35+ Years of Freedom of Information Action

Japan Plutonium Overhang Origins and Dangers Debated by U.S. Officials

Published: Jun 8, 2017
Updated: Aug 1, 2018
Briefing Book #597

Edited by William Burr

For more information contact
William Burr: 202/994-7000 and nsarchiv@gwu.edu

Proliferation Risks of Japanese Plutonium Surpluses Troubled U.S. Officials

Origins, Dangers of Japan’s Excess Supply Dates Back Decades, Forward to 2018

Controversy Continues Today Over Whether Reprocessing by Japan Should Continue

Update – August 1, 2018 – see box below

Japan Announces Policy Change on Plutonium Overhang

Possible Turning Point for Nuclear Nonproliferation Efforts

Internal Debates, Media Coverage, Pressure from Allies and Neighbors, and Economic Realities Compel Retreat from Decades-Long Plutonium Delusion


Washington D.C., August 1, 2018 - On 31 July 2018, the Japanese Atomic Energy Commission announced that “Japan will reduce the size of its plutonium stockpile.” The move marks a potential turning point on an issue that has carried difficult and troubling implications for nuclear nonproliferation policy. For years, the JAEC has been operating reprocessing facilities to turn spent reactor fuel into plutonium for use in fueling reactors. A new reprocessing facility in the works at Rokkasho would produce even more plutonium, but the surpluses of plutonium accumulated far beyond any need for reactor fuel. The surpluses have raised concern for years about the vulnerability of plutonium stocks to terrorism and Japanese nuclear weapons potential, but also unease that a reprocessing program had been setting a bad precedent internationally.

What the JAEC announcement means in practice is unclear but according to a Reuters story, pressure from China and the United States had an impact on Japanese decision-making. Other sources indicate that Foreign Minister Tarō Kōno played a key role in pushing a policy change forward (suggesting the role of international influence).  In any event, that the U.S. may have shown concern to Japan is consistent with the more critical perspective on reprocessing that developed during the Obama presidency and that the current administration has continued.

In 2017, the National Security Archive contributed to the policy discussion by publishing documents from the late 1970s and 1980 (see below), which presented the debate within the Carter administration on Japanese reprocessing. While some senior officials wanted to give Tokyo license to reprocess using U.S.-supplied uranium—which became official U.S. policy during the Reagan administration--others argued that Japan would develop plutonium surpluses far beyond what could be used as reactor fuel. The publication of the U.S. documents received extensive media attention in Japan, including Japan Times, and inspired a major article in The Bulletin of the Atomic Scientists.


Washington, D.C., June 8, 2017 – Japan’s long-standing aspirations to develop a "plutonium economy" troubled U.S. officials going back decades as early as the Jimmy Carter administration, according to documents posted today by the nongovernmental National Security Archive at The George Washington University and the Nuclear Nonproliferation International History Project at the Woodrow Wilson International Center for Scholars. 

The Japanese government appealed repeatedly in the late 1970s for authority to utilize American spent fuel for reactor experiments and for acceptance of the country’s right to resource self-sufficiency. Tokyo’s position sparked intense debate within the Carter administration, between those who wanted to avoid damaging ties with Japan and those – including the president – who placed a high priority on curbing the availability of sensitive nuclear technologies. Among the newly declassified documents in this e-book is a National Security Council memo expressing concern that the inevitable surplus from Japan’s desired processing plans would “more than swamp” global requirements and create a significant proliferation risk involving tons of excess plutonium by the year 2000. Indeed, as a result of reprocessing activities since then, Japan possesses 48 tons of plutonium and could be producing more, with no clearly defined use, when a new reprocessing facility goes on line in 2018, unless Washington and Tokyo renegotiate a nuclear agreement that expires that same year.

Today’s posting is part of a growing body of records being compiled by the National Security Archive’s Nuclear Vault that flesh out largely unknown aspects of the history of Japan’s nuclear program, and more generally the inherent dangers of proliferation of nuclear materials.

