Download or read book Six Sigma Evaluation of the High Level Waste Tank Farm Corrosion Control Program at the Savannah River Site written by P. J. Hill and published by . This book was released on 2003 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Six Sigma is a disciplined approach to process improvement based on customer requirements and data. The goal is to develop or improve processes with defects that are measured at only a few parts per million. The process includes five phases: Identify, Measure, Analyze, Improve, and Control. This report describes the application of the Six Sigma process to improving the High Level Waste (HLW) Tank Farm Corrosion Control Program. The report documents the work performed and the tools utilized while applying the Six Sigma process from September 28, 2001 to April 1, 2002. During Fiscal Year 2001, the High Level Waste Division spent $5.9 million to analyze samples from the F and H Tank Farms. The largest portion of these analytical costs was $2.45 million that was spent to analyze samples taken to support the Corrosion Control Program. The objective of the Process Improvement Project (PIP) team was to reduce the number of analytical tasks required to support the Corrosion Control Program by 50 percent. Based on the data collected, the corrosion control decision process flowchart, and the use of the X-Y Matrix tool, the team determined that analyses in excess of the requirements of the corrosion control program were being performed. Only two of the seven analytical tasks currently performed are required for the 40 waste tanks governed by the Corrosion Control Program. Two additional analytical tasks are required for a small subset of the waste tanks resulting in an average of 2.7 tasks per sample compared to the current 7 tasks per sample. Forty HLW tanks are sampled periodically as part of the Corrosion Control Program. For each of these tanks, an analysis was performed to evaluate the stability of the chemistry in the tank and then to determine the statistical capability of the tank to meet minimum corrosion inhibitor limits. The analyses proved that most of the tanks were being sampled too frequently. Based on the results of these analyses and th e use of additional Six Sigma tools, the team identified improvements that allow sampling frequencies to be extended without increasing the overall risk associated with the Corrosion Control Program. Overall, the team identified improvements to the process that would reduce the number of analytical tasks required to support the corrosion control program by approximately 77 percent reducing analytical costs by $1.2 million per year.

Download or read book Treatment Tank Corrosion Studies for the Enhanced Chemical Cleaning Process written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radioactive waste is stored in high level waste tanks on the Savannah River Site (SRS). Savannah River Remediation (SRR) is aggressively seeking to close the non-compliant Type I and II waste tanks. The removal of sludge (i.e., metal oxide) heels from the tank is the final stage in the waste removal process. The Enhanced Chemical Cleaning (ECC) process is being developed and investigated by SRR to aid in Savannah River Site (SRS) High-Level Waste (HLW) as an option for sludge heel removal. Corrosion rate data for carbon steel exposed to the ECC treatment tank environment was obtained to evaluate the degree of corrosion that occurs. These tests were also designed to determine the effect of various environmental variables such as temperature, agitation and sludge slurry type on the corrosion behavior of carbon steel. Coupon tests were performed to estimate the corrosion rate during the ECC process, as well as determine any susceptibility to localized corrosion. Electrochemical studies were performed to develop a better understanding of the corrosion mechanism. The tests were performed in 1 wt.% and 2.5 wt.% oxalic acid with HM and PUREX sludge simulants. The following results and conclusions were made based on this testing: (1) In 1 wt.% oxalic acid with a sludge simulant, carbon steel corroded at a rate of less than 25 mpy within the temperature and agitation levels of the test. No susceptibility to localized corrosion was observed. (2) In 2.5 wt.% oxalic acid with a sludge simulant, the carbon steel corrosion rates ranged between 15 and 88 mpy. The most severe corrosion was observed at 75 C in the HM/2.5 wt.% oxalic acid simulant. Pitting and general corrosion increased with the agitation level at this condition. No pitting and lower general corrosion rates were observed with the PUREX/2.5 wt.% oxalic acid simulant. The electrochemical and coupon tests both indicated that carbon steel is more susceptible to localized corrosion in the HM/oxalic acid environment than in the PUREX/oxalic acid environment. (3) The corrosion rates for PUREX/8 wt.% oxalic acid were greater than or equal to those observed for the PUREX/2.5 wt.% oxalic acid. No localized corrosion was observed in the tests with the 8 wt.% oxalic acid. Testing with HM/8 wt.% oxalic acid simulant was not performed. Thus, a comparison with the results with 2.5 wt.% oxalic acid, where the corrosion rate was 88 mpy and localized corrosion was observed at 75 C, cannot be made. (4) The corrosion rates in 1 and 2.5 wt.% oxalic acid solutions were temperature dependent: (a) At 50 C, the corrosion rates ranged between 90 to 140 mpy over the 30 day test period. The corrosion rates were higher under stagnant conditions. (b) At 75 C, the initial corrosion rates were as high as 300 mpy during the first day of exposure. The corrosion rates increased with agitation. However, once the passive ferrous oxalate film formed, the corrosion rate decreased dramatically to less than 20 mpy over the 30 day test period. This rate was independent of agitation. (5) Electrochemical testing indicated that for oxalic acid/sludge simulant mixtures the cathodic reaction has transport controlled reaction kinetics. The literature suggests that the dissolution of the sludge produces a di-oxalatoferrate ion that is reduced at the cathodic sites. The cathodic reaction does not appear to involve hydrogen evolution. On the other hand, electrochemical tests demonstrated that the cathodic reaction for corrosion of carbon steel in pure oxalic acid involves hydrogen evolution. (6) Agitation of the oxalic acid/sludge simulant mixtures typically resulted in a higher corrosion rates for both acid concentrations. The transport of the ferrous ion away from the metal surface results in a less protective ferrous oxalate film. (7) A mercury containing species along with aluminum, silicon and iron oxides was observed on the interior of the pits formed in the HM/2.5 wt.% oxalic acid simulant at 75 C. The pitting rates in the agitated and non-agitated solution were 2 mils/day and 1 mil/day, respectively. A mechanism by which the mercury interacts with the aluminum and silicon oxides in this simulant to accelerate corrosion was proposed.

