U.S. Nuclear Weapons Tests




Updated December 4, 2020
U.S. Nuclear Weapons Tests
Press reports in May 2020 indicated that officials in the
Control, said “I am unaware of any particular reason to test
Trump Administration had discussed whether to conduct an
at this stage.”
explosive test of a U.S. nuclear weapon. The United States
has observed a voluntary moratorium on nuclear explosive
The “zero-yield” standard conveyed by the Comprehensive
testing since 1992, although it has maintained the ability to
Test Ban Treaty requires states to refrain from conducting
resume these tests at the Nevada Nuclear Security Site
“any test that produces a self-sustaining, supercritical chain
(NNSS). Since 1993, it has used a program known as
reaction of any kind.” Such a reaction is necessary for a
Science-Based Stockpile Stewardship to maintain
nuclear detonation. However, neither the CTBT nor the
confidence in the safety, security, and effectiveness of its
U.S. unilateral test moratorium prohibits subcritical
nuclear arsenal.
experiments (i.e., those that do not produce a nuclear yield).
The United States conducts these types of experiments at its
Limits on U.S. Nuclear Tests
Nevada National Security Site.
By its own count, the United States conducted 1,054
explosive nuclear tests between 1945 and 1992. In 1992,
The U.S. State Department has raised questions about
Congress passed and President George H.W. Bush signed
Russia and China’s compliance with the CTBT’s zero-yield
into law the Hatfield-Exon-Mitchell Amendment
standard. In its annual arms control Compliance Report, the
establishing a temporary and unilateral moratorium on
State Department assessed that Russia has conducted
underground testing of U.S. nuclear weapons (P.L. 102-
nuclear weapons-related experiments with more than zero
377, §507). The United States has been a party since 1963
yield in the past, although it could not confirm that they had
to the Limited Test Ban Treaty, under which it is obligated
done so in 2019. It also noted that China is pursuing
to refrain from conducting nuclear weapons test explosions
activities at its nuclear weapons test site that might allow it
in the atmosphere, outer space, or under water. The United
to conduct such experiments in the future. Some analysts
States is also party to the Threshold Test Ban Treaty of
and experts following developments in China questioned
1974, which bans underground nuclear weapons tests
this assertion, noting that the alleged activities at China’s
having an explosive force of more than 150 kilotons.
testing facility do not violate the CTBT. Moreover, they
note that, if the United States and China ratified the CTBT
After declaring its testing moratorium in 1992, the United
and the treaty entered into force, the United States could
States advocated for and participated in negotiations on the
then call for on-site inspections of test sites if suspected
Comprehensive Test Ban Treaty (CTBT). This treaty,
violations occurred. Other U.S. analysts view Russian and
which opened for signature in 1996, would ban all nuclear
Chinese efforts as a reason for the United States to
explosions. President Clinton submitted the treaty to the
withdraw its signature from the CTBT and possibly resume
Senate for advice and consent to ratification in 1997. The
explosive tests.
Senate rejected the treaty on October 13, 1999, by a vote of
48 for, 51 against, and one present.
Science-Based Stockpile Stewardship
In 1993, President Clinton signed two Presidential Decision
As of March 2020, 184 states had signed the CTBT and 168
Directives (PDDs) that affected the U.S. nuclear testing
had ratified it. For the treaty to enter into force, 44 specified
program. PDD-11 continued the voluntary moratorium and
states must ratify it. Of the 44 required states, 36 have
directed the Department of Energy to formulate a specific
ratified, three have not signed (India, North Korea, and
safeguard program to protect the U.S. capability to resume
Pakistan), and another five have not ratified (China, Egypt,
U.S. nuclear testing if needed. PDD-15 set the policy for
Iran, Israel, and the United States). In the years since the
the U.S. stockpile stewardship plan, which would allow it to
treaty opened for signature, India, Pakistan, and North
maintain and sustain the nuclear stockpile under the
Korea have conducted explosive tests.
moratorium or an eventual CTBT. The National Nuclear
Security Administration (NNSA) produces an annual
Although the treaty has not entered into force, each
plan—known as the Stockpile Stewardship and
subsequent U.S. President has indicated that the United
Management Plan (SSMP)—that outlines the goals,
States will continue to observe its unilateral moratorium.
programs, and projects intended to provide this high level
The Trump Administration’s 2018 Nuclear Posture Review
of confidence in the stockpile (50 U.S.C. §2523). NNSA
says, “The United States will not resume nuclear explosive
conducts subcritical experiments and uses other tools to
testing unless necessary to ensure the safety and
maintain stockpile reliability without nuclear explosive
effectiveness of the U.S. nuclear arsenal, and calls on all
testing. It also “maintains the readiness to conduct an
states possessing nuclear weapons to declare or maintain a
underground nuclear test, if required, to ensure the safety
moratorium on nuclear testing.” In June 2020, Ambassador
and effectiveness of the Nation’s stockpile or if otherwise
Marshall Billingslea, Special Presidential Envoy for Arms
directed by the President.”
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U.S. Nuclear Weapons Tests
In the National Defense Authorization Act for 2003 (P.L.
