Salt Lake City-based EnergySolutions has replaced its CEO, announcing the appointment of David Lockwood to the position in a statement Monday.EnergySolutions is a publicly traded nuclear services company with about 5,000 employees. It handles decommissioning and remediation for a range of projects. They include the decommissioning of Illinois’ Zion Nuclear Station and a contract with Toshiba to help decontaminate water at the Fukushima Daiichi nuclear plant in Japan.Lockwood succeeds Val John Christensen, who EnergySolutions said will become a strategic adviser to the company. An EnergySolutions board member, Lockwood, 52, previously worked as a partner at investment management firm ValueAct Capital and has held executive positions at software and financial services companies. He has a bachelor’s degree from Miami University of Ohio and an MBA from the University of Chicago."The board determined that the time is right for new leadership, so that the company is positioned to take advantage of its full long-term potential in a changing industry environment," said Chairman Steven R. Rogel.In the announcement, the company also revised its earnings outlook downward for 2012. Adjusted EBITDA guidance dropped $20 million, to between $130 million and $140 million.