Nuclear Engineering Commons^™

Modeling, Fabrication, And Optimization Of Niobium Cavities Phase Ii: Third Quarterly Report, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. The second phase has resulted in an experimental setup of a fluid flow experiment with experimentation to be completed in the third year. Other experimental activities include the evaluation of a vacuum system and various vacuum equipment …

Stress Corrosion Cracking Of Type 422 Stainless Steel For Applications In Spallation-Neutron-Target Systems, Ramprashad Prabhakaran

Transmutation Sciences Materials (TRP)

Introduction

• This research program is aimed at evaluating different types of environment-induced degradation of candidate target materials for applications in transmutation of spent nuclear fuels (SNF).

• Transmutation refers to the elimination of long-lived actinides and fission products from SNF.

Objectives

• Evaluate susceptibility of candidate target materials to stress corrosion cracking (SCC) and localized corrosion (pitting and crevice) in neutral and acidic aqueous environments at ambient and elevated temperatures

• Determine the extent and morphology of cracking in tested materials as functions of experimental and environmental variables including pH, temperature, loading conditions and specimen geometry

• Develop mechanistic …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

During the past two years (2001-2002) of this project, the primary effort was focused on evaluating the effect of hydrogen on the cracking behavior of candidate target materials namely, Alloys EP-823, HT-9 and 422 in aqueous environments of different pH values at ambient and elevated temperatures. More recently, emphasis is being placed to evaluate the cracking behavior of these materials in molten lead-bismuth eutectic (LBE) environment at much higher testing temperatures so as to compare the cracking susceptibility in environments containing molten metals and aqueous solutions, respectively. The most recent tests to evaluate the cracking susceptibility were primarily based on …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics: Quarterly Progress Report 12/1/02- 2/28/03, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The Lead-Bismuth eutectic (LBE) has been determined from previous experimental studies by the Russians and the European scientific community to be a potential material that can be used as a spallation target and coolant for the AAA proposed application.

Properly controlling the oxygen content in LBE can drastically reduce the LBE corrosion to structural steels. However, existing knowledge of material corrosion performance was obtained from point-wise testing with very limited density. The transport of oxygen and corrosion products, their interaction and variation of corrosion/precipitation along the flow are not well understood.

The first subtask of this project involves using a …

Experimental Investigation Of Steel Corrosion In Lead Bismuth Eutectic (Lbe): Characterization, Species Identification, And Chemical Reactions, John Farley, Dale L. Perry, Allen L. Johnson

Transmutation Sciences Materials (TRP)

The goal of the present research is to achieve a basic understanding of corrosion of steels by Lead Bismuth Eutectic (LBE). Liquid LBE is under consideration in the transmuter as both a spallation target and as a blanket coolant. There have been previous studies of LBE, especially by the Russians, who have over 80 reactor-years experience with LBE coolant in their Alpha-class submarine reactors. The Russians found that the presence of small amounts (ppm) of oxygen in the LBE significantly reduced corrosion. However, a fundamental understanding and verification of its role in the corrosion of steels is still very incomplete. …

Corrosion Of Steel By Lead Bismuth Eutectic: Quarterly Report November- December 2002 January 2003, John Farley

Transmutation Sciences Materials (TRP)

We continue to get valuable data from sputter depth profiling of steel samples. We meet weekly to discuss progress. We took depth-profiling data on D9 steel that had been exposed to LBE. This the first time we have examined this type of steel. This is important because it will enable us to separate out two effects and determine their effect on corrosion: composition of the steel vs surface preparation.

We started to plan a small experiments using a crucible of heated LBE, with the research program to be conducted at UNLV, on basic aspects of corrosion in this system. The …

Developing A Sensing System For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic: Quarterly Progress Report (Nov. 01 – Jan. 31, 2002), Yingtao Jiang, Bingmei Fu, Woosoon Yim

Transmutation Sciences Materials (TRP)

The design of the new apparatus for oxygen measurement/calibration has been completed. This new apparatus shall be of great importance for the UNLV researchers to conduct the research work in the campus.

Calibration Of Ysz Sensors For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic, Xiaolong Wu, Ramkumar Sivaraman, Ning Li, Wei Hang, T. W. Darling, Yingtao Jiang, Woosoon Yim, Bingmei Fu

Transmutation Sciences Materials (TRP)

Although liquid lead-bismuth eutectic (LBE) is a good candidate for coolant in the subcritical transmutation blanket, it is known to be corrosive to stainless steel, the material of the carrying tubes and containers. Such longterm corrosion problem can be prevented by producing and maintaining a protective oxide layer on the exposed surface of stainless steel. For this purpose, it is required to accurately control the concentration of oxygen dissolved in LBE. Currently, YSZ (Yttria Stabilized Zirconia) oxygen sensors, based on an existing automotive oxygen sensor, with molten bismuth saturated with oxygen as the reference, have been selected for oxygen-concentration measurement. …

Modeling, Fabrication, And Optimization Of Niobium Cavities: Final Phase, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. This is the third and final phase of the study.

