ANS Virtual Annual Meeting: Wednesday recap

June 10, 2020, 10:02PMUpdated June 11, 2020, 10:20AMNuclear News

Wednesday, June 10, recap

Materials aging

The Aging of Materials session, sponsored by the Materials Science and Technology Division (MSTD), was chaired by Kallie Metzger, MSTD chair and a principal engineer for Westinghouse Electric Company. Three presentations were featured during the session on the effects of harsh environments on materials.

In his presentation, “A computational investigation of the behavior of interstitial helium in W-Mo alloys,” Adib Samin noted that future nuclear energy systems will require the use of durable, corrosion-resistant, radiation-tolerant, thermally stable materials that can withstand the harsh environments of nuclear reactors. Samin, an assistant professor in the Department of Engineering Physics at the Air Force Institute of Technology, said that his investigation focused on materials to be used in the “facing components” of fusion reactors.

Tungsten and tungsten alloys are important candidate materials, he said, but prolonged exposure to 14 MeV neutrons is known to cause significant transmutation in tungsten to a brittle state. Tungsten’s properties, however, may be improved through the use of molybdenum, Samin said.

In addition, Samin said that degraded structural materials that could find their way into the plasma could significantly interfere with the operation of the fusion reactor.

Samin concluded that he has been able to validate his investigation model only through other theoretical papers and that he would welcome experimental validation if a party wanted to collaborate with him.

Brent Shumaker, senior engineering manager for AMS Corporation, presented “Development of Cable Aging Acceptance Criteria for Nuclear Facilities,” concerning a project underway by AMS, Oak Ridge National Laboratory, and Pacific Northwest National Laboratory (PNNL). Shumaker said that the development of criteria is critical because cable aging is an important issue as existing nuclear power plants seek license extensions.

The project is performing condition monitoring tests on cables by subjecting them to accelerated radiation and thermal aging in the laboratory. The data collected during the tests will be used to provide the nuclear industry with “a comprehensive, condition based assessment program for cable polymers,” Shumaker said.

Shumaker said that the project’s baseline data collection is complete, and that some groups of cables have been shipped to PNNL for irradiation. Of those groups, some have been returned to AMS, in Knoxville, Tenn., by PNNL. Those irradiated cables are now undergoing thermal aging.

Adam Deatherage, an applications engineer for AMS Corporation, also discussed cable aging in his talk, “Application of Condition Monitoring Technologies for Aging Electrical Cables.” He said that the previous presentation by Shumaker provided good background information for Deatherage’s talk.

Deatherage presented “a case study where both in situ and laboratory measurements were used to assess the aged condition of electrical cables in a commercial nuclear power plant.” The cables tested had been pulled from 40 years of use at a nuclear power plant. Heat, mechanical stress, radiation, water, voltage, and chemical are environmental and internal stressors on cables, he said.

A cable’s electrical properties tend to degrade slowly over time, until the insulation material becomes significantly degraded. “At that point, the changes start to become more pronounced,” Deatherage said. “One key point I want to emphasize is that cable jacket material does degrade faster than the insulation material. So, while the insulation material is what you’re primarily concerned about when it comes to the electrical properties of the cable and its ability to perform its designed function, the cable insulation jacket can act as a leading indicator of degradation.”

Chemical treatment of radioactive waste

The session “Chemical Treatment of Radioactive Waste” was sponsored by the Fuel Cycle and Waste Management Division and chaired by Jean-Francois Lucchini of Los Alamos National Laboratory. The session centered around the issue of safe storage and the sound final disposal of the nuclear waste inventory. The speakers all discussed the challenges of storing or reprocessing waste and new developments of advanced treatment and conditioning processes of chemically durable waste forms.

Lucchini was the first speaker for his presentation on "Examples of Technology Applicable to In-Situ Waste Characterization." He said that issues that the LANL team face are the characterization of transuranic waste, the methods used to characterize it, and a determination on its transportation.

