Case 97-09

Pacific Northwest National Laboratory (PNNL)

Irradiation-Assisted Stress Corrosion Cracking

A Case Study of the R & D Value Mapping Project

Institute for Policy Research and Development

School of Public Policy

Georgia Institute of Technology

Atlanta, GA 30332-0345

Unedited Draft

This case was written by Jongwon Park. Comments or questions should be directed to Jongwon Park at (404)894- or, by e-mail, jpark@mgt-sun2.iac.gatech.edu. The Research was sponsored by the Department of Energy, Office of Basic Energy Sciences, Contract ER45562. The views presented here are the case author’s and do not necessarily represent those of the Department of Energy or Georgia Institute of Technology.

Pacific Northwest National Laboratory (PNNL)

Irradiation-Assisted Stress Corrosion Cracking

Project Summary

This Case outlines the Irradiation-Assisted Stress Corrosion Cracking (IASCC) research conducted by Stephen M. Bruemmer and Edward P. Simonen in Pacific Northwest National Laboratory (PNNL). Although BES funding comprises a third of the IASCC research, it provided a core basis of basic research on corrosion cracking problem upon which collaboration with electric utility industry and international community was performed.

The Irradiation-Assisted Stress Corrosion Cracking (IASCC) research addresses basic science issues dealing with radiation effects on material microstructure and microchemistry, and their influence on interfacial and environmental dynamics. Employing high-resolution electronic microscope and computer simulation, this research attempts to find out what happens to materials under radiation and hostile environments. Mechanistic understanding of irradiation and environmental effects on materials performance have direct implications on the safe operation of nuclear reactor systems and the temporary and permanent storage of nuclear waste.

The most important impact of the IASCC project rests on the development and refinement of analytical techniques, refinement of high resolution microscope, and computer programs. Though the focus of research has been on basic understanding of the cracking process, most contributions of this research came from the collaboration with industry, which utilized the tools and techniques developed in the course of basic research. The coordination of basic and applied research and management of the funding from various sources deserve much attention. The setting in a national laboratory, unique in performing private contract, is an interesting phenomenon. Collaboration with different types of organizations results in different research orientations and outcomes.

I. Project Description

The Irradiation-Assisted Stress Corrosion Cracking (IASCC) case is a joint research project of two equally engaged PIs from different fields. Stephen M. Bruemmer who studied radiation effects and Edward P. Simonen who was interested in fundamental studies of stress corrosion, formed the IASCC program in 1987 primarily supported by BES. This research has been focused on the mechanisms controlling the development of irradiation-induced microstructures and microchemistries, and their influence on interfacial properties and environmental cracking. Bruemmer and Simonen categorize the IASCC project as basic science research in that its primary goal is to understand the fundamental mechanisms of cracking of various materials exposed to radiation. At the same time, the IASCC’s practical implications on the corrosion-cracking problems of nuclear power reactor enabled the PIs to perform various cooperative projects with the electric utility industry based upon both short term contract and long-term partnership, especially with the Electric Power Research Institute (EPRI).

II. Technical Background

          The Irradiation-Assisted Stress Corrosion Cracking (IASCC) research addresses basic science issues dealing with radiation effects on material microstructure and microchemistry, and their influence on interfacial and environmental dynamics. Employing high-resolution electronic microscope and computer simulation, this research attempts to find out what happens to materials under radiation and hostile environments. Mechanistic understanding of irradiation and environmental effects on materials performance have direct implications on the safe operation of nuclear reactor systems and the temporary and permanent storage of nuclear waste. Radiation phenomena, such as displacement damage, ionization, or transmutations, are known to affect the corrosion and stress corrosion behavior of materials in light water reactors, fusion first wall and blanket structures, and nuclear waste canisters in deep geologic storage. One can easily imagine the disastrous and costly effects of core component failure in any nuclear reactor system and storage facilities.

