Memorandum to the Files by Gary R. Bray, ACDA/NP/NE [Bureau of Nonproliferation and Regional Arms Control, Nuclear Energy Division], "Japanese Plutonium Supply and Demand Update," 11 October 1979, unclassified
National Security Archive
A 1979 U.S. arms‑control memo revises Japan’s plutonium balance, exposing how reprocessing assumptions became a diplomatic lever in the Cold‑War non‑proliferation debate.
Source: Memorandum to the Files by Gary R. Bray, ACDA/NP/NE [Bureau of Nonproliferation and Regional Arms Control, Nuclear Energy Division], "Japanese Plutonium Supply and Demand Update," 11 October 1979, unclassified Date: Jun 1, 1979 Archive: Smith records, box 17, Japan June-Dec 1979 Collection: Japan Plutonium Overhang Origins and Dangers Debated by U.S. Officials Jun 8, 2017
Editorial Analysis
Original analysis by the DriftSeas editorial desk. The complete primary-source document, transcribed from the National Security Archive scan, appears in full below.
Re‑evaluating Japan’s Plutonium Outlook, 1979
The memorandum dated 11 October 1979 is a routine internal update from the Arms Control and Disarmament Agency’s Nuclear Energy Division. Authored by Gary R. Bray, it was circulated among senior U.S. officials tracking the balance of plutonium that Japan could produce, reprocess, and ultimately use in fast‑breeder (FBR) and advanced thermal (ATR) reactors. The memo follows an earlier March 1979 briefing that warned of a shortfall in the 1980s and a surplus in the 1990s. New data—most notably the anticipated contribution from the United Kingdom’s Windscale Magnox reprocessing and Japan’s own pilot‑scale FBR fuel reprocessing—prompted a revision of that outlook.
The document sits at the intersection of two broader Cold‑War currents. First, the United States was negotiating the 1979 “Plutonium Management and Disposition” framework with its allies, seeking to prevent the spread of reprocessing technology that could fuel a latent nuclear‑weapons capability. Second, Japan’s burgeoning commercial nuclear program, embodied in the Joyo, Fugen, and the planned Monju breeder, was a test case for how a non‑nuclear‑weapon state could handle a growing inventory of weapons‑grade plutonium without triggering proliferation alarms. The stakes were amplified by the 1975 Nuclear Non‑Proliferation Treaty (NPT) safeguards regime, which required the International Atomic Energy Agency (IAEA) to verify that reprocessing activities remained peaceful.
Bray’s memo foregrounds a series of assumptions that reveal where U.S. anxieties lay. The “general conclusion” that Japan would have “more than enough plutonium” by the end of the decade hinges on three operational milestones: the Tokai‑Mura reprocessing plant coming on line, successful pilot‑scale reprocessing of FBR fuel in Japan, and the return of plutonium from European reprocessors. Each of these steps required U.S. export‑control approvals, a fact Bray emphasizes by noting Japanese concerns about “U.S. approval to operate that facility.” The memo therefore reads as a risk‑assessment rather than a neutral forecast; it flags the very approvals that could become diplomatic levers.
The “extreme cases” paragraph is especially telling. Bray concedes that both a severe shortage and a sizable excess are “equally credible,” underscoring the lack of reliable intelligence on Japanese reprocessing capabilities. This ambivalence mirrors internal debates within the U.S. government at the time—some officials argued that a Japanese surplus would pressure the United States to develop its own fast‑breeder fleet, while others feared that surplus plutonium could be diverted to weapons programs, either domestically or through black‑market channels.
A subtle but significant observation appears near the end: the memo suggests that Japan may be using only Magnox‑derived plutonium in its FBR experiments, implying that the United States has “no direct control over the reprocessing of Japanese FBR fuel.” If accurate, this would mean that a substantial portion of Japan’s plutonium supply chain was insulated from U.S. licensing, complicating any attempt to monitor or restrict its flow. The reference to a hypothetical 1,500 MTU/year LWR reprocessing plant—capable of generating 10,000–15,000 kg of plutonium with “no stated end use”—serves as a warning scenario, hinting at the policy discussions that later culminated in the 1990s “Plutonium Management and Disposition Agreement” between the United States and Russia.
In hindsight, the memo’s projections were only partially borne out. Japan’s Monju breeder suffered repeated technical setbacks and was eventually shut down, while the country never built the massive LWR reprocessing plant foreseen in the worst‑case scenario. Nonetheless, the document captures a moment when U.S. analysts were grappling with the dual imperatives of supporting Japan’s peaceful nuclear ambitions and preventing a latent proliferation pathway. Its detailed accounting of supply sources—Windscale Magnox, Tokai‑Mura, European reprocessing—provides a rare quantitative glimpse into the calculations that underpinned U.S. nonproliferation policy in the late 1970s.
