Dear friends,


To provide some further context for the information sent by Los Alamos

Study Group and Greenpeace on the B-61 Mod. 11, here is an update of an

earlier version of PSR's "Issue Brief: Unresolved New Nuclear Weapons

Development Issues," which analyzes the relationship between warhead

modifications the CTBT and necessary changes in U.S. policy.


D. Kimball





February 2, 1997

(e-mail version)


Daryl Kimball, Director of Security Programs, Physicians for

Social Responsibility*

* Thanks to Greg Mello from the Los Alamos Study group for

extensive comments and suggestions and to Tom Collina of the

Union of Concerned Scientists for his input.






The end of the Cold War has vastly reduced the impetus for

qualitative improvements in the nuclear weapons arsenals of the

declared nuclear weapons states. However, legal and political

barriers to the development and deployment of nuclear weapons of

new design or the development and deployment of modified versions

of existing nuclear weapons are not yet well established. These

barriers to new weapons development are vulnerable to an

ambiguous and often contradictory set of government policies,

public statements, and long-range programs.


While the recently signed Comprehensive Test Ban Treaty (CTBT)

will create a considerable technical and political barrier to the

development and deployment of new and advanced nuclear weapons,

it will not permanently guarantee that new or modified nuclear

weapons cannot or will not be developed and deployed. In

addition, it is important that the nuclear weapons laboratories

do not pursue stockpile maintenance programs that modify existing

warhead designs, an action which could degrade confidence in

expected performance of modified warheads and could therefore

create pressure to resume nuclear testing.


United States and international security would be strengthened if

President Clinton and his advisors would "no new nuclear weapons

policy" that clearly establishes that:


1) the U.S. will not pursue the development of new types of

nuclear weapons or new military capabilities for existing



2) that all activities of the "science-based stockpile

stewardship" program related to U.S. nuclear weapons shall

be conducted to assure the continuing safety and reliability

of existing weapons, and not for the development of new

types of nuclear weapons or new military capabilities for

existing warheads; and


3) the U.S. shall not make design changes to the nuclear

components -- the "physics packages" -- of weapons in the

U.S. stockpile.



A clear, "no new nuclear weapons" policy would positively affect

at least three areas of nuclear weapons and military policy. It

would: a) facilitate the early entry-into-force of the

Comprehensive Test Ban; b) end the qualitative nuclear arms race

between and among the declared nuclear weapons states and the

proliferation of nuclear weapons in the nuclear weapons capable

states; and c) reinforce the benefits of numerical reductions in

nuclear weapons arsenals; d) lead to a curtailment of the Energy

Department's expensive "stockpile stewardship" program.


A U.S. declaration of a clear "no new nuclear weapons" policy can

and should lead to a multilateral moratorium on the development

and deployment of new types of nuclear weapons or new military

capabilities for existing warheads (through modifications of

existing designs) among the declared and undeclared nuclear

weapon states. For example, France's representative to the

Conference on Disarmament when announcing France's support for a

zero-threshold test ban treaty on August 10, 1995 stated that:


"France does not intend to design new types of weapons, nor

to increase the number and power of existing weapons, no to

develop miniaturized weapons, no to modify the role of

nuclear weapons in our defense policy."


No existing U.S. policy clearly addresses this point.



Current U.S. Policies, Statements on Nuclear Weapons



According to briefing materials released by the Department of

Defense in September 1994 on its Nuclear Posture Review, there is

to be "no new design warhead production" by the Energy Department

and the nuclear weapons laboratories.


More recently, Arms Control and Disarmament Agency (ACDA)

Director John Holum has addressed the issue of the United States'

view of the impact of the recently signed Comprehensive Test Ban

on nuclear weapons development. In his January 23, 1996 address

to the Conference on Disarmament, he stated that:


"...the safe maintenance of existing weapons design is a far

cry from the confident development of new ones. The latter

requires nuclear explosive tests, which the CTBT would

preclude .... [The] quest for efficiency and flexibility is

the most basic reason why countries might test. It is also a

most potent catalyst for arms races. To avert it is the test

ban's core value and a profound one.... So let there be no

mistake -- the CTBT will help impede the spread of nuclear

weapons. But its great practical impact will also be for

arms control -- to end the development of advanced new

weapons and keep new military applications from emerging."


