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LIFE ESTIMATION OF HIGH LEVEL WASTE TANK STEEL FOR F-TANK FARM CLOSURE PERFORMANCE ASSESSMENT

Description: High level radioactive waste (HLW) is stored in underground storage tanks at the Savannah River Site. The SRS is proceeding with closure of the 22 tanks located in F-Area. Closure consists of removing the bulk of the waste, chemical cleaning, heel removal, stabilizing remaining residuals with tailored grout formulations and severing/sealing external penetrations. A performance assessment is being performed in support of closure of the F-Tank Farm. Initially, the carbon steel construction materials of the high level waste tanks will provide a barrier to the leaching of radionuclides into the soil. However, the carbon steel liners will degrade over time, most likely due to corrosion, and no longer provide a barrier. The tank life estimation in support of the performance assessment has been completed. The estimation considered general and localized corrosion mechanisms of the tank steel exposed to the contamination zone, grouted, and soil conditions. The estimation was completed for Type I, Type III, and Type IV tanks in the F-Tank Farm. The tank life estimation in support of the F-Tank Farm closure performance assessment has been completed. The estimation considered general and localized corrosion mechanisms of the tank steel exposed to the contamination zone, grouted, and soil conditions. The estimation was completed for Type I, Type III, and Type IV tanks in the F-Tank Farm. Consumption of the tank steel encased in grouted conditions was determined to occur either due to carbonation of the concrete leading to low pH conditions, or the chloride-induced de-passivation of the steel leading to accelerated corrosion. A deterministic approach was initially followed to estimate the life of the tank liner in grouted conditions or in soil conditions. The results of this life estimation are shown in Table 1 and Table 2 for grouted and soil conditions respectively. The tank life has been estimated under ...
Date: October 1, 2007
Creator: Subramanian, K
Partner: UNT Libraries Government Documents Department

STRESS CORROSION CRACKING SUSCEPTIBILITY OF HIGH LEVEL WASTE TANKS DURING SLUDGE MASS REDUCTION

Description: 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.
Date: October 18, 2007
Creator: Subramanian, K
Partner: UNT Libraries Government Documents Department

CORROSION OF LEAD SHIELDING IN MODEL 9975 PACKAGE

Description: Experiments were performed to determine the corrosion rate of lead when exposed to off-gas or degradation products of organic materials used in the model 9975 package.[1] The experiments were completed within the framework of a parametric test matrix with variables of organic configuration, temperature, humidity and the effect of durations of exposure on the corrosion of lead in the 9975 package. The room temperature vulcanizing (RTV) sealant was the most corrosive organic species in the testing, followed by the polyvinyl acetate (PVAc) glue. The Celotex{copyright} material uniquely induced measurable corrosion only in situations with condensed water, and to a much lesser extent than the PVAc glue and RTV. The coupons exhibited faster corrosion at higher temperatures than at room temperatures. There was a particularly pronounced effect of condensed water as the coupons exposed in the cells with condensed water exhibited much higher corrosion rates. In the 9975 package, the PVAc glue was determined to be the most aggressive due to it's proximity in the design. The condition considered most representative of the package conditions is that of the coupon exposed to the Celotex{copyright}/glue organic exposed in the ambient humidity conditions. The corrosion rate of 2 mpy measured in the laboratory experiments for this condition is considered to be a bounding condition to the 9975 package conditions when the laboratory results are extrapolated to actual package conditions, and is recommended as a conservative estimate for package performance calculations.
Date: March 15, 2006
Creator: Subramanian, K
Partner: UNT Libraries Government Documents Department

