Damaged seawater pump used to cool cores of Fukushima-Daiichi reactors. Credit: IAEA Image Bank.

When Japanese officials acted out of desperation and used seawater to cool the cores at the Fukushima-Daiichi reactors last year, it looks like they made the right call. But, others that might be tempted to use seawater to cool fuel rods in the future might not be so lucky.

ACerS emeritus member and University of California, Davis professor, Alexandra Navrotsky, Notre Dame researcher Peter Burns and several of their colleagues have offered some cautionary food for thought. They say in a new paper in the Proceedings of the National Academy of Sciences that there does seem to be a mechanism for how nuclear fuel rods could be corroded by contact with sea water.

It should immediately be pointed out that the authors aren’t in any way suggesting that this type of corrosion happened during the Fukushima-Daiichi incident, and they say there is no evidence of uranium dispersion during that episode due to the seawater.

However, they say it appears there is a way for the fuel rod–seawater combination to form “uranium compounds that could potentially travel long distances, either in solution or as very small particles,” according to a UC Davis news release.

The release quotes Navrotsky, a distinguished professor of ceramic, earth and environmental materials chemistry, as saying, ”This is a phenomenon that has not been considered before. We don’t know how much this will increase the rate of corrosion, but it is something that will have to be considered in future.”

The uranium compounds in the fuel rods are thought to be generally insoluble in ordinary water. Nevertheless, she says it was previously known that if some of the water is converted to peroxide (radiation has the ability to do this conversion), the peroxide can then oxidize the uranium in the rods to uranium-VI, forming spherical uranium peroxide clusters that can dissolve in water.

The new wrinkle in this is that Navrotsky et al. discovered that if alkali metal ions are present — such as the sodium that is plentiful in seawater — the uranium peroxide clusters ”are stable enough to persist in solution or as small particles even when the oxidizing agent is removed.”

So, the worrisome scenario is one where seawater comes in contact with the rods and forms these clusters. The clusters dissolved in the seawater are then carried away. Because, according to Navrotsky, little is known about quickly these uranium peroxide clusters break down in the seawater, the clusters may hang around for months or years before being converted back into a common form of uranium that will precipitate out to the bottom of the ocean.

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Here’s what we are hearing (some information from news releases):

Superior safety for next gen high-temperature reactor: China receives first glass-to-metal sealed hermetic penetration assembly from Schott for testing

China’s first commercial high-emperature reactor in the province of Shandong will be one of the most modern nuclear power plants in the world. Employing only the safest and most reliable technology available today, Schott has been selected to supply its hermetic glass-to-metal sealed Electrical Penetration Assemblies. The first feedthrough has now been delivered to the Institute of Nuclear and New Energy Technology at Tsinghua University for testing and training purposes.

DuPont Glass Laminating Solutions announces price increase

In a release, officials from DuPont Glass Laminating Solutions announced a price increase of 6 percent for all DuPont Butacite, Butacite G, Spallshield, The Wedge polyvinyl butyral and SentryGlas ionoplast products globally. The price increases, which go into effect Jan. 1, 2012, are in response to sustained high raw material and transportation costs, according to the release.

CPSC postpones making changes to mandatory ‘reasonable testing programs’ applicable to safety glass

The US Consumer Product Safety Commission has abandoned, at least for the immediate future, its plan to specify and regulate the required content of “reasonable testing programs” of manufacturers of non-children’s consumer products, including architectural glass, that are subject to CPSC safety standards, such as 16 CFR 1201, and that must containcertifications of compliance with those standards. This will bode well for safety glazing manufacturers, says Kim Mann, general counsel of Glass Association of North America.

American fuel cell bus program delivers “Buy America”- compliant fuel cell bus to SunLine Transit Agency

Ballard Power Systems announced that it has, together with consortium partners BAE Systems and ElDorado National Inc., successfully deployed a “Buy America”-compliant, zero-emission fuel cell bus for SunLine Transit Agency in Palm Springs, Calif. The “Buy America” regulation requires the manufacturing of the bus and key components in the United States, in alignment with objectives set out by the Federal Government. This bus was developed under the Federal Transit Administration’s) National Fuel Cell Bus Program, which facilitates the development of commercially viable fuel cell bus technologies and related infrastructure for deployment in revenue service.

