Why China stopped making fissile material for nukes

Some western scholars have expressed growing concern about China’s expansion of its nuclear arsenal and what they see as a “sprint to parity” with the United States. One scholar even claimed that China could have built as many as 3,000 nuclear weapons, far above the estimate of Western intelligence agencies, which assume that China has between 200 and 300. As a comparison, the United States and Russia each keep roughly 7,000 nuclear weapons. If China had any interest in parity, that would leave it with an awfully long way to go.

It is true, though, that Beijing has been expanding its arsenal of nuclear warheads at a modest pace. In practice, however, this is less cause for alarm than might at first seem to be the case. China’s decision-making about the size of its nuclear arsenal and whether to undertake modernization is determined mainly by its policies of no first use and minimum deterrence. “No first use” is fairly self-explanatory: Beijing has declared that it will not strike another country with nuclear weapons unless that country does so to China first. The goal of China’s “minimum deterrence” policy, meanwhile, is to have a small arsenal of nuclear warheads capable of counterattack, enough that at least some survive an initial nuclear attack by an enemy.

Beyond these policy restraints on the size of China’s nuclear arsenal, any large expansion would still be constrained by its limited inventory of fissile material. In fact, China’s production history of military-grade plutonium and highly enriched uranium (HEU) demonstrates that it has never intended to pursue nuclear-weapons parity with the United States. China never officially declared that it halted HEU and plutonium production for weapons, but newly available public sources—including memoirs by former nuclear-complex workers, remarks by former officials, academic publications, and satellite imagery—show that it stopped in 1987. (I discuss these findings in greater depth in the recent report “China’s Fissile Material Production and Stockpile.”)

Based on these new sources, China’s current stockpile of weapon-grade fissile material consists of about 14 tons of HEU and 2.9 tons of plutonium. The new HEU estimate is significantly lower than other recent estimates, while the new plutonium figure is significantly higher. The new estimates show that China could still have the smallest military stockpile of HEU and plutonium among the five nuclear-weapon states recognized by the Nuclear Nonproliferation Treaty. As a comparison, the current stock of weapon-grade fissile material in the United States is estimated to include 599 tons of HEU and 87.6 tons of plutonium.

Assuming each Chinese warhead contains about 4 kilograms (kg) of plutonium in its primary stage and about 20 kg of highly enriched uranium in its secondary stage, a military inventory of about 2.9 tons of plutonium and 14 tons of HEU would support around 730 thermonuclear warheads. Given the huge gaps between Chinese and US fissile materials stocks and nuclear weapon arsenals, it is difficult to imagine China would even attempt to achieve parity.

A charged history. China initiated its nuclear-weapon program in 1955 with assistance from the Soviet Union. In 1958, China started construction of its first gaseous-diffusion enrichment plant at Lanzhou with advice from Soviet experts. Moscow withdrew all its experts in August 1960, though, forcing China to enter a new stage of nuclear self-reliance. On January 14, 1964, the Lanzhou plant began to produce HEU, which made possible China’s first nuclear test on October 16, 1964.

Construction on China’s first plutonium production reactor, meanwhile, began at Jiuquan in March 1960, but slowed down after the Soviet experts withdrew. The reactor finally reached criticality in October 1966.

Concerned about increasing tensions with the Soviet Union and the growing US military presence in the region, in 1964 China began to relocate its military- and heavy-industrial complexes to its southwestern and northwestern hinterlands. These so-called “third-line” projects were located in these areas to protect them from Soviet or American attack. The more vulnerable “first-line” sites were in China’s border and coastal areas, and “second-line” sites were in central regions. Chinese leader Mao Zedong considered the third-line construction campaign a key part of his national defense strategy, and third-line projects were required to be built quickly.

In March 1964, Beijing began site selection for a new set of nuclear-material production facilities in the third-line area, facilities required to be “near mountains, scattered and concealed” in the words of many Chinese publications. Beijing began construction on a gaseous diffusion enrichment plant at Heping in 1966. That same year, it decided to build Plant 816, a plutonium production complex that duplicated the one at Jiuquan, in caves under a mountain. Construction on this third-line plant started in February 1967, but the extremely hard rock made progress very slow. China ended the unfinished project in early 1980.