* * * * *

Japan’s Plutonium Overhang: Debates During the Carter Administration

By William Burr

Plutonium, a key element of nuclear weapons, has been an issue in U.S.-Japan relations for decades. During the administration of Jimmy Carter, the Japanese government pressed Washington for permission to process spent reactor fuel of U.S. origin so that the resulting plutonium could be used for experiments with fast breeder nuclear reactors. The government of Japan wanted to develop a “plutonium economy,” but U.S. government officials worried about the consequences of building plants to reprocess reactor fuel. According to a memo by National Security Council staffer Gerald Oplinger, published for the first time by the National Security Archive, the “projected plants would more than swamp the projected plutonium needs of all the breeder R&D programs in the world.” They “will produce a vast surplus of pure, weapons grade plutonium amounting to several hundred tons by the year 2000.” That stockpile “would constitute a danger in itself” and “it would eventually drive these nations, and those watching their example, into the recycle of plutonium in today's generation of reactors for economic reasons,” which the Carter White House saw as a waste of resources.

That the White House leaned against reprocessing spent nuclear reactor fuel frustrated the government of Japan, which saw (and still does) its energy future in using plutonium to fuel advanced reactors. By 1979, Gerard C. Smith, the president’s representative on nonproliferation policy, wanted Japan to be given leeway so it could reprocess without getting U.S. consent. Worried that Japan and other close allies perceived the United States as an “unreliable” nuclear supplier, Smith hoped to avoid “major damage” to the relationship with Tokyo. His initiative touched off debate within the Carter administration, evidence of which is published today by the National Security Archive.

Today’s posting demonstrates how the Carter White House’s critical approach to plutonium reprocessing came under fire from within and outside the administration. Among the documents published are:

  • The record of a conversation between Smith and Minister of State for Science and Technology Iwazo Kaneko, who gave a fervent defense of a plutonium economy: given Japan’s energy needs, it was “essential … to make maximum use of plutonium, particularly in fast breeder ” While Japan had to take nonproliferation concerns into account at the same time it had “the right to use nuclear energy for peaceful purposes.” 
  • A memorandum by Assistant Secretary of State Richard Holbrooke supporting Smith’s position, arguing that a failure to change the U.S. approach to Japanese reprocessing “would suggest … that we are insensitive to their most basic security and economic requirement” and could “also open a fissure in our relationship with the most profound consequences for US interests.”
  • Memoranda by top advisers to Secretary of State Edmund Muskie, Leon Billings and Berl Bernhard, who raised questions about Gerard Smith’s motives. Billings advised Muskie to take into account “the bias of State Department negotiators,” especially Smith’s background as a “life-long nuclear power advocate” who sees “current resistance [to nuclear power] in this country as something which should be overcome.”
  • A critique of Smith’s proposal by Policy Planning Staff official Robert Gallucci, who argued that it was a mistake to assume that a move toward plutonium breeder reactors was inevitable.
  • “There is still no accepted way to have breeders without having fuel loadings which would each contain enough plutonium to fabricate hundreds of nuclear weapons.”
  • A report by the U.S. Embassy in Tokyo on a report by the Japanese Atomic Energy Research Institute, which concluded that Japan did not need the second reprocessing plant. According to White House commentary on the report, it was “something of a bombshell” by providing “confirmation we have yet seen of the basic premises underlying the President's 1977 policies: that the need for large scale reprocessing and commercial use of plutonium remains distant and uncertain.”

