Audit Report: DOE-OIG-20-57

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September 30, 2020

Tank Waste Management at the Hanford Site

The Department of Energy’s Office of River Protection manages the River Protection Project at the Hanford Site (Hanford).  The Office of River Protection’s mission is to safely, efficiently, and effectively treat tank waste.  It is responsible for the storage, retrieval, treatment, and disposal of radioactive waste contained in the waste tanks and the closure of all tanks and associated equipment.  Washington River Protection Solutions, LLC is the contractor in charge of managing the tank waste until it is prepared for disposal.  The mission of the River Protection Project is to protect the Columbia River by safeguarding the nuclear waste stored in underground tanks and to manage the waste safely and responsibly until it can be treated for final disposition.

After decades of plutonium production activities at Hanford, about 56 million gallons of radioactive waste remains stored at Tank Farms.  In order to store the waste until treatment and disposal, the Department constructed 177 underground tanks, with capacity ranging from 55,000 to over 1 million gallons each.  Of these tanks, 149 are a single-shell tank (SST) design that consists of a carbon-steel tank encased in concrete with a design life of about 20 years.  These tanks were built between 1943 and 1964.  Currently, all SSTs are well past their design life and do not meet current regulatory requirements. The remaining 28 tanks were built between 1968 and 1986 with a double-shell tank (DST) design.  The DSTs have a carbon-steel inner tank with a separate steel liner surrounding it.  The tank liners are separated by an air space, or annulus, of about 30 inches, which is armed with a leak detection system.  Unlike the SSTs, the DSTs meet current Federal and state regulations.  We initiated this audit to determine if the Department can safely store tank waste at Hanford until the end of the cleanup mission.

We found that there is a risk that the Department may be challenged to safely store tank waste at Hanford until the end of the cleanup mission.  Specifically, the conditions of the SST and some DST have deteriorated over time and sufficient DST space may not be immediately available to accommodate additional failed tanks.  Despite the deteriorating conditions of the tanks over time, the DSTs will need to contain the tank waste until at least 2047.  We also found that the waste pipeline that extends between the two areas is not in service. 

According to Department officials, the Department has implemented various actions to manage tank waste in a manner that balances risk with cleanup completion.  For example, some actions already completed include forming a Tank Integrity Expert Panel, performing SST and DST Integrity Evaluations, performing major upgrades to Tank Farm systems, and addressing the lack of DST space.  However, the risks posed by additional tank failures remain a concern.  Until the issues we identified are addressed, the Department faces an increased risk to the safe storage of its tank waste while the cleanup mission remains incomplete.

Topic: Environmental Management