Appleton brings LED efficiency and long-life performance to hazardous location ATEX/IECEx emergency lighting

Appleton, a leading manufacturer of electrical products for hazardous and non-hazardous applications, has brought the superior efficiency, long life and reliability of Light Emitting Diodes technology to industrial emergency lighting with the introduction of its new FDBAES Series of flameproof, self-contained emergency luminaries, the latest addition to Appleton’s growing LED product line.

Andersen cutting 250 jobs mostly in Bayport

A continued slump in the housing market translates to another round of layoffs at Andersen Corp. The Bayport-based door and window giant said Tuesday it will 250 jobs by the end of December.

US and Japanese companies begin $37 million Smart Grid project in Hawaii

Hitachi, Cyber Defence Institute, and Mizuho Corporate Bank recently announced that the companies have been selected as contractors for a smart grid demonstration project on Maui Island in Hawaii, spearheaded by the New Energy and Industrial Technology Development Organization as the result of feasibility study which was conducted from May to September this year by Hitachi and other companies. Serving as the project leader, Hitachi will take a leading role and coordinate the entire project.

Siemens increases stake in Marine Current Turbines

British tidal energy company, Marine Current Turbines Ltd, today announces that Siemens is increasing its share in the company to 45%. MCT has evolved from a pioneer to a technology leader in horizontal axis marine current turbines and now has 25 employees. In February 2010 Siemens acquired a minor stake in the Bristol-based company and thus entered the marine tidal current market. Financial details of the announcement are not disclosed.

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Professor Zhu of Queensland University of Technology shows jars of sodium titanate nanofibers and nanotubes that pull radioactive cesium and iodine isotopes from contaminated water by ion exchange. Credit: QUT

The release of radioactive materials after the recent tsunami destruction of the Fukshima-Dai nuclear power plant has reignited public awareness to the problem of capturing nuclear waste on a grand scale. Less dramatically, but more common and just as important to control, are small scale leaks from nuclear power plants and radioactive waste generated by medical tests and research. Capturing and containing radioactive stuff is no small challenge, but a new study shows that small—nanoscale small—may be the way to go.

Researchers at Queensland University of Technology in Australia, in collaboration with a group at Penn State University, may have found a cheap, effective, nonreversible way of capturing radioactive cesium and iodine wastes using titanate-base nanofibers and nanotubes.

A multi-institution, international team led by QUT professor, Huaiyong Zhu, has published a paper demonstrating that Na₂Ti₃O₇ nanofibers and nanotubes can effectively capture and store Cs⁺ and I^- ions. Sodium titanate has the advantage of being easy and economical to synthesize through hydrothermal processes.

Cesium isotopes can be captured by inorganic cation exchange with materials like silico-titanates, zeolites, clay minerals, layered zirconium phosphates and layered sulfides. These materials are able to withstand high radiation levels and high temperatures, and they are blessed with a high ion-exchange capacity. Unfortunately, the ion-exchange process is reversible, which means radioactive ions can be released back into solution when exposed to water.

Sodium titanate has a layered structure where TiO₆ octahedra form the basic structural units, with Na⁺ ion between the layers, and the radioactive ¹³⁷Cs⁺ isotope is captured in a simple ion exchange.

The team compared the chemisorption properties of two forms of sodium titanate: nanofibers and nanotubes. The nanotubes had a greater absorptive capacity and were able to remove to remove about 80 percent of the ions from solutions compared to only about 36 percent ion removal by the nanofibers.

During uptake, the nanofiber morphology is maintained, but if enough Cs⁺ ions are absorbed, the titanate layers deform. When a large concentration of Cs⁺ ions is absorbed, a phase transformation occurs and creates microporous tunnels in the layered structure. The diameter of the tunnels is narrower than the diameter of the cesium ion, thus immobilizing the ion and rendering the exchange irreversible.