The risk of nuclear of proliferation was a significant element in Jimmy Carter’s presidential campaign, which raised questions about the hazards of nuclear energy and attacked the Ford administration for ignoring the “deadly threat posed by plutonium in the hands of terrorists.” Not long after his inauguration, Carter signed Presidential Directive 8, which declared that “U.S. non-proliferation policy shall be directed at preventing the development and use of sensitive nuclear power technologies which involve direct access to plutonium, highly enriched uranium, or other weapons useable material in non-nuclear weapons states, and at minimizing the global accumulation of these materials.” Consistent with this, Carter called for an indefinite deferral of commercial reprocessing and the recycle of plutonium in the U.S. and restructuring U.S. breeder reactor programs to develop “alternative designs to the plutonium breeder.” He also directed U.S. nuclear R&D spending to focus on the “development of alternative nuclear fuel cycles which do not involve access to weapons useable materials.” [i]

To develop an international consensus on those ideas, Carter called for an International Nuclear Fuel Cycle Evaluation (INFCE) program, which partly aimed at promoting “alternative, non-sensitive, nuclear fuel cycles.” That goal and the critical approach toward reprocessing were complex diplomatically because, as noted, key allies such as Japan were committed to the goal of a “plutonium economy.” The 1974 Indian nuclear test had made Washington more sensitive to the proliferation risk of reprocessing, which dismayed the Japanese because Washington had formerly encouraged reprocessing. At Tokai Mura village, Tokyo was completing a facility that it would use for reprocessing U.S.-supplied reactor fuel. An earlier nuclear energy agreement with Japan provided the Carter White House with leverage over Japan’s reprocessing plans; nevertheless, Carter recognized that Washington could not “impose [its] will.” He avoided diplomatic tensions by approving a compromise permitting reprocessing at Tokai Mura village. The Japanese planned on going further by building a large plant for commercial reprocessing.

The compromise on Tokai Mura notwithstanding, Carter’s nonproliferation policy continued to rankle Tokyo, especially with the passage of the Nuclear Nonproliferation Act (1978). Criticizing the NNPA, Ryukichi Imai, a leading figure in the Japanese nuclear industry [See Document 4], said that “The United States no longer can impose upon the world its version of truth, but, by attempting to do so, it can cause enormous disturbances.” The Act called for the renegotiation of earlier bilateral nuclear energy agreements, but what especially bothered Tokyo was that it prohibited reprocessing of U.S. supplied fuel without U.S. approval. That strengthened the so-called “MB [Material Balance]-10” procedure that Washington had been following for years with respect to Japanese shipments of spent fuel for reprocessing in France and the United Kingdom. It was this procedure that Gerard Smith wanted so that Japan would not have to ask for permission routinely.[ii]

An important theme of early Carter administration diplomacy, one that was central to Smith’s thinking, was “trilateralism.” Smith was, with Zbigniew Brzezinski and David Rockefeller, one of the founding fathers of the Trilateral Commission, formed in the early 1970s in order to enhance U.S. relations with Japan and the European Community. Like his colleagues, Smith worried about the impact of the 1971 “Nixon shocks” on Japan and Western Europe and sought to strengthen post-World War II multilateralism to prevent the kind of political and economic rivalries that had destabilized international relations during the 1930s. Trilateralists also worried about divisions that could weaken the West in the face of Soviet and Third World challenges. For the Carter administration, these goals proved difficult in practice and relations with trans-Atlantic and trans-Pacific allies were rocky.[iii] Nevertheless, the trilateral frame of mind made Smith sensitive to the concerns of Washington’s Japanese and Western European partners about nuclear energy issues, believing that failure to take a sympathetic approach could have an adverse diplomatic impact.

