With the symbol Pu on the Periodic Table, plutonium is an element with an atomic number of 94, which means its nucleus has 94 protons. As a heavy metal it has many more neutrons than protons, but more on that later.

Plutonium is categorized as a heavy metal that is unstable, which means it is radioactive. More importantly, it is fissionable, meaning it splits apart easily when neutrons collide with a plutonium atom. This collision releases energy.

Interestingly uranium gives life to plutonium in the sense that plutonium is produced through beta decay from uranium. Once plutonium is produced, uranium is needed to help plutonium live up to its full potential.

Plutonium-239 is a key material for nuclear weapons, particularly in an implosion-type nuclear weapon, primarily found in modern arsenals. These weapons use conventional explosives to compress a plutonium core to a supercritical state, initiating a chain reaction.

In a nuclear weapon, the plutonium pit is compressed by conventional explosives, which is timed to create a symmetrical implosion, applying the same inward pressure on the entire pit. Thus, the pit reaches a supercritical state. This means that the plutonium nuclei are packed densely enough for neutrons released by fission to cause further fissions at an accelerating rate—cause a stable chain reaction.

To start a chain reaction, an external neutron source, often a device called a neutron initiator, is used. This ensures enough neutrons are present at the moment the pit becomes supercritical.

In a thermonuclear weapon, the energy released from the fission reaction in the plutonium pit compresses and heats a secondary fusion stage. This secondary stage usually contains isotopes like deuterium (discovered by American chemist Harold C. Urey for which he was awarded the Nobel Prize for Chemistry in 1934) and tritium (discovered in 1934 by the physicists Ernest Rutherford, M. L. Oliphant, and Paul Harteck), which undergo fusion reactions under the extreme conditions generated by the primary fission explosion.

Precise engineering ensures that both uranium and plutonium interact seamlessly, achieving the desired explosive yield. While uranium and plutonium are both “heavy metals,” a “classical” metaphor will prove useful to explain how uranium and plutonium work together with uranium as the conductor of an orchestra and plutonium as the star soloist.

Uranium, particularly uranium-235, sets the stage for the entire nuclear reaction. Just as a maestro leads the orchestra and ensures that all elements come together harmoniously, uranium initiates the nuclear chain reaction in the secondary stage of a thermonuclear weapon where it leads to a more significant fusion reaction. The virtuoso plutonium-239, with its higher likelihood of fission upon neutron impact, takes on the pivotal role of driving the core fission reaction in modern nuclear weapons. Plutonium’s implosion mechanism requires precision for its masterful execution.

Plutonium’s implosion reaction is the centerpiece, releasing immense energy and driving the explosive power of the bomb. Its ability to sustain a rapid chain reaction is crucial, similar to how a virtuoso’s skill ensures the success of a performance. Both elements must work in harmony.

To continue with the metaphor of an orchestra, just as some orchestras perform in the orchestra pit, uranium and plutonium work together via a pit. To optimize yield and efficiency of uranium-235 and plutonium-239, a plutonium pit is surrounded by a uranium tamper in a thermonuclear weapon. This arrangement leverages the high-speed neutrons produced by fusion to induce additional fission in the uranium-235, thereby boosting the explosion’s overall yield.

The plutonium pit is typically composed of a sphere or shell of plutonium-239, a fissile isotope capable of sustaining a nuclear chain reaction. The pit often contains a small amount of gallium to stabilize its crystal structure, preventing the plutonium from becoming brittle.

On October 1, 2024, the US Department of Energy’s National Nuclear Security Administration (NNSA) verified completion of the first production unit (FPU) of a plutonium pit for the W87-1 modification program. A plutonium pit is a necessary component in America’s nuclear warheads. The NNSA is currently rebuilding the capability to manufacture plutonium pits, at the rate of no fewer than 80 pits per year.

In the end, what is important to keep in mind is that plutonium and uranium work together in the nation’s nuclear weapons. Through great science and even better designs, plutonium and uranium work together to ensure a safe, secure, and effective nuclear arsenal.

Alex Littlefield is Chief of Staff at the National Institute for Deterrence Studies (NIDS). The views expressed are his own.

Plutonium-239 and Its Relationship with Uranium-235 in Thermonuclear Weapons was originally published on Global Security Review.

Key Issues Include:

Korea and Russia News

1. North Korean ICBM and Military Collaboration with Russia
   • North Korea recently launched its most powerful intercontinental ballistic missile (ICBM) to date, signaling its intent to counter U.S.-South Korean alliances. Following this, the U.S. and South Korea held joint air drills as a show of force.
   • Reports indicate North Korean troops in Russian uniforms are heading to Ukraine, marking a potentially destabilizing support for Russia’s war efforts. North Korea may seek advanced nuclear technology from Russia as part of their cooperation.
2. Strategic Reactions and Military Developments
   • The U.S. and South Korea have pledged deeper military and technology cooperation, emphasizing nuclear defense scenarios. Meanwhile, North Korea’s alignment with Russia is raising concerns about heightened regional instability and the potential extension of the Ukraine conflict.

