Prologue: April 7, 1977
Seventy-seven days into Jimmy Carter’s presidency, on the afternoon of April 7, 1977, he walked into the White House Rose Garden to announce that the United States would not reprocess its spent nuclear fuel.
The statement was brief. He had been working on it since the transition. It drew directly from the themes he had campaigned on through 1976 — proliferation, nuclear restraint, moral leadership — and from the October 28, 1976 decision Gerald Ford had made five days before his defeat at the polls. Carter was, in effect, making Ford’s decision formal and national. “We will defer indefinitely the commercial reprocessing and recycling of plutonium produced in the U.S. nuclear power programs,” Carter said. The Barnwell plant, on which Allied-General had spent approximately $250 million, would not receive a federal operating license. The West Valley facility would not be restarted. The proposed reprocessing infrastructure that the civilian nuclear industry had assumed would eventually follow the construction of the first commercial reactors was being cancelled, from the top, by a president who had himself served in the reactor-engineering program his decision would shape.
Carter had been a submarine officer. He had spent two years, from 1952 to 1953, in Rickover’s program. He had studied nuclear physics and engineering at the Naval Reactors training school, had served briefly aboard the USS *Seawolf* in preparation for the sodium-cooled reactor that never flew, and had left the Navy in October 1953 when his father’s death required him to return to Georgia to manage the family peanut warehouse. He was, as he would often say, the only American president with direct nuclear propulsion training. He understood, more precisely than any of his predecessors, what the technology could and could not do. He understood the fuel cycle. He understood what reprocessing was, what it required, and what it produced.
His decision to shut it down was, in that sense, informed. It was not a reflexive response to public anxiety about plutonium — though public anxiety about plutonium was rising, and would rise further. It was a policy choice made by a man who had considered the matter and concluded that the risks of reprocessing proliferation outweighed the benefits of closed-fuel-cycle economics. It was also, as critics of the decision noted then and have noted since, a choice made without meaningful consideration of whether alternative fuel cycles — the thorium-uranium-233 cycle chief among them — might offer different proliferation characteristics than the plutonium cycle whose infrastructure he was shutting down. To Carter, as to Ford before him, reprocessing was reprocessing. It produced fissile material. The specific fissile material it produced — plutonium-239 with its Pu-240 contamination, or uranium-233 with its U-232 contamination — was, from a proliferation-policy perspective, a technical detail.
The difference, however, was consequential. Uranium-233, which the thorium cycle produced, came out of any reactor containing significant quantities of U-232, whose decay daughters emitted gamma radiation so intense that any U-233 weapon would announce its presence to radiation detectors and would give its assemblers radiation doses making weapon assembly itself hazardous. This was not a theoretical observation. It was a 1944 observation, made by Glenn Seaborg in a memorandum that had effectively ended U-233’s serious consideration as a weapons material at Los Alamos. Plutonium-239, by contrast, could be separated from its Pu-240 contaminant with sufficient effort — the implosion weapon design at Los Alamos had been developed precisely to solve that problem — and once separated, Pu-239 was bomb material straightforwardly. These were facts known inside the weapons community. They were not widely known outside it. And they did not figure in Carter’s April 7 statement, which treated reprocessing as a single policy category.
The Oak Ridge team that had spent twenty years developing the molten-salt breeder — the team that had been formally ended in the 1976 budget — watched the Carter announcement from Tennessee. There was nothing left for them to do. The program had been cancelled. The reactor was in caretaker status. The files were going into archive storage. And now the broader fuel-cycle infrastructure that would have been required to scale the thorium breeder to commercial deployment was being closed at the presidential level. The technology they had developed would not be needed. The chemistry they had engineered would not be practiced. The knowledge they had accumulated over twenty years of laboratory work would be catalogued in ORNL technical reports and then, for most practical purposes, forgotten.
The long silence had begun.
The Thorium Coda at Shippingport
Four months after Carter’s Rose Garden announcement, on August 26, 1977, the Shippingport Atomic Power Station in western Pennsylvania achieved first criticality on a newly loaded thorium-uranium-233 core. Nearly two decades after the plant had first produced power, and twenty years after Eisenhower had remotely triggered ground-breaking in 1954, Shippingport was being used for one final experimental purpose: to demonstrate that a light-water reactor — specifically, the first civilian reactor Rickover’s team had built — could breed on thorium.
The project was called the Light Water Breeder Reactor, or LWBR. It had been authorized in 1965, conceived by Rickover personally, and designed and built over twelve years by the same Bettis Atomic Power Laboratory team that had built the original Shippingport core and every subsequent naval-reactor core. The LWBR’s fuel consisted of 39 core modules containing a zoned mixture of thorium-232 (as ThO₂) and uranium-233 (as UO₂). The core was rated at 60 megawatts electric, installed in the pressure vessel of the original Shippingport PWR, and designed to demonstrate that even a solid-fueled water-cooled reactor — the least favorable of all proposed breeder architectures — could achieve a breeding ratio above 1.0 with the superior physics of the thorium-uranium-233 cycle. No other American reactor program had ever pursued thorium as a primary fuel.
Rickover, in the years before the LWBR began operating, had become an unlikely thorium advocate. He was by then in his late seventies. He had commanded the Naval Reactors Branch for thirty years. He had been kept on active duty past every mandatory retirement age by the personal intervention of a succession of presidents — beginning with Eisenhower in 1954 and continuing through Carter, who had served as one of his officers and who as president retained a personal loyalty to his former commander. Rickover had, over those thirty years, built the American nuclear navy. He had also come to believe that the civilian nuclear industry his submarine program had seeded was in serious trouble, that the fuel cycle it had adopted was unwise, and that the thorium cycle offered advantages the industry had been foolish to abandon. He had said so publicly, in ways that made the nuclear industry uncomfortable. The LWBR was his technical demonstration of his belief.
