DOE seeks heavy water reuse partners

The US Department of Energy’s (DOE’s) Office of Environmental Management (EM) has issued a request for information (RFI) seeking industry input on the beneficial reuse of up to 530,000 gallons of heavy water currently stored at the Savannah River Site (SRS) in South Carolina. The heavy water inventory was previously used as a moderator in tritium and plutonium production reactors.

“The heavy water inventory at Savannah River Site represents a significant strategic national asset,” EM Assistant Secretary Tim Walsh said. “This RFI is an important step toward identifying industry partners who can help maximise the value of this resource in support of American energy security.”

The RFI invites input from a broad range of stakeholders, including industry with demonstrated needs and expertise in heavy water processing and entities interested in exploring the development of new facilities or leasing land directly at the SRS. Heavy water has unique properties that can be used for advanced nuclear applications, cutting-edge research and the production of medical isotopes. DOE said the RFI “is a critical step towards maximising the value of this strategic resource by identifying pathways for its domestic processing, purification and repurposing”.

DOE-EM seeks to explore innovative pathways for repurposing the heavy water to address critical domestic needs. Specifically, the RFI seeks to:

• Identify potential applications for heavy water, deuterium, or derived isotopes that can directly benefit US domestic markets and strengthen national supply chains.
• Assess technical capabilities for handling, processing, de-tritiating, and purifying heavy water, particularly where tritium is present.
• Evaluate collaboration frameworks with external partners, including potential on-site facility development at SRS, to facilitate the efficient utilisation of the heavy water.
• Inform future strategy for the long-term management of the heavy water inventory, potentially leading to future solicitation or partnership opportunities.

SRS currently stores approximately 530,000 gallons of heavy water (deuterium oxide, D2O) at the −40 level in the moderator storage tank in the C, K, and L reactor buildings and drums stored in the L and K reactor facilities.

These facilities have structurally robust, thick-walled engineering to isolate the radioactive material. The −40 Level Moderator Storage Tanks located in the C, K, and L reactor buildings tanks hold bulk volumes of heavy water. The −40 level refers to the basement/sub-surface elevation of the heavy concrete reactor structures, providing exceptional radiation shielding and physical security against external impacts.

While C, K, and L reactors are no longer operational, their hardened process areas have been converted into long-term strategic material storage. C Reactor functions as a primary hub specifically for consolidated heavy water moderator storage. Portions of the inventory with varying levels of tritium contamination and enrichment are kept in sealed industrial drums. These are stored inside designated facility boundaries within the K and L reactor complexes, allowing for flexible segregation of the material by purity level.

The heavy water storage integrates into the wider nuclear material disposition infrastructure across these specific site locations. Beyond heavy water drums, the National Nuclear Security Administration (NNSA) uses the reinforced K-Reactor building for the secure consolidation and inspection of non-pit plutonium. The Disassembly Basin, housed inside the former L-Reactor building, features concrete walls 2.5-7 feet thick. It holds 3.4m gallons of light water to shield and safely cool used nuclear fuel (UNF) from domestic and foreign research reactors before chemical reprocessing.

DOE notes that the heavy water inventory, “stored in various moderator tanks and drums, exhibits varying levels of contaminants, tritium, and deuterium enrichment”. The heavy water was previously used as a moderator in tritium/plutonium production reactors and was retained due to its high deuterium concentration, making it a valuable resource.

Currently, DOE does not possess a dedicated facility for the de-tritiation of heavy water. While the Savannah River National Laboratory (SRNL) has demonstrated expertise in de-tritiation and can support the development of project plans, cost estimates, and independent reviews, any direct engagement with SRNL for such services would need to be negotiated separately between the interested party and SRNL. DOE said industry partners are free to pursue collaboration with any entity they deem appropriate for de-tritiation or other processing needs.

“Furthermore, DOE may have an interest in receiving and utilising the tritium once it has been successfully separated from the heavy water by an industry partner. This potential arrangement would provide a beneficial disposition pathway for the tritium and support internal DOE programmatic requirements.”

Five nuclear reactors were constructed at SRS in the early 1950s to produce plutonium and tritium for nuclear weapons. However, none of the reactors could produce these materials, or even enter the initial start-up process, until the 400/D area at SRS came online. The massive 400/D area, one of the first production areas completed at SRS, was constructed for the sole purpose of supplying the reactors with heavy water.

The reactors at SRS were unlike those at the Hanford Site in Washington state that produced plutonium for the Trinity test and the atomic bomb dropped on Nagasaki. Those reactors were “moderated” with graphite. SRS reactors were heavy water moderated – heavy water is much better than graphite at moderating neutrons during the fission process, but it can also cool the reactors. Completion of the reactors at SRS was staggered so they could be brought online as 400/D produced the amount of heavy water they each required.

Heavy water operations at SRS had ceased by 1982, having produced what was needed plus a sizeable surplus. Most was used in SRS reactors or otherwise domestically, while much was sold to other countries. By 1989 all of the reactors were shut down, further adding to the heavy water stockpile.

The heavy water can be disposed of by immobilising it in grout, but this is expensive and labour intensive. The Hydrogen Processing Group at SRNL was approached by DOE’s Office of Science to explore ways of removing the tritium from the heavy water to enable its re-use.

The Hydrogen Processing Group has investigated the existing methods for tritium removal, including simple distillation, combined electrolysis catalytic exchange and cryogenic distillation and favours an approach that incorporates all three methods. “Putting them altogether, we can treat 100% of the water, get back 100% of the heavy water, and get tritium gas that DOE can sell,” said Lucas Angelette Angelette, SRNL’s technical lead on the project.

Moreover, the heavy water contains rare and valuable isotopes of oxygen that, like deuterium, are useful in medicine. One of these isotopes is used in PET scans and can be worth thousands of dollars. The group is putting together cost estimates for both a pilot scale system and full production facility. Some funds are already available for purchasing capital equipment for the pilot system.

Meanwhile, DOE is now hoping industry will take on the task. Responses to the RFI are requested by 21 September.