11 research outputs found
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Annual Report for EMSP #86803 -- Underground Corrosion After 32 Years: A Study of Fate and Transport
Researchers from Department of Energy (DOE) National Laboratories at the Idaho and the Savannah River Sites recovered and are analyzing part of a final set of stainless steel specimens buried by the National Bureau of Standards in 1070 at Site D, near Wildwood, NJ. Findings included estimates for 32-year corrosion rates, transport of corrosion product, and elucidation of the site’s hydrogeobiochemistry. An interdisciplinary research team unraveled the complicated interrelationships among metal integrity, corrosion rates, corrosion mechanisms, soil properties, soil microbiology, plant and animal interaction with corrosion products, and fate and transport of metallic ions. This research provides long-term corrosion and transport data that can reduce the uncertainty associated with long-term waste storage and improve fate and transport modeling predictions throughout the DOE complex. The research also provides improvements in several characterization techniques
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Underground Corrosion after 32 Years: A Study of Fate and Transport
Improved estimates for corrosion rates in variably saturated porous media are required by the U.S. Department of Energy to maintain long-term storage of radioactive contaminants in stainless steel containers. To better define these parameters, research was undertaken to complete the National Institute of Standards and Technology's (NIST) long-term study of buried stainless steel began 35 years ago. The 1970 study was initiated by the National Bureau of Standards (NBS), now known as NIST, when over 1000 specimens--including stainless steel Types 201, 202, 301, 304, 316, 409, 410, 430, and 434-configured as plates, U-bend, and tubes in both annealed and cold worked conditions with various treatments--were buried at six distinctive soil-type sites throughout the United States. During the first eight years of the study, four of five planned removals were completed with specimens retrieved after one, two, four, and eight years at each of the six sites. The fifth and final set of specimens remained undisturbed for over 34 years
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Long-Term Underground Corrosion of Stainless Steels
In 1970, the National Institute of Standards and Technology (NIST) implemented the most ambitious and comprehensive long-term corrosion behavior test to date for stainless steels in soil environments. Over thirty years later, one of the six test sites was targeted to research subsurface contamination and transport processes in the vadose and saturated zones. This research directly applies to environmental management operational corrosion issues and long term stewardship scientific needs for understanding the behavior of waste forms and their near-field contaminant transport of chemical and radiological contaminants at nuclear disposal sites. This paper briefly describes the ongoing research and the corrosion analysis results of the stainless steel plate specimens recovered from the partial recovery of the first test site
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Underground Corrosion of Activated Metals, 6-Year Exposure Analysis
The subsurface radioactive disposal site located at the Idaho National Laboratory contains neutronactivated metals from non-fuel nuclear-reactor-core components. A long-term underground corrosion test is being conducted to obtain site-specific corrosion rates to support efforts to more accurately estimate the transfer of activated elements in the surrounding arid vadose zone environment. The test uses nonradioactive metal coupons representing the prominent neutron-activated materials buried at the disposal location, namely, Type 304L stainless steel (UNS S30403), Type 316L stainless steel (S31603), nickel-chromium alloy (UNS NO7718), beryllium, aluminum 6061-T6 (A96061), and a zirconium alloy (UNS R60804). In addition, carbon steel (the material presently used in the cask disposal liners and other disposal containers) and a duplex stainless steel (UNS S32550) are also included in the test. This paper briefly describes the ongoing test and presents the results of corrosion analysis from coupons exposed underground for 1, 3, and 6 years
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The Underground Corrosion of Selected Type 300 Stainless Steels After 34 Years