The legacy of this memorandum extends beyond the specific numbers it cites. It illustrates how technical assessments of fuel cycles became inseparable from diplomatic negotiations over export controls, IAEA safeguards, and bilateral security assurances. The very language of “extreme cases” and “credible” scenarios foreshadows the risk‑based frameworks that now dominate nuclear‑security analysis. For scholars of Cold‑War nuclear diplomacy, the memo is a concise case study of how the United States managed the paradox of encouraging civilian nuclear power in an ally while vigilantly tracking the by‑products that could, under different circumstances, feed a weapons program.
[Dist ?] UNITED STATES ARMS CONTROL AND DISARMAMENT AGENCY
October 11, 1979
MEMORANDUM TO THE FILES
FROM: ACDA/NP/NE - Gary R. Bray [nRB]
SUBJECT: Japanese Plutonium Supply and Demand Update
The last set of graphs and tables detailing the Japanese plutonium supply and demand situation was developed early in March 1979. The general conclusion of that paper was that the Japanese would experience a shortage plutonium for their FBR and ATR programs during the decade of 1980 to 1990 but would have a large excess of plutonium during the 1990's.
Additional information has become available and the attached paper reflects on improved plutonium supply picture for the 1980's. The most important changes in the supply situation are the addition of plutonium arising from the reprocessing of magnox fuel at Windscale and the reprocessing of spent FBR fuels on a laboratory and pilot plant scales in Japan during the 1980's.
The general conclusion reached by the attached paper is that Japan will have more than enough plutonium to conduct its FBR and ATR programs presently planned for the 1980's and will in fact have an excess of plutonium by 1990. This conclusion is based on the assumption that all announced programs in the area of plutonium utilization meet their respective schedules, goals and objectives both in the area of supply and demand. This includes the operation of the Tokai Mura reprocessing facility, reprocessing of some FBR spent fuel as well as deployment of another LMFBR and a large ATR facility.
It is recognized that several different scenarios can be developed. On one hand an extreme case could be presented that all or most of the programs related to the supply of plutonium fall short of their objectives while the reactor deployment programs remain on schedule resulting in a large plutonium shortfall. On the other hand an extreme case can be presented in which all plutonium supply programs met their objectives but deployment of FBR's and ATR's are delayed resulting in an excess of plutonium. Both cases are equally credible.
The Japanese can be expected to dispute the conclusion of the attached paper. First the Japanese will state that the reprocessing of FBR spent fuel during the 1980's is a research and development program and as such is not directed at the production of plutonium. Therefore, the quantity of plutonium recovered from their FBR reprocessing program is very difficult to predict. Secondly, the Japanese will state that the recovery of plutonium at the Tokai Mura reprocessing facility is dependent on the U.S. approval to operate that facility and upon the Japanese technical ability to maintain the reprocessing facility in an operable mode. And finally, the Japanese will point to the fact that the return of the plutonium from Western European reprocessing of Japanese spent fuel will depend upon the Western Europeans meeting their operational schedules and upon the U.S. approvals to return the recovered plutonium to Japan and is, therefore in doubt. The U.S. approval for the return of recovered plutonium from Europe could be delayed until 1986 or later depending on when the plutonium is available.
A separate observation is also important. It appears, but has not been confirmed, that the Japanese have used only magnox generated plutonium in their FBR program and presently plan to continue that mode of operations. If this is true the U.S. has no direct control over the reprocessing of Japanese FBR fuel and the resultant recovered plutonium.
The projected excess of plutonium in Japan by 1990 occurs without the operation of a large (1,500 MTU/year) LWR reprocessing facility. If such a reprocessing facility were to be placed in operation in Japan the only reasonable use that could be made of the recovered plutonium would be thermal recycle in existing LWR's.
ACDA/NP/NE:GRBray:nw
DECLASSIFIED Authority NND 66817
Japanese Plutonium Supply and Demand Dates
October 12, 1979
The following graph and table update information relative to the Japanese plutonium supply and demand situation. The two major changes to the information presented during March 1979 is, first, the addition of the quantity of plutonium being recovered from the continuing reprocessing of magnox fuel at Windscale, and secondly, the addition of the quantity of plutonium to be recovered from reprocessing of FBR spent fuels scheduled to be reprocessed in Japan during the 1980's.
Spent magnox fuel is generated from Takai-1 a gas cooled 159 MWe reactor. This spent fuel is being shipped to the UK and reprocessed on a continuing bases. There is approximately 70kg of plutonium per year recovered from the reprocessing of this magnox fuel. At present there is approximately 400kg of Japanese plutonium on inventory at Windscale. The Japanese are presently planning to utilize this plutonium to fabricate the next core for Joyo.
The Japanese have a two phase program for the reprocessing of FBR spent fuel. A FBR fuel reprocessing test facility will be constructed in Japan by 1987. Preliminary design for the construction of this facility has already been completed. Meanwhile, a chemical processing facility is now under construction at Tokai Works with completion scheduled for mid fiscal 1980. The stated reprocessing capacity of this facility is approximately 120 kg HM/day.