The reactor operated successfully from August 1977 through October 1, 1982. Over those five years it accumulated over 29,000 effective full-power hours of energy and generated more than 2.1 billion kilowatt-hours of electricity into the western Pennsylvania grid. After shutdown, the 39 core modules were shipped to the Naval Reactor Facility at the Idaho National Engineering Laboratory, where postirradiation examination over the following years confirmed that the reactor had indeed bred — with a measured breeding ratio of 1.014, representing a net increase of 1.4 percent in fissile inventory over the five-year operating period. It was a small positive number. It was also a positive number, which meant that the reactor had functioned as designed. A light-water reactor had bred on the thorium cycle.
The demonstration proved what Wigner and Weinberg had argued in 1945, what the 1959 Task Force had accepted, and what every thorium-cycle proponent since had asserted: that thorium-uranium-233 chemistry offered sufficiently favorable breeding economics to work even in the unfavorable solid-fueled, water-cooled configuration. It did not prove that a commercial light-water breeder was economic — 1.4 percent breeding gain was far too small to support the complex reprocessing required — but it proved, at the scale of a commercial power plant, that the physics worked.
Shippingport was decommissioned after the LWBR core’s removal. The pressure vessel was cleaned and sealed. The reactor that had begun American civilian nuclear power in December 1957 was finished as an operating plant twenty-five years later. The site was restored to a greenfield condition over the following six years, becoming the first commercial power reactor to be fully decommissioned in the United States. The Shippingport site is today an open field adjacent to the Beaver Valley Power Station, with no visible remnant of the reactor that was the first civilian nuclear plant in the country.
The LWBR program’s final technical reports were written through the 1980s and 1990s at Bettis and at Idaho. They constituted a complete experimental record of light-water thorium breeding. They were not widely read outside Naval Reactors. The post-irradiation examination confirmed breeding; the academic nuclear-engineering community acknowledged the result; and the commercial utility industry, which was by then cancelling construction projects rather than ordering new ones, had no institutional interest in a breeder technology at all, much less one that required reprocessing infrastructure that Carter’s April 1977 decision had effectively shut down.
What the LWBR had demonstrated — that thorium could breed even under conditions unfavorable to the concept — went unacknowledged by the industry. The Bettis reports on LWBR operations and the Oak Ridge reports on the MSRE sat in the same archives through the 1980s and 1990s, drawing roughly the same level of attention, which was very little. Both told the same story: that the thorium cycle worked, that the engineering was real, and that America had stopped pursuing both at essentially the same moment.
Rickover, who had been the primary advocate within the Navy for the LWBR experiment, retired from active duty on January 31, 1982, at the age of eighty-two, after sixty-three years of naval service. He died four years later, on July 8, 1986. He had outlived the MSR program by a decade. He had outlived his own thorium experiment, operationally, by only four years. His death coincided, within a few months, with Chernobyl.
Three Mile Island-2
At four in the morning on March 28, 1979, a pressure-operated relief valve in the secondary coolant loop of Unit 2 at the Three Mile Island Nuclear Generating Station opened as it was supposed to — and then failed to close as it was supposed to. The stuck-open valve allowed primary coolant water to escape from the pressurizer. The reactor’s instrumentation did not display the valve position directly; it displayed only the command signal, which had reverted to closed. The operators, looking at instrument readings that indicated water level was increasing in the pressurizer, believed they had too much water in the primary loop and acted accordingly — reducing the flow of emergency core cooling water that had automatically initiated. The reactor core, which they were attempting to cool, was actually uncovering. Water above the fuel was boiling off. Fuel elements were overheating. Zirconium cladding was reacting with steam to produce hydrogen gas. Fission-product release was beginning. The core partially melted.
By the end of the first day of the accident, the state of Pennsylvania had begun considering evacuation. By the end of the second day, President Carter had dispatched a team led by Harold Denton of the Nuclear Regulatory Commission to take operational control. By the end of the third day, a hydrogen bubble in the reactor vessel was being monitored for the risk of internal detonation. Governor Dick Thornburgh recommended the evacuation of pregnant women and small children from within five miles of the plant. Carter himself and his wife Rosalynn flew to Middletown, Pennsylvania on April 1 and toured the control room, a gesture intended to demonstrate that the plant was now under control. No one had been directly killed. The reactor had not breached containment. A small amount of radioactive gas had been released to the atmosphere, at a level that epidemiological studies over the subsequent decades would fail to associate with any measurable population health impact. Technically, the accident was contained. Institutionally, it was a catastrophe.
Through the spring and summer of 1979, the Three Mile Island accident dominated American public consciousness of nuclear power in a way that no previous reactor event had. The combination of the early confusion about whether the plant was under control, the partially-melted core whose extent was not well understood at the time, the hydrogen bubble, and the March 1979 release of *The China Syndrome* (a film about a nuclear plant accident, released twelve days before the real one) produced a public narrative in which commercial nuclear power had proven itself unreliable and dangerous. Utilities that had already placed orders before 1979 would, in most cases, proceed to complete construction. Utilities that had been considering new orders did not place them. The last new American reactor order of the twentieth century had actually been placed in 1978, before the accident; no new reactor would be ordered in the United States again until 2007, a 29-year drought.
Alvin Weinberg, from his position at the Institute for Energy Analysis at Oak Ridge Associated Universities, had been warning about exactly this class of accident for nearly a decade. He had been speaking publicly about loss-of-coolant accidents, about the adequacy of emergency core cooling systems, about the consequences of a core melt in a large commercial reactor, since the early 1970s. He had argued, from the stance of a scientific elder who had helped design the first commercial reactors, that the light-water reactor was not optimally safe and that the industry would be vulnerable to a serious accident whose consequences it had not adequately considered. He had been criticized, from inside and outside the nuclear establishment, for giving comfort to the opposition. He had been removed from his laboratory directorship in part because of those arguments. And then, in March 1979, the accident he had been describing abstractly had actually happened.