In the late 1960s, with China concerned about a possible war with the Soviet Union, Beijing initiated a second campaign to rapidly build nuclear-material production facilities in the third-line area. Given the very slow progress of Plant 816 and the urgent need for backup for the Jiuquan complex, in 1968 Beijing decided to quickly build another plutonium production complex at Guangyuan. Construction started on the Guangyuan reactor in October 1969 and it became operational in December 1973. China also decided in 1969 to build an additional third-line facility, an enrichment plant at Hanzhong, to be called Plant 405. That plant, however, did not start operation until the 1990s, and when it did, is was using Russian centrifuges that had been imported for civilian purposes.

Some accounts suggest that China attempted to build another underground reactor for plutonium production called Plant 827 in the 1970s. While there was a Plant 827, the available information suggests that it was a military heavy-water tritium production reactor. Beijing started building it in 1970 near Yichang in Hubei province. The effort entailed construction of two heavy-water reactors in caves—a tritium-production reactor and a civilian power reactor—plus a radiochemical research institute located downstream beside the Yangtze River. The plant’s employees described the venture as “two reactors and one chemical engineering project” (liang dui yi hua). The project has been called an early effort to explore and develop nuclear power in China. The radiochemical research institute was likely intended to do research and development on reprocessing the spent fuel from the power reactor. However, Plant 827 was never finished. Like Plant 816, the third-line plutonium production complex, it was terminated in the early 1980s after Beijing pursued its “military-to-civilian conversion” policy, a national program to encourage the entire defense industry to shift its focus from military products to the civilian sector.

Meanwhile, in light of the continuing grim confrontation with the Soviet Union, in 1976 Beijing required the reactors and gaseous-diffusion enrichment plants to increase production under the Fifth Five-Year Plan (set for 1976 to 1980.) After ten years of operation, the Lanzhou plant had just reached its original design capacity of about 0.1 million separative work units (SWU) per year in mid-1975. (An SWU is a measure of the effort required to separate isotopes of uranium during an enrichment process.) The plant increased its output by around 70 percent by 1980 by raising cascade flow rates and improving separation membranes. The Heping gaseous-diffusion enrichment plant, which began operating in June 1970, had reached its design capacity of 0.11 million SWU per year in 1975. As with Lanzhou, the Heping plant pursued the goal of increasing its output during the Fifth Five-Year Plan, and by 1980 had increased its production capacity by 1.5 times its original designed capacity, to 0.16 million SWU per year.

After nine years in operation, the Jiuquan reactor reached its intended power level of 600 megawatts thermal (MWt) in mid-1975. Subsequently, a great deal of effort went into increasing its plutonium production rate over the course of the Fifth Five-Year Plan, and the rate had gone up by 20 percent by 1979, a year ahead of schedule. The Guangyuan reactor achieved criticality in December 1973 and its intended power level of 600 MWt by October 1974. By increasing the power and uranium irradiation level, the Guangyuan reactor was able to increase its plutonium production rate by 30 percent by 1978, leading to it being dubbed the “1.3 reactor.” Together the Jiuquan and Guangyuan reactors reached the goal of becoming “2.5 reactors” as required under the Fifth Five-Year Plan.

A big shift. Driven mainly by security concerns, China continued for a while to increase fissile materials production for weapons, but at the outset of the 1980s it suddenly reduced production as part of its national campaign of military-to-civilian conversion. By the end of the 1980s, it would cease making HEU and plutonium for weapons altogether.

The process that would lead to this outcome started in 1978, when China adopted a policy of economic reform and an open-door policy that allowed foreign businesses to establish themselves in the country. China shifted its focus from military to economic development based on Deng Xiaoping’s judgement that there would be “no large world wars within the next twenty years.” It was a big shift from Mao Zedong’s strategy of constant war preparation.

In April 1979 the Second Ministry, which oversaw nuclear affairs, proposed that the nuclear industry should focus on military-to-­civilian conversion. After 1981, the central government reduced investment in building infrastructure to produce nuclear material and decreased its production of HEU and plutonium. Meanwhile, the government began to increase its investment in the civilian nuclear sector.