Holum commented at a Geneva press conference on the same day



"That is what we believe a comprehensive test ban will and

should accomplish: that there should be no further

development of new nuclear weapon designs."


Similarly, President Clinton urged in his 1996 State of the Union

Address that:


"We must end the race to create new nuclear weapons by

signing a truly comprehensive nuclear test ban treaty this



The Preamble of the Comprehensive Test Ban Treaty, signed on

September 23 by the President, states that:


"... Recognizing that the cessation of all nuclear weapon

test explosions and all other nuclear explosions, by

constraining the development and qualitative improvement of

nuclear weapons and ending the development of advanced new

types of nuclear weapons, constitutes an effective measure

of nuclear disarmament and non-proliferation in all its

aspects ..."





However, at the same time the 1994 Nuclear Posture Review

specifies "no new design warhead production," it also instructs

the Department of Energy and the nuclear weapons laboratories to

"maintain the capability to design, fabricate, and certify new

[nuclear] warheads." The DOE's response to this mandate is its

"stockpile stewardship and management" (SS&M) program -- a

collection of expensive new nuclear bomb facilities and upgrades

which the DOE claims are needed to maintain a "safe" and

"reliable" nuclear arsenal in the absence of underground nuclear

testing. It is currently estimated to cost $40 billion over the

next 10 years.(1)


Although statements by U.S. officials (such as Holum's January

23, 1996 statement) suggest that the stockpile stewardship

program is not capable of certifying (and deploying) new nuclear

weapons without nuclear explosive testing, according to the DOE,

"it would be unreasonable to say that these stewardship

capabilities could not be applied to the design of new weapons,

albeit with less confidence than if new weapons could be nuclear

tested."(2) The nuclear weapons laboratories and DOE officials

have suggested privately that the capability to fabricate and

certify new warheads would only be exercised if nuclear testing

were resumed. However, this crucial caveat is missing from the

summary of the Nuclear Posture Review.


Unfortunately, the DOE has NOT demonstrated that its proposed

stockpile stewardship program is necessary to maintain stockpile

reliability nor has the DOE evaluated other reasonable, less-

costly, and less new nuclear weapons development/deployment

capable methods. Further, the DOE has not thoroughly evaluated

the program's nuclear arms control and non-proliferation impacts.


As a result of these factors, this well-funded and high profile

program has created considerable concern about the United States'


commitment to the CTBT and the purpose of ending the qualitative

arms race. In addition, it has led to considerable concern about

the effectiveness of the CTBT in limiting the ability of the

advanced nuclear weapon states to improve their arsenals. This

has become a central basis of opposition to the Treaty by India,

one of the 44 named states that must ratify the CTBT before it

formally enters into force.





An initial part of the SS&M program is the series of six proposed

"subcritical" nuclear weapons experiments to be conducted

underground at the Nevada Test Site. The subcriticals were

originally scheduled to take place prior to the conclusion of the

CTBT negotiations but were postponed in June 1996 due to protests

from foreign governments and U.S. non-governmental groups. The

reaction to these proposed experiments over the last several

months provides a clear example of the negative impact of a

robust SS&M program on U.S. non-proliferation and disarmament



The "subcriticals" would not technically violate the terms of the

CTBT, but they would contribute to the weapons laboratories'

knowledge about nuclear weapons design. Like most of the rest of

the SS&M program, the Energy Department has not demonstrated that

the proposed subcritical experiments are necessary to maintain a

"safe" and "reliable" nuclear stockpile. In addition, the

subcriticals create difficult, new verification challenges

because they would take place underground at the Nevada Test and

will produce seismic and isotopic signatures that are virtually

indistinguishable from low-yield critical nuclear explosions.

Consequently, the subcriticals have fortified concerns among some

states that the United States and the other declared nuclear

powers are still interested in developing new nuclear weapons. In

the absence of the verification and on-site inspection (OSI)

mechanisms available under the CTBT after it enters into force,

the U.S. will have to demonstrate to the international community

that the subcriticals do not violate the terms of the CTBT. The

subcriticals' non-proliferation costs far outweigh their dubious

technical benefits and should therefore be cancelled.