In contrast, Cs⁺ uptake by nanotubes results a significant change in the aspect ratio: They become more squat and wide. The layered structure of the tubes remains (there is no mention of a phase change), but the interlayer space expands, which may swell the nanotubes.

Nanofibers and nanotubes absorb iodine through a different mechanism. Because I^- is an anion, a direct ion exchange with sodium is impossible. By coating sodium titanate nanofibers and nanotubes with nanoparticles of silver oxide (Ag₂O), iodine ions can be stuffed into the nanofibers or nanotubes by means of several chemical reactions involving intermediate compounds, hydration and dehydration. The chemistries and crystallographies involved combine to provide excellent absorption properties. Follow-up tests showed that the leaching rate of iodine back into solution was very low. Thus, Ag₂O-coated titanate nanofibers and nanotubes also show promise as effective candidates for capturing radioactive iodine.

In a press release from QUT, paper co-author Zhu says, “One gram of the nanofibers can effectively purify at least one ton of polluted water.” If so, the material should be an easy and cost-effective addition to the toolkits at facilities working with or managing radioactive wastes that contain cesium and iodine isotopes.

(The paper does not address disposal of the nanofibers/nanotubes after the ion-exchange capture is completed.)

In the US, Zhu collaborated with ACerS member Sridhar Komarneni, a professor at Penn State University.

The paper is “Capture of Radioactive Cesium and Iodide Ions from Water Using Titanate Nanofibers and Nanotubes,” Angewandte Chemie International Edition (doi: 10.1002/anie201103286).

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The ACerS Nuclear & Environmental Technology Division wants to invite all MS&T’11 attendees to join them for several NETD-related events for the big meeting in Columbus, Ohio.

NETD has assembled a very strong technical program for this year’s conference. Two symposia covering a range of technical topics that are likely to be of particular interest to NETD members are scheduled, with presentations from industry, government and academic experts.

Details of the sessions are below, and the complete list of presentations may be found at the MS&T’11 homepage.

Materials Science Challenges for Nuclear Applications:

Monday Oct. 17, 2011
Ion Irradiation Effects –  2:00 p.m.
Defects in Irradiated Alloys – 3:40 p.m.

Tuesday Oct. 18, 2011
Simulation of Reactor Materials – 8:00 a.m.
Defects and Diffusion in Materials – 0:00 a.m.
Nanostructured Materials – 2:00 p.m.
Microstructure Evolution – 3:20 p.m.

Wednesday Oct. 19, 2011
Nuclear Fuels - 8:00 a.m.
Materials Degradation - 2:00 p.m.

Thusday Oct. 20, 2011
High Temperature Materials - 8:00 a.m.

Materials for Nuclear Waste Disposal and Environmental Cleanup

Wednesday Oct. 19, 2011
Waste Forms for Nuclear Disposition - 2:00 p.m.
Processing and Characterization of Salts for Nuclear Waste Disposal - 4:00 p.m.

Thursday Oct. 20, 2011
Materials and Processes for Nuclear Materials Storage and Handling - 8:00 a.m.
Vitrification and Glass Characterization for Nuclear Materials Disposal - 2:00 p.m.

In addition, attendees are invited join the NETD leadership for our annual Division meetings during the conference:
NETD Executive Committee Meeting: Sunday, Oct. 16, 2011 2:30-4:30 p.m.; Renaissance Columbus Downtown Hotel, Room 31

NETD Annual Business Meeting: Monday, Oct. 17, 2011, 5:45-6:45 p.m.; Greater Columbus Convention Center, Room C221

Finally, on behalf of the NETD, Division Chair Alex Cozzi (SRNL) sends word about the winner of this year’s D.T. Rankin Award and plus the names of the winners of the student stipend awards.

NETD has selected John Marra as the winner of the Rankin Award for MS&T’11, which recognizes a member of the division who has demonstrated exemplary service. Marra served as chair of the NETD in 1994-1995 and as trustee from 1997-2000. The D.T. Rankin Award will be presented at the NETD Annual Business Meeting at MS&T’11.