The first phase has resulted in improving the basic understanding of multipacting and the process of chemical etching. The second phase has resulted in an experimental setup …

Modeling, Fabrication, And Optimization Of Niobium Cavities, Robert A. Schill Jr., Mohamed Trabia, William Culbreth

Transmutation Sciences Materials (TRP)

One of the key technologies for the deployment of accelerator driven transmutation systems is the accelerator itself. To increase the efficiency of the high-power accelerators needed to support the transmutation mission, the national and international accelerator teams have proposed using elliptical superconducting niobium cavities. This project is tasked with examining the impacts of the design and fabrication technologies for these elliptical niobium cavities on their performance. Niobium was selected primarily due to its behavior at low temperatures.

One of the major sources of energy loss from a superconducting accelerator cavity is a process known as multiple impacting (or “multipacting”) of …

Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Allen L. Johnson, Dale L. Perry

Transmutation Sciences Materials (TRP)

Materials for transmuter systems must be able to tolerate high neutron fluxes, great temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge in that the corrosive behaviors of materials in LBE are not well understood. Most of the available information on LBE systems has come from the Russians, who have over 80 reactor-years experience with LBE coolant in their Alpha-class submarine reactors. The Russians found that the presence of small amounts of oxygen (on the order of parts per million) in the LBE significantly reduced corrosion. However, a fundamental understanding and verification of its …

Surface Studies Of Corrosion Of Stainless Steel By Lead Bismuth Eutectic, Daniel Koury, Brian D. Hosterman, John Farley, Dale L. Perry, D. Parsons, J. Manzerova, Allen L. Johnson

Transmutation Sciences Materials (TRP)

Why is Lead Bismuth Eutectic Important?

• Changing national security stances have led to reexamination of nuclear waste reprocessing

• Dangerous actinides can be separated and

• Transmuted into safer products, creating a waste form dangerous for only hundreds of years, in addition to the production (up to 1/3 of the original fission energy) of useful energy

• Non-moderating coolants or spallation targets for production of fast neutrons is required for transmutation

• Russian experience with LBE coolants in their nuclear submarine fleet makes LBE an attractive possible transmutation coolant technology

• Corrosion of steel by LBE is an important …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials, Ajit K. Roy, Brendan O'Toole, Zhiyong Wang, David W. Hatchett

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the potential for the environmentally-assisted cracking of candidate target materials for applications in spallation-neutron-target systems, such as accelerator-driven system for the transmutation of waste. The materials selected for evaluation and characterization are martensitic stainless steels (SS) including Alloys HT- 9, EP 823 and Type 422 stainless steel.

More recently, this experimental program has been expanded to evaluate the effect of molten lead-bismuth eutectic (LBE) on the corrosion behavior of target materials in the presence of oxygen. Since the materials performance laboratory (MPL) at UNLV currently cannot accommodate this type of testing, …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The corrosion of structural materials is a major concern for the use of lead-bismuth eutectic (LBE) systems for nuclear applications such as in transmuter targets or fast reactors. Corrosion in liquid metal systems can occur through various processes, including, for example, dissolution, formation of inter-metallic compounds at the interface, and penetration of liquid metal along grain boundaries. Predicting the rate of these processes depends on numerous system operational factors: temperature, system geometry, thermal gradients, solid and liquid compositions, and velocity of the liquid metal, to name a few. Corrosion, along with mechanical and/or hydraulic factors, often contributes to component failure. …

Modeling Of Corrosion In Oxygen Controlled Lead Bismuth Eutectic Systems With The Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen, Kanthi Kiran Dasika, Chao Wu

Transmutation Sciences Materials (TRP)

Objectives:

• To simulate a 2-D model of the Materials Test Loop by approximating it to be a toroid with a pie cross section for the purpose of comparing the simulated results with the analytical results.
• The temperature and concentration profiles on the wall boundaries imposed are similar to the actual test model.
• Geometry effects have great influence on local corrosion rate.
• A 2-D benchmark problem and a sudden expansion case are studied which show good consistency to analytical solution.
• Results from 2-D sudden expansion problem are similar to experimental data obtained by other researchers.