Weinberg did not say I told you so. He published a series of careful analytical pieces in the years following the accident, in journals and in chapters of books, that used Three Mile Island to support the case he had been making for thirty years: that fluid-fueled reactors, and in particular molten-salt reactors, offered a safety architecture fundamentally different from the one that had failed at Three Mile Island. Molten salt reactors did not rely on high-pressure primary coolant. They did not depend on emergency core cooling systems to prevent meltdown. They were configured, by the physics of the liquid fuel, to respond to loss of cooling by automatic fuel drainage into a passively-cooled dump tank. The fuel could not melt because it was already molten; the hazard was containment of an intensely radioactive liquid, not prevention of fuel-cladding failure. These arguments appeared in various Weinberg publications through the late 1970s and early 1980s. They were read by a very small technical community. They did not reach the utilities. They did not reach the general public. They reached a handful of nuclear engineering graduate students who would, decades later, rediscover them.
The industry’s response to Three Mile Island was to reform the operating practices of light-water reactors, not to reconsider the reactor architecture. The Institute of Nuclear Power Operations, established in December 1979, implemented rigorous operator training, incident reporting, and operational review procedures across the entire American commercial nuclear fleet. These reforms were, by every metric, successful. Commercial American reactor operating performance improved dramatically through the 1980s and 1990s, approaching and in some cases exceeding ninety-percent capacity factors by the turn of the century. Three Mile Island was, operationally, the last significant American commercial nuclear incident. The industry that had been humbled by the accident recovered within a decade.
But the recovery was operational, not strategic. The period of reactor construction had ended. The period of new reactor-design development had ended. The civilian nuclear industry of the 1980s and 1990s operated the fleet it had built, improved its performance, and essentially stopped doing anything else. Advanced-reactor research, which had been a significant federal line item in the 1960s and 1970s, was scaled back through the 1980s and effectively ended by the early 1990s. The Department of Energy that had succeeded the AEC in October 1977 — itself in turn succeeded by the Nuclear Regulatory Commission as the civilian-reactor regulator — maintained a small advanced-reactor program, but at funding levels that could sustain research rather than development. The reactor-architecture innovations that might have grown from the MSR work, or from the LWBR experiment, or from the high-temperature gas reactor programs that had also operated in the 1960s and 1970s, were not pursued.
The nuclear industry of the late twentieth century became, in effect, a museum that was also a working power plant. It operated what it had. It did not build anything new.
The Fast Breeder Collapses
The Liquid Metal Fast Breeder Reactor program that had killed the molten-salt breeder in 1969 died itself in 1983.
The Clinch River Breeder Reactor Project had been authorized by Congress in 1970, on the assumption that a commercial-scale LMFBR demonstration would be operating in eastern Tennessee by the late 1970s, that commercial breeder deployment would follow in the 1980s, and that by the end of the twentieth century American electricity would be increasingly generated by a fleet of plutonium-breeding fast reactors whose fuel cycle was closed. The original project cost had been estimated at $400 million. Private utilities had agreed to contribute approximately $257 million of that, with the remaining federal share to be spent by the Atomic Energy Commission over a development period of about ten years.
The project had failed to meet any of its original schedules or budgets. Environmental reviews in the early 1970s delayed construction. Cost estimates escalated almost continuously — to $700 million by 1972, to $1.7 billion by 1975, to $3.2 billion by 1981, and, in the General Accounting Office’s estimate at the time of cancellation, to approximately $8.8 billion for the complete project including operating costs and an associated reprocessing plant that had not yet been built.
President Carter had proposed to cancel the project in 1977 as part of his nuclear-policy reset, arguing that it was economically unjustified, technologically outdated, and dangerous from a proliferation standpoint. He had failed to get congressional support for cancellation. Senator Howard Baker of Tennessee, who was the Senate Majority Leader during the critical years, had made the project a priority of his home-state political operation, and the combination of Tennessee jobs and institutional momentum had kept Clinch River alive through the Carter administration despite the White House’s opposition.
Reagan’s election in 1980 had given the project a reprieve. The Reagan administration supported the LMFBR in principle; the Department of Energy under James Edwards pushed construction forward; ground was broken at the site in eastern Tennessee in August 1982. By 1983 the visible construction at the site was substantial. The reactor building, the secondary loop infrastructure, and much of the supporting facilities had been built.
But the political support had eroded faster than the construction had progressed. An unusual coalition opposing continued funding had emerged: the Heritage Foundation on the right, citing the ten-fold cost overrun and the absence of economic justification; Ralph Nader’s Congress Watch on the left, citing proliferation and safety concerns; the Sierra Club, the Union of Concerned Scientists, and a half-dozen environmental organizations; plus a significant body of fiscal conservatives in Congress who viewed the project as a welfare program for Tennessee. On October 26, 1983, the United States Senate voted fifty-six to forty to delete further funding for Clinch River from the fiscal 1984 supplemental appropriations bill. Eight senators who had voted to support the project in 1982 changed their votes in 1983. The House had not even bothered to include funding for the project in its own appropriation. With both chambers against continuation, the project was over.
At the time of cancellation, the federal government had spent approximately $1.6 billion of public money on Clinch River over thirteen years. No reactor had been completed. No electricity had been generated. The partially-constructed site was, over the following years, dismantled and returned to TVA as open land.
What had killed the MSR in 1969 had now killed itself in 1983. The LMFBR program that had been the AEC’s highest priority through the 1960s and 1970s, that had consumed $400 million per year at its peak, that had justified the cancellation of every alternative breeder concept — was dead. The commercial fast-breeder deployment that had been the theoretical destination of the entire American breeder program since the late 1940s had been definitively abandoned. No commercial fast breeder would ever operate in the United States.