Cozzi reports that the winners of the student travel stipend awards (for MS&T’11) are:

Steven Hsieh, University of Washington;

Kathlene Lindley, Iowa State University

Ashish Singh, Oklahoma State University

Blake Whitley, University of Alabama

The winning students have been asked to attend the NETD General Business Meeting at MS&T’11 (see above), where they will be introduced to division members and awarded the stipends.

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While nuclear energy policy issues are being worked out on a nation-by-nation basis, research on technological challenges continues apace, at least for now. Disposal of high-level nuclear waste is an essential, but expensive, part of the nuclear energy cycle.

Nuclear waste glasses are borosilicate compositions. Aluminum from fuel rod claddings enters the waste stream and brings a fair amount of sodium along with it. (Aluminum cladding is dissolved in nitric acid, which is then neutralized with sodium hydroxide.) The aluminum concentration limits the amount of waste that can be loaded into a glass composition because the presence of it and sodium leads to crystallization of nepheline (NaAlSiO₄).

Precipitation of nepheline has two detrimental effects. First, it pulls glass forming constituents out of the glass, and second, nepheline has less long-term durability than the glass phase. The first effect-loss of glass formers-reduces the waste load that can be accommodated, which means increased costs to produce and store larger volumes of waste glasses.

A key question is how much aluminum can be loaded into the glass formulation. A new paper published in the International Journal of Applied Glass Science looks at this question. A group out of the Pacific Northwest National Laboratory compiled historical data for 523 simulated waste glass compositions and analyzed the amount of nepheline crystallized as a function of composition.

Two approaches were used: plotting of nepheline volume fractions on the Al₂O₃-SiO₂-Na₂O phase diagram for three boron content ranges, and mapping of compositions into a quadrant system based on two indicators, those being “nepheline discriminator” and “optical basicity.”

Using the phase diagram approach, nepheline volume fractions were plotted on the ternary diagram for three ranges of boron content (less than 5 weight percent, 5 to 10 weight percent, and more that 10 weight percent).

The quadrant system evaluates compositions based on a plot of optical basicity against “nepheline discriminator.” The ND is a composition-based index to predict compositions that are more susceptible to nepheline crystallization and is a function of the silica content normalized to the overall composition.

Optical basicity is related to the overall state of oxygen in the glass melt, and therefore is related to the glass structure. (It’s linked to the dissociation of silicates to produce oxygen ions in the melt, similar to the way acids dissociate to produce hydrogen ions in aqueous solutions.) OB is useful to predict trends in transport properties, such as viscosity, diffusion, electrical and thermal conductivity, etc. It is expected that nepheline will not form for compositions below a certain threshold ND and OB levels.

Data were analyzed with these two frameworks for 523 compositions.

Two results emerged from the phase diagram plots: the nepheline formation region is smaller for higher B₂O₃ compositions, and there are regions in the low-Na₂O side of the ternary where nepheline does not form, despite high alumina contents.

The ND analysis showed that nepheline formation is suppressed for high-silica compositions. Nepheline crystallization is not expected for low OB values. The paper explains, “Reducing OB requires adding acidic components or removing very basic components.” That is, to reduce the OB in high-Al₂O₃ glasses, Na₂O must be reduced (increasing Al₂O₃ content), or substituting in lower basicity alkali or alkaline earth elements, or increasing B₂O₃ content. The paper notes, “A trade-off is reached when adding components that reduce waste loading.”

By working the trade-off, for example, by using ND to identify favorable compositions on the ternary diagram and then modifying compositions for optimal OB, it may be possible to expand the “composition space [that] is available for formulating high waste loading.”

This study only considered the thermodynamic aspect of crystallization, but the authors note that the kinetics of cooling and heat treatment are important in the nucleation and crystal growth process. The researchers suggest that kinetics also may help expand the range of desirable waste glass compositions.

See “Nepheline Crystallization in Nuclear Waste Glasses: Progress Toward Acceptance of High-Alumina Formulations,” by John S. McCloy et al. (doi: 10.1111/j.2041-1294.2011.00055.x).

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