LIFE ESTIMATION OF TRANSFER LINES FOR TANK FARM CLOSURE PERFORMANCE ASSESSMENT

Description: A performance assessment is being performed in support of closure of the F-Tank Farm. The performance assessment includes the life estimation of the transfer lines that are used to transport waste between tanks both within a facility (''intra-area'' transfer) and to other facilities (''inter-area'' transfers). The transfer line materials of construction will initially provide a barrier to contaminant escape. However, the materials will degrade over time, most likely due to corrosion, and will no longer provide a barrier to contaminant escape. The life estimation considered the corrosion of the core pipe under exposure to soil, estimated the thickness loss due to general corrosion, and the percentage of wall area breached due to localized corrosion mechanisms. There are three types of transfer lines that are to be addressed within the performance assessment: Type I, Type II/IIA and Type III. The life of the transfer lines were estimated as exposed to soil. Localized and general corrosion of the transfer lines exposed to soil was estimated to provide input to the fate and transport modeling of the performance assessment. Pitting corrosion was found to be the controlling mechanism for the degradation of the transfer lines and their consequent ability to maintain confinement of contaminants. It is assumed that 75% of the transfer line is needed intact to provide this confinement function, i.e. once 25% of the line wall is breached, the lines are considered incapable of confining contaminants. It is recommended that the percentage breached curves be utilized for each transfer line as shown in Figure 1 for the various stainless steel transfer lines.
Date: October 1, 2007
Creator: Subramanian, K
Partner: UNT Libraries Government Documents Department

Test Plan to Update SRS High Level Waste Tank Material Properties Database by Determining Synergistic Effects of Dynamic Strain Aging and Stress Corrosion Cracking

Description: The structural integrity of High Level Waste tanks is defined by the demonstrated confinement of the waste by the tank structure under design basis conditions. a comprehensive test plan is presented here to develop a mechanical and corrosion properties database to develop a fundamental understanding of the synergistic effects of DSA and SCC due to high temperature service of the HLW tanks.
Date: March 20, 2002
Creator: Subramanian, K.H.
Partner: UNT Libraries Government Documents Department

Fracture Toughness Testing of ASTM A285 Steel for Fracture Analysis of Savannah River Site Storage Tanks

Description: The fracture toughness properties of A285 steels are being measured at specific material and test conditions for application to elastic-plastic fracture mechanics analysis of storage tanks at the Department of Energy Savannah River Site.
Date: May 15, 2001
Creator: Subramanian, K. H.
Partner: UNT Libraries Government Documents Department

Vapor Corrosion Program Plan

Description: Radioactive wastes are contained in 48 underground storage tanks at the Savannah River Site (SRS). The materials and structures of the tanks provide a confinement function by maintaining leak integrity and structural stability. It is essential that the potential changes in properties of the structural materials due to service environment be evaluated and that conditions that can cause significant (active) degradation be avoided or mitigated. Aging mechanisms are those which cause changes in the materials including degradation of the materials. Degradation is either a reduction of the mechanical properties (e.g., loss of toughness or ductility), or a loss of net section of materials (e.g., cracking, pitting, thinning), or both which reduces the level of confinement inherent in the original installed condition and could lead to failure of confinement.
Date: May 22, 2002
Creator: Subramanian, K.H.
Partner: UNT Libraries Government Documents Department

Pitting Corrosion in the Vapor Space and Liquid/Air Interface of High Level Radioactive Waste Tanks

Description: Corrosion in the vapor space and at the liquid/air interface of the Department of Energy (DOE) high level waste (HLW) tanks have emerged as potentially active corrosion mechanisms. Controls on the solution chemistry are in place to preclude the initiation and propagation of further nitrate induced pitting and stress corrosion cracking. However, recent experience has shown that steel not in contact with the bulk waste solution but exposed to the ''vapor space'' above the bulk waste and the liquid/air interface may be vulnerable to pitting or stress corrosion cracking. Experimentation was performed to determine the influence of steel surface characteristics and solution chemistry on pitting rates within the vapor space and at the liquid/air interface on ASTM A537 steels, the materials of construction of the tanks. The results suggest that inhibited bulk solution chemistry does not ensure pitting protection within the vapor space when there are surface inhomogeneities. However, the characteristic residual salts on the steel play a key role in the pitting characteristics.
Date: January 30, 2004
Creator: Subramanian, K.H.
Partner: UNT Libraries Government Documents Department

Fracture Toughness Properties of Savannah River Site Storage Tank ASTM A285 Low Carbon Steel