The irony of the timing did not escape Seaborg, who was by then in his early seventies and writing his memoirs at Lawrence Berkeley Laboratory. In the volume he would publish in 1993 on his AEC years under Nixon, Seaborg would write, with the benefit of fourteen years of hindsight: *”Alvin Weinberg may well have been right. The AEC, with the Joint Committee’s active connivance, may well have erred in putting too many of its breeder eggs in the LMFBR basket. While correctly stating the case for alternative concepts in budget presentations, we gave them only token support compared to the massive emphasis on the LMFBR. When presidential support was sought, it was for the LMFBR only, and when the LMFBR was elevated to the status of a national goal with additional budgetary support, it all but assured that the alternatives would recede further into the shadows.”*
This was a man who had voted for the LWBR over the MSBR in November 1969 acknowledging, in 1993, that the alternatives — including the MSBR — had deserved better than what he had been able to give them. It was one of the more honest post-hoc assessments in American science policy. It was also, by 1993, of purely historical interest. The MSBR program had been ended seventeen years earlier. The Oak Ridge team that had built it was dispersed. The reactor itself, MSRE, had been in caretaker status for twenty-four years. Seaborg’s self-indictment in print would not cause any of those decisions to be revisited.
What the collapse of the LMFBR did, institutionally, was open a question that had been closed since the early 1950s. The question was: why were breeder reactors needed at all? The LMFBR program had been justified on the premise that uranium would be scarce, that civilian nuclear power would expand rapidly, and that the plutonium economy was the long-term basis for American energy. By 1983, all three premises had been falsified. Uranium was cheap and abundant. Civilian nuclear power had stopped expanding. The plutonium economy had been cancelled by both Ford and Carter. A breeder reactor program was, in the economic and political environment of 1983, a solution to a problem that did not exist.
This argument would apply equally to the LMFBR and to the MSBR. It was an argument against breeding in general, at least for the short-term future. The MSR community, to the extent it still existed, accepted this assessment. MacPherson wrote in his 1985 retrospective that “we no longer expect a crisis in the availability of uranium for at least 50 yr. Even with some renewed growth, it is unlikely that breeders will be needed before 2035 to 2050. With this delay in the need for breeders, the primary current interest should be for reactors that are economical and that have other features of merit that might encourage a revival of new reactor construction.” The case for the MSR, in 1985, was no longer a case for breeding. It was a case for a different architecture altogether — cheaper, simpler, safer, capable of eventually being modified to breed when breeding was economically sensible, but primarily useful as an alternative to the light-water reactors that the industry was actually operating.
No one was listening. The nuclear industry had enough problems with the reactors it had.
The Weapons Complex Falls Silent
The weapons-production complex that the Borden-McMahon-Dean expansion of 1950-1955 had built — the Hanford reactors, the Savannah River heavy-water reactors, the gaseous diffusion plants, the component fabrication facilities at Rocky Flats and Amarillo — had been operating continuously since the early 1950s. Some of it had been modernized; much of it had not. The original wartime reactors at Hanford had been retired through the 1960s as the newer Savannah River reactors came online. The newer Savannah River reactors themselves, by the late 1980s, were approaching thirty years of operating life and showing their age.
On January 7, 1987, the N Reactor at Hanford was shut down for a six-month safety review. The reactor had been operating since 1963, producing plutonium for weapons and steam for a cogeneration power plant that sold electricity into the regional grid. Its design, with a graphite moderator and water cooling, shared some features with the Chernobyl RBMK reactor that had experienced a catastrophic accident nine months earlier in April 1986. Energy Secretary John Herrington had directed a panel of experts, chaired by Louis Roddis Jr. — the same Louis Roddis who had been one of Rickover’s six officers at Oak Ridge in 1946 — to assess N Reactor safety in light of Chernobyl. The panel had concluded that a Chernobyl-like accident could not occur at Hanford, but also that the reactor was “less safe than commercial U.S. plants.” A six-month shutdown for $50 million in safety modifications was ordered. The six-month shutdown became permanent. The reactor was placed in cold standby in 1988 and never restarted.
The Savannah River reactors followed over the next four years. C Reactor had been shut down in June 1985 after a leak and never restarted. P Reactor was taken offline in June 1988 as part of normal operations and never restarted either; in February 1991 it was formally designated for permanent shutdown. L Reactor, which had been in and out of operation through the 1980s, was placed in standby in April 1988 and permanently shut down in April 1993 without another restart. K Reactor, the last of the original five, ran briefly for a test in June 1992 — the last time a reactor at the Savannah River Site would ever be critical — and in November 1993 Energy Secretary Hazel O’Leary announced that it would not be restarted. By mid-1988, production of weapons materials at Savannah River had effectively ceased. By November 1993, it was over permanently.
Over their thirty-plus years of operation, the Savannah River reactors had produced approximately 36 metric tons of weapons-grade plutonium — a significant fraction of the American nuclear stockpile’s fissile inventory. They had produced most of the tritium that sustained American thermonuclear weapons through their 12.3-year decay half-life. They had produced the U-233 — approximately two metric tons of it, over the 1960s and 1970s — that now sat in storage buildings at Oak Ridge awaiting a purpose that would never materialize. They had been, from Truman’s signature on the 1950 letter authorizing Du Pont’s construction through their final shutdown in 1992, the plutonium production infrastructure of the American nuclear weapons program. Their shutdown was, in a certain real sense, the end of active American nuclear weapons production.
The Cold War provided the context. The Soviet Union had collapsed by 1991. The Strategic Arms Reduction Treaty had been signed in July 1991 and ratified in 1994. George H. W. Bush and Boris Yeltsin had agreed to sharp reductions in nuclear warhead counts. The American nuclear stockpile was being reduced, not expanded. The infrastructure that had been built to support expansion had become, almost overnight, infrastructure that no longer had a mission.
