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End Run
Simulating
Nuclear Explosions under the Comprehensive Test Ban Treaty
Top of Report
III. U.S. NUCLEAR WARHEAD DESIGN
ACTIVITIES FOR NAVAL STRATEGIC FORCES
Sandia National Laboratory vice presidents Roger
Hagengruber and Heinz Schmitt have recently confirmed that Sandia and Los
Alamos National Laboratory are engaged in the full-scale development of a
nuclear weapon design.[6] Information contained in a May
1997 Department of Defense report ("Nuclear Weapon Systems Sustainment
Programs") and the declassified February 1996 Department of Energy
'Green Book' ("Stockpile Stewardship and Management Plan")
clarifies the nature of this nuclear design work. Additional documentation
regarding the Sandia/Los Alamos design effort was recently obtained through
the FOIA by the Los Alamos Study Group in Santa Fe, N.M., and these Sandia
vu-graphs are attached as Appendix II (print report only).
This nuclear weapons design effort is conducted
within the SLBM Warhead Protection Program (SWPP), a Navy/Department of
Energy(DOE) collaboration. The SWPP was established to "maintain the
capability to jointly develop replacement nuclear warheads for the W76/Mk4
and W88/Mk5 should new warheads be needed in the future." [7] The program currently focuses
on two nuclear weapon designs: a design which re-uses plutonium pits
("Pit Re-Use Project"), for which Lawrence Livermore National
Laboratory has nuclear explosive package (NEP) design responsibility, and a
LANL "high-margin" NEP design incorporating a new pit
("Replacement Warhead Project"). Both warhead designs are
intended for the Mk5 re-entry body. The SWPP does not now encompass
production, but does include "prototyping" and flight testing.
The "Pit Re-Use Project:"
- is scheduled for Experimental and
Computational Assessment through 2000, and Certification/Prototyping
of the design through 2002; [8]
- contains "major elements of a
traditional design program, with the exception of nuclear
testing," [9]
- design and certification process includes
advancing computational models, hydrodynamic testing, and may include
flight testing of design elements;
- warhead
may incorporate a new Arming, Fuzing, and Firing (AF&F) system
based on the system now under development for the W76/Mk4 SLBM
warhead;
- warhead design is likely to be based on the
W89-Alt recycled pit warhead design (intended for the Short-Range
Attack Missile-2), which was explosively tested at least once before
underground testing ceased in September 1992. [10]
The "Warhead Replacement Project:"
- is scheduled for Conceptual Design through
1997, Experimental and Computational Assessment through 2002, and
Certification/ Prototyping through 2004; [11]
- will "include major elements of a traditional
Phase 3 design program, with the exception of nuclear testing.." [12]
- ("traditional Phase 3" refers to
the process of full-scale engineering development of a complete warhead
system);
- according to the Sandia vu-graphs, the
"Replacement Warhead is a new design that will not have UGTs
[i.e. underground tests] for certification;
- requires the new
experimental capabilities of the Stockpile Stewardship Program to
"assess and evaluate the expected nuclear performance…" [13]
The general design
criteria for the Pit Re-Use/Warhead Replacement Projects are indicated by
the following statement:
Replacement warheads reflect no new weapon requirements
but the desirable replacement characteristics include decreased sensitivity
to aging, increased design margins, increased ability for surveillance by
above-ground testing, and the ability to be certified without an underground
test (italics added). [14]
In the argot of nuclear
weapon designers, a "high-margin design" is one with an increased
design margin for achieving its intended nuclear explosive performance. An
increased primary performance design margin is usually achieved by
increasing both the amount of plutonium in the pit and the energy delivered
by the chemical high explosive. However, such changes usually decrease the
"safety margin," i.e., the margin against producing nuclear yield
in the event of an accidental one-point detonation of the high explosive
(HE).