Description: A materials test program was developed to measure mechanical properties of ASTM A285 Grade B low carbon steel for application to structural and flaw stability analysis of storage tanks at the Department of Energy (DOE) Savannah River Site (SRS). Under this plan, fracture toughness and tensile testing are being performed at conditions that are representative of storage tank
Date: May 22, 2002
Creator: Subramanian, K.H.
Partner: UNT Libraries Government Documents Department

Review of Corrosion Inhibition in High Level Radioactive Waste Tanks in the DOE Complex

Description: Radioactive waste is stored in underground storage tanks at the Department of Energy (DOE) Savannah River Site (SRS). The waste tanks store supernatant liquid salts, consisting primarily of sodium nitrate, sodium nitrite, sodium hydroxide, and sludge. An assessment of the potential degradation mechanisms of the high level waste (HLW) tanks determined that nitrate- induced pitting corrosion and stress corrosion cracking were the two most significant degradation mechanisms. 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 the tanks. These controls are based upon a series of experiments performed using simulated solutions on materials used for construction of the tanks. The technical bases and evolution of these controls is presented.
Date: March 8, 2004
Creator: Subramanian, K.H.
Partner: UNT Libraries Government Documents Department

PROBABILITY BASED CORROSION CONTROL FOR HIGH LEVEL WASTE TANKS: INTERIM REPORT

Description: 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.
Date: April 23, 2008
Creator: Hoffman, E & Karthik Subramanian, K
Partner: UNT Libraries Government Documents Department

MICROSTRUCTURAL FEATURES AFFECTING PROPERTIES AND AGING OF TRITIUM-EXPOSED AUSTENTIC STAINLESS STEEL

Description: A project to implement a life-cycle engineering approach to tritium reservoirs has been initiated through the DOE - Technology Investment Projects. The first task in the project was to develop a comprehensive list of microstructural features that impact the aging performance of the tritium reservoirs. Each of the participating sites (SRNL, SNL, LANL, KCP) independently developed a list of features deemed integral to tritium reservoir performance based upon operational and design experience. An integrated list of features was ultimately developed by the project team that could be included in the modeling process. The features of interest were chosen based upon their impact on the following key factors in controlling crack growth: (1) the H/He solubility or diffusivity within the materials, (2) the stress/strain state at the crack tip, (3) material threshold for crack extension, and (4) microstructure based fracture distance, commonly estimated by grain size for intergranular fracture. Wherever possible, key references were identified to substantiate the effects on the tritium embrittlement phenomenon of the various microstructural features. Each of these features was chosen based upon their impact to the cracking phenomenon of interest. The features chosen were typically associated with orientation, morphology, and distribution of phases and inclusions, grain and grain boundary characteristics, and initial mechanical properties. Phase and inclusion content and distribution were determined to play a key role in the cracking phenomenon. The presence of {delta}-ferrite in the weld and strain-induced martensite in the primarily austenitic matrix are known to facilitate hydrogen diffusion and the interfaces have been observed as a hydrogen assisted fracture path. The morphology, size, and distribution of inclusions and precipitates, particularly on the grain boundaries, influence cracking since they trap hydrogen and facilitate intergranular fracture. Compositional banding and nitrogen concentration were also included as features of interest. The microstructural features of interest included ...
Date: January 10, 2004
Creator: Subramanian, K & Michael Morgan, M
Partner: UNT Libraries Government Documents Department