What followed, over the 1990s and 2000s, was the slow unwinding of the weapons complex into a different kind of operation. The sites did not close; they became the largest environmental-cleanup operations the Department of Energy had ever undertaken. Hanford’s B through F reactors, long retired, had left behind high-level waste tanks at the 200 Area that would require decades of remediation. Savannah River had left behind approximately 34 million gallons of high-level radioactive waste in storage tanks that would require processing into glass form for long-term disposal. Rocky Flats had been closed after an FBI raid in 1989 revealed environmental compliance failures, and the site would eventually be cleaned up and converted to a wildlife refuge. The weapons complex transitioned, through the 1990s, from production to waste management.
The specific piece of this history that would matter for the thorium story — though no one noticed it at the time — was the U-233 inventory. When the Savannah River reactors had produced U-233 in the 1960s, the material had been transferred to Oak Ridge for purification and storage. By the mid-1970s there were approximately two metric tons of U-233 at Oak Ridge in various chemical forms, housed primarily in Building 3019 at the Oak Ridge National Laboratory campus. The material was strategically valuable in principle — it was fissile, usable either as weapons material (with the U-232 contamination penalties Seaborg had identified in 1944) or as reactor fuel — and it was physically dispersed in a way that made consolidation and inventory control difficult. It had no active mission. It was, through the 1990s, a legacy inventory with no budget assigned to it, maintained in its storage configuration because no one had made a decision about what else to do with it.
The decision would come later. It would come, when it came, as a cleanup decision rather than a fuel-cycle decision — a judgment that the material was a liability whose continued storage was not justified. It would not come in the 1990s, while the larger cleanup task at Savannah River and Hanford was consuming the Department of Energy’s environmental-management attention. Through the end of the 1990s, the U-233 at Oak Ridge sat in Building 3019, cataloged and accounted for but without a mission.
The World Elsewhere
While the American weapons complex was winding down and the American civilian nuclear industry was operating the fleet it had built without plans for expansion, the rest of the world’s nuclear programs followed trajectories of their own.
The French nuclear program continued to build. Through the 1980s and 1990s, France constructed approximately sixty commercial reactors and achieved roughly seventy-five percent of its electricity from nuclear — the highest share of any large economy. The French had followed their own engineering direction, with gas-cooled reactors initially and then, from the 1970s forward, a standardized family of pressurized-water reactors derived under license from Westinghouse. France had also built the Phénix fast breeder at Marcoule and the much larger Superphénix at Creys-Malville, which operated intermittently from 1985 to 1998 before being cancelled. France had, briefly, experimented with molten-salt reactor concepts through the late 1960s and 1970s, but had never built a significant prototype. The French nuclear industry was, by 2000, a successful and mature one — but it was an industry of solid-fueled reactors. The thorium cycle was, for France, a research topic rather than a program.
The Soviet nuclear program, which had pursued a diverse set of reactor architectures through the Cold War, was disrupted by the Soviet collapse. Several of the Soviet laboratories that had worked on molten-salt reactor concepts — at the Kurchatov Institute, at Obninsk, at Dimitrovgrad — continued small research programs through the 1990s and 2000s under the Russian Federation, but their work was poorly connected to the Western nuclear community and only fragmentarily published in English. The Kurchatov team under Viktor Novikov published several papers in the early 1980s and continued molten-salt reactor theoretical work through the 2000s, but no significant Russian experimental program was mounted. The Soviet MSR tradition remained, through the 1990s, a thin research line rather than a developmental program.
India was different.
In 1954, the Indian physicist Homi Bhabha had laid out a three-stage plan for Indian nuclear power that was explicitly built around India’s resource situation: modest uranium deposits, very large thorium deposits (about a quarter of the world’s estimated reserves, concentrated in the monazite sands of the southern coast). Bhabha’s plan had three sequential stages. The first stage would be pressurized heavy-water reactors fueled with natural uranium, which India could mine domestically without requiring enrichment technology. The first-stage reactors would produce plutonium as a byproduct. The second stage would use that plutonium in fast breeder reactors that also contained thorium in a blanket, converting the thorium to uranium-233 while producing additional plutonium. The third stage would use the uranium-233 thus produced as fuel in thermal reactors — likely heavy-water or molten-salt — designed around the thorium cycle. The full three-stage program would take many decades to implement, but its end point was a civilian nuclear power system that ran essentially on Indian thorium, with minimal dependence on imported uranium. It was the program Indian resource endowment practically required.
Bhabha had died in an airplane crash on January 24, 1966, while the Indian program was still in its earliest phase. His successors had continued the work. Through the 1970s, 1980s, and 1990s, India had built a fleet of pressurized heavy-water reactors — the CANDU-derived units at Rawatbhata, Kakrapar, Kalpakkam, Narora, and elsewhere — fueled with natural uranium and producing plutonium for the second-stage program. India had, in 1985, brought online the Fast Breeder Test Reactor at Kalpakkam, a small sodium-cooled fast reactor that served as the training ground for Indian breeder technology. The FBTR had operated continuously from 1985 through the 2010s, providing several decades of Indian engineering experience with sodium coolant, metallic and mixed-oxide fuels, and fast-reactor neutronics.
India had also, from the 1970s onward, sustained a parallel research program on thorium. The Bhabha Atomic Research Centre at Trombay had pursued laboratory-scale thorium fuel-cycle chemistry continuously since the early 1960s. The Indian program had demonstrated thorium fuel fabrication, thorium fuel irradiation in research reactors, and U-233 separation chemistry from thorium targets at sufficient scale to produce the several hundred kilograms of U-233 that would eventually become Indian strategic inventory. By the end of the 1990s, India had more first-person laboratory experience with the thorium fuel cycle than any other country on earth.
