Hanford leaking tanks

Energy submitted to Ecology for review a proposed “Leak Response Plan” in August 2023. Ecology is reviewing the Leak Response Plan now with Energy. This will be incorporated into the Hanford Sitewide Permit renewal, Revision 9A (Rev. 9 permit). This will be a generic plan for the entire SST system. Federal and state rules require a “contingency plan” for responding to leaks as part of a permit.

After Ecology reviews the Leak Response Plan, it will be included in the draft Rev. 9A permit public comment period, anticipated to begin in 2025. The Leak Response Plan is also an enforceable document under the Tri-Party Agreement. For any future single-shell tank leaks, Energy will follow the single-shell tank leak response plan.

An evaluation, which is described in more detail below, will consider the practicability of using certain processes or equipment for near term removal of liquid wastes from tanks B-109 and T-111.

In December 2023, Energy submitted the results of an evaluation of the practicability of accelerating retrieval schedules for the leaking tanks B-109 and T-111. The term retrieval generally refers to removal of waste from a tank in preparation for tank closure.

Among other elements, the evaluation was required to consider various infrastructure and technology developments that could potentially accelerate the removal of waste from tanks B-109 and T-111 and/or mitigate residual tank leakage risks. This evaluation was due in December 2023, pursuant to the Tri-Party Agreement (Milestone M-062-40).

The evaluation also evaluates the practicability of deploying certain technologies for selective removal of the liquid fraction of the tank waste (referred to as partial liquid retrieval or removal of drainable liquids) from the leaking tanks. The inclusion of this element of the evaluation was clarified pursuant to a settlement agreement with Heart of America Northwest.

Specifically, this element of the evaluation will consider options for use of the following technologies or processes:

• Enhanced salt well pumping
• In-Tank Pretreatment System (ITPS) 

This part of the evaluation will also consider the treatment and disposal pathway for the removed liquid waste, specifically including mobile options such as transport of the removed liquid waste by truck to a double-shell tank, treatment facility, or other option.

Ecology and the public will have access to the results of Energy’s evaluation when reviewing and commenting on the draft Rev. 9 permit and Leak Response Plan in 2024.

Regulatory requirements for single-shell tank leak detection, monitoring, and reporting are described in a Tri-Party Agreement primary document, RPP-9937 (Revision 5C). The requirements in this document will be incorporated into the Hanford Sitewide Permit renewal, Revision 9A (Rev. 9 Permit).

Detecting a leak is difficult 

Determining whether a single-shell tank is actively leaking is a complex process because the tanks are buried and because the leaks are relatively small and travel very slowly through the soil.

Workers removed a majority of the liquids in Hanford’s 149 single-shell tanks in the mid-1980s through the early 2000s as part of Hanford’s interim stabilization program. The liquid waste was moved to the site’s 28 double-shell tanks.

Any remaining liquids in the single-shell tanks are mostly entrained within the tanks’ sludge waste, which has a consistency similar to pudding. Over time, some liquid seeped out of both sludge and saltcake in the tanks. Rainwater and snowmelt can also intrude into the tank, adding to the volume of liquid waste that could then leak.

Tank monitoring

RPP-9937 requires the U.S. Department of Energy (Energy) to measure and monitor single-shell tank waste levels in various ways. For example, Energy collects quarterly monitoring data from inside the tanks by:

• Monitoring the surface level of waste in some tanks using a device called an ENRAF — a weight on a cable;
• Using instruments called liquid observation wells in some tanks to measure liquids contained within the waste; and 
• Taking liquid level measurements under the surface of the solid waste.

Energy also collects monitoring data from outside of some tanks. One method, called dry well logging, monitors the migration of past tank leaks. This involves drilling shallow holes in the ground, called boreholes, to monitor for contamination. However, dry well logging is not considered a reliable method for detecting new leaks.

Instead, Energy uses electrical technology while retrieving waste from a tank to detect if a new leak begins during retrieval. This technology uses electrodes to measure and detect changes in the moisture and conductivity of the soil surrounding a tank.

Leak assessment 

RPP-9937 also describes a process that our agency and Energy must follow when a potential single-shell tank leak has been detected. Energy uses historical monitoring data and predictive modeling to estimate the waste level in each tank. When new monitoring data falls below a set range and the level decrease cannot be explained by a normal occurrence such as liquid evaporation, Energy must notify our agency and initiate a formal leak assessment process.

A formal leak assessment is performed by a panel of subject matter experts. These experts review all available data to determine if a tank is actively leaking, or if there is some other explanation for what is happening. For example, decreases in waste levels could result from tank waste releasing gases, or as a result of an instrument malfunction.

In addition, the surface of the waste in a tank can consist of many valleys and hills which might change as waste shifts under monitoring equipment. Energy’s experts evaluate these shifts and other potential causes during the leak assessment process to determine if there is an actual active leak.

Once a leak is confirmed, Energy must formally notify our agency of the release and we must try to agree on how to respond to the leak. If we cannot reach agreement, our agency has authority to take enforcement action through an Administrative Order or civil penalties, if appropriate.

The Agreed Order builds on the single-shell tank leak detection requirements set forth in RPP-9937 by requiring Energy to evaluate the practicability of developing new or improved technologies to detect and measure single-shell tank leaks with increased accuracy and sensitivity. Energy must submit the results of this evaluation to our agency, as a new Tri-Party Agreement primary document by Aug. 25, 2024. The practicability evaluation was submitted early after completing the review, Ecology will provide a response letter that reflects Ecology’s decision, that will be documented in the TPA Administrative Record.