Recently, interest in long-term underground corrosion has greatly increased because of the ongoing need to dispose of nuclear waste. Additionally, the Nuclear Waste Policy Act of 1982 requires disposal of high-level nuclear waste in an underground repository. Current contaminant release and transport models use limited available short-term underground corrosion rates when considering container and waste form degradation. Consequently, the resulting models oversimplify the complex mechanisms of underground metal corrosion. The complexity of stainless steel corrosion mechanisms and the processes by which corrosion products migrate from their source are not well depicted by a corrosion rate based on general attack. The research presented here is the analysis of austenitic stainless steels after 33½ years of burial. In this research, the corrosion specimens were analyzed using applicable ASTM standards as well as microscopic and X-ray examination to determine the mechanisms of underground stainless steel corrosion. As presented, the differences in the corrosion mechanisms vary with the type of stainless steel and the treatment of the samples. The uniqueness of the long sampling time allows for further understanding of the actual stainless steel corrosion mechanisms, and when applied back into predictive models, will assist in reduction of the uncertainty in parameters for predicting long-term fate and transport
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Comparison of Cleaning Methods for Analysis of Underground Beryllium Corrosion
The subsurface radioactive disposal site located at the Idaho National Laboratory contains neutronactivated beryllium metals from non-fuel nuclear-reactor-core components. A long-term underground corrosion test is being conducted to obtain site-specific corrosion rates of the disposed beryllium to support efforts to more accurately estimate the transfer of activated elements in the surrounding arid vadose zone environment. During the corrosion analysis, two cleaning methods were used. This paper describes the cleaning methods and presents a comparison of the results
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Digging for Treasure - Unique Fate and Transport Study
In 1970, scientists at the National Bureau of Standards (NBS), now called the National Institute of Standards and Testing (NIST), implemented the most ambitious and comprehensive long-term corrosion behavior test for stainless steels in soil environments. This study had historic significance since the NBS 1957 landmark corrosion textbook compiled by Romanoff did not include stainless steels, and this 1970 research set forth to complete the missing body of knowledge. To conduct the test, NIST scientists buried 6,324 coupons from stainless steel types, specialty alloys, composite configurations, multiple material forms, and treatment conditions at six distinctive soil-type sites throughout the country. Between 1971 and 1980, four sets of coupons were removed from six sites to establish 1-year, 2-year, 4-year, and 8-year corrosion rates data sets for different soil environments. The fifth and last set of coupons (approximately 200 at each site) remains undisturbed after 32-years, providing a virtual buried treasure of material and subsurface scientific data. These buried coupons and the surrounding soils represent an analog to the condition of buried waste and containers. Heretofore, the samples were simply pulled from the soil, measured for mass loss and the corrosion rate determined while the subsurface/fate and transport information was not considered nor gathered. Funded through an Environmental Management Science Program (EMSP) proposal, the Idaho National Engineering and Environmental Laboratory (INEEL) operated for the U.S. Department of Energy by Bechtel-BWXT Idaho, LLC (BBWI), is chartered to restart this corrosion test and concurrently capture the available subsurface/fate and transport information. Since the work of retrieving the buried metal coupons is still in the planning stage, this paper outlines the interdisciplinary team of scientists and engineers and defines the benefits of this research to long-term stewardship, subsurface science, and infrastructure protection programs
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Long Term Corrosion/Degradation Test Six Year Results
The Subsurface Disposal Area (SDA) of the Radioactive Waste Management Complex (RWMC) located at the Idaho National Engineering and Environmental Laboratory (INEEL) contains neutron-activated metals from non-fuel, nuclear reactor core components. The Long-Term Corrosion/Degradation (LTCD) Test is designed to obtain site-specific corrosion rates to support efforts to more accurately estimate the transfer of activated elements to the environment. The test is using two proven, industry-standard methods—direct corrosion testing using metal coupons, and monitored corrosion testing using electrical/resistance probes—to determine corrosion rates for various metal alloys generally representing the metals of interest buried at the SDA, including Type 304L stainless steel, Type 316L stainless steel, Inconel 718, Beryllium S200F, Aluminum 6061, Zircaloy-4, low-carbon steel, and Ferralium 255. In the direct testing, metal coupons are retrieved for corrosion evaluation after having been buried in SDA backfill soil and exposed to natural SDA environmental conditions for times ranging from one year to as many as 32 years, depending on research needs and funding availability. In the monitored testing, electrical/resistance probes buried in SDA backfill soil will provide corrosion data for the duration of the test or