades, the U.S. stockpile has become smaller (with fewer weapons—3,750 as of September 2020) and less diverse (with fewer types of weapons systems). Today, seven types of weapons systems are in the stockpile. Some of these systems include variants—different models that have been updated to be safer or to meet changing military requirements.
Los Alamos designed and is responsible for four of these weapons systems: the B61 bomb and the W76, W78, and W88 warheads. Lawrence Livermore National Laboratory is responsible for the other three systems: the B83 bomb, and the W80 and W87 warheads.
On average, the weapons for which Los Alamos is responsible are older than most people who work at the Laboratory. All but a handful of these weapons are significantly older than the oldest weapon tested during the nuclear testing era, and all weapons contain components that are older than the oldest components tested during a nuclear test. “Thus, every modern-day assessment of our weapons involves extrapolation,” Webster says. “Confidence in these extrapolations demands world-class science, technology, and engineering, as well as cutting-edge experimental and computational capabilities.” This approach is called stockpile stewardship.
Through stockpile stewardship, Los Alamos works in conjunction with other labs, plants, and sites across the nuclear enterprise to assess and ensure the safety, security, and effectiveness of the B61, W76, W78, and W88.
Each weapon requires surveillance (a thorough physical examination of a representative sample weapon that starts at the Pantex Plant and continues at other sites) and routine maintenance. If at any time Los Alamos becomes concerned about the health of a weapon, the weapon may be retired, or in some cases, refurbished via a life extension, alteration, or modification, each of which provides various degrees of updates that enable the United States to maintain a credible nuclear deterrent without producing new weapons or conducting underground nuclear tests.
Each September, Los Alamos’ assessments of its weapons systems culminate in a letter from the Lab director to the secretary of energy, the secretary of defense, and the chair of the Nuclear Weapons Council. This letter informs the president of the United States of the director’s confidence that the B61, W76, W78, and W88 are safe, secure, and effective as a result of sustainment and modernization efforts.
Stockpile Stewardship Tools
The success of stockpile stewardship at Los Alamos—the continued assessment and maintenance of the B61, W76, W78, and W88—is largely due to the development of the tools and infrastructure required to understand what happens to weapons materials and components as they age. Investments in scientific, experimental, engineering, and computational capabilities at Los Alamos allow the Laboratory to confidently extend the service lives of the nation’s nuclear weapons without full-scale underground testing.
“We are entering an unprecedented and exciting transformation of the Laboratory campus,” says David Teter, associate Laboratory director for Infrastructure and Capital Projects. “We are investing approximately $1 billion per year for the next five to ten years to modernize the infrastructure required to deliver on stockpile stewardship now and into the future.”
Perhaps more than any other capability, high-performance computing has facilitated the success of stockpile stewardship. Many modern weapons experiments generate enormous amounts of data that can be used in or compared against computer calculations so that scientists and engineers can make informed decisions about the nation’s deterrent.
To manage all this information, the Lab maintains world-class modeling, simulation, and visualization capabilities, including some of the world’s most powerful supercomputers. Currently, the Trinity supercomputer enables large-scale data analysis and visualization capabilities that help scientists test their hypotheses and solutions. In 2023, the Lab will activate two new supercomputers, Crossroads and Venado, which will advance Los Alamos’ ability to study the most complex physical systems for science and national security.
Data that is compared against supercomputer simulations is generated at facilities such as the Laboratory’s Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility. Each axis of the building contains an accelerator that’s used to produce radiographs (high-powered x-ray images) of a mock nuclear device as it detonates inside a spherical confinement vessel. During these types of detonations, the device implodes at speeds greater than 2.5 miles per second, and the radiographs allow scientists to “see” the movement of materials.
Like DARHT, the Lab’s proton radiography (pRad) facility at the Los Alamos Neutron Science Center also images internal characteristics of explosions. Here, a high-energy proton beam is captured on video as it probes a range of materials under extreme pressures, strains, and strain rates.
Los Alamos scientists also obtain data at the Laboratory’s many high-explosive laboratories and firing sites. The experimental work carried out at these places provides scientists and engineers with important information on aging explosives, as well as new and safer explosive formulas.
The Laboratory’s 233,000-square-foot Plutonium Facility is the only fully operational plutonium science and manufacturing facility in the nation. Here, researchers can safely investigate the material properties of plutonium as well as other radioactive elements. In 2009, Los Alamos was named the nation’s Plutonium Center of Excellence for Research and Development by the National Nuclear Security Administration (NNSA).
Finally, the Lab’s Sigma facility supports prototype fabrication, materials research, and research and development in metallurgy and ceramics—all of which can be applied to a variety of weapons activities.
Los Alamos Director Thom Mason says these facilities—most of which are in the process of being updated—are perhaps more essential now than at any time since the height of the Cold War. “The importance of our mission at Los Alamos has been really highlighted with the geopolitical tensions we see around the world,” he says. “With our state-of-the-art tools and infrastructure, our people are helping ensure the reliability of the deterrent that serves as the ultimate guarantor of our security.”
Los Alamos’ large and relatively remote campus enables quite a bit of on-site explosives and experimental work, but projects requiring nuclear materials or significant amounts of high explosives are conducted at the even larger and more remote Nevada National Security Site (NNSS). The Laboratory maintains full-time employees at NNSS to facilitate this work and collaborates closely with NNSS employees.