A high-margin design
for a secondary would presumably be one that generates its nominal (or
higher) design yield over the widest possible range of primary yields. It
is not known whether a new secondary design effort is part of the Los
Alamos/Sandia high margin Replacement Warhead project, or whether an
existing secondary will be used. Given that existing warhead designs are
usually optimized to use all available space on board the re-entry vehicle
(RV), at least consideration of a new secondary design is strongly
implied by recent vu-graphs presented at a "SWPP Program Review
Meeting" in May 1997. These vu-graphs (Appendix II, print report only)
indicate that Sandia has been participating in a "trade off study with
LANL on physics package orientation [within the re-entry body (RB)] to
support orientation decision of 5/14 [i.e. May 14, 1997]."
At issue in such
discussions is the orientation of the nuclear explosive package with
respect to the tapered end of the RB -- in other words, which component --
primary or secondary -- will face the tighter volume constraints on its
design? [15] Another Sandia vu-graph,
entitled "Replacement Warhead Safety Features," indicates that
the primary for this warhead will have Insensitive High Explosive (IHE) --
a major design change, as this explosive is considerably less energetic per
unit volume than the HE it replaces. A "robust" IHE primary with
an increased performance margin would therefore likely require more space
within the RV -- hence the need to review -- and possibly reverse -- the
orientation of the NEP and consider a different secondary design from that
of the existing W88.
The Stockpile
Stewardship and Management Plan states that the new SLBM warhead design
effort will stress increased safety margins. As noted above, given the
offsetting design criterion for an increased performance margin, it will
likely involve a considerable nuclear design effort to achieve both
objectives. The same Sandia vu-graph referenced in the preceding paragraph
indicates that in addition to IHE, the new warhead will also have a Fire
Resistant Pit (FRP), and that new AF&F system and use control features
"may be implemented." Dr. Ray Kidder of LLNL estimated in December 1991 that production
of a safer new warhead design incorporating IHE to replace the W88 warhead
would require four nuclear explosive tests -- three development tests and a
production verification test. [16]
Some background on the
Navy's strategic forces may be useful in understanding the SLBM Warhead
Protection Program. Under the second Strategic Arms Reduction Treaty (START
II), the submarine leg of the U.S. strategic triad will account for about
half of all accountable, deployed warheads. Most of the Navy's strategic warheads are of the W76
design, about 3500 of which were produced between 1978 and 1987. About 400
W88 warheads were produced from 1988 to 1991; W88 production was terminated
prematurely due to the closure of the Rocky Flats plant near Denver,
Colorado. Both the W88 and W76 warheads were designed at Los Alamos
National Laboratory. The W88 is heavier and has a much higher yield (475
kilotons) than the W76 (100 kilotons). [17]
In 1990 the W88 warhead, its associated re-entry body
the Mk5, and the Trident II D5 submarine-launched ballistic missile (SLBM)
were identified as a system with the potential for accident scenarios
involving chemical explosion, the release of plutonium, and even nuclear
explosion. [18] At issue were the Reagan-era
(and earlier) decisions to forgo Insensitive High Explosives,
Fire-Resistant Pits, and Class 1.3 solid rocket fuel in the Trident II
design in order to maximize its military capability.
Several options were considered to improve the safety
characteristics of the Trident II system. However, none of the
billion-dollar plus options were judged to provide cost-effective accident
mitigation. The dominant accidental detonation scenario, the dropping of a
fully loaded missile during missile loading operations, was alleviated by a
simple change in loading procedures that provided for installation of
warheads after a missile was placed in its launch tube on board the
submarine.