India had also, through the 1990s, sustained a public commitment to the third-stage thorium reactor program. The Indian Atomic Energy Commission under Homi Sethna and later chairs had maintained the three-stage framework as the official long-term plan, with specific roadmap documents published at roughly decadal intervals. The Advanced Heavy Water Reactor — AHWR — was under active design at BARC through the late 1990s, conceived as a vertical-pressure-tube boiling-light-water-cooled, heavy-water-moderated reactor, fueled with a mix of thorium-232 with plutonium-239 or uranium-233, designed to generate roughly 65 percent of its power from thorium and to serve as a bridge technology from the second to the third stage of the Bhabha plan. The Prototype Fast Breeder Reactor — the second-stage demonstration — had been approved in principle and was in preliminary engineering design at the Indira Gandhi Centre for Atomic Research at Kalpakkam. Neither reactor had been built by the end of the century. Both remained, at the close of the 1990s, official programs on extended schedules.
The significance, for the American thorium story, was twofold. First, India had retained continuous institutional memory of thorium as a reactor fuel cycle throughout the same period in which the American thorium effort had been dormant. Indian nuclear engineers read the old ORNL reports. Indian graduate students wrote theses on molten-salt reactors and thorium fuel chemistry throughout the 1980s and 1990s. An engineer at BARC in 1995 had access to a living technical tradition of thorium reactor design that no American engineer in 1995 had access to, because no American institutional equivalent existed. Second, the Indian program would continue its long march toward the second and third stages into the twenty-first century — at paces determined by Indian political and economic circumstances, but always within a framework that had been established in 1954 and had never been abandoned.
While America forgot the thorium cycle through the 1980s and 1990s, India remembered it. The books were being written elsewhere.
Silence at Oak Ridge
Building 7503 at Oak Ridge National Laboratory, which had housed the Aircraft Reactor Experiment in 1954 and the Molten Salt Reactor Experiment from 1965 to 1969, stood through the 1980s and 1990s in a kind of institutional limbo. The reactor was in caretaker status: defueled in 1969, with the fuel salt removed to storage and the containment sealed. The building itself was still standing, still maintained, still occasionally visited by Oak Ridge personnel for environmental monitoring. It was not actively decommissioned, but it was not used. It was simply there — a concrete-and-steel structure on the laboratory’s sprawling reservation, in an area that had been the center of the aircraft-nuclear-propulsion and fluid-fuel-reactor programs from the 1940s through the 1960s, now quiet.
The laboratory around it had continued. Oak Ridge National Laboratory, which had become in Weinberg’s time a major multi-program national laboratory, remained a significant research institution through the 1980s and beyond. Its work through those decades focused on fusion research, on neutron scattering, on environmental research, on materials science, on computational biology. It had largely left reactor engineering behind. The reactor engineering community at Oak Ridge, which had numbered in the thousands during the MSRE years, had dispersed through the 1970s and 1980s — some to retirement, some to the laboratory’s other programs, a few to industry, a few to universities, a few to the nascent Department of Energy bureaucracy.
A small group of former MSR engineers, operating under various contracts through the late 1970s and 1980s, continued producing reports on molten-salt technology. These were technical-summary and design-study documents, not experimental programs. They were intended to preserve the accumulated knowledge of the MSR program for future reference, in case it was ever needed. Some were published as ORNL technical reports and entered the laboratory’s official documentation system. Others were working papers, distributed in small numbers to specialists, and filed at the laboratory and in personal collections. The names on these reports — Paul Haubenreich, Murray Rosenthal, Lamar McCurdy, Dunlap Scott, Leslie Dresner, and others — would be familiar only to a very specialized community.
The reactor’s fuel salt, which had been drained from the MSRE and stored in tanks at the building in 1969, was eventually removed from the reactor site and transferred to long-term storage in other Oak Ridge facilities. The uranium-233 that had been used to refuel the reactor in 1968 joined the larger U-233 inventory in Building 3019. The fission products that had accumulated in the fuel salt during four years of MSRE operation decayed according to their respective half-lives; the long-lived fission products, principally strontium-90 and cesium-137, remained in the material, contributing to the handling challenge that any future use of the salt would have to address.
Alvin Weinberg, who had been removed as laboratory director in 1973, founded the Institute for Energy Analysis at Oak Ridge Associated Universities in 1975 and directed it until 1985, when he retired into a “distinguished fellow” position. In that role and then in semi-retirement, Weinberg continued to write about nuclear energy, reactor safety, alternative reactor concepts, and — through the 1980s — the emerging science of atmospheric carbon dioxide accumulation and global warming. He was among the earliest senior American scientists to argue that carbon dioxide from fossil fuel combustion represented a long-term threat to climate stability, and that nuclear energy, if safely deployable at scale, represented the only plausible replacement for fossil fuels that did not depend on technologies that had not yet been demonstrated.
His arguments, through the 1980s and 1990s, were read by a small community. He published frequently in technical journals and less frequently in general-audience publications. He was occasionally interviewed for science journalism; his profile was highest around the publication of his 1992 book *Nuclear Reactions: Science and Trans-Science* and his 1994 autobiography *The First Nuclear Era*. He continued to maintain that the molten-salt reactor represented the best available civilian nuclear-power architecture, that the American decision to terminate it had been a mistake, and that the thorium fuel cycle would eventually be recognized as superior to the plutonium cycle that had been embedded in American institutional practice. These arguments were received by Weinberg’s academic peers with varying degrees of engagement, by the nuclear industry with polite disinterest, and by the general public not at all.
The American nuclear establishment of the 1980s and 1990s — the Nuclear Energy Institute, the Electric Power Research Institute, the major reactor vendors at Westinghouse and General Electric, the Department of Energy’s Office of Nuclear Energy — knew about Weinberg’s positions. It found them uninteresting. The industry was operating its existing fleet; advanced reactor concepts were research topics on which federal money was being carefully minimized; the thorium cycle was, from any rational commercial perspective, a topic of purely historical interest. Weinberg was, in the mainstream nuclear community’s assessment, a distinguished elder whose insistence on an obsolete architecture made him progressively marginal.
