Double-shell Tanks Research Articles

Tracking Sensor Location by Video Analysis in Double-Shell Tank Inspections

Double-shell tanks (DSTs) are a critical part of the infrastructure for nuclear waste management at the U.S. Department of Energy’s Hanford site. They are expected to be used for the interim storage of partially liquid nuclear waste until 2050, which is the target date for completing the immobilization process for all Hanford nuclear waste. At that time, DSTs will have been used about 15 years beyond their original projected lifetime. Consequently, for the next approximately 30 years, Hanford DSTs will undergo periodic nondestructive evaluation (NDE) to ensure their integrity. One approach to perform NDE is to use ultrasonic data from a robot moving through air slots, originally designed for cooling, in the confined space between primary and secondary tanks. Interpreting ultrasonic sensor output requires knowing where measurements were taken with a precision of approximately one inch. Analyzing video acquired during inspection is one approach to tracking sensor location. The top edge of an air slot is easily detected due to the difference in color and texture between the primary tank bottom and the air slot walls. A line fit to this edge is used in a model to calculate the apparent width of the air slot in pixels at targets near the top edge that can be recognized in video images. The apparent width of the air slot at the chosen target in a later video frame determines how far the robot has moved between those frames. Algorithms have been developed that automate target selection and matching in later frames. Tests in a laboratory mockup demonstrated that the method tracks the location of the ultrasonic sensor with the required precision.

Tracking Robot Location for Non-Destructive Evaluation of Double-Shell Tanks

(1) Background: Non-destructive evaluation of double-shell nuclear-waste storage tanks at the U.S. Department of Energy’s Hanford site requires a robot to navigate a network of air slots in the confined space between primary and secondary tanks. Situational awareness, data collection, and data interpretation require continuous tracking of the robot’s location. (2) Methods: Robot location is continuously monitored using video image analysis for short distances and laser ranging for absolute location. (3) Results: The technique was demonstrated in our laboratory using a mockup of air slot and robot. (4) Conclusions: Location tracking and display provide decision support to inspectors and lay the groundwork for automated data collection.

History of the First Double-Shell High-Level Nuclear Waste Tank at the Hanford Site

Approximately 55 million gallons of radioactive and chemically hazardous waste are stored at the Hanford site in underground single-shell and double-shell tanks constructed of carbon steel. In 2012...

Corrosion Management of the Hanford High-Level Nuclear Waste Tanks

The Hanford site is located in southeastern Washington State and stores more than 200,000 m3 (55 million gallons) of high-level radioactive waste resulting from the production and processing of plutonium. The waste is stored in large carbon steel tanks that were constructed between 1943 and 1986. The leak and structurally integrity of the more recently constructed double-shell tanks must be maintained until the waste can be removed from the tanks and encapsulated in glass logs for final disposal in a repository. There are a number of corrosion-related threats to the waste tanks, including stress–corrosion cracking, pitting corrosion, and corrosion at the liquid–air interface and in the vapor space. This article summarizes the corrosion management program at Hanford to mitigate these threats.

More Weight on the Job

This article discusses that new methods and heavier equipment are expected to hasten the nuclear waste transfer at the Hanford Site’s tank farms. The site includes old processing plants, groundwater that exceeds safe levels of radioactivity, and high-level radioactive waste held in 149 aging tanks—some more than 60 years old—that lie underground just 10 miles from the Columbia River. The objective is to remove the highly radioactive waste from the old tanks, which have a single shell construction, and transfer it to 28 newer, more-secure double-shell tanks nearby, where the waste will safely reside until it can be treated in facilities now under construction. There are approximately 53,000,000 gallons of nuclear and chemical waste stored in the tanks at the Hanford Site. Bechtel National Inc., another of the prime contractors for Office of River Protection, is building a treatment plant that will process the wastes being stored in the underground tanks into a stable glass form for permanent disposal in a federal geological repository.

History and Operation of the Hanford High-Level Waste Storage Tanks

Abstract The Hanford Site is a 560-square-mile (1,450-km2) complex established by the U.S. government in 1943 to produce plutonium for nuclear weapons, ultimately bringing an end to World War II. Plutonium production activities continued after the war through 1991, at which point the site's mission changed from plutonium production to environmental cleanup and restoration. Production activities at the site resulted in a broad range of contaminated materials and facilities, including 57 million gallons of high-level (i.e., highly radioactive) nuclear waste in liquid and solid forms. The high-level waste was stored as it was created, first in single-shell tanks built between 1943 and 1964, then in more robust double-shell tanks constructed between 1968 and 1986. Due to waste leakage in a small number of single-shell tanks and the potential for additional single-shell tank failures, all single-shell tanks were removed from service by 1980. All pumpable liquid has been transferred to sound double-shell tanks....

Immobilized Low-Activity Waste Performance Assessment:2001 Version

ABSTRACTThe Hanford Immobilized Low-Activity Waste Performance Assessment[1] examines the longterm environmental and human health effects associated with the planned disposal of the vitrified low-activity fraction of waste presently contained in Hanford Site tanks. The tank waste is the byproduct of separating special nuclear materials from irradiated nuclear fuels over the past 50 years. This waste is stored in underground single- and double-shell tanks. The tank waste is to be retrieved, separated into low-activity and high-level fractions, and then immobilized by vitrification. The U.S. Department of Energy (DOE) plans to dispose of the low-activity fraction in the Hanford Site 200 East Area. The high-level fraction will be stored at the Hanford Site until a national repository is approved.This report provides the site-specific long-term environmental information needed by the DOE to modify the current Disposal Authorization Statement for the Hanford Site[2]. The original Disposition Authorization Statement was based on the 1998 version[3] of this performance assessment, which was conditionally accepted by DOE [4].The calculations in this performance assessment show that a “reasonable expectation” exists that the disposal of the immobilized low-level fraction of tank waste from the Hanford Site can meet environmental and health performance objectives. As shown by the sensitivity studies, this conclusion remains valid despite the conceptual designs of the disposal facility and the ILAW packaging having undergone changes.

High-priority Hanford Site radioactive waste storage tank safety issues: An overview

High-activity radioactive waste has been stored in large underground storage tanks at the U.S. Department of Energy's Hanford Site in eastern Washington State since 1944. Since then, more than 227,000 m 3 (60 Mgal) of waste have accumulated in 177 tanks. These caustic wastes consist of many different chemicals. The waste forms include liquids, slurries, salt cakes, and sludges. A number of safety issues have been raised about these wastes, and resolution of these issues is a top priority of the U.S. Department of Energy. A waste tank safety program has been established to resolve these high-priority safety issues. This paper will deal with three of these issues. The issues described are the release of flammable vapors from single- and double-shell tanks, and the existence of organic chemicals and/or ferrocyanide ion-containing fuel-rich mixtures of nitrate and nitrite salts in single-shell tanks. Extensive management controls are employed to ensure that the tanks in question continue to be maintained a safe manner through issue resolution. In addition, comprehensive monitoring, characterization, and applied and basic research efforts have been initiated to support resolution of issues and to prevent creation of future problems associated with potentially incompatible wastes. The safety efforts will also support actions related to the planned retrieval and disposal of the wastes in these storage tanks. Such efforts will also provide the basis for safe near-future remediation of these tanks on an as-needed basis and will define the envelope of safety to support the disposal of all high-level waste in the Hanford Site tanks.