The international fuel cycle conference that Carter sought led to a number of international meetings during 1978 and 1979, but it did not arrive at the alternatives to reprocessing plutonium that the White House had sought. Owing to divisions among the nuclear states and developing countries seeking broad scope in developing fuel cycles, the INFCE did not rank the various nuclear fuel cycles according to the proliferation risk that they posed; nor did it find any technical means to eliminate or reduce the proliferation risks involved in reprocessing. Nor did it produce an across-the-board acceptance of the U.S. view that thermal recycling (the use of plutonium as reactor fuel) was economically disadvantageous. Moreover, some countries, such as Japan and France wanted the U.S. to make decisions that had been deferred while the INFCE was conferred, such as on the reprocessing of U.S.-origin fuel.[iv]

Catching up with the deferred decisions, among other issues, gave Smith an opportunity to suggest policy changes aimed at mitigating Japanese and Western European concerns. During the summer of 1980, with Carter’s approval, Smith held discussions with Japanese and West European nuclear energy officials, but the administration’s defeat in November meant that his agenda could not produce any results. Nevertheless, what Smith sought foreshadowed developments during the Reagan administration, which in 1987 reached an agreement, approved by Congress the next year, that gave Japan “comprehensive advanced consent” to reprocess. Tokyo could go forward with plans, still unrealized, to develop breeder reactors fueled with plutonium. CAC was an important concession and was controversial in the United States owing to concerns about political and environmental hazards of plutonium storage and transport. The internal Reagan administration record of the negotiations with Japan remains classified but is the subject of ongoing declassification requesting by the National Security Archive

Since the 1988 agreement Japan’s nuclear plans have gone awry. The Fukushima disaster raised questions about nuclear energy as a power source while the Monju fast breeder reactor turned out to be a tremendously expensive boondoggle, which the Japanese government decided to decommission in late 2016 (during more than 20 years it operated only 250 days). The government remains interested in developing plutonium-fueled fast reactors but that is a remote prospect. Plans to use plutonium in a mixed oxide (MOX) reactor fuel have come to naught. At present, therefore, Japan has no clearly defined use for the 48 tons of separated plutonium that it owns, some 11 tons of which are on Japanese territory.[v] The surpluses, which emerged as anticipated, continue to worry arms control experts, including some, such as Robert Gallucci, who were involved in the 1980 debate.[vi] Terrorists would need only a few kilograms of plutonium for a weapon with mass destruction potential. In the meantime, the Rokkasho reprocessing facility is scheduled to go on-line in 2018.[vii] The industrial scale facility is slated to separate 8 tons of plutonium maximum annually, although Japan has no specific plans for using most of it. 2018 is the same year that the 1988 U.S.-Japan agreement is slated to expire, although whether the Trump administration has any interest in renegotiating it remains to be seen.[viii] Meanwhile, the South Korean government, which cannot reprocess, under existing agreements with Washington, asks why it cannot do what Japan has been doing.

When NSC staffer Gerald Oplinger wrote that the plutonium surplus would constitute a “danger in itself,” he probably assumed an environmental hazard and possibly a proliferation risk and vulnerability to terrorism. He did not mention the latter risks, although the reference to surpluses of “weapons grade” material evoked such concerns. While Japanese reprocessing plants would be producing reactor-grade plutonium, it nevertheless has significant weapons potential.[ix] On the question of Japan’s nuclear intentions, the documents from this period that have been seen by the editor are silent; it is not clear whether U.S. officials wondered whether elements of the government of Japan had a weapons option in the back of their mind. Any such U.S. speculation, however, would have had to take into account strong Japanese anti-nuclear sentiment, rooted in terrible historical experience, Japan’s membership in good standing in the nonproliferation community, and that since the days of Prime Minister Sato, the “three Nos” have been official national policy: no possession, no manufacture, and no allowing nuclear weapons on Japanese territory.[x] According to a 1974 national intelligence estimate, Japan was keeping “open” the possibility of a weapons capability and had the resources to produce weapons in a few years, but the intelligence agencies were divided over the likelihood of such a development. The CIA, State Department intelligence, and Army intelligence saw such a course of action as highly unlikely without a collapse of U.S. security guarantees and the emergence of a significant threat to Japan’s security.[xi]

Sources for this posting including State Department FOIA releases as well as recently declassified records at the National Archives, including the records of Gerard C. Smith and Secretary of State Edmund Muskie. Many documents on Japan from the Smith files are awaiting declassification review.



