Depending on who you ask, the impending closure of a major Philadelphia refinery will either increase U.S. vulnerability to a terrorist attack on its energy supply or simply shift demand to other suppliers of petroleum products.

Senior officials from federal Energy and Homeland Security departments debated the loss of U.S. refining capacity with industry representatives and politicians at a field hearing of a congressional committee outside Philadelphia on Monday.

According to Brandon Wells, director of the Homeland Infrastructure Threat and Risk Analysis Center at the U.S. Department of Homeland Security, the planned shutdown of the Sunoco plant in July won't undermine America's energy security.