For example, Los Alamos is leading the Advanced Sources and Detectors (ASD) Project at NNSS. The project, also known as Scorpius, is a 125-meter-long linear induction accelerator that will be installed in an underground laboratory. The device will allow scientists to take multiple images of subcritical experiments—contained experiments that incorporate nuclear materials but are configured so no self-sustaining nuclear fission reaction occurs.
“Scorpius will give us an unprecedented level of detail about the behavior of our current and future stockpile,” says ASD senior director Mike Furlanetto. “That detail will allow us to certify that the stockpile will remain safe, secure, and effective without needing to return to nuclear testing.”
Scheduled to be operational by 2030, the accelerator represents a partnership among Los Alamos, Lawrence Livermore, and Sandia national laboratories, which are each responsible for different parts of the machine.
Los Alamos also partners with Livermore, Sandia, and other institutions to run experiments at their facilities, such as Livermore’s National Ignition Facility and Sandia’s Z Machine. Likewise, researchers from other institutions perform experiments at Los Alamos facilities.
Although Los Alamos is primarily a research and development institution, the Laboratory has always done some manufacturing of nuclear and nonnuclear weapons components. Two of those components are plutonium pits and detonators.
A plutonium pit is the core of a nuclear weapon—a compressed pit generates nuclear energy. Los Alamos produced the first plutonium pits in 1945 and has conducted limited pit production over the years. But from 1952 to 1989, the majority of plutonium pits for U.S. nuclear weapons were manufactured at the now-defunct Rocky Flats Plant near Denver, Colorado.
These pits are now at least 34 years old, and research is continually being done to understand how their age might affect their performance. “As plutonium ages, it undergoes changes, and decay impurities build up—both of which could impact the way the pit works,” explains David Gubernatis, deputy division leader in the Pit Technologies Division at Los Alamos. To assuage any concerns, NNSA has tasked Los Alamos with developing a pit production program to replace all aging pits in the stockpile. Another facility, the Savannah River Site, has also been tasked with producing pits.
Pit production will not require new plutonium but rather salvaged plutonium from existing pits that are not in use. “Plutonium is very recyclable,” Gubernatis says. “What we’re doing is removing aged plutonium from old pits, then reprocessing that plutonium into new pits.”
Los Alamos is currently developing the processes for manufacturing pits for the Lawrence Livermore–designed W87 warhead. In 2022 and into 2023, the Lab has manufactured many development pits, which are pits that are not meant to go into weapons but are part of the research and development phase of the pit mission.
“Los Alamos’ workforce demonstrated its technical and operational leadership to the nation through producing development pits over the past few years,” says David Dooley, senior director of the Defense Programs Office. “We’ve solved technical challenges, enhanced expertise, and improved disciplined operations. We’re pleased with our progress and successes that will support our continued efforts in the pit mission.”
Eventually, Los Alamos will produce “war-reserve” pits that meet all design, manufacturing, and quality requirements. These pits will be shipped to Pantex, where they will be placed inside stockpiled weapons.
For a plutonium pit to implode inside a nuclear weapon, the pit must be compressed uniformly by the high explosives that surround it. The high explosives are triggered by small devices called detonators. Since 1989, detonators for all nuclear weapons in the U.S. stockpile have been manufactured by Los Alamos.
“Detonator production is key to the Los Alamos mission and the nation’s nuclear deterrent,” says Patrick Garcia, senior director of the Lab’s Non-Nuclear Production Office. “The unique skills of our engineers, technicians, and inspectors are implemented every day to reliably and repeatedly produce, package, and ship detonators with their accompanying cable assemblies. The team continues to grow to be in position to meet current and future needs of the nation’s nuclear stockpile.”
Over many decades, detonators have evolved to be smaller and safer. Los Alamos is currently advancing optical detonators for stockpiled weapons. Optical detonators are initiated by lasers (as opposed to electrical power) and thus are less likely to inadvertently detonate. The Lab’s Detonator Production division is also exploring new capabilities, such as additively manufacturing (similar to 3D printing) detonator components. “Utilizing additive manufacturing capabilities will continue the progression of detonator manufacturing technology,” Garcia says. “We are now working on the foundation for additive manufacturing of detonators with the objective that they meet the same level of technical and quality standards of our current detonators—able to perform their function in a qualified and certified weapon system.”
Looking Forward: The W93
“The overarching purpose of the Los Alamos weapons program is to ensure the current and future effectiveness of the United States’ nuclear deterrent,” Webster explains. “We must lead the nation in evaluating, developing, and ensuring effectiveness of our nuclear deterrent, including in design, production, and certification of current and future nuclear weapons.”
One potential future weapon is the W93 warhead, which would be deployed on both Ohio- and Columbia-class submarines beginning in the 2030s. As the warhead’s lead physics design agency—the organization responsible for the design and certification of the nuclear warhead package and some of the nonnuclear components—Los Alamos must determine if the W93’s proposed military requirements are technically feasible. If a design moves forward, the W93’s nuclear components will likely be based on currently deployed and previously tested weapons. However, the W93 would incorporate modern technologies that improve safety, security, and flexibility to address future threats.
“At any moment in time, the nation’s nuclear deterrent must be fit-for-purpose,” Webster continues. “In a changing world, we must be prepared for any situation. Since the 1940s, Los Alamos has risen to that challenge, and we will continue to guarantee the value of the nuclear deterrent today and into the future.” ★