Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2018)

Fuentes, Roderick E.; Shukla, Prashant Kumar; Peters, Brent; Hitchcock, Dale

doi:10.2172/1557969

Cited by 3 publications

(8 citation statements)

References 9 publications

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“…However, in more dilute solutions, at low chloride levels, the fluoride is present and is a known pitting agent for carbon steel [6]. In order to separate the chloride and fluoride effects, fifteen tests were statistically selected for electrochemical experiments and historical CPP data with fluoride was analyzed with approximately 110 data points [7]. Logistic regression was performed with the results and with the additional experiments from tests at PF between 1 and 2.…”

Section: New Limits Pitting Corrosionmentioning

confidence: 99%

“…In addition, the effect of concentrated hydroxide solutions up to 6 M was also studied with an additional thirteen tests. [7]. Therefore, selection of 10% of the recommended dosage was to determine minimum VCI concentration needed for the secondary liner application.…”

Section: Task 1: New Limits Pitting Corrosion Testingmentioning

confidence: 99%

“…16 a,b) Schematic and a photo of the near infrared diode laser based QEPAS sensor system for analyzing concentrations of two gases (NH3 and CH4), c) Sensor Head, and d) Close-up image of the fiber-coupled QEPAS acoustic detection module (ADM) [7]. …”

mentioning

confidence: 99%

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Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

Fuentes

Shukla

Crossland

et al. 2020

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VCIs formulations were added during mid-course of experiments, i.e., after coupons have experienced corrosion in the untreated GW simulant. Three tests were conducted using VCI-A and VCI-B. The first two tests were conducted using 100% recommended dosages of VCI-A and VCI-B. The third test was conducted at 10% of the recommended dosage of VCI-B. Following conclusions are made from the experimental data and results:  The corrosion rate data indicated that 10% of the recommended dosage is insufficient in mitigating corrosion. This observation is consistent with a prior study which also concluded that VCIs' effectiveness vanishes at 10% of the recommended dosages for the aboveground tank bottom underside application.  The data also showed that 100% recommended dosages of VCI-A and VCI-B mitigated pitting corrosion of weathered coupons. Specifically, VCI-A mitigated pitting corrosion in immersed, Level 2, and Level 3 coupons, whereas VCI-B mitigated pitting corrosion in immersed, Level 1, and Level 3 coupons. Statistical significance of corrosion rate decrease in Level 1 coupons for 100% recommended dosage of VCI-A and Level 2 coupons for 100% recommended dosage of VCI-B could not be established; this may be due to choice of coupons' surface orientation being vertical during the tests, leading to limited and uneven weathering during groundwater only and groundwater plus VCI exposures. 3. Long term OCP Drift Tests OCPs of carbon steel were measured in three simulants from the new limits testing. Two sets of coupons, with three coupons in each set, were fabricated with differing surface conditions. The coupons' surface conditions included a 600-grit polished surface, and a surface with mill-scale plus corrosion products from legacy carbon steel (rail car steel AAR TC-128). Two coupons, one coupon from each set, were placed in each chemistry, and OCPs of the coupons were monitored for five months. OCPs of the coupons with polished surfaces evolved in the anodic direction with respect to the initial values, whereas OCPs of two of the three coupons with mill-scale plus corrosion products evolved in cathodic direction with respect to the initial values. Terminal OCP of one mill-scale plus corrosion products coupon was about 100 mV anodic with respect to the initial value. CPP data of the polished coupons before OCP evolutions showed mixed responses, i.e., a clear delineation between pitting and no-pitting cannot be made, and CPP data after OCP evolutions remained mixed (category 3), indicating that change in OCP values did not affect the CPP responses. Following exposures of the coupons during OCP evolutions, CPP data for the mill-scale plus corrosion products coupons in the three simulants showed negative hysteresis (category 1), which is a sign of no-pitting. The OCP and CPP data indicate that simulant chemistry and surface condition affect extent and direction of OCP evolution, however, OCP evolution does not affect the pitting susceptibility. Electrochemical Impedance Spectroscopy (EIS) spectra of the polished coupon...

