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Security Implications of Plutonium
Stockpiles in Asia and Beyond
Sharon Squassoni
Research Professor, George Washington University

1．Nuclear energy: unavoidably dual-use
Nuclear energy is unavoidably dual use. Fissile material -- that is, enriched uranium and separated plutonium - has both civilian and military purposes. Some material is better suited for bombs than other material.
Highly enriched uranium (over 90% enriched in U-235) and plutonium that has relatively little of the isotopes
240 and 241 are considered weapons-grade fissile material (see Fig. 1).

Fig. 1 Nuclear energy: unavoidably dual-use

2．Where to draw the line? The Acheson-Lilienthal Report
The real question is, if everything is dual-use, where do you draw the line? Some parts of the fuel cycle are
more sensitive and riskier than others. Do you simply monitor HEU and Pu or do you limit or prohibit its

production, stockpiling and/or use? Almost 75 years ago, right after the development of nuclear weapons in1946, there was a landmark document called the Acheson-Lilienthal Report. Experts on the panel included J.
Robert Oppenheimer, and the report divided fuel cycle activities into safe and unsafe activities (see Fig. 2).
On the safe side were quite a few things.
I’d like to point out how our views have changed over time. In 1946 the idea was that radioisotopes, small
research reactors, and power reactors fueled with so-called “denatured” fissile material (in that category, lowenriched uranium and reactor-grade plutonium) were all on the safe side of the fuel cycle, and you could

monitor those activities. The unsafe side of the fuel cycle included uranium mining and milling, uranium
enrichment, breeder reactors (fast reactors that produce more plutonium than they consume), reprocessing
plants (spent fuel separation plants), and research and development into nuclear weapons. The 1970 Nuclear
Nonproliferation Treaty only prohibits the transfer of or transfer of control of nuclear weapons; the1JUNE 2022Vol.

manufacture or acquisition of nuclear weapons and seeking or receiving assistance in the manufacture of suchweapons. While this may be interpreted as prohibiting R&D into nuclear weapons, the treaty clearly did notconclude that uranium mining and milling, enrichment, breeder reactors or reprocessing plants were too
unsafe to engage in nationally.

Fig. 2 In Acheson-Lilienthal Report

3．Forgotten lessons
The Acheson-Lilienthal report is mostly remembered for its emphasis on internationalization of nuclear
energy, and to reduce the risks from and spread of nuclear weapons. The report was correct about some things,
but wrong about others. It correctly predicted the enduring attractiveness of nuclear weapons to states, evenjust one year after the bombing of Hiroshima and Nagasaki. It also concluded that a vast inspection effort
would be necessary in order to ensure the peaceful uses of nuclear energy. Yet, the authors of the report knewthat those vast inspections were not possible. That is why they optimistically suggested internationalizing theparts of the fuel cycle deemed “unsafe.” As it turned out, there has been very little internationalization. The
Acheson-Lilienthal Report was also completely wrong on the denaturing of plutonium, which cannot be madeunusable in a bomb by changing the isotopic composition. The report was right to assume LEU, containing
less than 6% U-235, cannot be directly used in a bomb. In fact, US-Russian cooperation to downblend HEU
into LEU was predicated on this concept. However, such LEU can be enriched further for use in nuclear
weapons and therefore needs to be tracked. Those were the forgotten lessons of the Acheson-Lilienthal report.
What have we learned in the last 75 years? We know that plutonium cannot be denatured. We know thatreactor grade plutonium works in a bomb, as the US testing program demonstrated. Fifty-two years ago, theNuclear Nonproliferation Treaty (NPT) did not prohibit uranium enrichment or spent fuel reprocessing.Just a
few short years after, in 1974 when India tested a nuclear weapon, suppliers of nuclear equipment, materials
or technology recognized the necessity of halting the spread of enrichment and reprocessing. They establishedthe Nuclear Suppliers Group for that purpose and those efforts continue today.

We learned also that plutonium recycling costs are very high, both for using that fuel in reactors and also
increasing the costs for final disposal. Plutonium can be put in mixed oxide fuel (MOX fuel), but spent MOX
fuel is going to be even more radioactive than fuel from a thermal, light water reactor.

4.Multilateralization?
On internationalization of the fuel cycle, we have the experience of multinational enrichment and

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reprocessing in URENCO and Eurochemic. Neither experiment solved proliferation problems. In the case ofURENCO, we know very famously that AQ Khan, the so-called father of the Pakistani nuclear bomb, stole
supplier information from URENCO, used it for Pakistan’s nuclear weapons program and then further
developed a clandestine network of suppliers in the late 1990s and early 2000s. Eurochemic did not have an
obvious impact on proliferation of reprocessing technology, but there are fewer technical secrets associatedwith chemical separation.