          Heavy-ions, neutrons, and protons are three sources of irradiation that influence alloy metallurgy, mechanical stress, and corrosive environment, resulting in the IASCC. Since the program began in 1987, the IASCC project performed research in four major areas:

   Irradiation effects on microstructure and microchemistry evolution

   Prediction of radiation-induced segregation

   Deformation mechanisms in irradiated microstructures

   Synergistic effects of grain boundary chemistry and strength on intergranular stress corrosion cracking (IGSCC)

          Internal interfaces in materials (called grain boundaries) are created during initial procession at high temperatures and stresses. They have unique structures and chemistries dependent on the bulk alloy composition and the component temperature and stress history. Local grain boundary microstructure and microchemistry can be further altered during exposure due to equilibrium and nonequilbrium processes. In many critical structural alloys that grain boundary microchemistry controls its susceptibility to environment-induced cracking. Interfacial microstructure plays an important role in determining the extent of the microchemistry change and will independently influence how the grain boundary region deforms which, in turn, impacts its resistance to fracture. In short, the IASCC project studies why and how cracking occurs under which condition and how to prevent the cracking. By understanding the relationship between grain boundary characteristics and environmental degradation, it is possible to find the cause for component failure of various metal alloys, to develop diagnostic tools and remedial actions, and to help to design cracking resistant materials.

          The primary contribution of the IASCC project has been achieved through collaborative activities with electric utility industry and other government agencies. For example, Bruemmer and Simonen helped to understand and solve the cracking problems in various components of reactors such as electric power turbine rotors, critical piping and support structures, steam generator tubing, and reactor core components.

III. Project History

          The origins of the IASCC research can be traced back to 1960s when the Atomic Energy Commission (AEC) supported research on radiation effects on fundamental defect properties. BES inherited some parts of the radiation effects program in the late 1970s and Simonen worked on this program. Pacific Northwest National Laboratory (PNNL) participated in this radiation effects program because the reactors were there. The government’s interests in nuclear power had been weakened and the program was phased out during the 1980s. In the early 1980s, Bruemmer participated in another BES program on fundamental studies of stress corrosion. Those two BES programs, radiation effects and stress corrosion program, were merged and formed the IASCC program in 1987. Since 1987, Bruemmer and Simonen collaborated on the IASCC program to the present.

          Edward P. Simonen is a senior research scientist in structural materials research section of the materials science department of PNNL, received Ph.D. in metallurgy at Iowa State University in 1972. Stephen M. Bruemmer is a staff scientist and technical group leader in materials interfaces and microstructural services groups, of structural materials research section of the materials science department in PNNL, received Ph.D. in materials science and engineering at Oregon Graduate Institute. Bruemmer worked in PNNL for twenty years.

          The IASCC program began as a small project entirely supported by BES with a strong emphasis on fundamental understanding of the cracking with little interests in industrial application and remained that way during 1980s. During this time period, the research was focused on accelerator based experiments and simulations on basic mechanistic understanding of cracking, not directly related to the engineering problem. Simonen described the common attitude about the industrial application as, "Don’t subsidize Westinghouse." The atmosphere in BES turned around to emphasizing industry cooperative research in early 1990s. In 1992 the collaborations with industry jumped up, which, in turn enabled the IASCC program to expand its funding base.

The most beneficial industry collaboration was the partnership with Electronic Power Research Institute (EPRI), which began around 1992. Funded by electric power industries who pay membership fees to join and share the research results, EPRI operates as a spokesperson of American power industry in the area of electric power related research. Working with EPRI, Bruemmer and Simonen examined impurity segregation effects on the performance of commercial turbine rotor steels. The IASCC research team worked for a long time to understand fundamental relationships between grain boundary impurity segregation and a materials resistance to environment-induced failure, which was the basis of collaborative work in turbine rotor steels. Based on this study, critical level of phosphorus grain boundary enrichment was found to promote embrittlement. Nondestructive techniques to quantitatively evaluate the extent of segregation and degree of embrittlement were developed, the most successful of which was called picric-acid-etching test.

Another collaborative research with the EPRI was stress corrosion cracking of steam generator tubing that continued to hamper operation of pressurized water reactor systems. Grain boundary microstructural effects on the micromechanics of the cracking process were examined. As a result of this research, one of the links that connects interfacial deformation to the cracking process in the stress corrosion cracking mechanism was established.

Though the EPRI is the most important industry partner for the IASCC program, Bruemmer and Simonen handled many small contracts with individual power companies, both domestic and international.

In performing collaborative research, the IASCC team applied their unique capabilities for analytical techniques and high resolution microscopy that they developed and refined while doing basic research. Bruemmer and Simonen emphasize that the key to the successful joint research was not only their technical capabilities, but also the institutional arrangement which enabled them to work under the private contract with industry. In many national labs, and even other research groups in the PNNL, they are not allowed to contract with private party. Private contracts were important in two aspects – expanding funding base and access to unique test materials that industry provided.

