The Last Time I Saw

The Last Time I Saw – Concrete

Not much thought about by energy types, but exceptionally important in the construction of a nuclear power plant, concrete would seem an unchangeable item. After all, it’s been in use since Roman times. But that, as MIT demonstrates, is remarkably unimaginative thinking – the creation of cement, a component of concrete, accounts for 5 to 10 percent of the carbon emissions in the world (though that range is so broad, we think they should say, “If we had to guess.”) So how to make it more energy efficient?

In the January issue of the Journal of the Mechanics and Physics of Solids, the team reports that the source of concrete's strength and durability lies in the organization of its nanoparticles. The discovery could one day lead to a major reduction in carbon dioxide emissions during manufacturing.

It’s all about the nanoparticles.

He [Franz-Josef Ulm] and Georgios Constantinides, a postdoctoral researcher in materials science and engineering, studied the behavior of the nanostructure of cement. They found that at the nano level, cement particles organize naturally into the most densely packed structure possible for spherical objects, which is similar to a pyramid-shaped pile of oranges.

The guys poked various cements with nanoparticle needles to create a kind of taxonomy.

The C-S-H [calcium-silicate-hydrate] particles (each about five nanometers, or billionths of a meter, in diameter) have only two packing densities, one for particles placed randomly, say in a box, and another for those stacked symmetrically in a pyramid shape (like a grocer's pile of fruit). These correspond exactly to the mathematically proved highest packing densities allowed by nature for spherical objects: 63 and 74 percent, respectively. In other words, the MIT research shows that materials pack similarly even at the nano scale.

And?

If the researchers can find--or nanoengineer--a different mineral to use in cement paste, one that has the same packing density but does not require the high temperatures during production, they could conceivably cut world carbon dioxide emissions by up to 10 percent.

Yes, it’s pretty deep-dish. And creating that new mineral – ah, there’s the rub – may well prove as carbon intensive as creating cement. Nobody knows. But it’s fascinating that someone (Ulm and Constantinides being the someones) decided to do the deep-dish look at concrete and begin to ideate a replacement for it. Obviously, very early days, but enormous potential. Do read the whole thing.

Architect Aron Losonczi has developed a new type of concrete [this story is from 2006] that transmits light by adding "optical fibers" into the mix. The fibers are used to shift light at each end, producing a "see-through" effect. Called LiTraCon, "the blocks are a combination of 'optical fibers' and concrete, mixed so that the fibers create a fine glass aggregate within the concrete." The glass fibers then transfer light from one side of the block to the other, creating the effect of light transmission.

Perhaps Ulm and Constantinides need to have a chat with Mr. Losonczi.

Activists' Claims Distort Facts about Advanced Reactor Design

Below is from our rapid response team . Yesterday, regional anti-nuclear organizations asked federal nuclear energy regulators to launch an investigation into what it claims are “newly identified flaws” in Westinghouse’s advanced reactor design, the AP1000. During a teleconference releasing a report on the subject, participants urged the Nuclear Regulatory Commission to suspend license reviews of proposed AP1000 reactors. In its news release, even the groups making these allegations provide conflicting information on its findings. In one instance, the groups cite “dozens of corrosion holes” at reactor vessels and in another says that eight holes have been documented. In all cases, there is another containment mechanism that would provide a barrier to radiation release. Below, we examine why these claims are unwarranted and why the AP1000 design certification process should continue as designated by the NRC. Myth: In the AP1000 reactor design, the gap between the shield bu...

How many nuclear plants does it take to meet the world's energy needs?

Several weeks ago Joshua Pearce at Clarion University in Pennsylvania released a study titled “ Thermodynamic limitations to nuclear energy deployment as a greenhouse gas mitigation technology .” In the study he stated... nuclear energy production would have to increase by 10.5% per year from 2010 to 2050 to both replace fossil-fuel-energy use and meet the future energy demands. This line, of course, made the headlines and has been picked up by several outlets and blogs . When looking into his calculations for this statement, he made one assumption error that overstated the above sentence by nearly a factor of three. Page 121, Section 4.1 of the study states: Richard Smalley pointed out that in 2004, the global economy consumed the equivalent of 220 million barrels of oil per day, which converted into electricity terms is the equivalent of 14.5 TeraWatts (TW), or 14,500,000 MegaWatts (MW) (2005). … With a nuclear plant having about 1000 MW (1 GW) of capacity, we would need 14,500...

What Happens During a Refueling Outage?

You may have noticed over the past few weeks that a number of nuclear plants are shut down for refueling outages or are resuming operations after just returning from one. This type of routine outage usually occurs in the spring or fall when electricity demand is low so that nuclear reactors can replace about one-third of the spent fuel rods with new fuel and conduct other routine maintenance and repairs at the plant. To get a better sense of how refueling works at a nuclear energy facility, I spoke with Marcus Nichol, NEI’s senior project manager for used fuel storage and transportation, and asked him to explain the basics. Why does a nuclear plant need to replace one-third of its fuel? Nichol: The main purpose of a refueling outage is to replace older fuel that is depleted—meaning it can no longer efficiently produce energy from nuclear fission reactions—with new fuel. This “used fuel” has typically been used in the reactor for four-and-a-half to six years before it is pe...

NEI Nuclear Notes

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