Category: Union of Concerned Scientists (UCS)

How Do Nuclear Weapons Work?

How Do Nuclear Weapons Work?

At the center of every atom is a nucleus. Breaking that nucleus apart—or combining two nuclei together—can release large amounts of energy. Nuclear weapons use that energy to create an explosion.

Modern nuclear weapons work by combining chemical explosives, nuclear fission, and nuclear fusion. The explosives compress nuclear material, causing fission; the fission releases massive amounts of energy in the form of X-rays, which create the high temperature and pressure needed to ignite fusion.

Take a deep dive into nuclear weapons with the rest of this post, which includes accessible descriptions of fission and fusion, how nuclear weapons work, nuclear fuel, warheads in-depth, and more.

Voters Strongly Support a “No First Use” Nuclear Policy

Voters Strongly Support a “No First Use” Nuclear Policy

The President should declare that the United States will never start a nuclear war.

The choice to use nuclear weapons is the most momentous decision a president could ever take, with the fate of millions at stake. Just one bomb could kill hundreds of thousands of people, while a full-scale exchange could end life as we know it. Currently, the United States reserves the right to use nuclear weapons first in a conflict, and the authority to launch nuclear weapons lies solely with the president.

Adoption of a “No First Use” (NFU) policy means the United States would commit to never initiating a nuclear conflict. A NFU policy would reduce the risk of other countries using nuclear weapons against the United States and contribute to global stability through leading by example.

UCS commissioned polls in several states and has found strong support for a US NFU policy, and even stronger support for the idea that the presidential candidates should be talking about nuclear weapons issues on the campaign trail.

New Hampshire (University of New Hampshire poll, March 2019)
Residents who believe the United States should never use nuclear weapons first: 73%
Residents who believe it is important for presidential candidates to give their views on nuclear weapons: 84%

Iowa (Zogby Analytics poll, April 2019)
Residents who believe the United States should never use nuclear weapons first: 57%
Residents who believe it is important for presidential candidates to give their views on nuclear weapons: 82%

Michigan (Zogby Analytics poll, July 2019)
Residents who believe the United States should never use nuclear weapons first: 67%
Residents who believe it is important for presidential candidates to give their views on nuclear weapons: 82%

Ohio (Zogby Analytics poll, October 2019)
Residents who believe the United States should never use nuclear weapons first: 65%
Residents who believe it is important for presidential candidates to give their views on nuclear weapons: 84%

Georgia (Zogby Analytics poll, October 2019)
Residents who believe the United States should never use nuclear weapons first: 61%
Residents who believe it is important for presidential candidates to give their views on nuclear weapons: 86%

South Carolina (Zogby Analytics poll, February 2020)
Residents who believe the United States should never use nuclear weapons first: 62%
Residents who believe it is important for presidential candidates to give their views on nuclear weapons: 83%

Downloads

Georgia fact sheet

Iowa fact sheet

Michigan fact sheet

New Hampshire fact sheet

Ohio fact sheet

South Carolina fact sheet

US Missile Defense

US Missile Defense

Unproven, unaccountable, and unhelpful for reducing the nuclear threat.

Six hours north of Anchorage, Alaska, lies a sprawling, snow-covered military base called Fort Greeley. Three thousand miles to its south, outside Lompoc, California, is another major installation—Vandenberg Air Force Base.

The two bases are linked by a unique security objective: to destroy nuclear-tipped missiles bound for the United States, should they ever be launched from North Korea or another hostile state.

Unfortunately, the system creates far more problems than it solves, and it likely wouldn’t work in the event of an actual attack—a practical reality that money and research won’t fix.

Learn more about how missile defense works, oversight and accountability, and space-based missile defense.

Preventing Nuclear War

Preventing Nuclear War

It shouldn’t be easy to start a nuclear war. Campaign contact

By Madison Arnold-Scerbo, Outreach Associate

For more than 70 years, the world has faced the very real threat of nuclear war.

What if we lived without that danger hanging over our heads?

That’s what we’re fighting for, across the country and in the hallways of DC—and that’s why we need you.

Call for investments in public health & security, not nuclear weapons.

Nuclear war is a real and growing threat. The United States and Russia have left critical agreements and treaties, while actively planning to add new types of weapons to their arsenals.

Meanwhile, US nuclear policy remains rooted in the Cold War, increasing the risk that nuclear weapons could be used again.

It doesn’t have to be this way. With the right policy changes and a commitment to diplomacy, the United States can be a leader in reducing the nuclear threat—and you can help.

What we’re doing

  1. Engaging & educating presidential candidates,
  2. Pressuring Congress to support change,
  3. Holding the White House accountable through independent research and analysis,
  4. Increasing public demand for changing nuclear weapon policies.

What You Can Do

Space-based Missile Defense

Space-based Missile Defense

It may sound like a good idea. It really isn’t. In 1983, President Ronald Reagan proposed a military system, later dubbed “Star Wars,” that promised to protect the United States from nuclear attack. The basic idea was to use weapons based in space to knock down incoming intercontinental ballistic missiles (ICBMs).

Space-based Missile Defense: Not a Good Idea

Politicians have called for “space-based missile defense” for years. Unfortunately, it’s not a very good idea.

Reagan’s plan didn’t materialize, but the idea never went away. In 2018—against the Department of Defense’s wishes—Congress passed a bill calling for the Pentagon to start building space-based interceptors.

Unfortunately, it’s a terrible plan. Space-based missile defense is an ineffectual defense at best, and a very dangerous provocation at worst.

Understanding why space-based missile defense is a bad idea requires basic knowledge of how it works—and what it can and can’t do.

Click here for more information and interactive features about what missile defense systems are and why they’re prone to failure.

Security and Arms Control Webinars

Security and Arms Control Webinars

The Summer Symposium hosts security experts from across the globe, speaking on technical issues related to global security.

Published Mar 28, 2014 Updated Feb 9, 2017

Trying to join a webinar? View instructions here.

This page contains abstracts and archived recordings of lectures on global security issues, including missile defense, North Korea and Iran, nonproliferation, and US nuclear weapons. The lectures come from webinars, presented on Youtube, or in either shockwave (.swf) or video files that can be viewed in a web browser.

For more information, please contact:

  • George Lewis at Cornell University, gnl3 [at] cornell.edu
  • David Wright with the Union of Concerned Scientists, dwright [at] ucsusa.org

Note: As of January 1, 2017, webinars and lectures from this series will be posted exclusively on Youtube, accessible here. Older presentations can still be found here.

How to limit presidential authority to order the use of nuclear weapons

How to limit presidential authority to order the use of nuclear weapons

In the United States, the president has sole authority to order the use of nuclear weapons, for any reason and at any time. This arrangement is both risky and unnecessary.

The risks are not hypothetical. During the Watergate scandal, President Nixon was drinking heavily and many advisers considered him unstable. During the 1974 impeachment hearings, Nixon told reporters that “I can go back into my office and pick up the telephone and in 25 minutes 70 million people will be dead.” Defense Secretary James Schlesinger reportedly instructed the Joint Chiefs of Staff that “any emergency order coming from the President”—such as a nuclear launch order—should go through him or Secretary of State Henry Kissinger first. But Schlesinger had no legal authority to intervene, and it is not clear what would have happened if Nixon had ordered an attack.

The United States should modify its decision-making procedures to require that one or more officials concur with a presidential order to use nuclear weapons before the military carries it out.

This article, written by UCS members and published in the Bulletin of the Atomic Scientists, outlines the steps to take to ensure more leaders are involved in the decision to launch a nuclear attack.