until the probes fail. This report provides an update describing the current status of the test and documents results to date. Data from the one-year and three-year results are also included, for comparison and evaluation of trends. In the six-year results, most metals being tested showed extremely low measurable rates of general corrosion. For Type 304L stainless steel, Type 316L stainless steel, Inconel 718, and Ferralium 255, corrosion rates fell in the range of “no reportable” to 0.0002 mils per year (MPY). Corrosion rates for Zircaloy-4 ranged from no measurable corrosion to 0.0001 MPY. These rates are two orders of magnitude lower than those specified in the performance assessment for the SDA. The corrosion on the carbon steel, beryllium, and aluminum were more evident with a clear difference in corrosion performance between the 4-ft and 10-ft levels. Notable surface corrosion products were evident as well as numerous pit initiation sites. Since the corrosion of the beryllium and aluminum is characterized by pitting, the geometrical character of the corrosion becomes more significant than the general corrosion rate. Both pitting factor and weight loss data should be used together. For six-year exposure, the maximum carbon steel corrosion rate was 0.3643 MPY while the maximum beryllium corrosion rate was 0.3282 MPY and the maximum aluminum corrosion rate was 0.0030 MPY
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Examination of the 1970 National Bureau of Standards Underground Corrosion Test Welded Stainless STeel Coupons from Site D
A 1970 study initiated by the National Bureau of Standards (NBS), now known as the National Institute of Standards and Technology (NIST), buried over 6000 corrosion coupons or specimens of stainless steel Types 201, 202, 301, 304, 316, 409, 410, 430, and 434. The coupons were configured as sheet metal plates, coated plates, cross-welded plates, U-bend samples, sandwiched materials, and welded tubes. All coupons were of various heat-treatments and cold worked conditions and were buried at six distinctive soil-type sites throughout the United States. The NBS scientists dug five sets of two trenches at each of the six sites. In each pair of trenches, they buried duplicate sets of stainless steel coupons. The NBS study was designed to retrieve coupons after one year, two years, four years, eight years, and x years in the soil. During the first eight years of the study, four of five planned removals were completed. After the fourth retrieval, the NBS study was abandoned, and the fifth and final set of specimens remained undisturbed for over 33 years. In 2003, an interdisciplinary research team of industrial, university, and national laboratory investigators were funded under the United States Department of Energy’s Environmental Management Science Program (EMSP; Project Number 86803) to extract part of the remaining set of coupons at one of the test sites, characterize the stainless steel underground corrosion rates, and examine the fate and transport of metal ions into the soil. Extraction of one trench at one of the test sites occurred in April 2004. This report details only the characterization of corrosion found on the 14 welded coupons–two cross welded plates, six U-bends, and six welded tubes–that were retrieved from Site D, located near Wildwood, NJ. The welded coupons included Type 301, 304, 316, and 409 stainless steels. After 33 years in the soil, corrosion on the coupons varied according to alloy. This report discusses the stress corrosion cracking and crevice corrosion cracking of the U-bend coupons; the minimal corrosion found on the cross-bead plates; and the general, pitting, and crevice corrosion found on the welded tubes. In general, the austenitic Type 301, 304 and 316 samples showed little if any corrosion after 33+-years in the soil, whereas the ferritic alloys-Type 409 and 434– showed a spectrum of corrosion
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Underground Corrosion after 32 years: A Study of Fate and Transport, #80803 Annual Report, June 2005
Improved estimates for corrosion rates in variably saturated porous media are required by the U.S. Department of Energy to maintain long-term storage of radioactive contaminants in stainless steel containers. To better define these parameters, research was undertaken to complete the National Institute of Standards and Technology’s (NIST) long-term study of buried stainless steel began 35 years ago. The 1970 study was initiated by the National Bureau of Standards (NBS), now known as NIST, when over 1000 specimens—including stainless steel Types 201, 202, 301, 304, 316, 409, 410, 430, and 434—configured as plates, U-bend, and tubes in both annealed and cold worked conditions with various treatments— were buried at six distinctive soil-type sites throughout the United States. During the first eight years of the study, four of five planned removals were completed with specimens retrieved after one, two, four, and eight years at each of the six sites. The fifth and final set of specimens remained undisturbed for over 34 years