Download or read book Corrosion and Failure Processes in High level Waste Tanks written by and published by . This book was released on 1992 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: A large amount of radioactive waste has been stored safely at the Savannah River and Hanford sites over the past 46 years. The aim of this report is to review the experimental corrosion studies at Savannah River and Hanford with the intention of identifying the types and rates of corrosion encountered and indicate how these data contribute to tank failure predictions. The compositions of the High-Level Wastes, mild steels used in the construction of the waste tanks and degradation-modes particularly stress corrosion cracking and pitting are discussed. Current concerns at the Hanford Site are highlighted.

Download or read book STRESS CORROSION CRACKING SUSCEPTIBILITY OF HIGH LEVEL WASTE TANKS DURING SLUDGE MASS REDUCTION written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Aluminum is a principal element in alkaline nuclear sludge waste stored in high level waste (HLW) tanks at the Savannah River Site. The mass of sludge in a HLW tank can be reduced through the caustic leaching of aluminum, i.e. converting aluminum oxides (gibbsite) and oxide-hydroxides (boehmite) into soluble hydroxides through reaction with a hot caustic solution. The temperature limits outlined by the chemistry control program for HLW tanks to prevent caustic stress corrosion cracking (CSCC) in concentrated hydroxide solutions will potentially be exceeded during the sludge mass reduction (SMR) campaign. Corrosion testing was performed to determine the potential for CSCC under expected conditions. The experimental test program, developed based upon previous test results and expected conditions during the current SMR campaign, consisted of electrochemical and mechanical testing to determine the susceptibility of ASTM A516 carbon steel to CSCC in the relevant environment. Anodic polarization test results indicated that anodic inhibition at the temperatures and concentrations of interest for SMR is not a viable, consistent technical basis for preventing CSCC. However, the mechanical testing concluded that CSCC will not occur under conditions expected during SMR for a minimum of 35 days. In addition, the stress relief for the Type III/IIIA tanks adds a level of conservatism to the estimates. The envelope for corrosion control is recommended during the SMR campaign is shown in Table 1. The underlying assumption is that solution time-in-tank is limited to the SMR campaign. The envelope recommends nitrate/aluminate intervals for discrete intervals of hydroxide concentrations, although it is recognized that a continuous interval may be developed. The limits also sets temperature limits.