In the early 1980s, Beijing decided to cease work on the third-line nuclear facilities still under construction. It suspended the unfinished Plant 816 in June 1982, and ended it two years later. About 85 percent of the civil engineering work had been finished and more than 60 percent of the plant equipment had been installed. In the late 1980s, the plant was converted for non-nuclear civilian purposes, including fertilizer production, and in 1993 it was renamed the Chongqing Jianfeng Chemical Company. The project was declassified in 2002 and part of the site was opened as a tourist attraction in 2010. Meanwhile, Plant 827 closed around 1982, when its two heavy-water reactors were still at the design stage.

China’s fissile material makers had to find their own way to survive. On October 7, 1979, the Second Ministry submitted a request to the central government to be allowed to export enriched uranium to other countries. It received immediate approval from Deng Xiaoping, and in 1981, China began to supply low-enriched uranium (LEU) for the international market. This suggests that in 1980, the Lanzhou gaseous-diffusion enrichment plant likely stopped making HEU and shifted to producing LEU for civilian power or naval reactors. The Lanzhou plant was shut down on December 31, 2000 and demolished in 2017.

The Heping plant, meanwhile, is believed to have ended HEU production for weapons in 1987, and since then has produced enriched uranium products for non-weapon military or dual-use purposes.

Entering the 1980s, plutonium production decreased rapidly as well. The Jiuquan reactor was shut down by November 1986. As some Chinese publications noted, in August 1987, at a State Council meeting chaired by then-Vice Premier Li Peng, it was decided officially that the Jiuquan complex was to “close the reactor and stop reprocessing” (ting dui ting hua) and to “maintain the plant as a reprocessing base (for civilian purposes.)” The plant did stop plutonium production around that time. The reactor entered the decommissioning process in 1990.

After reaching a plutonium production peak in the late 1970s, the Guangyuan reactor likely reduced production in the early 1980s amid the military-to-civilian conversion campaign. It likely started the conversion work in September 1984. Some accounts suggest that conversion was complete in 1986, but that the plant never operated again due to safety concerns. It likely closed in 1986. In August 1987, the central government made a strategic decision to end military production and switch to civilian production at the Guangyuan complex, which could mean that China officially ended plutonium production in 1987. After 1988, the plant began conversion to civilian use, including for aluminum production, and in 1990 it entered the decommissioning process.

Will China join disarmament efforts? China’s history of fissile material production shows that when the country faced serious external threats, it rushed to increase stocks as it did with the third-line program. However, given an improved external security situation beginning in the late 1970s—in particular, normalized diplomatic relations between China and the United States—China pursued military-to-civilian conversion, which led it to cut off fissile material production in the 1980s. It did so even without being required to by international agreements, during a period when the global nuclear warhead inventory was at its peak. This history hints at how the international security situation will affect China’s attitude to any negotiations on a Fissile Material Cut-off Treaty, or involvement in the process of multilateral nuclear disarmament.

China has maintained a nuclear policy that features a no-first-use pledge, a lean but effective nuclear force, and avoidance of a costly arms race. Guided by a self-defense nuclear strategy, China’s ongoing nuclear modernization is solely aimed at ensuring the ability to retaliate under all circumstances. As such, US missile defense plans are a major driver shaping China’s nuclear weapon modernization plans, which currently include an expansion of its arsenal to include more and better intercontinental ballistic missiles (ICBMs). As the United States seeks to gain strategic nuclear primacy over China, China will surely take measures to recover the strategic balance.

China’s existing stockpile of fissile material would be sufficient for its current modernization programs. However, if the United States moves forward with plans for missile defense and space weapons, China may decide it needs more multiple independently targetable reentry vehicles (MIRVs) for its ICBMS or submarine-launched ballistic missiles in order to maintain its deterrence capability. That in turn might require more plutonium and HEU to fuel those weapons. If China believes it needs to retain the option of restarting fissile material production, it would likely be unwilling to join a Fissile Material Cut-off Treaty. Moreover, China’s limited stockpile of fissile materials puts a cap on its arsenal of weapons, which could influence the country’s decision on when to join a multilateral disarmament process.

On the other hand, China will likely constrain its nuclear expansion if the United States pledges to limit its missile defense plans and not neutralize or severely undermine Beijing’s nuclear deterrence capability. If the United States wishes to avoid a costly arms race and constrain any significant expansion of Chinese nuclear forces, the United States should abandon its pursuit of absolute security and accept mutual vulnerability with China.