10/20/93
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STANFORD -- As the threat of nuclear war recedes, the American public will demand safer weapons, and this has important implications for the Trident submarine-launched ballistic missiles and their nuclear warheads, says John R. Harvey, a physicist who directs the science program at the Stanford Center for International Security and Arms Control.
"Simply put, five years ago, at the height of the Cold War, the Trident program would have survived the negative political impact of a major accident; today, it very likely would not," write Harvey and Stefan Michalowski, a recent science fellow at the center, in a new report on Trident safety and ways to improve it.
Taking the Trident system out of service is not a viable option, Harvey said. The United States will scale back nuclear weaponry, but the submarine-launched Trident C-4 and D-5 missiles should be kept as the only element of U.S. strategic forces on day-to-day alert that could survive an unexpected attack from post-Soviet nuclear forces.
"Although the threat of an attack has certainly declined in recent years, those forces still have the ability to destroy the United States," Harvey said.
Harvey and Michalowski recommend accelerated development programs for one or both Trident warheads in order to test new designs before a potential ban on nuclear tests as early as 1996. (Currently the United States has a unilateral ban on nuclear testing, and President Clinton is considering whether to ask Congress to approve resumption of testing as a result of a recent test by China.) An accelerated program could result in increased spending on nuclear weapons research and development over the next three years, the researchers say.
Questions about Trident's safety, long debated within the Departments of Energy and Defense, first became public in 1990 in news media reports and the report of the House Armed Services Committee panel on nuclear weapon safety, chaired by Stanford physicist Sidney Drell. The Drell panel said Congress and the President needed a better quantification of Trident's safety risks and of the economic and security costs of a system redesign for enhanced safety. The new Stanford report addresses several of these issues.
Safety concerns arise, Harvey said, from the proximity of conventional high explosives, detonable solid propellant and plutonium in both the Trident C-4 and D-5 missiles. Toxic plutonium could be released into the atmosphere over a large urban area as a result of an accident or sabotage that caused an explosion or fire in the missile propellant.
"The C-4 and D-5 systems were developed in response to stringent military requirements imposed at the height of the Cold War. Decisions were made to maximize capability and survivability at some arguably increased safety risk," Harvey said. "These trade-offs would have been made differently if national security needs in the post-Cold War era could have been anticipated."
Specifically, Trident system designers were required to come up with a missile that could destroy Soviet missile silos and underground command centers from a submarine that could patrol in ocean areas far from Soviet territory. This required more powerful and heavier warheads, and a missile with a range of at least 4,100 nautical miles, Harvey said.
"Because the submarine was already designed," he said, "they had to find a way to increase the payload of a missile that could fit within the fixed volume of a Trident submarine launch tube."
The result was "an unusual feature in which the third stage projects through the central region of the post-boost vehicle," he said, placing the warhead's plutonium and sensitive high explosive very close to the third stage's highly energetic (Class 1.1) solid propellant, which is detonable.
Harvey and Michalowski estimated the latent cancer fatalities that might result from an accident that released 10 kilograms of plutonium at either of the Trident bases at Silverdale, Wash. (near Seattle), and Kings Bay, Ga. (near Jacksonville, Fla.).
Depending on a variety of assumptions, they estimate 20 to 3,000 additional latent cancer fatalities over the following 30 years. This compares to about 750 latent cancer deaths over the same time period and geography from naturally occurring radiation.
While the cancer consequences of an accident are not large compared with other causes of cancer, they concluded, ground cleanup costs, including associated litigation and decreased property values, could be very high.
"If an urban area were contaminated, these costs could be in the billions of dollars," they write. "Most importantly, public reaction to a nuclear weapons accident of this magnitude would be overwhelming. It would destroy confidence that nuclear operations, viewed by many as a necessary evil, were being undertaken with public safety foremost in mind. The resulting outcry could lead to termination of the Trident program."
Harvey and Michalowski recommend the government begin development of safer warheads with an eye to completing testing in 1996. "If warhead development cannot be completed by 1996 through an accelerated program or otherwise, then the President should press to maintain an option to conduct some nuclear tests after 1996."
It also may be necessary to produce new plutonium parts, they say, in which case, the Rocky Flats, Colo., plant, currently shut down for environmental cleanup, would need to be repaired and restarted or some other fabrication facility developed.
The START II treaty, calling for deep cuts in the number of nuclear warheads, will likely result in the removal of four of the eight warheads on each Trident missile, the researchers say, which makes safety-related changes even more attractive. "Safety-related fixes could be added with no net gain in weight and, hence, no loss in missile range," Harvey said.
Studying seven modification options, the researchers concluded that redesigned warheads would somewhat reduce the U.S. capacity to destroy hard targets. "Given the impressive accuracy of D-5, however, the decrease will be small" - in the range of 10 to 20 percent. "Besides, with the end of the Cold War, a requirement to hold such targets at risk is now less pressing," Harvey said.
Without access to classified data, the researchers said they could not conclusively pick one option as the best but suggested the Navy and Department of Energy focus on changing to high explosives less sensitive to detonation in the C-4 and D-5 warheads, removing some of the eight re-entry vehicles on each C-4 and D-5 missile, and either modifying their third stages to use non-detonable propellant or eliminating their third stages altogether.
The researchers also calculated how enhanced safety might reduce the ocean operating area of Trident submarines. Larger patrol areas enhance the submarine's survivability from attack. They found that changing to a safer Class 1.3 propellant for the missile's third stage would reduce the submarine's patrol area by 8 to 13 percent by reducing the missiles' range. However, by removing one of the eight re-entry vehicles on a C-4 or D-5 missile, all the lost missile range could be recovered. If the third stage were eliminated instead, range could be recovered by removing three re-entry vehicles on the D-5 and five on the C-4.
The estimated cost of the options studied ranged from $1.8 billion to $5 billion, and schedule delays range from two to five years, they said. They also suggested "rigorous outside peer review by impartial experts" of any development program.
The study was funded as part of the science program at the Center for International Security and Arms Control, which is funded by the Carnegie Corp. of New York.
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