Lucchini discussed the lab methods adapted to the field that could significantly improve the characterization of waste. He showed a video demonstrating the use of a Laser Induced Breakdown Spectroscopy handheld device.

Craig Barnes, of the University of Tennessee (UT), presented on behalf of his student Breanna Vestal on "Digestion of Zircaloy Cladding for UNF Using Sulfur Chloride Reagents.” The presentation focused on the need for efficiently recycling the Zr cladding since "approximately 25 percent of high-level radioactive waste from UNF rods is found in the Zr cladding. So, by removing the cladding, the amount of waste can be reduced by 25 percent," he said. Barnes described the results from the UT study and said that a recycling process could be accomplished through a low temperature chlorination digestion and subsequent purification protocol.

John Stanford, of the University of Idaho, presented on "Photodecomposition of Organoiodides to Molecular Iodine as Pretreatment for Adsorption." He said, "UNF recycling operations is an essential component of the advanced fuel cycle." Stanford focused on radioiodine "because it has a half-life greater than 15 million years, tendency to bio-accumulate, and is particularly mobile." Stanford said the study demonstrates the effectiveness of using titania as a photocatalyst for the decomposition of gaseous methyl iodide.

Managing hydrogen systems in nuclear facilities

The panel session“Managing Hydrogen Systems in Nuclear Facilities: Lessons Learned from the DOE Complex and Industry” was sponsored by the Nuclear Installations Safety Division and chaired by Kevin O'Kula, of Amentum Technical Services. O'Kula said the panel included "leaders from diverse fields . . . that collectively have over 130 years of experience…" with the objective "to gain insights from their expertise and experience on the use and management of hydrogen in nuclear and industrial systems."

Nick Barilo, director of the Center for Hydrogen Safety at the American Institute of Chemical Engineers (AIChE) and the Hydrogen Safety Program at Pacific Northwest National Laboratory (PNNL), kicked off the panel with a presentation on hydrogen safety considerations and resources based on a collaboration between PNNL and AIChE.

Barilo reviewed the uses and current status of hydrogen fuel cells in use by motor vehicles, noting that “while the numbers are currently about 18,000 cars around the world and 6,000 in the U.S., that number was only a few hundred back in 2015."

Barilo then focused on safety knowledge resources, first responder training, and the Hydrogen Safety Panel programs at the Center for Hydrogen Safety.

J. Steven Herring, director of the Universities Space Research Association’s Center for Space Nuclear Research, presented on the "High Temperature Steam Electrolysis Experience at the Idaho National Laboratory since 2004." Herring discussed the high-temperature electrolysis process when coupled to a reactor and he said that there were numerous uses for this process. He said that the process is the most efficient to generate hydrogen and that there are many uses of the technology.

David Cook, Distinguished R&D staff member, High Flux Isotope Reactor, at Oak Ridge National Laboratory, presented "Hydrogen Safety Experience with the High Flux Isotope Reactor [HFIR] Cold Neutron Source [CNS]." Cook described HFIR and the CNS hydrogen safety-design integration and he discussed lessons learned.

Cook concluded with some important lessons learned from the HFIR project. He said that some lessons learned are to "integrate design and safety from the beginning; include design margin systems; use the best codes and standards, components, materials, and gases (which is obvious, but not always followed); and constantly train operators and test extensively."

Joseph Shepherd, professor of aeronautics and professor of mechanical engineering at the California Institute of Technology, presented on "Hydrogen Combustion in Nuclear Power Plants--Lessons Learned and Ongoing Studies." Shepherd said that "hydrogen generation and combustion has been an acknowledged hazard in nuclear power since the 1950s." Shepherd also reviewed the lingering combustion issues, including a number of issues that were identified after the Fukushima accident, and some new issues surrounding the development of small modular reactors, accident tolerant fuels, and advanced reactor concepts. Shepherd said that one big problem that needs to be resolved is how to reduce the uncertainties around severe accident modeling.