The next important benchmark event was the beginning of international cooperation in 1994. Bruemmer and Simonen wanted to study the effects of neutron irradiation on cracking. However, neutron irradiation experiments were very costly and required four to five researchers. BES could not provide all the funding necessary for neutron irradiation research although BES funding almost tripled from around $ 200,000 until 1991 to $ 585,000 in 1992.

Bruemmer and Simonen were among the founders of two international cooperative groups -- Nuclear Fuels Irradiation Research group (NFR) and Cooperative IASCC Research Group (CIR). Europeans and Japanese had the same corrosion problems with boiling water and pressurized water reactors. Europeans in particular, were willing to invest for long term basic research unlike US utilities with less patience. Larry Nelson at EPRI, the head of corrosion division, was the key person for organizing these international groups. International cooperation generated enough funding necessary to perform neutron irradiation research from 1995 to the present. As a result of international cooperation, the annual budget of the IASCC program expanded to one to one and a half million dollars, that is, 2.5 to 3 times more in addition to BES funding.

In the history of the IASCC program, the coordination between basic and practical research, and the management of BES and outside funding have been a major challenge as well as an opportunity. Bruemmer and Simonen emphasized the importance of the BES funding in that it provided the core base for basic science research and allowed flexibility. Industry contracts are handled formally on the proprietary basis with direct and focused demand for the practical results. Because of security issues, DOD labs also work in a similar manner, formal, proprietary and focused on obtaining practical results. NRC and EPRI took more open approach in collaborating on basic science issues. International cooperation is also proprietary basis but more flexible in terms of research focus. Industry and DOE want to obtain the specific results: the degree of or possibility of cracking; the way of preventing or treating the cracking; in short, only the solution to the cracking problem.

When the interviewer asked about the influence of industry collaboration on research direction, Bruemmer and Simonen responded that collaboration had been beneficial overall. With the BES funding, they could work on basic science issues – the mechanism of cracking and grain boundary problems. Nonetheless, Bruemmer and Simonen responded that the orientation and mentality had changed as a result of industry collaboration. Because industry wants quick answer with cost constraints, the researchers had to keep up with industry demand. Simonen used an interesting metaphor to describe the difference between basic science and practical research, "We are like a hunter rather than a farmer, targeting something rather than planting seeds for ten years." Balancing basic and applied science was not easy at times. Bruemmer admitted some problems, "We plan around major industry directed research because the program has to act on it at that time. So the opportunities for basic science come out when those things coming in and basic science characteristics will have a critical interval." At the same time, they pointed out that industry sponsored research provided necessary test materials and data which they could always go back and study for basic mechanisms. They could also use these data and publish in basic science journals. It seems that this case potentially presents one of the happy marriage between basic and applied science in a single setting, further study may be beneficial in understanding the management of basic and applied research.

Cooperation with other government agencies was performed on the practical level. In late 1980s, Nuclear Regulation Commissions (NRC) and PNNL conducted research on the intergranular stress corrosion cracking (IGSCC) problems in stainless steels, which were widely used for critical piping and support structures in nuclear power reactors. This research established direct relationship among boundary chromium depletion, intergranular corrosion and stress corrosion cracking. This work was instrumental in the quantification of a nondestructive test (electrochemical potentiokinetic reactivation) to evaluate materials in service and is used to screen materials before being placed into service. A mechanistic based computer model was developed to predict the degree of sensitization in stainless steels which is widely used to evaluate expected sensitization development during fabrication, heat treatment and service exposure.

DOD defense labs, Knolls Atomic Power and Bettise Atomic Power Lab, also collaborated with the PNNL as the DOD labs had similar problems with nuclear submarine reactors, though in a smaller scale. The collaborations with DOD labs has been continued for five years to the present.

According to the field work proposal of the IASCC program, the research for FY 1998 to 1999 is focused on understanding the cause for cracking in neutron irradiation environments, related to mechanistic understanding of crack-tip behavior under synergistic effects of radiation, environment and stress. Goals for the present and future research include:

   Mechanistic research on nonequilibrium processes in neutron-irradiated stainless steels will continue to underpin joint activities with the Electronic Power Research Institute and the International Cooperative IASCC Research program.

   Fundamentals of defect-solute interactions will be interrogated using sequential transient thermal treatments and radiation.

   Environmental mechanisms for cracking in nonoxidizing environments will be explored through understanding of hydrogen uptake and elevated temperature corrosion.

   Microstructural evolution and stability will be related to competition between grain boundary sliding and matrix deformation.

4. Outputs and Impacts

1. Publications

TABLE 1. Publications

Detailed data on publications were not available. Bruemmer’s’ resume only lists some 50 major papers among 170 papers, which make it difficult to assess the relation with the IASCC program or year by year aggregation.