PERMEABILITY, SOLUBILITY AND DIFFUSIVITY OF HYDROGEN ISOTOPES IN STAINLESS STEELS AT HIGH GAS PRESSURES

Description: The Defense Waste Processing Facility (DWPF) is about to process High Level Waste (HLW) Sludge Batch 4 (SB4). This sludge batch is high in alumina and nepheline can crystallize readily depending on the glass composition. Large concentrations of crystallized nepheline can have an adverse effect on HLW glass durability. Several studies have been performed to study the potential for nepheline formation in SB4. The Phase 3 Nepheline Formation study of SB4 glasses examined sixteen different glasses made with four different frits. Melt rate experiments were performed by the Process Science and Engineering Section (PS&E) of the Savannah River National Laboratory (SRNL) using the four frits from the Phase 3 work, plus additional high B2O3/high Fe2O3 frits. Preliminary results from these tests showed the potential for significant improvements in melt rate for SB4 glasses using a higher B2O3-containing frit, particularly Frit 503. The main objective of this study was to investigate the durability of SB4 glasses produced with a high B2O3 frit likely to be recommended for SB4 processing. In addition, a range of waste loadings (WLs) was selected to continue to assess the effectiveness of a nepheline discriminator in predicting concentrations of nepheline crystallization that would be sufficient to influence the durability response of the glass. Five glasses were selected for this study, covering a WL range of 30 to 50 wt% in 5 wt% increments. The Frit 503 glasses were batched and melted. Specimens of each glass were heat-treated to simulate cooling along the centerline of a DWPF-type canister (ccc) to gauge the effects of thermal history on product performance. Visual observations on both quenched and ccc glasses were documented. A representative sample from each glass was submitted to the SRNL Process Science Analytical Laboratory (PSAL) for chemical analysis to confirm that the as-fabricated glasses corresponded to the defined ...
Date: September 12, 2005
Creator: Subramanian, K & Michael Morgan, M
Partner: UNT Libraries Government Documents Department

Corrosion Control Measures For Liquid Radioactive Waste Storage Tanks At The Savannah River Site

Description: The Savannah River Site has stored radioactive wastes in large, underground, carbon steel tanks for approximately 60 years. An assessment of potential degradation mechanisms determined that the tanks may be vulnerable to nitrate- induced pitting corrosion and stress corrosion cracking. Controls on the solution chemistry and temperature of the wastes are in place to mitigate these mechanisms. These controls are based upon a series of experiments performed using simulated solutions on materials used for construction of the tanks. The technical bases and evolution of these controls is presented in this paper.
Date: November 27, 2012
Creator: Wiersma, B. J. & Subramanian, K. H.
Partner: UNT Libraries Government Documents Department

CORROSION OF LEAD SHIELDING IN NUCLEAR MATERIALS PACKAGES

Description: Inspection of United States-Department of Energy (US-DOE) model 9975 nuclear materials shipping package revealed corrosion of the lead shielding induced by off-gas constituents from organic components in the package. Experiments were performed to determine the corrosion rate of lead when exposed to off-gas or degradation products of these organic materials. The results showed that the room temperature vulcanizing (RTV) sealant was the most corrosive organic species followed by the polyvinyl acetate (PVAc) glue. The fiberboard material induced corrosion to a much lesser extent than the PVAc glue and RTV, and only in the presence of condensed water. The results indicated faster corrosion at temperatures higher than ambient and with condensed water as expected. A corrosion rate of 0.05 mm/year measured for coupons exposed to the most aggressive conditions was recommended as a conservative estimate for use in package performance calculations.
Date: November 16, 2007
Creator: Subramanian, K & Kerry Dunn, K
Partner: UNT Libraries Government Documents Department

