The DOE and its predecessor agencies generated liquid radioactive waste as a byproduct of processing SNF for the production of nuclear weapons (DOE, 2009). These wastes were stored in large underground tanks at the

Hanford site, SRS, INL, and the West Valley Demonstration Project (WVDP) in New York State. The DOE Office of Environmental Manage­ment (EM) is now safely storing 333 million L (88 million gallons) of tank waste in 229 underground tanks at three sites:

1. Hanford: 204 million L (54 million gallons) in 177 tanks

2. SRS: 125 million L (33.1 million gallons) in 49 tanks

3. INL: 3.4 million L (0.9 million gallons) in three tanks.

Tank waste is by far the DOE’s most significant environmental, safety, and health challenge, as well as the largest cost element of the cleanup program. Many of these underground tanks, particularly at Hanford, have exceeded their design lives. The DOE expends significant resources and attention to monitoring and maintaining the tanks to ensure they are sound and leak free and that workers can safely perform the necessary tank maintenance and remediation.

The unique and hazardous nature of liquid RAW requires development of innovative technologies for waste retrieval and disposition. These include constructing treatment plants to convert liquid waste into a stable, long — lasting waste form such as glass until it can be safely disposed of in a geo­logical repository. These treatment plants house highly complex chemical and physical treatment processes and must be very robust to operate safely over many years and to protect workers from radiation fields and contami­nation. Thus, they are expensive to construct and operate and require advanced engineering and technologies.

The strategy for dealing with DOE’s tank waste is to:

• minimize the volume of high-activity waste to be solidified through treatment

• store glass canisters onsite until a federal repository is ready for perma­nent disposal

• solidify the low-activity waste (LAW) fraction and dispose onsite

• develop approaches to manage/treat/dispose of some tank wastes as other than HAW

• continue emptying and closing tanks according to compliance agreements.