Nuclear Testing in Tanks:
Subcritical Nuclear Tests Resume at Los Alamos
Tests May Help Certify New Trident Warhead
Greg Mello & Andy Lichterman
Above Ground Contained Plutonium Explosive Tests
Resume at U.S. Weapons Lab
Sometime in the last few months, Los Alamos National Laboratory in
New Mexico restarted a clandestine program of above ground subcritical
implosions of nuclear weapons primaries, code-named "Appaloosa." These
plutonium implosions are conducted above ground at Los Alamos in special
steel tanks six feet in diameter. The $40,000, two-inch-thick
tanks, manufactured from a special steel developed by the Navy for
submarines and ship armor, are deformed by the explosion and are used
just once. The tests use high-speed flash radiography to accurately
measure the size, shape, and density of the imploding pit.
Traditional implosion hydrotests -- so called because the imploding
metal is liquefied by explosive-driven shock -- use a mock pit made
from depleted uranium or other metal. These tests, by contrast,
use real plutonium, and so they are able to test not just the exact
shape and size, but the precise surface finish, the same welding and
joining processes, and all the exact metallurgical properties, both
static and dynamic, of the pit in a real weapon. This exact
simulation is possible because pits for the Appaloosa program can
be manufactured using a specially-prepared isotope, Pu-242 (code-name:
"Cider") which has a bare alpha-phase critical mass of 100 kilograms,
ten times that of Pu-239. After the shot, the Pu-242 can be
recovered and purified. It is virtually identical to Pu-239
in every other way.
This means that an exact copy of a nuclear weapon plutonium pit or
"trigger" can be fabricated from Pu-242 and imploded without a nuclear
explosion, allowing both extensive testing of actual pit designs and
collection of data for use in further nuclear weapons simulations.
Laboratory spokespersons have said that the test program now
beginning will use only Pu-242, and not Pu-239. Sub-scale Pu-239
vessel implosions have also, however, been done at Los Alamos. Once
an accurate physical history of the implosion is measured, the attendant
nuclear processes can be modeled and the yield of the primary predicted.
U.S. Weapons Laboratories Continue to Expand Their
Capability for Nuclear Weapons Hydrodynamic Testing
The size of the U.S. stockpile of Pu-242 is not publically known
with any accuracy, but it is growing. The processing of irradiated
Mark 42 targets at the Savannah River Department of Energy plant to
prepare Pu-242 is funded at $4.2 million this year. Pu-242,
together with flash radiography that is capable of producing precision
high-speed images of the inner contours of an imploding pit -- called
"core-punching" -- gives weapons designers the ability to precisely
test full-scale implosions of exact copies of nuclear weapons.
The United States has two powerful flash X-ray facilities operational
at the present time, one at Los Alamos and one at Livermore. A
third, the Dual Axis Radiographic Hydrodynamic Test facility, (DARHT)
is scheduled to come begin experiments with its first axis this summer
at Los Alamos. Both Los Alamos facilities can perform contained
Pu-242 tests. All three facilities can take multiple exposures
of a single implosion.
DARHT is expected to have a completed second axis by the end of 2002,
barring further schedule delays, enabling precision radiography from
two directions. Tens of millions of dollars have already been
spent on design of a fourth facility, the so-called Advanced Hydrotest
Facility (AHF), which is expected to have several diagnostic axes
when it comes on line near the end of the first decade of the next
century, at an expected cost of anywhere from $400 million to $1 billion.
Secrecy Still the Rule for Key U.S. Nuclear Weapons
Overall, the history of the U.S. Appaloosa program is shrouded in
secrecy. It is not known how many explosions have been conducted,
what the size of the explosions has been, how many of those explosions
involved the special Pu-242 isotope, or what the purposes of the experiments
have been. We believe the program was idle, but for one test,
during the 1982-1992 period, if not until last year.
Even so, the restart of these subcritical tests has been expected.
When lab watchdog groups (including the Los Alamos Study Group)
sued for an environmental review of the DARHT in 1994, we received
an admission that DARHT hydrotesting would include plutonium hydrotests
in vessels. The impact analysis subsequently produced for these
tests was classified. Any mention of the Pu-242 isotope was
itself classified until January of this year.
According to the Albuquerque Journal, the classification barrier
was maintained by the DOE Office of Nonproliferation. DOE Defense
Programs saw no need to keep "Cider" a secret, since the properties
of Pu-242 and the fact that it was being produced were already well
known. The classification thus did not arise from technical
proliferation concerns, but from politics. DOE may have feared
that any announcement that the U.S. could conduct very useful full-scale
nuclear weapons pit tests without technically violating the CTBT would
cause international political fallout, adding to the serious repercussions
that its underground subcritical tests (called "UGTs" at Los Alamos)
have already occasioned.
News of the tests began to leak out on November 17, 1998, when the
Defense Nuclear Facilities Safety Board (DNFSB) raised safety questions
regarding the start-up of an unspecified "classified activity" at
Los Alamos National Laboratory (LANL). The December 17, 1998
response from Dr. Victor Reis, Assistant Secretary of Energy for Defense
Programs, was likewise classified except for its cover letter, which
was provided to the Los Alamos Study Group in response to a Freedom
of Information Act (FOIA) request. Reis' letter made it clear
that the "classified activity" was in fact plutonium explosions in
vessels, as subsequent admissions from DOE and LANL officials confirmed,
together with the fact that Pu-242 was being used in the tests.
The Appaloosa tests, especially in the context of other ongoing experimental
efforts, raise several questions. First, what exactly are they for?
One plausible purpose is to help certify new pit production process
at Los Alamos. It is doubtful, however, that these tests are
strictly needed for this purpose. A certain second purpose is
to certify new warheads.