[i]. For developments during the Carter administration, see J. Samuel Walker, “Nuclear Power and Nonproliferation: The Controversy over Nuclear Exports, 1974–1980,” Diplomatic History 25 (2001): 215-249.

[ii]. Ibid, 241-242. For background on the U.S.-Japan agreements, see Eugene Skolnikoff, Tatsujiro Suzuki, Kenneth Oye, “International Responses to Japanese Plutonium Programs, Working paper of the Center for International Studies, Massachusetts Institute of Technology, August 1995, and Masakatsu Ota, “Filling the Gap - Writing Nuclear History of Japan from Different Angles” Presentation for Panel on Nuclear Latency, Asia-Pacific Nuclear History Institute, 10 November 2016, Seoul, South Korea.

[iii]. See Dino Knudsen, The Trilateral Commission and Global Governance: Informal Elite Diplomacy, 1972-1980 (London: Routledge, 2016).

[iv] . Eliot Marshall, “INFCE: Little Progress in Controlling Nuclear Proliferation,” Science 207 (28 March 1980): 1466-1467; Philip Grummet, “From NPT to INFCE: Developments in Thinking about Nuclear Non-Proliferation,” International Affairs 57 (1981): 553-564.

[v]. For a thorough exploration, see Masafumi Tokubo, “Closing Japan’s Monju Fast Breeder Reactor: The Possible Implications,” The Bulletin of the Atomic Scientists 73 (May-June 2017): 182-187.

[vi]. See Robert Gallucci’s presentation on the “Risks of Civil Plutonium,” at a symposum, “Remembering Paul Leventhal: Nuclear Lessons for a New Administration,” LBJ Washington Center, 13 April 2017, , For an earlier look at the problem, see Frans Berkout, Tatsujiro Suzuki, and William Walker, “The Approaching Plutonium Surplus: A Japanese/European Problem,” International Affairs 66 (1990): 523-543. For a recent study by the International Panel on Fissile Materials, see Masafumi Takubo and Frank von Hippel, Ending Reprocessing in Japan: An Alternative Approach to Managing Japan’s Spent Nuclear Fuel and Separated Plutonium, Research Report No. 12, November 2013.

[vii] . Some of the plutonium would be used for a fuel fabrication plant that would be used to produce uranium-plutonium mixed oxide (MOX) for fueling light water reactors. For a critical assessment of MOX by the International Panel on Fissile Materials, see Frank von Hippel and Gordon MacKerron, Alternatives to MOX: Direct-Disposal Options for Stockpiles of Separated Plutonium, Research Report No. 13 (2015).

[viii]. For recent efforts to bring the issue to the attention of policymakers, see Tokubo, “Closing Japan’s Monju Fast Breeder Reactor,” cited above and James Acton, “Time for a Nuclear Intervention with Japan,” Wall Street Journal, 15 May 2017. See also Masakatsu Ota, “End to Breeder Reactor, Plutonium Pile-up are Twin Problems for Japan’s Reprocessing Policy,” Japan Times, 21 September 2016.

[ix]. See articles by Gregg Jones at Proliferation Matters, J. Carson Mark, “Explosive Properties of Reactor-Grade Plutonium,” Science and Global Security 4 (1993): 111-128, and U.S. Department of Energy, Office of Arms Control and Nonproliferation, Nonproliferation and Arms Control Assessment of Weapons-Usable Fissile Material Storage and Excess Plutonium Disposition Alternatives, January 1997, 38-39.

[x]. Sato may have considered a nuclear weapons option for Japan as a bargaining tool to make diplomatic gains on the reversion of Okinawa. See Tristan Volpe, “Atomic Leverage: Compellence with Nuclear Latency,” Security Studies 26 (2017): 517-44.

[xi] . See Special National Intelligence Estimate 4-1-74, Prospects for Further Proliferation of Nuclear Weapons, 23 August 1974.