Unless the purpose of the stockpile stewardship program is

redirected and its scope is greatly reduced, it will become a

severe impediment to the ratification of the CTBT by several of

the 44 nuclear-capable nations that must ratify before the Treaty

enters into force, thus jeopardizing formal implementation.

Consequently, the United States' "no new nuclear weapons

development" policy should also make it clear that the "stockpile

stewardship" program shall be conducted to assure the continuing

safety and reliability of existing weapons, and not for the

development of new types of nuclear weapons or new military

capabilities for existing warheads.


Approaches to stockpile maintenance that do not require the

construction of an elaborate and provocative new generation of

nuclear weapons research and development facilities can and

should be pursued as an alternative to the current

Administration's stockpile stewardship plan. At the technical

level of stewardship, such approaches would focus either on

warhead component remanufacture as needed, which would involve

rebuilding today's warhead parts to the same technical

specifications and with the same materials used in their original

production, or on a more "passive" form of stewardship involving

the ongoing maintenance of the stockpile without rebuilding or

replacement of existing warheads. In such alternative approaches,

improvements to (or other modifications of) the warheads'

performance would would be unecessary and would not be





Regardless of whether the stockpile stewardship program can now -

- or at some future time -- develop, fabricate, and certify new

nuclear weapons without underground nuclear testing, the weapons

laboratories are now capable of and are engaged in modifying

existing nuclear warheads with the result -- in some cases -- of

creating nuclear weapons with new military capabilities.


Such activities blur the meaning and undermine the value of the

current "no new design warhead production" policy that is part of

the Nuclear Posture Review. It further underscores the need for a

"no new nuclear weapons" policy statement declaring that the

United States will not pursue the development of new types of

nuclear weapons, including modifications leading to new military

capabilities for existing warheads.


In addition, because modification of existing warhead designs

(for whatever purpose) could also degrade confidence in expected

performance of modified warheads and could therefore create

pressure to resume nuclear testing, the United States' "no new

nuclear weapons" policy should also prohibit design changes to

the nuclear components -- the "physics packages" -- of weapons in

the U.S. stockpile.


* Modifications and New Military capabilities: Since 1995,

the U.S. nuclear weapons laboratories have been developing and

producing a modification (Mod. 11) of the B-61 nuclear bomb -- a

gravity bomb capable of producing a range of nuclear yields.(5)

The B-61 Mod. 11, which will reportedly became operational in

January 1997, provides the United States military with a weapon

with unique military capabilities -- limited earth penetration

with a low-yield nuclear warhead that produces less collateral

damage than other U.S. nuclear weapon systems. The impetus for

the B-61 Mod. 11 is the desire to have the capability to destroy

hardened underground targets without "widespread" radioactive

contamination -- such as Libya's alleged underground chemical

weapons manufacturing plant.(6)


Development and production of the B-61 Mod. 11 was approved

outside the regular budget process and without Congressional

debate, by means of a classified reprogramming request approved

by selected Congressional committee chairmen. It is not clear

whether deployment of the B-61 Mod. 11 has been approved. The

cost of these activities is not known. In addition, the nuclear

weapons laboratories have also been commissioned to pursue

modifications of the Trident D-5 missile warheads, the W76 and



Modifications of existing nuclear weapons designs are considered

by the nuclear weapons laboratories not to be "new" weapons, but

minor modifications of existing weapons, because, they

purportedly do not involve modifications of the weapons primary,

or "physics package," but modifications of the non-nuclear

components of the bomb. However, Department of Defense officials

are reported to consider the B-61 Mod.11 to be the equivalent of

a new weapon because it will have increased military

effectiveness compared to earlier B-61 variants. The difference

of opinion highlights the fact that, as a Los Alamos National

Laboratory official recently said, "nobody's defined what a new

weapon is."(7)


