The department estimated this summer that the shipments of low-level radioactive waste would begin this month.
The delay may give Energy Secretary Steven Chu more time to consider a request from U.S. Rep. Jim Matheson, D-Utah, to halt the shipments.
Matheson wants Chu to suspend disposal of depleted uranium from SRS and from facilities in Paducah, Ky., and Portsmouth, Ohio, until the Nuclear Regulatory Commission develops new rules for disposal of the material.
Depleted uranium is different from other low-level radioactive waste because it becomes more radioactive over time for up to 1 million years. The NRC recognized that distinction earlier this year and is taking public comments on how it should be handled.
The rule-making process for the waste isn't expected to be finished until 2012 at the earliest.
SRS spokesman Jim Giusti said today that the site is in the process of preparing to pack and load the roughly 10,000 metric tons of waste. The material will be shipped to EnergySolutions' disposal facility 70 miles west of Salt Lake City via rail car.
Giusti says the shipments will likely be completed by July.
EnergySolutions spokesman Mark Walker says there's no reason to delay disposal of the waste.
"We have been safely disposing of depleted uranium at Clive for nearly 20 years. We have conducted a performance assessment and meet all current NRC standards. We are currently starting the process to conduct a new performance assessment," Walker wrote in a statement. "We do not believe, as suggested by Congressman Matheson in his letter, that the Department of Energy should delay its shipments of DU to Clive."
The company has already voluntarily amended its license to dispose of depleted uranium under stricter guidelines that it believes will meet or exceed any the NRC develops.
However, environmental groups contend there's no way to know what the NRC will require and that waiting a few years is reasonable when it comes to protecting the health and safety of future generations.
So far, though, those pleas have been dismissed by state officials. The Utah Radiation Control Board denied a request last month to put a moratorium in place until NRC rule making is finalized.
Instead, the board said EnergySolutions should retroactively make disposal of the waste comply with whatever the new NRC rules will be.