He continued to write. He continued to make his case. The small community that read him — a few academic nuclear engineers, a few retired industry researchers, a handful of graduate students who had been assigned his papers — formed, over the 1980s and 1990s, a kind of dormant network. They knew where the ORNL technical reports were. They knew the arguments. They were not in any position to act on them, because there was no program to act through. They waited.
His first wife Margaret had died in 1969, shortly before the MSRE’s shutdown. He had remarried in the early 1970s, to Genevieve DePersio. Weinberg continued to work, through the 1980s and 1990s, at the Institute for Energy Analysis offices in Oak Ridge and from his home in the city. By the end of the 1990s he was eighty-four years old, still writing, still corresponding with former colleagues and with the occasional newer reader who had found his work. He had, by then, spent nearly sixty years arguing for nuclear technologies that were not being built and against nuclear risks that he believed were not being adequately managed. The mainstream nuclear community had largely stopped engaging with his arguments. He continued making them.
End of the Century
The twentieth century closed on an American nuclear industry that had not ordered a new reactor in twenty-one years.
The last new commercial American reactor order had been placed in 1978. Three Mile Island in March 1979 had been followed by the cancellation of dozens of reactors already under construction and the termination of most that had been ordered but not yet built. The surviving fleet — approximately 104 commercial reactors at 65 sites across thirty-one states — operated at increasingly high capacity factors through the 1990s, reaching an industry average of approximately ninety percent by 1999. The reactors themselves were well-managed, reliable, and productive. What the industry was not doing was growing. No new plants were being planned. No new designs were being developed for commercial deployment. The research programs that had pursued alternative reactor architectures through the 1960s and 1970s had been scaled back through the 1980s and, with a few exceptions, essentially ended by the early 1990s.
The Department of Energy’s Office of Nuclear Energy maintained a small advanced-reactor research program through the late 1990s, focused primarily on adaptations of existing architectures: a modular high-temperature gas reactor concept that had been under development since the 1980s, some work on improved light-water reactor fuel cycles, and a small program supporting academic research at American universities. The funding levels were modest. The working assumption, across the department and the industry, was that new reactors would eventually be built when market conditions justified them, and that they would be evolutionary improvements on light-water reactor technology — larger, safer, more standardized, but architecturally continuous with the reactors that had been built from 1957 forward. There was no institutional constituency for a fundamental reactor-architecture reconsideration. There was no program to fund one.
Meanwhile, the Department of Energy had been pursuing, since the mid-1990s, a systematic modernization of its scientific and technical information infrastructure. The Office of Scientific and Technical Information, headquartered in Oak Ridge, had inherited from the Atomic Energy Commission and its successors a physical archive of roughly three million technical reports running from the Manhattan Project forward. Most of these existed only as paper copies, filed in laboratory libraries and DOE document warehouses around the country. Access to any of them required either visiting a physical facility or making a formal document request and waiting weeks for paper or microfiche copies.
Beginning in the mid-1990s, as the internet and web technologies matured, OSTI began systematically scanning, indexing, and making searchable the non-classified portion of its archive. The work was slow. Early full-text digitization was labor-intensive, storage was expensive, and search indices were primitive by the standards of later years. But the project proceeded, in the quiet way that government archival projects proceed. By the end of 1999, a fraction — not yet a large fraction, but a growing one — of the DOE’s historical nuclear research literature was available through OSTI’s web-accessible databases. The 1970 *Nuclear Applications & Technology* special issue on molten-salt reactors was not yet available online in 1999. The ORNL-5018 program plan from December 1974 was not yet available online in 1999. The Haubenreich-Engel MSRE operational papers were not yet available online in 1999. All would become available, as searchable full-text PDFs, over the following several years. In 1999, the process was underway but not yet consequential.
The digitization project was not motivated by any interest in the thorium cycle, the molten-salt reactor, or the alternative-reactor research that had been cancelled in the 1970s. It was a general archival modernization effort, driven by information-technology economics and the government’s document-access obligations. Its eventual consequence for the thorium story was entirely accidental. But the consequence would be real. The documents that had sat on paper in laboratory libraries and government warehouses through the 1980s and 1990s were, as the century turned, beginning their transition into something that could be found by anyone with an internet connection and a reason to look.
No one, at the end of 1999, was yet looking in large numbers.
At Oak Ridge, Building 7503 continued in caretaker status. The MSRE, defueled in 1969, had by the end of 1999 been in its non-operational configuration for thirty years — as long as it had taken from Fermi’s Chicago Pile-1 in December 1942 to Rickover’s retirement-age-deferred command of Naval Reactors in 1972, and almost as long again as the entire civilian nuclear era up to that point. The building stood. The reactor vessel stood inside it. The fuel salt was in storage. The uranium-233 produced at Savannah River in the 1960s and used to refuel the MSRE in October 1968 was in Building 3019. Everything that had been preserved had been preserved. What remained to be determined was whether any of it would ever be used again.
Alvin Weinberg was eighty-four years old. Kirk Sorensen was completing his master’s degree in aerospace engineering at the Georgia Institute of Technology. He had not yet encountered the molten-salt reactor. He had not yet heard of Weinberg. The community that would, in the following decade, gather around the thorium cycle and attempt to revive it as a commercial technology did not yet exist — not because the relevant individuals did not exist, but because they had not yet discovered what was, by 1999, becoming findable on the internet.
The silence that had begun with Carter’s Rose Garden announcement on April 7, 1977, was, as the twentieth century ended, still silence. The documents were preserved. The materials were preserved. The person who had led the molten-salt reactor program was still alive. But the active work had stopped, and the public memory of what had been attempted and cancelled had almost entirely faded. An educated American in 1999 could reasonably have believed that the only kind of nuclear reactor ever considered for commercial civilian power in the United States was the light-water reactor. The alternatives had existed, had been built, had been operated, had been documented — and had been, for practical purposes of the public understanding of nuclear power, forgotten.