Integrating energy storage systems

Papers presented at the “Energy Storage Systems and Integration with NPPs” sessions argued that such systems could be integrated with nuclear power plants to increase flexibility and potentially enhance revenues. The session was chaired and moderated by W. Neal Mann, a doctoral student in mechanical engineering at the University of Texas.

Charles Forsberg, principal research scientist at the Massachusetts Institute of Technology, presented the findings from his paper, co-authored with Tadashi Narabayashi of the Tokyo Institute of Technology, titled “Base-Load Light-Water Reactors with Variable Electricity Using Crushed-Rock Heat Storage and Steam Peaking Plant with High-Efficiency Steam Injectors.”

"When we talk about adding storage to a nuclear reactor,” Forsberg said, “we have a two-part challenge: you have to have a heat storage technology, and you need some kind of peaking power plant to take that heat when you need peak power and convert it into electricity.”

Forsberg stressed the latter portion of that challenge, noting, “This is a two-part system. If you add storage, you have to add a peaking power plant, and that peaking power plant may be designed differently than a baseload plant to convert steam into electricity.”

Forsberg’s paper examined a system to enable a baseload light-water reactor to provide variable electricity to the grid, including peak electricity production rates significantly greater than the baseload output of the reactor. The system uses crushed rock as a very-low-cost heat storage media coupled to a low-cost peak-electricity steam plant using steam injectors that replace the steam plant feedwater heating system.

"The reason for this strategy is very simple—heat transferal costs money,” Forsberg said. “And this is a strategy to minimize heat transfer fluid inventory and cost, where inventory is determined by the maximum rate of heat transfer to and from storage. This is all about minimizing front-end capital costs.”

Medical isotopes market

Wednesday’s panel session on “Balancing Competition and National Needs in the Medical Isotopes Market”featured a discussion about the growing field of medical isotope production and the implications for criticality safety. The panel was designed to highlight challenges, advancements, and current or future needs in the field.

William Magwood IV, director general of the Nuclear Energy Agency, began the session with a history of molybdenum-99 (Mo-99 or moly-99), the parent isotope of technetium‑99m that is estimated to be used in about 50,000 medical procedures in the United States each day.

Magwood said the continued supply issue of having ample Mo-99 has been one of the great frustrations in his career. “Moly-99 remains to be the most important single isotope in medicine today,” he said. “But while it’s been popular for many, many years, it’s also been a source of worry. We always worry about the supply. This has been a concern for so many years that it’s hard to believe that we haven’t fully solved the issue.”

He said he’s optimistic about a suite of new entrepreneurial technologies that have potential to serve this market. “My hope is we’ll be able to rely on technetium‑99m well into the future, but to do that without having to worry about where the supply is coming from because we’ve solved the problem.”

Joseph Christensen, lead criticality safety engineer at SHINE Medical Technologies, pointed out that there are only a few facilities left in the world that can conduct appropriate critical safety experiments and the resources to conduct new experiments. “We’ve lost our capability to do critical experiments with solutions,” he said.

Christensen said another criticality accident could be on the horizon, adding that “we’re a little overdue” for one. He said he feels that way because of the growing industry for medical isotopes production combined with new technologies at a time when there’s been a drawdown in long-term knowledge management. “You’ve got a lot of moving parts here that are ripe for criticality safety concerns,” he said. “How we choose to respond to these challenges and considerations will determine whether or not the growth of the medical isotopes industry will lead to a significant criticality incident or not.”

Coming up on June 11:

10:00 a.m-11:45 a.m. (EDT)

Technical Sessions

Experimental Thermal Hydraulics—II

ANS Position Statement on the Use of Low Enriched Uranium in Space–Panel

Nuclear Fuels—II

Robotics and Remote Systems: General

Reactor Analysis Methods—III

Data, Analysis and Operations in Nuclear Criticality Safety—II

12:15 p.m.-2:00 p.m. (EDT)

Technical Sessions

Nuclear Fuels—III

Reactor Physics Design, Validation and Operational Experience

Data, Analysis and Operations in Nuclear Criticality Safety—III

Why the STEM Community Should Run for Office and How to Do It

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