ADVANCED OXIDATION: OXALATE DECOMPOSITION TESTING WITH OZONE

Description: At the Savannah River Site (SRS), oxalic acid is currently considered the preferred agent for chemically cleaning the large underground Liquid Radioactive Waste Tanks. It is applied only in the final stages of emptying a tank when generally less than 5,000 kg of waste solids remain, and slurrying based removal methods are no-longer effective. The use of oxalic acid is preferred because of its combined dissolution and chelating properties, as well as the fact that corrosion to the carbon steel tank walls can be controlled. Although oxalic acid is the preferred agent, there are significant potential downstream impacts. Impacts include: (1) Degraded evaporator operation; (2) Resultant oxalate precipitates taking away critically needed operating volume; and (3) Eventual creation of significant volumes of additional feed to salt processing. As an alternative to dealing with the downstream impacts, oxalate decomposition using variations of ozone based Advanced Oxidation Process (AOP) were investigated. In general AOPs use ozone or peroxide and a catalyst to create hydroxyl radicals. Hydroxyl radicals have among the highest oxidation potentials, and are commonly used to decompose organics. Although oxalate is considered among the most difficult organic to decompose, the ability of hydroxyl radicals to decompose oxalate is considered to be well demonstrated. In addition, as AOPs are considered to be 'green' their use enables any net chemical additions to the waste to be minimized. In order to test the ability to decompose the oxalate and determine the decomposition rates, a test rig was designed, where 10 vol% ozone would be educted into a spent oxalic acid decomposition loop, with the loop maintained at 70 C and recirculated at 40L/min. Each of the spent oxalic acid streams would be created from three oxalic acid strikes of an F-area simulant (i.e., Purex = high Fe/Al concentration) and H-area simulant (i.e., H ...
Date: February 29, 2012
Creator: Ketusky, E. & Subramanian, K.
Partner: UNT Libraries Government Documents Department

SAVANNAH RIVER SITE TANK CLEANING: CORROSION RATE FOR ONE VERSUS EIGHT PERCENT OXALIC ACID SOLUTION

Description: Until recently, the use of oxalic acid for chemically cleaning the Savannah River Site (SRS) radioactive waste tanks focused on using concentrated 4 and 8-wt% solutions. Recent testing and research on applicable dissolution mechanisms have concluded that under appropriate conditions, dilute solutions of oxalic acid (i.e., 1-wt%) may be more effective. Based on the need to maximize cleaning effectiveness, coupled with the need to minimize downstream impacts, SRS is now developing plans for using a 1-wt% oxalic acid solution. A technology gap associated with using a 1-wt% oxalic acid solution was a dearth of suitable corrosion data. Assuming oxalic acid's passivation of carbon steel was proportional to the free oxalate concentration, the general corrosion rate (CR) from a 1-wt% solution may not be bound by those from 8-wt%. Therefore, after developing the test strategy and plan, the corrosion testing was performed. Starting with the envisioned process specific baseline solvent, a 1-wt% oxalic acid solution, with sludge (limited to Purex type sludge-simulant for this initial effort) at 75 C and agitated, the corrosion rate (CR) was determined from the measured weight loss of the exposed coupon. Environmental variations tested were: (a) Inclusion of sludge in the test vessel or assuming a pure oxalic acid solution; (b) acid solution temperature maintained at 75 or 45 C; and (c) agitation of the acid solution or stagnant. Application of select electrochemical testing (EC) explored the impact of each variation on the passivation mechanisms and confirmed the CR. The 1-wt% results were then compared to those from the 8-wt%. The immersion coupons showed that the maximum time averaged CR for a 1-wt% solution with sludge was less than 25-mils/yr for all conditions. For an agitated 8-wt% solution with sludge, the maximum time averaged CR was about 30-mils/yr at 50 C, and 86-mils/yr at 75 C. ...
Date: January 20, 2011
Creator: Ketusky, E. & Subramanian, K.
Partner: UNT Libraries Government Documents Department

Computational modeling and experimental studies on NO{sub x} reduction under pulverized coal combustion conditions. Third quarterly technical progress report, July 1, 1995--September 30, 1995

Description: An experimental plan outlining the first year`s activity was sent to Dr. Lori Gould, Project Officer/Contracting Officer`s Technical Representative on April 24, 1995. An approval was received with some questions on June 15, 1995. However, with some foresight of the director of the in-house combustion group of the PETC, Dr. Ekmann, a tentative hold-off on the purchase of the equipment was requested by the project officer on June 29, 1995. Enclosed with that request were some of Dr. Ekmann`s concerns. The research team spent the month of July in study of pertinent literature as well as in the preparation of the responses to Dr. Gould`s comments and Dr. Ekmann`s concerns. These responses included the choice of the reactor, reactor design, rate of gas heating, detailed test matrix and answers to host of other comments. Upon review of the above information submitted on July 24, 1995 by the Rust research team, the project officer called for a conference call on September 6, 1995 which involved the PI (Dr. Kumpaty), the research consultant (Mr. Subramanian), Dr. Gould and Dr. Ekmann. Dr. Ekmann insisted that further calculations be made on the rate of gas heating without taking radiation into account. Accordingly, calculations pertaining to the rate of gas heating based on convection were performed and submitted to Dr. Ekmann on September 13, 1995. This report contains the information emerged through the dialogue between the Rust College research team and the PETC represented by Dr. Gould and Dr. Ekmann during this quarter.
Date: December 31, 1995
Creator: Kumpaty, S.K. & Subramanian, K.
Partner: UNT Libraries Government Documents Department