Download or read book Evaluation of stainless steel tank corrosion in ICPP high level radioactive waste service written by T. L. Hoffman and published by . This book was released on 1983 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book PROBABILITY BASED CORROSION CONTROL FOR WASTE TANKS written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As part of an ongoing study to evaluate the discontinuity in the corrosion controls at the SRS tank farm, a study was conducted this year to assess the minimum concentrations below 1 molar nitrate, see Figure 1. Current controls on the tank farm solution chemistry are in place to prevent the initiation and propagation of pitting and stress corrosion cracking in the primary steel waste tanks. The controls are based upon a series of experiments performed with simulated solutions on materials used for construction of the tanks, namely ASTM A537 carbon steel (A537). During FY09, an experimental program was undertaken to investigate the risk associated with reducing the minimum molar nitrite concentration required to confidently inhibit pitting in dilute solutions (i.e., less than 1 molar nitrate). The experimental results and conclusions herein provide a statistical basis to quantify the probability of pitting for the tank wall exposed to various solutions with dilute concentrations of nitrate and nitrite. Understanding the probability for pitting will allow the facility to make tank-specific risk-based decisions for chemistry control. Based on previous electrochemical testing, a statistical test matrix was developed to refine and solidify the application of the statistical mixture/amount model to corrosion of A537 steel. A mixture/amount model was identified based on statistical analysis of recent and historically collected electrochemical data. This model provides a more complex relationship between the nitrate and nitrite concentrations and the probability of pitting than is represented by the model underlying the current chemistry control program, and its use may provide a technical basis for the utilization of less nitrite to inhibit pitting at concentrations below 1 molar nitrate. FY09 results fit within the mixture/amount model, and further refine the nitrate regime in which the model is applicable. The combination of visual observations and cyclic potentiodynamic polarization scans indicates a potential for significant inhibitor reductions at nitrate concentrations near 1.0 M without a significant increase in corrosion risk. The complete data sets from FY08 and FY09 testing have determined the statistical basis to confidently inhibit against pitting using nitrite inhibition with the current pH controls. Future testing will complete the spectrum of nitrate concentrations around 1 molar. These results will be combined to provide a complete spectrum for corrosion controls with a risk based component.

Download or read book DETERMINATION OF CORROSION INHIBITOR CRITERIA FOR TYPE III written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dissolution of salt from Type III/IIIA waste tanks at the Savannah River Site may create solutions with inhibitor concentrations below those currently required (0.6M OH− and 1.1M OH− + NO2−) per the Corrosion Control Program for high nitrate salt solutions (5.5 to 8.5M NO3−). An experimental program was conducted to evaluate the corrosion susceptibility of grade A537 carbon steel for waste simulants containing 4.5-8.5M NaNO3 with maximum inhibitor concentrations of 0.6M NaOH and 0.2M NaNO2. These maximum inhibitor concentrations used in this program are at a reduced level from those currently required. Current requirements were initially established for the Types I, II and IV tanks made of A285 carbon steel. The experimental program involved corrosion testing to evaluate the pitting and stress corrosion stress corrosion cracking (SCC) susceptibility of the Type III/IIIA waste tank materials. The program was conducted in two phases; the results of the first phase were reported previously (WSRC-STI-2006-00029). In this second phase, the corrosion specimens were modified to represent the 'as-fabricated' condition of the tank wall, and included specimens with mill scale, ground welds and stress-relief heat treatments. The complete description of the corrosion testing and the results are reported herein. The collective corrosion test results for A537 carbon steel in high nitrate waste simulants (4.5 - 8.5M) with the maximum inhibitor concentrations of 0.6M NaOH and 0.2M NaNO2 were as follows: (1) In long-term non-polarized U-bend testing, heat treatment, similar to the waste tank stress relief regime, reduced the incidence of cracking over the 18-month test period. Vapor space SCC was found to initiate on non-heat treated U-bend coupons. (2) In polarized U-bend testing, cracking occurred on U-bend coupons that had welds prepared similar to those in the waste tanks, i.e. ground and heat treated. (3) In electrochemical testing, pitting occurred on all coupons independent of heat treatment, inhibitor concentration, temperature, surface preparation, or welding. (4) In slow strain rate testing, cracking occurred on samples tested in solutions containing up to the maximum inhibitor concentration. The primary conclusion derived from this experimental program is that A537 carbon steel exposed to high nitrate (> 5.5M) solutions at inhibitor levels below the current specifications (0.6M OH− and 1.1M OH− + NO2−) are susceptible to localized corrosion in the form of pitting and stress corrosion cracking. Long-term storage (e.g., greater than 100 days) of dissolved salt solutions not meeting the current inhibitor specifications for high nitrate salt chemistries in Type III waste tanks shall be avoided. Short term storage (e.g., less than 100 days) at low temperatures (e.g., less than 50 C) in these tanks is permissible for waste removal purposes. The stress relief process reduces the risk of SCC in the Type III waste tanks. On the other hand, the current inhibitor specifications should be strictly followed for the Type I, II and IV waste chemistry to prevent initiation of localized corrosion mechanisms. These tanks were not stress relieved and are more susceptible to SCC.

