1955: The U.S. and Brazil sign an Atoms for Peace agreement for nuclear cooperation.
1956: The National Atomic Energy Commission (CNEN) is created.
1957: Brazil’s first research reactor, the IEA-R1, a pool light water reactor, goes critical.
1960: A second research reactor, the IPR-RI, a Triga Mark I light water reactor, goes critical.
1965: A third research reactor, the Argonauta, an Argonaut light water reactor, goes critical.
1971: Brazil orders a light-water power reactor from Westinghouse.
1975: West Germany agrees to provide Brazil with 8 nuclear power plants and facilities for a complete nuclear fuel cycle. In fact, only one reactor is supplied under the agreement.
Late 1970s: A secret “parallel” program intended to develop an atomic bomb begins. The program seeks to develop a graphite reactor to produce plutonium, and both laser and gas centrifuge technology to enrich uranium.
1980: Brazil and Argentina agree to cooperate in developing the nuclear fuel cycle.
1984: Angra I, the Westinghouse reactor, begins commercial operations.
1985: Joint Declaration of Nuclear Policy with Argentina.
1987: Brazil announces that researchers have succeeded in enriching uranium.
1987: A West German intelligence report says equipment from Brazil’s safeguarded nuclear program is leaking into the secret parallel program.
1988: Brazil adopts a new constitution restricting nuclear activities to peaceful uses and giving congress authority over nuclear affairs.
1988: A fourth research reactor, the IPEN / MB-01, a light water critical assembly, goes critical.
1990: Secret parallel nuclear bomb program is formally exposed.
1990: Secret shaft apparently intended for testing nuclear weapons in the Cachimbo mountains is symbolically closed.
1990: Argentina and Brazil sign the Foz de Iguacu Declaration on Common Nuclear Policy renouncing nuclear weapons and pledging to develop a system of safeguards.
1991: Argentina and Brazil sign a bilateral agreement for the exclusively peaceful use of nuclear energy, creating the Argentine-Brazilian Accounting and Control Commission (ABACC) to verify implementation of the agreed-upon safeguards.
1994: A Quadrapartite Agreement for nuclear inspections enters into effect between Brazil, Argentina, the IAEA, and the ABACC.
1994: Brazil enters into the Treaty for the Prohibition of Nuclear Weapons on Latin America and the Caribbean (Treaty of Tlatelolco).
1996: Brazil joins the Nuclear Suppliers Group.
1996: The Brazilian Navy announces that it has suspended plans to build a nuclear-powered submarine due to a shortage of funds.
1997: An agreement with the United States for peaceful nuclear cooperation is submitted to the U.S. Congress.
1998: Brazil ratifies both the NPT and the CTBT.
2001: The Angra II light water power reactor begins commercial operation.
2003: Brazil announces it still plans to build a nuclear submarine.
2003: Brazil announces that it will enrich uranium at a commercial-scale facility in Resende.
2004: Brazil prevents IAEA inspection of equipment at the facility in Resende, claiming it needs to protect its superior technology.