What the next century would bring was uncertain. The nuclear industry’s growth had been stopped for two decades and showed no signs of resuming. The weapons complex had stopped producing materials and was transitioning to cleanup. The advanced-reactor research programs had been scaled back repeatedly and were, at their late-1990s levels, sufficient to maintain a few dozen researchers at a few national laboratories and universities, but not to develop a new commercial technology. The institutional infrastructure that had, in the 1960s, built the MSRE and pursued the MSBR reference design was gone — not physically destroyed, but dispersed, retired, reassigned.
The century closed on an America that had, fifty years earlier, launched a broad program of reactor-technology development and had, over the course of those fifty years, narrowed to a single architecture, operated that architecture for thirty years, and stopped building new reactors entirely. It was an unusual outcome for a technology that had, in 1950, been believed to represent the energy future of the world. It was an outcome for which there were many explanations, none of them entirely satisfactory — the accidents at Three Mile Island and Chernobyl, the cost overruns, the rise of natural gas as a competing fuel, the political disempowerment of the industry, the safety regulations, the waste-disposal difficulties, the public sentiment. What the outcome was not explained by, in any of the standard accounts, was the specific reactor-architecture decisions that had been made — and unmade — through the 1940s and 1950s and 1960s. Those decisions had shaped the technology the industry had tried to deploy. The explanations the industry offered for its difficulties treated the technology as given.
A few people, in the final years of the century, were beginning to notice the gap.
Notes on Sources
The Carter April 7, 1977 statement in the Prologue is drawn from the statement itself, available through the Jimmy Carter Presidential Library, and from the *Public Papers of the Presidents*. Context on Carter’s nuclear-engineering background is from his autobiography *A Full Life: Reflections at Ninety* (Simon & Schuster, 2015) and from Peter Bourne’s *Jimmy Carter: A Comprehensive Biography from Plains to Postpresidency* (Scribner, 1997).
Chapter Twenty-Nine, on the Shippingport Light Water Breeder Reactor, draws on the program’s published technical reports, particularly the Fuel Summary Report issued by the Idaho National Engineering and Environmental Laboratory (Illum, Olson, and McCardell, 1999, DOE/ID-10690), which documents the LWBR’s five-year operating history, its 29,000 effective full-power hours, and its postirradiation examination results confirming a breeding ratio of 1.014. The general history of Rickover’s involvement in the LWBR program draws on Francis Duncan’s *Rickover and the Nuclear Navy: The Discipline of Technology* (Naval Institute Press, 1990), which continues the Hewlett-Duncan history from the 1962 endpoint of *Nuclear Navy* through Rickover’s retirement in 1982.
Chapter Thirty, on Three Mile Island, draws on the Kemeny Commission Report (*The Accident at Three Mile Island: The Need for Change*, Report of the President’s Commission on the Accident at Three Mile Island, October 1979) and on J. Samuel Walker’s *Three Mile Island: A Nuclear Crisis in Historical Perspective* (University of California Press, 2004). The account of Weinberg’s 1970s safety arguments is from Weinberg’s autobiography *The First Nuclear Era* (AIP Press, 1994), Chapters 9 and 10.
Chapter Thirty-One, on the Clinch River Breeder Reactor cancellation, draws on the Congressional Research Service report *The Clinch River Breeder Reactor Project* (CRS Report 83-136, June 1983) and on the contemporary Chemical and Engineering News coverage of the October 26, 1983 Senate vote. The Seaborg self-indictment quotation is from Glenn Seaborg, *The Atomic Energy Commission Under Nixon* (St. Martin’s Press, 1993). The MacPherson 1985 assessment is from H. G. MacPherson, “The Molten Salt Reactor Adventure,” *Nuclear Science and Engineering* 90, 374-380 (1985).
Chapter Thirty-Two, on the weapons-complex shutdowns, draws on Michele Stenehjem Gerber’s *On the Home Front: The Cold War Legacy of the Hanford Nuclear Site* (University of Nebraska Press, 2007 edition) for the N Reactor narrative; and on Rodney Carlisle and Joan Zenzen’s *Supplying the Nuclear Arsenal* (Johns Hopkins University Press, 1996) for the Savannah River reactor operational history and the weapons-complex institutional history. The description of the U-233 inventory at Oak Ridge at the end of the 1990s draws on contemporary Department of Energy inventory documentation and on historical ORNL records.
Chapter Thirty-Three, on India’s three-stage program, draws on Raja Ramanna’s *Years of Pilgrimage: An Autobiography* (Viking/Penguin India, 1991), on the published documentation of India’s Department of Atomic Energy through the 1990s, and on secondary literature including M. V. Ramana’s *The Power of Promise: Examining Nuclear Energy in India* (Penguin, 2012). The specific AHWR and PFBR status as of the end of the 1990s is drawn from contemporary IGCAR and BARC technical publications.
Chapter Thirty-Four, on Weinberg’s post-directorship career and the silence at Oak Ridge, draws primarily on Weinberg’s own autobiography *The First Nuclear Era* (AIP Press, 1994) and on his 1992 book *Nuclear Reactions: Science and Trans-Science* (American Institute of Physics). The description of ORNL’s institutional trajectory in the post-MSR era draws on the laboratory’s own published history.
Chapter Thirty-Five, on the end of the twentieth century, draws on the Office of Scientific and Technical Information’s own published history of its digital archive programs; on Department of Energy annual reports and Office of Nuclear Energy budget documentation from the late 1990s; and on general histories of the American commercial nuclear industry through the period, including Matthew Wald’s contemporaneous *New York Times* reporting. The narrative frame — that the twentieth century closed on an American nuclear industry that had not ordered a new reactor in twenty-one years — is a matter of historical record. The specific characterization of the MSR community as not yet having formed by the end of 1999 is consistent with the author’s subsequent observation of the community’s formation in the early and mid-2000s.