Download or read book Corrosion Study for Waste Tanks to High and Salt Concentration Conditions written by and published by . This book was released on 1995 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book PROBABILITY BASED CORROSION CONTROL FOR HIGH LEVEL WASTE TANKS written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Controls on the solution chemistry (minimum nitrite and hydroxide concentrations) are in place to prevent the initiation and propagation of pitting and stress corrosion cracking in high level waste (HLW) tanks. These controls are based upon a series of experiments performed on carbon steel coupons in simulated waste solutions. An experimental program was undertaken to investigate reducing the minimum molar nitrite concentration required to confidently inhibit pitting. A statistical basis to quantify the probability of pitting for the tank wall, when exposed to various dilute solutions, is being developed. Electrochemical and coupon testing are being performed within the framework of the statistical test matrix to determine the minimum necessary inhibitor concentrations and develop a quantitative model to predict pitting propensity. A subset of the original statistical test matrix was used to develop an applied understanding of the corrosion response of the carbon steel in the various environments. The interim results suggest that there exists some critical nitrite concentration that sufficiently inhibits against localized corrosion mechanisms due to nitrates/chlorides/sulfates, beyond which further nitrite additions are unnecessary. The combination of visual observation and the cyclic potentiodynamic polarization scans indicate the potential for significant inhibitor reductions without consequence specifically at nitrate concentrations near 1 M. The complete data sets will be used to determine the statistical basis to confidently inhibit against pitting using nitrite inhibition with the current pH controls. Once complete, a revised chemistry control program will be devised based upon the probability of pitting specifically for dilute solutions which will allow for tank specific chemistry control implementation.

Download or read book Six Sigma and Beyond written by D.H. Stamatis and published by CRC Press. This book was released on 2002-11-12 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: The final volume of this series presents a synopsis of the curriculum that a typical Six Sigma program should follow. It differs from the preceding six volumes in that it is an implementation volume, therefore the information is geared towards helping readers formalize their own training. The book establishes the minimum requirements for the Six Si

Download or read book The Six Sigma Performance Handbook Chapter 11 Frequently Asked Questions written by Praveen Gupta and published by McGraw Hill Professional. This book was released on 2004-10-22 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following is a chapter from Praveen Gupta's The Six Sigma Performance Handbook, which gives results-oriented help with Six Sigma initiatives. With this handbook, you will learn how to optimize performance and sustain breakthrough results. This book also gives a quick, straight forward tutorial on the use of the statistical tools which form the bases for Six Sigma project success. The handbook shows you how to simplify Six Sigma methods for cost-effective implementations that work best in your organization.

Download or read book Statistical Quality Control for the Six Sigma Green Belt written by Bhisham C. Gupta and published by Quality Press. This book was released on 2007-06-30 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a desk reference and instructional aid for those individuals currently involved with, or preparing for involvement with, Six Sigma project teams. As Six Sigma team members, Green Belts help select, collect data for, and assist with the interpretation of a variety of statistical or quantitative tools within the context of the Six Sigma methodology. The second in a four-book series geared specifically for these Green Belt activities, this book provides a thorough discussion of statistical quality control (SQC) tools. These tools are introduced and discussed from the perspective of application rather than theoretical development. From this perspective, readers are taught to consider the SQC tools as statistical “alarm bells” that send signals when there are one or more problems with a particular process. Guidance is also given on the use of Minitab and JMP in doing these various SQC applications. In addition, examples and sample problems from all industries appear throughout the book to aid a Green Belt's comprehension of the material.