ICBM Report to Congress on LGM-35A Sentinel

1. Program Overview
   • The LGM-35A Sentinel, set to replace the aging Minuteman III, forms the land-based leg of the U.S. nuclear triad. The Sentinel will enhance the U.S.’s deterrent capabilities with an expected procurement of 634 missiles, modernized silos, and facilities across strategic areas
2. Funding and Development
   • The FY2025 budget includes $3.7 billion from the Department of Defense and $1.1 billion for the W87-1 warhead from the National Nuclear Security Administration. Modernization will involve upgrades to 450 silos and over 600 facilities, establishing the Sentinel as a long-term, modular system to address future threats
3. Strategic Justifications
   • As a critical element of U.S. defense, the Sentinel program is designed to meet evolving threats, preserve industrial capabilities, and ensure cost-effective lifecycle management. The Air Force targets initial deployment in 2029.

Get the full report!

ICBM EAR Report October 28th 2024 was originally published on Global Security Review.

Cirincione begins his article, “President Joe Biden has a terrible nuclear policy. A re-elected President Donald Trump’s would be much worse.” President Trump, should he win, will likely follow the path of every new president since 1994 and conduct a Nuclear Posture Review, and, like the last three presidents, follow a path that reflects the threat facing the United States. Until something concrete takes place, Cirincione is merely speculating by attributing the plan of some conservative organizations, Project 2025, to Donald Trump.

Cirincione also willfully misrepresents the record of the Biden administration when he writes that Biden has “authorized the largest nuclear weapons budgets since the Cold War.” This suggests President Biden supports nuclear weapons. The Biden Nuclear Posture Review called for the retirement of the B-83, the nation’s only megaton class nuclear capability. Biden also proposed canceling the sea launched cruise missile-nuclear (SLCM-N) and eliminating the nuclear hedge. Neither of these efforts are the actions of a man who supports the nuclear arsenal. Biden, however, had the misfortune of dealing with a reality that was inconsistent with his ideology, something that is never a problem for disarmament groups because they have no responsibility to protect the country.

Cirincione claims that Trump’s nuclear policy is informed by the “new conservative manifesto Project 2025.” When Trump was recently asked about Project 2025 he said that he has never heard of it. He even went on Truth Social to write, “I know nothing about Project 2025.” This is certainly not something Trump would lie about. Trump is, in fact, relying on a small number of officials from his first administration for advice and guidance. He does not need the Heritage Foundation or any other think tanks to tell him what to think.

Understood for what it says, rather than the conspiratorial insinuations of many progressives, Project 2025’s nuclear arsenal related proposals are largely accurate and well-reasoned. An honest assessment of the coming decade clearly indicates a need to expand the American nuclear arsenal to counter a growing Russian, Chinese, and North Korean nuclear capability. When Cirincione writes, “These proposals [from Project 2025] would add unnecessary new weapons to an already expansive nuclear arsenal” he is merely denying the reality facing the United States.

This country is already well behind Russia in the size and capability of its nuclear arsenal and will fall behind China within a decade. The United States will soon face three autocratic regimes with a collective arsenal several times greater than the American arsenal.

Cirincione goes on to criticize every nuclear policy prescription in Project 2025, suggesting that none are necessary. Nothing could be further from the truth. Contrary to his critique, prioritizing nuclear weapons programs over other defense programs is a wise move. Nuclear deterrence is the cornerstone of American defense policy—ensuring that adversaries think twice before considering aggressive action against the United States.

Interestingly, Cirincione fails to acknowledge that former President Barack Obama made an agreement with the US Senate in 2010 in which the Senate agreed to ratify New START in return for modernization of all three legs of the nuclear triad. Presidents Obama, Trump, and Biden all honored this agreement in the main, even if they sought change on the margins.

Cirincione even goes so far as to criticize modernizing the National Nuclear Security Administration’s Manhattan Project-era infrastructure and production complex. This is not a radical move but a sensible effort that was needed decades ago. The desire of Joe Cirincione and other disarmament advocates to allow the nuclear weapons complex to atrophy into obsolescence is a dangerous path that only wealthy idealists with tall fences can contemplate. It is only because of three decades of neglect that Americans are now forced to modernize all three legs of the nuclear triad.

In other words, Joe Cirincione and his fellow travelers in the disarmament community advocated for the actions that led the nation down the path it is now on. Today, both Republican and Democrat administrations recognize the trouble facing the nation, even as disarmament advocates complain about efforts to fix the problems they helped create. It is simply an example of the Dunning-Kruger effect at work.

Tying Donald Trump to Project 2025 and vilifying both is an effort to obfuscate and avoid having a substantive discussion about the nuclear breakout of China, Russia’s nuclear threats, and other meaningful issues that challenge the mantra of the disarmament community.

What is perhaps most disappointing is just how far the Bulletin has fallen. Rather than engaging in meaningful discussion on nuclear issues, the journal is increasingly publishing articles that read more like an excerpt from Antonio Gramsci’s Prison Notebooks or Herbert Marcuse’s “Repressive Tolerance.” They, like Cirincione’s own article, seem more interested in advancing the radical ideology of modern-day Marxists than having a fact-based debate over the role of nuclear weapons in national security. This penchant for the absurd makes it hard to take a once-conscientious publication and its contributors seriously.

James Ragland is a Fellow at the National Institute for Deterrence Studies. Views expressed are the author’s own.

Joe Cirincione is Wrong about Donald Trump was originally published on Global Security Review.