According to documents obtained by the Los Alamos Study Group using
the FOIA process, LANL has a 2003 deadline for certification of a
new warhead for the Navy's Trident D-5 (Trident II) ballistic missile.
It is the first admittedly "new" warhead expected to be certified
in the U.S. without nuclear explosive testing. The Lawrence
Livermore National Laboratory in California also is working on a warhead
design for this missile, which will use existing plutonium pits. By
contrast, the Los Alamos design, if selected, would require a manufacturing
campaign that could involve up to nearly 3,000 plutonium pits, assuming
no changes in the current floor imposed by the U.S. Congress on nuclear
weapons stockpile size. The Los Alamos design is to be certified
over a three-year campaign of hydrodynamic testing, which reportedly
began last year.
Los Alamos has also recently begun two other series of experiments
on dynamically shocked plutonium. In one series, the so-called
plutonium "mini-flyer" experiments, a laser is used to accelerate
a metal plate that strikes plutonium at speeds of circa 350 meters/second.
These experiments can be conducted on a one-day turnaround basis,
giving very rapid data acquisition. A second series of tests
are being done at Los Alamos' high-speed plutonium "gas gun," apparently
using coupons cut from newly-manufactured pits.
In addition to these three series of tests, the underground subcritical
tests at Nevada -- the most recent of which reportedly involved two
halves of a newly-manufactured pit for the modern W-88 missile warhead
made at Los Alamos -- are slated to continue for the foreseeable future.
These four categories of dynamic experiments - underground subcriticals
using weapons-grade plutonium; above-ground subcritical Pu-242 tests;
miniature, rapidly repeatable mini-flyer experiments, and gas-gun
experiments - along with a wide battery of static laboratory tests,
add to a more than a half-century of experimental data on pit performance
and plutonium metallurgy. Together, they comprise a highly advanced
and redundant suite of techniques that appears to go far beyond what
is required to maintain existing nuclear weapons.
These activities raise a number of questions:
- What is the best way to track contained vessel tests?
- What countries are conducting tests of this kind?
- How can it be assured that tests deemed subcritical have no nuclear
- Are these tests necessary for any purpose consistent with effective
nonproliferation and test ban regimes?
- What is the significance of an increasingly sophisticated array
of nuclear weapons component testing and simulation facilities and
techniques for the Nonproliferation Treaty Article VI commitment
by the nuclear weapons states "to pursue negotiations in good faith
on effective measures relating to cessation of the nuclear arms
race at an early date and to nuclear disarmament...?"
In a climate where tensions among the nuclear weapons states are rising,
it is time to scrutinize closely the activities the nuclear weapons
states claim they need to maintain their arsenals, before today's virtual
arms race once more turns real.
- The United States is resuming a program of above ground plutonium
explosive testing in containment vessels at the Los Alamos National
Laboratory in New Mexico. These tests will use Pu-242, a plutonium
isotope with a higher critical mass than weapons grade plutonium.
This will enable nuclear warhead designers to test devices
which closely resemble full scale nuclear weapon primaries, the
first stage of a thermonuclear warheads.
- Although the U.S. Government is no longer conducting underground
nuclear tests, it is pressing forward with a vigorous program of
nuclear weapons component testing and simulation. This program,
known as the "Stockpile Stewardship and Management" Program, will
cost more than $45 billion over the next decade, and will include
the construction of several new nuclear weapons component testing
and simulation facilities.
For additional information go to: Stockpile
Stewardship & Management.
- A key part of this program is so-called "subcritical" tests in
which fissile materials, usually plutonium, are explosively tested.
This allows further knowledge about the functioning of nuclear
weapons components to be gained. Subcritical tests, because
their energy yield is small and because they are conducted at sites
where a variety of other nuclear tests can occur, make verification
of a comprehensive test ban more difficult.
For additional information go to: Subcritical
Testing and Test Ban Verification.
- Together with an extensive array of other methods for conducting
plutonium tests, these above-ground plutonium 242 tests give the
United States an ability to test nuclear weapons components and
designs far beyond that required to maintain the existing arsenal
in a safe and reliable condition, and may increase the ability of
the U.S. to deploy new nuclear weapons designs.
Los Alamos hopes to be able to certify a new design for submarine-launched
warheads by 2003, using these and other testing programs.
Sources on Pu-242 Testing at Los Alamos
- Letter, John T. Conway, Chairman,
Defense Nuclear Facilities Safety Board, to Victor Reis, Assistant
Secretary for Defense Programs, U.S. Department of Energy, November
- Letter, Victor Reis, Assistant
Secretary for Defense Programs, U.S. Department of Energy to John
T. Conway, Chairman, Defense Nuclear Facilities Safety Board, December
- Los Alamos National Laboratory, Memorandum, N.R. Borch to J.
Boettner, "History of Selection of HSLA-100 for Confinement Vessels,"
July 23, 1996.
- Los Alamos National Laboratory, Diagram, "Single
Axis HSLA-100 Vessel Assembly."
- Los Alamos National Laboratory, "Conceptual Design Plan: Contained
Explosives Test Complex," 1995.
- Nuclear Weapons and Materials Monitor, "Los
Alamos to Use Pu-242 in Explosives Tests at DARHT," February
1, 1999, pp. 3-4.
- Ian Hoffman, "Lab Critics: Tests
will Mock Nuke Blasts," Albuquerque Journal, January
14, 1999, p. 1.
- John Fleck, "LANL Mum on Plan to
Detonate Plutonium,"Albuquerque Journal, May 28, 1996,
- Seymour Sack, Laboratory Associate, Lawrence Livermore National
Laboratory, "DAHRT Considerations," 1992.