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Corrosion Susceptibility Assessment of Tank 241-AN-106 in Supporting Double-Shell Tank Corrosion Control at Hanford Site

The chemical and radioactive waste at the Hanford Site is currently stored in 131 single-shell tanks and 27 double-shell tanks (DSTs). The DSTs were built between 1968 and 1986, and each has a capacity of about 1 million gallons. Figure 1 is one typical design of the DSTs. Double shell means that each tank consists of a primary tank within a secondary tank. The primary and secondary tanks are also known as liners, and both are made from carbon steel.

Product Number: 51323-18786-SG
Author: Sheewa X. Feng, Jason S. Page
Publication Date: 2023
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The chemical and radioactive waste at the Hanford Site is currently stored in single-shell tanks and double-shell tanks constructed of carbon steel. The corrosion management of these tanks has largely focused on the complex waste chemistries. New waste chemistry limits for corrosion control of the double-shell tanks were developed based on statistically designed test matrices and data analysis driven by the failure of the primary liner of one tank, and they were implemented in 2019 to minimize the risk of both stress corrosion cracking and pitting corrosion. With the implementation of the new chemistry limits, the waste in four double-shell tanks was declared to be out-of-specification, and recovery action plans are currently in place. Corrosion testing was conducted in suspected or confirmed out-of-specification tank waste to assess the actual corrosion risk of these tanks. This paper summarizes work conducted in assessing corrosion susceptibility of waste collected from Tank 241-AN-106. Corrosion testing included: (i) linear polarization resistance to determine general corrosion rate, (ii) cyclic potentiodynamic polarization to determine pitting corrosion susceptibility, (iii) ASTM G192 testing to determine repassivation potential, (iv) long-term coupon exposure testing, (v) crevice corrosion testing, and (vi) corrosion potential monitoring. The results indicated that the tank wastes from 241-AN-106 were benign to the carbon steel liner with respect to general corrosion and pitting corrosion although one solid layer was out-of-specification because of low hydroxide concentration.

The chemical and radioactive waste at the Hanford Site is currently stored in single-shell tanks and double-shell tanks constructed of carbon steel. The corrosion management of these tanks has largely focused on the complex waste chemistries. New waste chemistry limits for corrosion control of the double-shell tanks were developed based on statistically designed test matrices and data analysis driven by the failure of the primary liner of one tank, and they were implemented in 2019 to minimize the risk of both stress corrosion cracking and pitting corrosion. With the implementation of the new chemistry limits, the waste in four double-shell tanks was declared to be out-of-specification, and recovery action plans are currently in place. Corrosion testing was conducted in suspected or confirmed out-of-specification tank waste to assess the actual corrosion risk of these tanks. This paper summarizes work conducted in assessing corrosion susceptibility of waste collected from Tank 241-AN-106. Corrosion testing included: (i) linear polarization resistance to determine general corrosion rate, (ii) cyclic potentiodynamic polarization to determine pitting corrosion susceptibility, (iii) ASTM G192 testing to determine repassivation potential, (iv) long-term coupon exposure testing, (v) crevice corrosion testing, and (vi) corrosion potential monitoring. The results indicated that the tank wastes from 241-AN-106 were benign to the carbon steel liner with respect to general corrosion and pitting corrosion although one solid layer was out-of-specification because of low hydroxide concentration.

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