* Modifications and Confidence in Expected Warhead

Performance: In addition to the modifications of the B-61, W76,

and W88 nuclear warheads, dozens of other warhead modifications

are being studied by nuclear weapons laboratory scientists. In

addition to the fact that such modifications can lead to warheads

with new military capabilities, modifications of the the warhead

primaries ("physics packages"), for the sake of increased

robustness, safety, or any other purpose, may degrade confidence

in the warheads expected performance. Inadequately tested designs

have been thre principle cause of historic problems in the

stockpile and should be scrupulously avoided. This would preclude

repackaging nuclear explosives into new warhead or bomb

configurations, the development of new, but untested designs, as

well as the modification of existing physics packages for any



As a result, the U.S. "no new nuclear weapons" policy should also

prohibit design changes to the nuclear components -- the "physics

packages" -- of weapons in the U.S. stockpile and to retain and

deploy nuclear weapons which have been fully tested in in their

actual military configuration.


The August 1995 JASON report support these points and presents

the technical case for not modifying the nuclear stockpile.(8)

The body of the report is still classified, but pertinent

language can be found in the unclassified summary. The JASONs

examined the entire U.S. nuclear testing record and their first

conclusion was:


"The United States can, today, have high confidence in the

safety, reliability, and performance margins of the nuclear

weapons that are designated to remain in the enduring

nuclear stockpile. This confidence is based on understanding

gained from 50 years of experience and analysis of more than

1000 nuclear tests, including the results of approximately

150 nuclear tests of modern weapon types in the past 20

years." (9)


Recommendation 3 addresses the issue of warhead modifications:


"The individual weapon types in the enduring stockpile have

a range of performance margins, all of which we judge to be

adequate at this time. In each case wea have identified

opportunities for further enhancing their performance

margins by means that are straightforward and can be

incorporated with deliberate speed during scheduled

maintenance or remanufacturing activities. However, greatest

care in the form of self-discipline wil be required to avoid

system modifications, even if aimed at "improvements," which

may compromise reliability."


A "no new nuclear weapons" policy prohibiting design changes to

the nuclear components of U.S. nuclear weapons -- for whatever

purpose -- would be consistent with the approach to stockpile

stewardship described on page 4.





1. Final Programmatic Environmental Impact Statement for

Stockpile Stewardship and Management, U.S. Department of

Energy, September 1996.

2. Final Programmatic Environmental Impact Statement for

Stockpile Stewardship and Management, U.S. Department of

Energy, September 1996, p. S-46.

3. Stephanie Nebehay, "Pakistan Criticises West on Nuclear Test

Ban," Reuters Ltd., May 23, 1996.

4. See Chapter V: "Change Nuclear Doctrine and Focus A Core

Stewardship Program on One Design Laboratory and Sandia," in

CBO Papers: The Bomb's Custodians, Congressional Budget

Office, Washington, DC, July 1994.

5. Jonathan Weisman, "Burrowing nuclear warhead will take out

the atomic trash," The Oakland Tribune, September 22, 1995.

6. Terry Atlas, "Clinton weighs action on Libya: Plant may pose

threat of chemical weapons," The Chicago Tribune, April 24,


7. "Scientists Say Policy Barring New Nuclear Weapon Designs Is

Unclear: Mods shouldn't offer increased capability," Inside

the Pentagon, August 15, 1996.

8. "Nuclear Testing (Unclassified Summary and Conclusions),"

Sidney Drell et. al., JASON, The MITRE Corporation, McLean,

VA. Report commissioned by DOE Office of Defense Programs.

9. In arriving at these and other conclusions, the JASONs

relied on three key assumptions: 1) The U.S. intends to

maintain a credible nuclear deterrent; 2) The U.S. remains

committed to the support of world-wide nonproliferation

efforts [including a "zero-yield" CTBT]; and 3) The U.S.

will not encounter new military of political circumstances

in the future that cause it to abandon the current policy --

first announced by President Bush in 1992 -- of not

producing new nuclear weapon designs.




Daryl Kimball

Physicians for Social Responsibility

Fourteenth Street, N.W., Suite 700, Washington, D.C. 20005

Telephone (202) 898-0150 Fax (202) 898-0172