The W76 warhead was the first to be subject to the
DOE Dual Revalidation Process. In March 1997 testimony before the Senate
Appropriations Committee, Livermore National Laboratory director Bruce
Tarter described Dual Revalidation:
Dual Revalidation
is a formalized peer review process, developed in consultation with the
DoD, to assess the condition of U. S. stockpiled weapons. Two teams perform
the evaluation, one with personnel from the laboratory that originally
designed the weapon and the other with experts from the second nuclear
design laboratory. Sandia participates on both teams. Each Dual
Revalidation is managed by a DoD/DOE Project Officers Group and is expected
to take two to three years to complete. [19]
Before or during the Dual Revalidation process for
the W76, an 'issue' with this warhead was encountered. The specific nature
of this problem is classified but it has been cited as evidence that the
Stockpile Stewardship and Management Plan is developing the appropriate
computational and experimental capabilities:
It has been over
four years since the last nuclear test. During that time, we have
successfully addressed an issue with the Trident I (W76) warhead by using a
combination of analysis, new experimental data, archived test and
manufacturing data, and most importantly the collective judgment of the two
weapon design laboratories.
This success,
using the experimental and testing tools available today, provides
confidence that the even more powerful computing and testing tools to be
developed will allow us to solve future stockpile problems without nuclear
testing. [20]
The Stockpile Stewardship and Management Plan
contains little unclassified information on the W76 'issue.' It states that
"traditional weapons design codes were not developed to handle this
phenomenon," and that "designers were able to resolve a real
surveillance issue through calculations which were validated by laboratory
experiments and by using archived NTS (Nevada Test Site) data." [21]
The Department of Energy has decided to implement War
Reserve plutonium pit manufacturing at Los Alamos National Laboratory. Such
capabilities are scheduled to be in place by approximately 2003. [22] The DOE plans to manufacture
a W88 pit in fiscal year 1998 as a demonstration of this capability. Los
Alamos will employ different manufacturing techniques and materials than
were used originally at Rocky Flats:
Most of these
changes in materials and processing are not expected to have a noticeable
impact on the nuclear performance of the W88 primary based on past nuclear
test experience. However, two of the proposed changes warranted further
evaluation. The use of cast plutonium material instead of wrought plutonium
and the equator welding technique. [23]
The DOE states that certification of the nuclear
performance of the Los Alamos-produced W88 pits will require the
computational and experimental capabilities of the Stockpile Stewardship
Program, in particular experiments to be performed at the Nevada Test Site.
The total pit manufacturing capacity at Los Alamos will probably range from
50-80 pits per year.
The broad Stockpile Stewardship and Management
strategy regarding the Navy's strategic warheads involves:
(1) surveillance
and annual certification of the existing W76 and W88 warheads, and
replacement of the W76 neutron generator, (tritium) gas transfer, and
AF&F systems with new-design components;
(2) the
development through 2003 of three options for the production of new Naval
strategic warheads -- manufacture by a new net shape casting method of a
small number of new W88 surveillance pit replacements to make up for those
lost in destructive testing; a Re-Used Pit option; and a New Pit option;
and
(3) possible
Full-Scale Engineering Development (FSED) of a W88/W76 replacement warhead
or warheads beginning around 2004.
There are several issues regarding these systems that
appear to be instigating the Navy to examine future SLBM warhead options:
the prospect of W76 aging and the possibility of a crippling
"common-mode" failure in that weapon; lingering W88 (and W76)
safety concerns; and issues of remanufacture and weapon certification
without recourse to underground testing. Of more than passing significance
is the fact that one of the Navy strategic warhead replacement options
includes not only all new non-nuclear components but a new-pit primary (and
possibly secondary) with "increased design margins" -- hence this
option constitutes a new nuclear weapon design -- albeit for the
apparent primary purpose of achieving increased confidence in nuclear
weapons performance rather than increased military effectiveness or novel
military applications. But the latter attributes can also be achieved by non-nuclear
modifications to other aspects of the nuclear weapon system, such as
missile guidance upgrades and "repackaging" for new, more
demanding weapon delivery configurations.
Hence any "new" nuclear weapon design --
despite disclaimers of any radical new design objectives -- will have to
meet the military characteristics (MCs) and Stockpile-to-Target (STS)
performance requirements needed to realize new or improved military
capabilities for the overall system. In this sense, increased confidence in
the performance of the nuclear explosive package represents a significant
contribution to the overall improvement in military capability, and thus
warheads developed for this purpose are not only "new" in the
literal sense, but also represent a potential for new or improved nuclear
military capability, contrary to the "vertical"
nonproliferation objective of the CTB.
