Saudi Arabia has constructed with Chinese help a facility for extracting uranium yellowcake from uranium ore, an advance in the oil-rich kingdom’s drive to master nuclear technology, according to Western officials with knowledge of the site. The facility, which hasn’t been publicly disclosed, is in a sparsely populated area in Saudi Arabia’s northwest and has raised concern among U.S. and allied officials that the kingdom’s nascent nuclear program is moving ahead and that Riyadh is keeping open the option of developing…