co-sponsored, with Senator Kit Bond, an amendment to the Energy Policy Act of 2003 relaxing restrictions on the export of specific types of enriched uranium that were first enacted in the Schumer Amendment to the Energy Policy Act of 1992. The original Schumer amendment placed increased controls on U.S. civilian exports of weapons-grade highly enriched uranium (HEU) to encourage foreign users to switch to reactor-grade low-enriched uranium (LEU) for isotope production. HEU is attractive to terrorists because it can be used to create a simple nuclear weapon, while LEU cannot be used directly to make nuclear weapons. Burr's amendment allowed exports of HEU to five countries for creating medical isotopes. Burr was reelected four times with no substantial opposition. He never received less than 62% of the vote, and ran unopposed in 2002. United States Senate Elections 2004 In July 2004, Burr won the Republican primary to seek the U.S. Senate seat being vacated by John Edwards, who had retired from the Senate to run for vice president with presidential nominee John Kerry in the 2004 election, which they lost to incumbent president George W. Bush. He faced Democratic Party nominee Erskine Bowles and Libertarian Tom Bailey. Burr won the election by five percentage points. 2010 Burr defeated the Democratic nominee, North Carolina Secretary of State Elaine Marshall, with 55% of the vote. He is the first Republican since Jesse Helms to be reelected to the United States Senate from North Carolina. He also broke the "curse" that his seat held, being the first senator reelected to the seat since 1968 (when Sam Ervin won his final term). 2016 Burr defeated Democratic nominee Deborah K. Ross, 51%–45%. Burr was an advisor for Donald Trump's presidential campaign. 2022 On July 20, 2016, during his reelection campaign, Burr announced that, should he win that year's election (which he did), he would not seek reelection to a fourth term in 2022. Tenure and political positions In 2007, Burr ran for chair of the Senate Republican Conference, but lost to Senator Lamar Alexander of Tennessee by a vote of 31 to 16. In 2009, Senator Jon Kyl of Arizona, the Senate Republican Whip, appointed Burr Chief Deputy Whip in the 111th Congress. In 2007, Burr was named a deputy whip. In 2011, he announced his intention to seek the post of minority whip, the number two Republican position in the Senate, but he dropped