5. Where are we now?
The current state of negotiations with Iran shows just how weak the NPT is and the Joint Comprehensive Planof Action (JCPOA), the Iran Deal, shows how much more is necessary. The JCPOA includes limits on stocks,
on the level of enrichment, on research and development into more capable centrifuges, and monitoring on
centrifuge stockpiles and assembly. These are all necessary to limit a country’s capabilities because the NPT
contains no restrictions. On the other hand, we have had norms and standards to minimize highly enricheduranium, under the Nuclear Security Summits. Unfortunately, the latest deal between the US and Australia toshare nuclear submarine technology, called AUKUS, shows how limited that norm is. It applies to civilian
HEU use, not military use. Encouraging additional countries to use highly enriched uranium for what we callmilitary non-explosive purposes, naval reactors – not bombs but military – shows how narrow the HEU
minimization norm is.
On plutonium, there are no restrictions and no international norms to minimize plutonium. The International
Plutonium Management Guidelines, INFCIRC/549, constitute a voluntary arrangement among a few states tomake declarations on civil stocks. After twenty years of implementation, there is a discrepancy among thecountries participating in the kinds of information they provide and no specific formats for declaring
information. For example, China has declared very little material, if at all. So there are weaknesses there.

6. Japan is unique
Japan is the only country without nuclear weapons to enrich uranium and reprocess spent nuclear fuel. It is

the only non-nuclear weapons state with vast plutonium stocks. Those are two ways in which Japan is unique.
It is also among very few countries that have promoted transparency with regard to its nuclear program andnuclear material stockpiles.

7. Historical transparency
Japan has a long history of historical transparency, beginning in 1991 with the adoption of the no surplus

plutonium policy. Later in 1994, there was public sharing of information on separated plutonium andplutonium in spent fuel. In 1997, Japan joined the International Plutonium Management Guidelines. Thegovernment has slowly gotten a little more involved, providing a little more guidance to industry in terms of
their plans for plutonium consumption. In 2018, Japan said for the first time it would reduce stocks andmaintain the balance between supply and demand.

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8. US current views
The US and Japan have a long history in collaboration on advanced nuclear power, more recently cemented inthe US-Japan Climate Partnership which calls for collaboration on advanced nuclear power. Given the Biden
Administration’s focus on Asia, the IndoPacific, and positive promotion of nuclear energy, furthercollaboration is likely in store. Within the US Department of Energy, there has always been a tension
between the part of the Department that promotes nuclear energy (Office of Nuclear Energy) and the part thathas to deal with the consequences of that - the National Nuclear Security Agency (NNSA), now headed byformer Sandia laboratory official Jill Hruby. NNSA is likely concerned about plutonium stockpiles andreprocessing, but must contend with the Office of Nuclear Energy’s support for the benefits of reprocessing
for advanced reactors. The US, despite many years of not engaging in reprocessing, is now considering it forthe purpose of recycling fuel for advanced reactors.
9. The role of US Congress
Congress has little formal role in many of these issues, since the US-Japan Nuclear Cooperation Agreement
has been extended indefinitely and requires no further oversight from Congress. However, this does not meanthat members of Congress will not be sensitive to how Japan’s actions regarding plutonium and reprocessingmay affect other areas. One of those will certainly be US-South Korea nuclear cooperation. In the area ofdefense and security, the Congress and the Biden administration are very concerned about China’s nuclear
modernization. The latest estimates that China could triple its stockpile depend on an assumption that China
either has a lot of fissile material lying around, or that it will make fissile material in its breeder reactors. The
potential for Japan to do the same, and for South Korea and North Korea to follow suit, are clear. Finally onNorth Korea, congressmen may ask whether an increasing plutonium stockpile in Japan makes regional
security better or worse in the eyes of North Korea.
10. Recommendations
Japan has an opportunity to lead in East Asia. Some ideas that have arisen in the course of my research fromregional experts include the following: Japan could build interim storage; it could make progress on arepository for spent fuel; it could suggest, promote or propose a regional moratorium on reprocessing; it could
get involved in creating an international storage for plutonium; or it could swap ownership of plutonium touse it up more quickly. Lastly, Japan could be a leader in efforts to create real restraints on supply to meetdemand.

Sharon Squassoni
Sharon Squassoni is Research Professor of the Practice of International Affairs at the Elliott School, GeorgeWashington University in Washington, DC. She held senior positions at the State Department, Arms Controland Disarmament Agency and the Congressional Research Service before leaving government service tobecome a scholar at the Carnegie Endowment for International Peace. She led the Proliferation Prevention
Program at the Center for Strategic & International Studies from 2010 to 2018. She is on the Science andSecurity Board of the Bulletin of Atomic Scientists, the PIR Center and the Center for Arms Control andNonproliferation. Her research, writing and policy-making has focused on reducing risks from nuclear
energy and weapons for three decades.

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※This paper is based on the author’s presentation at the international symposium “Growing Plutonium
Stockpiles and the Rokkasho Reprocessing Plant: Reality of Nuclear Fuel Cycle and Security in East Asia” ,Dec. 18-19, 2021. The views expressed here are those of the author.
※This project is supported by a grant from “act beyond trust” (abt) .

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