Notes
6. "U.S. Labs Redesigning
Nuclear Warheads," The Washington Times, July 23, 1997, p. A9.
"Labs Craft Warhead Backup," Albuquerque Journal, July 23,
1997, p. A1. "National Labs Working on Warhead Replacement," Albuquerque
Tribune, July 23, 1997, p. A10.
7. "Nuclear Weapon Systems
Sustainment Programs," Office of the Secretary of Defense, May 1997,
p. 18 (this document can be accessed on the World Wide Web at http://www.dtic.mil/defenselink/pubs/dswa/index.html#cover').
8. "Stockpile Stewardship and
Management Plan," U.S. Department of Energy, Office of Defense
Programs, February 29, 1996, p. IV-3. Note that this schedule is identified
in Figure IV-1 as for the Proposed Budget for FY97.
9. "Stockpile Stewardship and
Management Plan," p. IV-15.
10. The possible use of the W-89
recycled pit design as a safer replacement for theW88 was noted in 1991 by
Dr. Ray Kidder of Livermore, although he also noted that a total of four
tests would be required to replace the W88 with the recycle pit version of
the W-89, of which only 1-2 were conducted prior to the moratorium. See Assessment
of the Safety of U.S. Nuclear Weapons and Related Nuclear Test
Requirements: A Post-Bush Initiative Update, UCRL-LR-109503, Dec. 10,
1991, p.4-6.
11. "Stockpile Stewardship and
Management Plan," p. IV-3. Note that this schedule is identified in
Figure IV-1 as for the Proposed Budget for FY97. The "Gantt Chart for
Replacement Warhead Project (19 June 1997)" is given in Appendix II
(print report only). There it is indicated that Design, Certification, and
Testing of the Replacement Warhead will continue through 2003.
12. "Stockpile Stewardship and
Management Plan," p. IV-16.
13. "Stockpile Stewardship and
Management Plan," p. IV-16.
14. "Nuclear Weapon Systems
Sustainment Programs," p. 18. This statement is given also in the
"Stockpile Stewardship and Management Plan," p. II-10.
15. For example, according to Roger
Baleras, the location of the secondary toward the front of a French SLBM
reentry body, with the primary at the rear, left a small space around the
secondary that posed "a special problem for the design." See
"A Report on Discussions Regarding the Need For Nuclear Test Explosions
to Maintain French Weapons Under a Comprehensive Test Ban, Paris France,
Nov. 2-7, 1994, FAS/NRDC, Washington D.C., January 1995, page 14.
16. R. Kidder, Assessment of the
Safety of U.S. Nuclear Weapons, p. 4.
17. "U.S. Nuclear Stockpile,
July 1997," NRDC Nuclear Notebook, The Bulletin of the Atomic
Scientists, July/August 1997, pp. 62-63.
18. "Nuclear Weapons
Safety," Report of the Panel on Nuclear Weapons Safety of the
Committee on Armed Services, House of Representatives, December 1990.
19. Prepared Statement of C. Bruce
Tarter, Director, University of California, Lawrence Livermore National
Laboratory, The Department of Energy's Budget Request for FY 1998 before
the House Committee on National Security, Subcommittee on Military
Procurement, April 10, 1997.
20. Testimony of Victor Reis,
Assistant Secretary for Defense Programs, U.S. Department of Energy, House
National Security Committee, Military Personnel, FY98 Budget, Nuclear
Weapons, April 10, 1997.
21. "Stockpile Stewardship and
Management Plan," pp. C-1 to C-3.
22. "Stockpile Stewardship and
Management Programmatic Environmental Impact Statement," U.S.
Department of Energy, September 1996, Volume I, p. 3-105.
23. "Stockpile Stewardship and
Management Plan," p. II-8.
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