Development Of A Mechanistic Understanding Of High-Temperature Deformation Of Alloy Ep-823, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The purpose of this task is to evaluate the mechanical properties of Alloy EP-823 at temperatures relevant to the transmutation processes. Testing has been initiated to evaluate the tensile properties of martensitic Alloy EP-823 stainless steel at temperatures ranging from ambient (25 °C) to 600°C. The test materials were thermally treated prior to the evaluation of their tensile properties. The deformation characteristics of these tensile specimens, upon completion of testing, will be evaluated by surface analytical techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Developing A Sensing System For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic, Yingtao Jiang, Bingmei Fu, Woosoon Yim

Transmutation Sciences Materials (TRP)

Lead-bismuth eutectic (LBE) is a candidate as a spallation target in sub-critical transmutation systems and as a coolant in nuclear programs. One of the primary concerns with LBE systems is the corrosion of stainless steel, the primary structural material used in nuclear systems. To mitigate this problem, trace levels of oxygen can be introduced into the system, causing the formation of a protective oxide layer at the interface between the LBE and steel. To protect the steel components, this oxide layer must be properly maintained. However, too much oxygen will produce unwanted oxide precipitation within the coolant and elsewhere in …

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements, Ajit K. Roy

Transmutation Sciences Materials (TRP)

One of the greatest challenges in evaluating the performance of materials in the real world is the determination of residual stresses, or the stresses induced in a material. Plastic deformation of metals and alloys produces an increase in the number of lattice imperfections known as dislocations, which by virtue of their interaction results in higher state of internal stress and reduces ductility. These stresses, if not properly annealed (released) can significantly degrade the long-term performance of the materials.

Due to the high temperatures and radiation fields typically encountered in most nuclear systems, such as accelerator-driven transmutation systems (ADS) and nuclear …

Fundamental And Applied Experimental Investigations Of Corrosion Of Steel By Lbe Under Controlled Conditions: Kinetics, Chemistry, Morphology, And Surface Preparation, Allen L. Johnson, John Farley, Dale L. Perry

Transmutation Sciences Materials (TRP)

An innovative research program is proposed to investigate the corrosion of steel by lead alloys, and in particular lead-bismuth eutectic (LBE). In our previous work, some steels were found to be far more resistant to corrosion by LBE than others depending on surface preparation (cold working). This program would allow testing of crucial hypotheses about the causes of the observed increased corrosion resistance. We propose to build a new test facility at UNLV to expose steel samples to LBE as well as facilities to prepare steel samples as indicated by our work.

The unique capabilities of the test system will …

Corrosion Of Steel By Lead Bismuth Eutectic: Quarterly Report August September October 2002, John Farley

Transmutation Sciences Materials (TRP)

We continued with sputter depth profiling of 316 and 316L steel samples that have been exposed to LBE. We also calibrated the sputter depth profiling using a sample of SiO₂ on Si, and the SEM. This is a valuable independent determination of the thickness of oxide layers.

In the laboratory, progress continues using the XPS machine. Experiments have been performed on steel samples using Argon ions to mill away the surface of the sample, thereby making measurements as a function of depth. This "ion beam milling" proceeds slowly through the oxide layer that covers the steel sample. We are …

Developing A Sensing System For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic: Quarterly Progress Report (Aug. 01 – Oct. 31, 2002), Yingtao Jiang, Bingmei Fu, Woosoon Yim

Transmutation Sciences Materials (TRP)

After two month intensive work in LANL, some preliminary sensor calibration curves have been obtained. Further data analysis shall be performed to assess the theoretical and measured data. Also, a new experimental apparatus shall be designed and located in UNLV to continue the left work.

Technical Progress:

• A set of calibration curves of voltage vs. temperature ranging from 300⁰C to 500⁰C under various oxygen concentrations in liquid LBE for the YSZ oxygen sensor has been obtained and has been reported in one paper.

• A meeting with LBE committee and other faculty members in AAA …

Development Of A Mechanistic Understanding Of High-Temperature Deformation Of Alloy Ep-823 For Transmutation Applications: Annual Progress Report (September 2001 – August 2002), Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The purpose of this project is to evaluate the elevated temperature tensile properties of Alloy EP-823, a leading target material for accelerator-driven waste transmutation applications. This alloy has been proven to be an excellent structural material to contain the lead-bismuth-eutectic (LBE) nuclear coolant needed for fast spectrum operations. Very little data exist in the open literature on the tensile properties of this alloy. The test material will be thermally treated prior to the evaluation of its tensile properties at temperatures relevant to the transmutation applications. The deformation characteristics of tensile specimens, upon completion of testing, will be evaluated by surface …

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Ii Quarterly Report, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Multipacting is one of the major loss mechanisms in rf superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch. A nonuniform surface etch will leave some unclean areas with contaminants and micron size particles. These significantly affect mutipacting. Further, a nonuniform etch will leave areas with damaged grain structure, which is not good for superconducting properties. Typically, the depth of chemical …