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Section: New Limits Pitting Corrosionmentioning

confidence: 99%

Section: Task 1: New Limits Pitting Corrosion Testingmentioning

confidence: 99%

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Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

Fuentes

Shukla

Crossland

et al. 2020

Self Cite

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“…Thus, this approximation for the total halide would be conservative. 15 The carbonate and phosphate species were found to have little effect on the corrosion of carbon steel, so the concentration values for these ions were held constant at the respective mid-point of the range. It is important to understand this determination is specific to these series of tests and formulations.…”

Section: Role Of Fluoride and Variables Of Lower Significancementioning

confidence: 99%

Hanford Tank Waste Disposition Integrated Flowsheet: Corrosion Specification Development Final Report

Wyrwas

2018

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The Savannah River National Laboratory has developed a corrosion model to facilitate implementation of Hanford's Direct Feed Low Activity Waste flowsheet. The focus was specifically on secondary effluent waste stream compositions from the Hanford Waste Treatment and Immobilization Plant's melter off-gas treatment system returned to the Hanford Tank Farms (return stream.) The return stream compositions were predicted to contain components at relative concentrations that are significantly more corrosive toward the carbon steel waste tanks, specifically halide and sulfate anions, than the current waste compositions in the tank farms. Electrochemical tests were performed, utilizing a statistically designed matrix, to determine the corrosion chemistry limits that will mitigate pitting in the return stream. The current corrosion chemistry specifications for the Hanford Tank Farms do not mitigate for the halide concentrations that will be expected in the return stream. The model requires a 10:1 nitrite to total halide ratio, for stream compositions at a minimum of pH 10 and a maximum temperature of 40°C. The final specification may use other corrosion data that is being generated for the DST chemistry control limits to delineate between the effect of fluoride and chloride. This test program has employed statistically designed test matrices and electrochemical test methods to validate the corrosion model specifically at boundary regions to optimize corrosion control specifications. Revision vii

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“…SRNL-STI-2022-00060 Revision 0 viii SRNL conducted electrochemical tests to investigate pitting corrosion at current and anticipated DST waste chemistries and temperatures between 2015-2019 [2][3][4][5][6]. The testing utilized a protocol for cyclic potentiodynamic polarization (CPP), developed in conjunction with the Tank Integrity Expert Panel Corrosion Sub-group (TIEP-CSG), to assess the susceptibility of carbon steel to pitting corrosion in DST chemistries [7].…”

mentioning

confidence: 99%

Relationship Between the Marginal Probability of Failure for a CPP Test and the Recommended Corrosion Control Requirements for Hanford Double Shell Waste Tanks

Wiersma¹,

Harris²

2022

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The Hanford Site in Washington State currently stores millions of gallons of radioactive waste in underground, carbon steel, double shell tanks (DSTs) that were constructed between 1968 and 1986. A chemistry control and monitoring program has been established mitigate corrosion in order to extend the service life for the DSTs. The current waste temperatures in the DSTs are at historical lows (i.e., typically less than 50 •C). The previous chemistry control requirements were determined for conditions at temperatures significantly higher. SRNL undertook a statistically based investigation of the role of nitrate and halide ion (i.e., chloride and fluoride) induced pitting corrosion. The objective was to develop a comprehensive waste chemistry envelope for the simultaneous minimization of the pitting and SCC risks caused by halide and nitrate ions at the lower temperature conditions. On the basis of these tests, new chemistry control requirements were proposed and have since been implemented for pitting corrosion control.

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Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2018)

Cited by 3 publications

References 9 publications

Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

Hanford Double Shell Waste Tank Corrosion Studies (Final Report FY2019)

Hanford Tank Waste Disposition Integrated Flowsheet: Corrosion Specification Development Final Report

Relationship Between the Marginal Probability of Failure for a CPP Test and the Recommended Corrosion Control Requirements for Hanford Double Shell Waste Tanks

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