The Japanese are still planning to have approximately 5,600 MTU of spent fuel reprocessed in Western Europe during the decade 1980 to 1990. The plutonium recovered from this reprocessing is scheduled to start return to Japan by 1986.
DECLASSIFIED Authority NND 66 817
The plutonium demand situation is as presented by the Japanese in earlier meetings. The near term demands include fuels for both Joyo and Fugen and require approximately 270 kgs of plutonium per year. Later large quantities of plutonium will be required by Monju and a future ATR demo facility.
In summary, the attached graph shows that the present announced Japanese programs should provide more than enough plutonium to meet stated requirements without the introduction of a large reprocessing facility. If a large (1,500 MTU/year) reprocessing facility is placed in operations early in 1990's between 10,000 to 15,000 kgs of plutonium will be recovered with no stated end use.
Cumulative Japanese Plutonium Supply and Demand
Metric Tons Plutonium
20 16 12 8 4
80 81 82 83 84 85 86 87 88 89 90
Plutonium Supply
Plutonium Demands (FBR, ATR & Research)
DECLASSIFIED Author
Projected Japanese Plutonium Supply and Demand (Kg PuF)
| 1980 | 1981 | 1982 | 1983 | 1984 | 1985 | 1986 | 1987 | 1988 | 1989 | 1990 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Demand | |||||||||||
| annual for Joyo | 180 | 180 | 180 | 180 | 180 | 180 | 180 | 180 | 180 | 180 | 180 |
| cumulative for Joyo | 180 | 360 | 540 | 720 | 900 | 1080 | 1260 | 1440 | 1620 | 1800 | 1980 |
| annual for Fugen | 95 | 95 | 95 | 95 | 95 | 95 | 95 | 95 | 95 | 95 | 95 |
| cumulative for Fugen | 95 | 190 | 285 | 380 | 475 | 570 | 665 | 760 | 855 | 950 | 1045 |
| annual for Monju | 680 | 680 | 680 | 680 | 680 | 680 | 680 | ||||
| cumulative for Monju | 680 | 1360 | 2040 | 2720 | 3400 | 4080 | 4760 | ||||
| annual for ATR Demo | 600 | 600 | 300 | 300 | 300 | 300 | |||||
| cumulative for ATR Demo | 600 | 1200 | 1500 | 1800 | 2100 | 2400 | |||||
| annual for R&D | 50 | 50 | 50 | 50 | 50 | 50 | 50 | 50 | 50 | 50 | 50 |
| cumulative for R&D | 50 | 100 | 150 | 200 | 250 | 300 | 350 | 400 | 450 | 500 | 550 |
| annual Total Demand | 325 | 325 | 325 | 325 | 1005 | 1605 | 1605 | 1305 | 1305 | 1305 | 1305 |
| cumulative Total Demand | 325 | 650 | 975 | 1300 | 2305 | 3910 | 5515 | 6820 | 8125 | 9430 | 10,735 |
| Supply | |||||||||||
| MOX reprocessing at UK (Annual) | 400 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 70 | 70 |
| (cumulative) | 400 | 470 | 540 | 610 | 680 | 750 | 820 | 890 | 960 | 1030 | 1100 |
| Tokai reprocessing (Annual) | 600 | 1200 | 1200 | 1200 | 1200 | 1200 | 1200 | 1200 | 1200 | 1200 | 1200 |
| (cumulative) | 600 | 1800 | 3000 | 4200 | 5400 | 6600 | 7800 | 9000 | 10,200 | 11,400 | 12,600 |
| FBR-Fuels reprocessing (annual) | 90 | 180 | 180 | 180 | 180 | 180 | 180 | 680 | 1100 | 1100 | |
| (cumulative) | |||||||||||
| URG-UK&France reprocessing (annual) | 1000 | 1000 | 1000 | 1000 | 1000 | ||||||
| (cumulative) | 1000 | 2000 | 3000 | 4000 | 5000 | ||||||
| Annual Total Supply | 1000 | 1270 | 1450 | 1450 | 1450 | 1450 | 2450 | 2450 | 2950 | 3370 | 3370 |
| Cumulative Total Supply | 1000 | 2270 | 3720 | 5170 | 6620 | 8070 | 10,520 | 13,040 | 15,990 | 19,360 | 22,730 |
| Balance | |||||||||||
| annual balance | 675 | 945 | 1125 | 1125 | 445 | (-155) | 845 | 1145 | 1645 | 2065 | 2065 |
| cumulative balance | 675 | 1620 | 2745 | 3870 | 4315 | 4160 | 5005 | 6150 | 7795 | 9860 | 11,925 |
[IFIED]
NATIONAL SECURITY ARCHIVE
National Security Archive, Suite 701, Gelman Library, The George Washington University, 2130 H Street, NW, Washington, D.C., 20037, Phone: 202/994-7000, Fax: 202/994-7005, nsarchiv@gwu.edu