          Although not comprehensive, a document entitled Peer Review Information, prepared for Office of Program Analysis in April 1993, contained the list of publications directly related to the IASCC program during 1991-1993. According to this list, twelve articles were published in refereed journals such as Corrosion Journal, Journal of Nuclear Materials and Journal of Minerals, Metals and Materials from 1991 to 1993. Ten articles, many of which overlapped with journal articles, were published in refereed proceedings during the same time period.

          Asked about patent, Bruemmer and Simonen responded that patent was not the goal of the IASCC program.

2. Conferences and Symposia

          Both Bruemmer and Simonen attend International Symposium on Environmental Degradation of Nuclear Power Systems. It is a cross-cutting symposium: the topic is practical, held in every two years and approximately 300 people attends in each meeting. It functions as a forum in which the applied research community reports to user community that includes, managers and owners of nuclear reactors both public and private, venders who develop new materials. About 20 % of the attendees are researchers and the rest from user community. The discussion is lively focused on practical problems and many follow-up calls are received after the meeting. Bruemmer described this meeting as a "reality check" for researchers dealing with industry. Broad interactions with industry arise from this meeting.

          Nuclear Fuels Irradiation Research group (NFR) and Cooperative IASCC Research Group (CIR) are two international groups most relevant to the IASCC program. Each group has approximately 60 members. The orientation of these groups are more academic and exploratory as on going research are often presented for feedback. CIR represents the core research community concerned with the IASCC research. These groups are the forums for the academic users to interact.

BES strongly supported the leadership role of PNNL researchers in these international cooperative groups. Both Bruemmer and Simonen served as an organizer and chairperson of related committees of these meetings. For example, Simonen served as a Chairman for the Seventh International Symposium on Environmental Degradation of Materials in Nuclear Power Systems in 1995. Bruemmer is a task leader of mechanisms and modeling section of CIR. Overall, Bruemmer organized five symposia and served in four national or international committees. Simonen organized seven symposia and served in six different committees.

TABLE 2. Professional Society Affiliations

3. Personnel and Career Paths

          Bruemmer is an adjunct faculty member at Both the Oregon Graduate Institute and Washington State University and is teaching graduate-level material science courses at the Washington State University branch campus in Richland. Bruemmer initiated, and is helping guide research at Oregon Graduate Institute, Washington State University, University of Illinois and University of Michigan. Gary Was, chair of Nuclear Engineering Department at University of Michigan, is a co-PI of the IASCC program and a primary university connection for the program. Several graduate students from University of Michigan were involved with the IASCC program.

          Below is the list of past and present post docs and graduate students involved with the IASCC program at PNNL and directly supported by BES funding. Among those, two students were fully supported for five years: Deborah Damcott will defend her dissertation in fall 1998 and Dean Carter is writing his dissertation. Bruemmer and Simonen co-directed several other students' thesis research without direct support. Two post docs were supported: John Vertano found an employment at PNNL and Gary Song found an employment in private company -- Universal Oil Products.

Students Supported

Post Docs

   John Vertano, PNNL

   Gary Song, Universal Oil Products

Ph.D. and MS

   James Cole, University of Washington

   Deborah Damcott, New York University

   Dean Carter, University of Michigan

   Jeremy Busby, University of Michigan

   Tim Soran, Lockmore International

4. DOE funding

TABLE 3. DOE Funding during 1987-1993

          According to the TABLE 3, BES funding from DOE almost tripled in 1992. Though the exact number was not available, after 1993, the BES funding maintained the similar level -- around $400,000 dollars per year.

1990: $1,607,000

1991: $1,437,000

1992: $1,092,000

1993: $1,092,000

1994: $1,173,000

1995: $1,173,000

V. Conclusion

          The most important impact of the IASCC project rests on the development and refinement of analytical techniques, refinement of high resolution microscope, and computer programs. Though the focus of research has been on basic understanding of the cracking process, most contributions of this research came from the collaboration with industry, which utilized the tools and techniques developed in the course of basic research.

          The unusual arrangement of the research team, in which two PIs are both actively engaged in directing the research, should be noted. It is a result of historical formation of the joint research team of two formally separated research teams.

          Third, the coordination of basic and applied research and management of the funding from various sources deserve much attention. The setting in a national laboratory, unique in performing private contract, is an interesting phenomenon. Collaboration with different types of organizations results in different research orientations and outcomes.