The US Department of Energy, or DOE, plans to complete the Russian fuel return program by 2009 and estimates the program could cost about $100m, but this estimate and time frame may not be reliable because of uncertainties associated with planning future shipments. The shipments to date have all consisted of fresh (unused) HEU fuel, which DOE considers the highest priority for returning to Russia because it is more vulnerable to theft. DOE is facing delays in returning spent HEU fuel, which has been used in a reactor, in part because Russia is planning to conduct an environmental assessment for each shipment. DOE has asked Russia to conduct a single environmental for the spent HEU fuel assessment in all of the countries participating in the program to expedite future shipments of spent fuel, but so far Russia has not agreed to this. DOE is considering ways to accelerate the program that could also increase the cost of the program by more than $30m, the report says.