Hydrogen-Induced Embrittlement Of Candidate Target Materials For Applications In Spallation-Neutron-Target Systems: Quarterly Progress Report (June 01 – August 31, 2002), Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the effect of hydrogen on environment-assisted cracking of candidate target materials for applications in spallation-neutron-target (SNT) systems such as accelerator production of tritium (APT) and accelerator transmutation of waste (ATW). The materials selected for evaluation and characterization are martensitic stainless steels including Alloy HT-9, Alloy EP 823 and Type 422 stainless steel. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of these materials are being evaluated in environments of interest using tensile specimens under constant load and slow-strain-rate (SSR) conditions. Further, the localized corrosion behavior of these alloys …

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements: Quarterly Progress Report (June 1 – August 31, 2002), Ajit K. Roy

Transmutation Sciences Materials (TRP)

The purpose of this collaborative research project involving the University of Nevada Las Vegas (UNLV), the Idaho State University (ISU), and the Los Alamos National Laboratory (LANL) is to evaluate the feasibility of determining residual stresses in cold-worked, plastically-deformed, and welded materials using a nondestructive method based on positron annihilation spectroscopy. This technique uses γ-rays from a small MeV electron Linac to generate positrons inside the sample via pair production. This method is known to have capabilities of characterizing defects in thick specimens, that could not be accomplished by conventional positron technique or other nondestructive methods. The generated data will …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics-Task V: Final Report -Phase I 09/01/2001-08/30/2002, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The Lead-Bismuth eutectic (LBE) has been determined from previous experimental studies by the Russians and the European scientific community to be a potential material that can be used as a spallation target and coolant for the AAA proposed application. Properly controlling the oxygen content in LBE can drastically reduce the LBE corrosion to structural steels. However, existing knowledge of material corrosion performance was obtained from point-wise testing with only very sparse experimental data. Scientists have noticed that the concentration of oxygen dissolved in the liquid alloy could control the corrosion rate of steels exposed to Pb or Pb-Bi. At high …

Corrosion Of Steel By Lead Bismuth Eutectic: Quarterly Report For May-June-July 2002, John Farley

Transmutation Sciences Materials (TRP)

The goal of this project is to understand the basic science of corrosion in the steel/LBE system.

We are taking more data, typically using the newly installed X-ray Photoelectron Spectrometry (XPS) apparatus, and analyzing our existing data. Undergraduate students Denise Parsons and Julia Manzerova have helped a great deal in the analysis of the data. We can obtain the elemental composition as a function of position within the sample. This gives clues to the migration of materials, the composition of the protective oxide layer, and the basic science of the corrosion process. We found dramatic differences between the exposed and …

Developing A Sensing System For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic: Quarterly Progress Report (May 01 – July 31, 2002), Yingtao Jiang, Bingmei Fu, Woosoon Yim

Transmutation Sciences Materials (TRP)

Accurate measurement of the oxygen concentration in liquid Lead-Bismuth Eutectic (LBE) cooling system is critical in the active control of the corrosion at the interface between LBE and the stainless steel of transport tubes. Currently, LANL (Los Alamos National Laboratory) scientists have employed an automobile-style YSZ (Yttria Stabilized Zirconia) oxygen sensor unit to measure oxygen levels in an engineeringscaled LBE test system. Although the theoretical model for calculating oxygen concentration based on voltage measurement of YSZ sensor in static conditions is well understood, there is an urgent and strong need to obtain a complete set of calibration curves for YSZ …

Hydrogen-Induced Embrittlement Of Candidate Target Materials For Applications In Spallation-Neutron-Target Systems: Annual Progress Report (May 2001 – May 2002), Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the effect of hydrogen on environment-assisted cracking of candidate target materials for applications in spallation-neutron-target (SNT) systems such as accelerator production of tritium (APT) and accelerator transmutation of waste (ATW). The materials selected for evaluation and characterization are martensitic stainless steels including Alloy HT-9, Alloy EP 823 and Type 422 stainless steel. The susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of these materials are being evaluated in environments of interest using tensile specimens under constant load and slow-strain-rate (SSR) conditions. Further, the localized corrosion behavior of these alloys …

Development Of A Mechanistic Understanding Of High-Temperature Deformation Of Alloy Ep-823: Aaa Task-10 Quarterly (03/01, 2002 –05/31, 2002) Report, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The objective of this task is to evaluate the elevated temperature tensile properties of Alloy EP-823, a leading target material for accelerator-driven waste transmutation applications. The test material will be thermally treated prior to evaluation of its tensile properties at temperatures relevant to the transmutation applications. The deformation characteristics of tensile specimens, upon completion of testing, will be evaluated by surface analytical techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The overall results are expected to provide a mechanistic understanding of high-temperature deformation behavior of Alloy EP-823 as a function of heat treatment.

Highlights of Accomplishment

• …