NNSA has not allocated funding to maintain nuclear test
107-314, §3141), Congress mandated that the directors of
readiness as a separate program since FY2010. Instead, it
the three NNSA national laboratories and the Commander
funds the activities that support test readiness through other
of U.S. Strategic Command (STRATCOM) provide an
program areas in the NNSA Weapons Activities account
annual assessment of the safety, security, and reliability of
such as the Stockpile Research, Technology, and
the U.S. nuclear stockpile. They report to the Nuclear
Engineering (SRT&E) program. The Senate, in its version
Weapons Council, which then reports to the President. In
of the FY2021 National Defense Authorization Act (S.
each year since this law passed, the Nuclear Weapons
4049, §3166), would have made $10 million available to
Council has reported that the United States can maintain
NNSA for projects that could reduce the time needed to
confidence in the stockpile without resuming explosive
execute a nuclear test. The House, in its version (H.R. 6395,
nuclear testing. Nevertheless, the President could still
§3167), would have prohibited the use of funds to prepare
authorize an explosive test under certain conditions. The
for or conduct a test that produced a nuclear yield. The
Nuclear Matters Handbook, produced by the Department of
conference report did not include either provision.
Defense, says that “if an urgent issue with a weapon were to
arise that required a nuclear test, the Secretaries of Defense
NNSA has not offered an estimate of the cost of conducting
and Energy, the President, and Congress would be notified
a nuclear test; that cost would depend on the specific details
outside of the context of the annual assessment process.”
of the test. A test designed to demonstrate only a weapon
explosion would likely cost less than a fully instrumented
U.S. Test Readiness
test designed to evaluate the safety and reliability of a
Although the United States has observed a moratorium on
weapon that had been modified to address technical
nuclear testing since 1992, it has maintained the capability
concerns, or a test designed to demonstrate the capability
to resume testing within 24-36 months of a decision to do
and effects of a new type of weapon. Moreover, before
so. President Clinton established this timeline when he
conducting a fully instrumented test, NNSA would likely
signed PDD-15 in 1993, and it remains the goal today.
have to invest in the equipment and facilities needed to
According to a 2011 report to Congress from the
conduct the test, and possibly hire additional personnel with
Department of Energy, “a fully instrumented test to address
the necessary knowledge and skills. It may also have to
a complex stockpile problem would take 24 to 36 months,
meet additional environmental review requirements
and tests required for development of a new capability
mandated by U.S. laws before resuming testing.
might take up to 60 months.” However, “a very simple test
for political purposes could be conducted in as little as 6-10
Potential International Implications
months.” Drew Walter, speaking as the Deputy Assistant
According to May 2020 press accounts, some who argued
Secretary of Defense for Nuclear Matters, recently
for the United States to conduct a nuclear test asserted that
confirmed this assessment when he noted that the United
the test “could prove useful from a negotiating standpoint
States could conduct “a very quick test with limited
as Washington seeks a trilateral deal to regulate the arsenals
diagnostics ... within months.”
of the biggest nuclear powers.” According to one account,
“the apparent motive behind the proposal …was somehow
According to the 2011 report, NNSA maintains test
to add pressure on China” to join the talks.
readiness “by exercising capabilities and workforce at the
national security laboratories and the Nevada National
Others counter that the United States would undermine its
Security Site through the Stockpile Stewardship Program.”
arms control and nonproliferation objectives if it were to
Key among these capabilities are subcritical experiments,
conduct a nuclear test. Some Members of Congress and
along with “other high explosive driven experiments and
nongovernmental arms control advocates have spoken out
high energy density experiments” that allow personnel to
against the resumption of testing, saying it could harm the
maintain the skills needed for nuclear testing. NNSA also
United States’ decades-long policy of preventing nuclear
maintains the sites, facilities, and equipment that it would
proliferation, potentially leading other nuclear states to
use if the United States resumed explosive tests.
restart testing programs. This, in turn, could evolve into
nuclear or missile arms races, or new nuclear weapons
According to a 2012 National Academies of Sciences study,
states. A group of well-known physicists with experience in
the response time for resuming underground explosive
nuclear weapons issues explained their strong opposition to
testing would be driven more by the need to meet
a resumption of nuclear testing in a June 2020 letter to
regulatory requirements than by the technical needs of the
Senate Majority Leader Mitch McConnell, in which they
test or the need to restore equipment and facilities. NNSA
argued that there is no technical or military need for such a
has also indicated that “assuring full compliance with
test, and that it would have negative security consequences
domestic regulations, agreements, and laws relating to
for the United States. They argued, “A likely response to a
worker and public safety and the environment, and
US test would be a resumption of testing by Russia and
international treaties, would significantly extend the time
China, and perhaps also by North Korea, India, and
required for execution of a nuclear test.” At the same time,
Pakistan. This would further undermine the Nuclear Non-
according to the SSMP, the President can declare a national
Proliferation Treaty (NPT).”
emergency and waive all “applicable statutory and
regulatory restrictions” if he wants to conduct a test in
Mary Beth D. Nikitin, Specialist in Nonproliferation
months, rather than years.
Amy F. Woolf, Specialist in Nuclear Weapons Policy
IF11662
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U.S. Nuclear Weapons Tests


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https://crsreports.congress.gov | IF11662 · VERSION 2 · UPDATED