Whoever is elected to succeed U.S. Rep. Dan Newhouse in Congress will need an appetite for negotiating Cold War-era nuclear waste cleanup.Congress holds the purse strings for cleanup at the Hanford nuclear site, the 580-square-mile site that was left with radioactive and hazardous chemical waste and contamination.Hanford cleanupNearly two-thirds of the plutonium produced for the U.S.’s nuclear weapons program between World War II and the Cold Wa…