As part of this evaluation, Energy must analyze whether additional research and development is needed in order to make leak detection technologies accurate and sensitive enough to detect small leaks or minor changes in leak rates. If additional research and development is needed, the evaluation must establish the timeframe for completion and identify whether such development is technologically and economically practicable.

If this evaluation shows that it is practicable to develop and implement new or improved leak detection technologies, then our agency will work with Energy to establish the requirements and schedule for installation and operation through development of a work plan. Energy would need to submit a proposed work plan to us, as another Tri-Party Agreement primary document, within 90 days of our approval of the evaluation. Once we approve the work plan, Energy will be required to implement according to the approved schedule. Following implementation US DOE will revise RPP-9937.

Tank B-109 as well as tanks T-111 and T-101 are part of separate tank farms that were constructed between 1943 and 1944.

These three tanks are used to store mixed radioactive and chemically hazardous waste generated from decades of plutonium production.

B-109 background

Energy announced that Tank B-109 was actively leaking on April 29, 2021, following a formal leak assessment process that began in July 2020.

Tank B-109 received reprocessing waste from 1944 until 1976. Most of the tank's drainable liquid wastes were retrieved in 1985 and moved to a double-shell tank as part of Hanford's interim stabilization program.

Today, Tank B-109 holds about 123,000 gallons of waste, most of which is saltcake and sludge, with about 13,000 gallons of liquid. Energy estimates about 560 gallons of waste are leaking per year into the surrounding soil.

T-111 background

Single-shell Tank T-111 was most recently declared leaking in 2013, after earlier leak concerns in the 1970s. Energy chose to install an active ventilation system as a mitigation measure, which operated from July 2015 to April 2019.

In 2019, Energy determined that this system directly connected to Tank T-112, causing inadvertent evaporation from that tank.

Energy halted active ventilation of T-111 because the existing air permit didn't authorize ventilation of Tank T-112. Current liquid level decreases in Tank T-111 are at least as large as they were before and during the active ventilation, indicating that a different leak response action is needed for this tank.

Tank T-111 began receiving reprocessing waste in 1945.

Energy first suspected the tank was leaking in 1974. Between 1974 and 1976, workers transferred 63,000 gallons of waste to other tanks as part of a tank stabilization effort. Most of the tank’s drainable liquid wastes were retrieved and moved to a double-shell tank in 1995 as part of Hanford’s interim stabilization program.

In 1995, T-111 also underwent interim stabilization.

In 2013, Energy found T-111 had one of the highest decreases in liquid levels, among the single-shell tanks.

T-101 background

T-101 entered into service in 1944, and received waste from T Plant, and the BX and SX Tank Farms. The tank was deactivated in 1979 and declared an assumed leaker in 1992. This means the tank was suspected to have leaked at some point in the past. 

The tank has a capacity of 535,000 gallons, now holding 37,000 gallons of saltcake, 49,000 gallons of sludge, and about 7,000 gallons of supernatant.  

T-101 went through interim stabilization in 1993. 

In 2019’s the tank’s 1992 “assumed leaker” status was re-evaluated, and changed to “sound."

The most recent leak assessment recently completed in 2024 was initiated after a visual inspection showed reduced surface liquid and corresponding decreasing level trends. Following the assessment, the tank was determined to have its status changed from “sound” to “assumed leaker.”

Q: Are nearby communities, Columbia River, and groundwater at risk because of this leak?

A: Based on what we know about the volume of liquid leaking from tanks B-109, T-101, and T-111, the structure of the surrounding soils, and the depth of nearby groundwater sources, we do not believe either leak represents an imminent danger to nearby communities or to the Columbia River.

Energy estimates that it could take 25 or more years for the leaking waste from B-109 to reach groundwater, and that it could take 70 years for the leaking waste from T-111 to reach groundwater.

This leaking radioactive waste increases the risks of harm over the long-term. That’s why an enforceable order was necessary.

The measures in the Agreed Order are designed to stop the active leaks as soon as feasible, minimize the risks in the meantime, and ensure there is a response plan in place for new leaks.

Beyond the leak response plan required by the Agreed Order, there is an extensive groundwater treatment system covering much of the Hanford Site. This system extracts groundwater from under the site, and treats it to remove contamination. This system provides an additional level of protection.

The Agreed Order doesn’t require the continued operation of this system until the leaked waste reaches the groundwater. However, the order provides that all groundwater and corrective action requirements will be established through the Hanford Dangerous Waste Permit or the Tri-Party Agreement.

Q: When the leak was first announced, Energy said B-109 was leaking 3.5 gallons a day, which would be about 1,275 gallons a year. Why is there such a big difference in the leak amount being released today? (which Energy estimates at about 560 gallons per year)

A: According to Energy, the original leak estimate announced in April 2021 was based on a very conservative analysis of the change in the liquid levels in Tank B-109 at the time of assessment. Today’s estimate — about 1.5 gallons a day — is based on additional review of data collected between 2014 to 2021. Leak behavior from the tank can change with time and there are indications that the leak rate has decreased over the last year, but Energy is still evaluating that data.