Correlation of fracture toughness with impurity components. Final contract report

Description: This investigation was sponsored by the Los Alamos National Laboratory in an effort to understand better the phenomenon of stress assisted diffusion in cracked structures operating in corrosive environments. Work done on the extension of the existing ``Coupled Thermomechanical Diffusion`` theory to enable the prediction of diffusion of a solute species in stressed solids in the presence of cracks is presented here. Mathematical formalism is provided to support the intuitive notion that a singular solution for the concentration field can exist in crack tip neighborhoods driven by singular solutions for stresses that have been obtained within the framework of classical Linear Elastic Fracture Mechanics. It has been shown that under certain limiting assumptions, a singular solution for the concentration profile of the kind 1/{radical}r emerges from the governing equations. Both steady state and transient solutions were obtained. A numerical simulation using quarter point finite elements was carried out and the results obtained also indicated the presence of this singularity. A singular solution for the concentration profiles of diffusing species in crack tip neighborhoods was obtained by Gdoutos and Aifantis. The order of the singularity obtained in their investigation was different from that discovered in the present work as were the governing differential equations and the underlying assumptions of their model. In order to determine the reasons for the differences, a detailed study was undertaken comparing the two theories and their underlying assumptions, methodology and results. These comparisons also form part of the present work.
Date: March 23, 1992
Creator: Subramanian, K. & Smith, F. W.
Partner: UNT Libraries Government Documents Department

LIFE ESTIMATION OF HIGH LEVEL WASTE TANK STEEL FOR F-TANK FARM CLOSURE PERFORMANCE ASSESSMENT - 9310

Description: High level radioactive waste (HLW) is stored in underground carbon steel storage tanks at the Savannah River Site. The underground tanks will be closed by removing the bulk of the waste, chemical cleaning, heel removal, stabilizing remaining residuals with tailored grout formulations, and severing/sealing external penetrations. The life of the carbon steel materials of construction in support of the performance assessment has been completed. The estimation considered general and localized corrosion mechanisms of the tank steel exposed to grouted conditions. A stochastic approach was followed to estimate the distributions of failures based upon mechanisms of corrosion accounting for variances in each of the independent variables. The methodology and results used for one-type of tank is presented.
Date: January 12, 2009
Creator: Subramanian, K; Bruce Wiersma, B & Stephen Harris, S
Partner: UNT Libraries Government Documents Department

CORROSION OF LEAD SHIELDING IN NUCLEAR MATERIALS PACKAGES

Description: Inspection of United States-Department of Energy (US-DOE) model 9975 nuclear materials shipping package revealed corrosion of the lead shielding that was induced by off-gas constituents from organic components in the package. Experiments were performed to determine the corrosion rate of lead when exposed to off-gas or degradation products of these organic materials. The results showed that the room temperature vulcanizing (RTV) sealant was the most corrosive organic species used in the construction of the packaging, followed by polyvinyl acetate (PVAc) glue. Fiberboard material, also used in the construction of the packaging induced corrosion to a much lesser extent than the PVAc glue and RTV sealant, and only in the presence of condensed water. The results indicated faster corrosion at temperatures higher than ambient and with condensed water. In light of these corrosion mechanisms, the lead shielding was sheathed in a stainless steel liner to mitigate against corrosion.
Date: July 18, 2008
Creator: Subramanian, K; Kerry Dunn, K & Joseph Murphy, J
Partner: UNT Libraries Government Documents Department