Download or read book Corrosion Considerations for Life Management of Hanford High level Waste Tanks written by and published by . This book was released on 1993 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book CORROSION TESTING IN SIMULATED TANK SOLUTIONS written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Three simulated waste solutions representing wastes from tanks SY-102 (high nitrate, modified to exceed guidance limits), AN-107, and AY-102 were supplied by PNNL. Out of the three solutions tested, both optical and electrochemical results show that carbon steel samples corroded much faster in SY-102 (high nitrate) than in the other two solutions with lower ratios of nitrate to nitrite. The effect of the surface preparation was not as strong as the effect of solution chemistry. In areas with pristine mill-scale surface, no corrosion occurred even in the SY-102 (high nitrate) solution, however, corrosion occurred in the areas where the mill-scale was damaged or flaked off due to machining. Localized corrosion in the form of pitting in the vapor space of tank walls is an ongoing challenge to overcome in maintaining the structural integrity of the liquid waste tanks at the Savannah River and Hanford Sites. It has been shown that the liquid waste condensate chemistry influences the amount of corrosion that occurs along the walls of the storage tanks. To minimize pitting corrosion, an effort is underway to gain an understanding of the pitting response in various simulated waste solutions. Electrochemical testing has been used as an accelerated tool in the investigation of pitting corrosion. While significant effort has been undertaken to evaluate the pitting susceptibility of carbon steel in various simulated waste solutions, additional effort is needed to evaluate the effect of liquid waste supernates from six Hanford Site tanks (AY-101, AY-102, AN-102, AN-107, SY-102 (high Cl−), and SY-102 (high nitrate)) on carbon steel. Solutions were formulated at PNNL to replicate tank conditions, and in the case of SY-102, exceed Cl− and NO3− conditions, respectively, to provide a contrast between in and out of specification limits. The majority of previous testing has been performed on pristine polished samples. To evaluate the actual tank carbon steel surface, efforts are needed to compare the polished surfaces to corroded and mill-scale surfaces, which are more likely to occur in application. Additionally, due to the change in liquid waste levels within the tanks, salt deposits are highly likely to be present along the tank wall. When the level of the tank decreases, a salt deposit will form as the solution evaporates. The effects of this pre-existing salt, or supernate deposit, are unknown at this time on the corrosion effect and thus require investigation. Additionally, in the presence of radiation, moist air undergoes radiolysis, forming a corrosive nitric acid condensate. This condensate could accelerate the corrosion process in the vapor space. To investigate this process, an experimental apparatus simulating the effects of radiation was designed and constructed to provide gamma irradiation while coupons are exposed to a simulate tank solution. Additionally, ammonia vapors will also be introduced to further represent the tank environment.

Download or read book Characterization of the Corrosion Behavior of the Carbon Steel Liner in Hanford Site Single shell Tanks written by and published by . This book was released on 1994 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: Six safety initiatives have been identified for accelerating the resolution of waste tank safety issues and closure of unreviewed safety questions. Safety Initiative 5 is to reduce safety and environmental risk from tank leaks. Item d of Safety Initiative 5 is to complete corrosion studies of single-shell tanks to determine failure mechanisms and corrosion control options to minimize further degradation by June 1994. This report has been prepared to fulfill Safety Initiative 5, Item d. The corrosion mechanisms that apply to Hanford Site single-shell tanks are stress corrosion cracking, pitting/crevice corrosion, uniform corrosion, hydrogen embrittlement, and microbiologically influenced corrosion. The corrosion data relevant to the single-shell tanks dates back three decades, when results were obtained from in-situ corrosion coupons in a few single-shell tanks. Since that time there have been intertank transfers, evaporation, and chemical alterations of the waste. These activities have changed the character and the present composition of the waste is not well characterized. All conclusions and recommendations are made in the absence of relevant laboratory experimental data and tank inspection data. The report attempts to identify the failure mechanisms by a literature survey of carbon steel data in environments similar to the single-shell tank wastes, and by a review of the work performed at the Savannah River Site where similar wastes are stored in similar carbon steel tanks. Based on these surveys, and in the absence of data specific to Hanford single-shell tanks, it may be concluded that the single-shell tanks identified as leakers failed primarily by stress corrosion cracking due to the presence of high nitrate/low hydroxide wastes and residual stresses. In addition, some failures may be attributed to pitting under crevices in low hydroxide locations.

Download or read book Evaluation and Prevention of Corrosion Leaks on Buried Storage Tanks written by and published by . This book was released on 1981 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Reaction of Formic and Nitric Acids with Savannah River Site Radioactive HLW Sludge in the DWPF Pretreatment Steps written by and published by . This book was released on 1993 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: