Brazil’s Nuclear Puzzle

October 22, 2004, p. 617

Brazil is planning to commission later this year a uranium enrichment plant that, if configured to do so, could fuel several nuclear weapons annually. As a member of the Nuclear Nonproliferation Treaty (NPT), Brazil has promised not to make such weapons and is obliged to allow the International Atomic Energy Agency (IAEA) to ensure this is the case. But this spring Brazil took the extraordinary step of barring the plant’s doors to the IAEA’s inspectors.

Brazil and the IAEA are now negotiating over how much access the IAEA will have. The outcome will set a precedent for Iran and for any other country that decides to build an enrichment plant while a member of the treaty.

At its announced capacity, Brazil’s new facility located at Resende will have the potential to produce enough U-235 to make five to six implosion-type warheads per year.[1][2] By 2010, as capacity rises, it could make enough every year for 26 to 31[3] and by 2014 enough for 53 to 63.[4]

Brazil has pledged to enrich uranium to only 3.5% U-235, the concentration required by its two power reactors. This would be too weak to fuel a bomb, which typically requires a concentration of 90% or above. If Brazil should change its mind, its stockpile of uranium already enriched to 3.5 or 5% will have received more than half the work needed to bring it to weapon grade.[5][6] This confers what is known as “breakout capability”—the power to make nuclear weapons before the world can react. Such a power is what the United States and some European countries fear Iran is aiming at.

Iran, too, plans to field thousands of centrifuges at a new enrichment facility at Natanz and claims that its sole purpose is to produce low-enriched reactor fuel. If Brazil succeeds in denying the IAEA access to its centrifuges, Iran can demand the same treatment. Under the NPT, there is no legal ground for treating the two countries differently.

There is little evidence that Brazil actually intends to become a nuclear weapon power. Brazil’s science and technology minister Eduardo Campos declared earlier this year that “the Brazilian nuclear project is intended exclusively for peaceful purposes.”[7] He pointed out that Brazil has joined the Treaty of Tlatelolco, as well as the NPT, both of which forbid Brazil to make nuclear weapons. Brazil has also adopted a new constitution that does the same.

These statements, however, must be seen in light of Brazil’s nuclear history. During the 1980s, Brazil ran a secret effort to build an atomic bomb that ran in parallel with the public program to make electricity. It was administered by the military, and hidden from the IAEA. In 1990, the program was openly repudiated by Brazil’s newly elected President, Fernando Collor de Mello.[8] Brazil then joined the NPT and accepted international inspection.

But now, Brazil has built a physical screen around its centrifuges at Resende for the express purpose of preventing inspectors from seeing them. Brazil says it has done this to protect its advanced technology from leaking out to competitors. The IAEA, however, has a long history of protecting commercial secrets. Brazil is thus a serious challenge to the IAEA’s authority.

The real effect of the screen will be to make it harder—if not impossible—for the IAEA to do its job. The IAEA must account for all the enriched uranium the plant makes and must ensure that it is used only to fuel peaceful power reactors. Brazil contends that the inspectors will be allowed to see everything going into Resende and everything coming out and that that should be sufficient. But with a screen in place, it will be difficult to be sure the centrifuges are not hooked up to a hidden supply of uranium. Such a hookup would allow Brazil to stockpile enriched material while inspectors believe that the facility is less efficient than it really is. And since there is no requirement that Brazil enrich a certain amount of uranium, no one would be the wiser. Unfortunately, the IAEA has already allowed the Brazilian Navy to shield a group of centrifuges for several years at a pilot plant, where uranium was enriched. Thus, Brazil can argue that if the IAEA could certify for years that the pilot-scale plant was not siphoning off any uranium, and could do so without seeing the centrifuges, the same should be possible at Resende.

One response to this argument is that the throughput of the plants is different. Resende will have the capacity to enrich enough uranium for dozens of bombs per year. If the machines are shielded, the inspectors can only measure input and output and then calculate the “material unaccounted for.” This is the amount of uranium assumed to be hung up somewhere in the system. Every plant has some. The question is whether the amount makes sense. At Resende, the amount could be considerable, whereas the amount at the pilot plant, given the limited number of centrifuges there, was fairly small.

It seems unlikely that Brazil is really concerned that the IAEA will illegally reveal industrial secrets. More likely, Brazil is trying to hide the origin of the centrifuges. In December 1996, Brazil arrested Karl-Heinz Schaab, a former employee of Germany’s MAN Technologie AG, a firm that developed centrifuges for the European enrichment consortium called Urenco.[9][10] German authorities wanted Schaab extradited to prosecute him for selling centrifuge blueprints to Iraq. There is evidence that Schaab and other experts were helping Brazil as well.[11] It follows that, if the IAEA inspectors were to see the Brazilian centrifuges, they might discover that Urenco’s design data had been transferred.

The United States has decided not to challenge Brazil’s new status and instead has tried to persuade Brazil to cooperate with the IAEA. Its inspectors were to arrive in Brazil 15 October to pursue a solution to the inspection dispute. The rest of the world should help the United States convince Brazil to put these concerns to rest and to be a good nuclear citizen.


[1] If one assumes that the plant’s first cascade will produce 20,000 SWU/year and that 16 kg of uranium enriched to 93.5% U-235 are needed for an implosion device. For SWU capacity, see [2].

[2] M. Hibbs, Nuclear Fuel, 7 July 2000.

[3] If one assumes 100,000 SWU/year.

[4] If one assumes 200,000 SWU/year.

[5] About 3000 kg of uranium feed requires ~3500 SWU to make one implosion bomb. The same feed needs more than 2000 SWU to enrich to 3.5%. See (6).

[6] T. B. Cochran et al., Nuclear Weapons Databook, vol. 2, U.S. Nuclear Warhead Production, (National Resources Defense Council, Washington, DC, 1987), Table 5.1, p. 127.

[7] “Brazil refuses to let UN inspectors into nuclear facility,”, 5 April 2004.

[8] J. Brooke, New York Times, 9 October 1990, p. A1.

[9] M. Hibbs, Nucleonics Week, 19 December 1996, p. 1.

[10] M. Hibbs, Nucleonics Week, 20 March 1997, p. 17.

[11] M. Hibbs, Nuclear Fuel, 23 March 1998, p. 5.