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Self-Healing Ceramics for Nuclear Safety
Roland Piquepaille writes "Pacific Northwest National Laboratory (PNNL) researchers have used supercomputers to simulate how common ceramics could repair themselves after radiation-induced damages. This is an important discovery because 'materials that can resist radiation damage are needed to expand the use of nuclear energy.' These ceramics, which are able to handle high radiation doses, could improve the durability of nuclear power plants. They also might help to solve the problem of nuclear waste storage. But read more for additional references about how this research could improve nuclear safety."
To replace the pottery my kids accidentally smash...
We're all hypocrites. We all have hidden parts, it's the contrast between them that make us more a hypocrite than others
Helpful, but more so for disposal of nuclear waste than for nuclear plants. IIRC, most of the critical components that would see very high radiation over their lifetime have to be metal or plastic for other reasons. If a good portion of those pieces could be replaced by ceramics in all respects, this would be a great advance.
For disposal and vitrification this would be a great advance. A huge element of uncertainty in the Yucca mountain facility comes from the caskets the waste is stored in. Ceramics would be more corrosion resistant than stainless steel and a 'self-healing' property would allow them to avoid becoming too brittle. Brittleness might be a key problem in long term storage like that. It would be interesting to see if the materials used in vitrification could take advantage of this. That's kind of a solved problem but it would be cool to change things up.
An interesting thing to see would be to watch how the material handles swelling. In a lot of cases, changes in dimensions is MUCH more important (in the long term) than other changes (to materials like poly-eurethane, steel, glass, not rubber or other plastics). I can see cracks and what not being fixed, but how about interstitial pockets being formed? Or gas evolution/absorption? Anyone have any information on that?
I am sick and tired of all the issues about super long-term storage. Far better AND cheaper to burn this up over a 100 years, then to pay the monster price of 10000 years of storage, and all the concern about it. OTH, these ceramics certainly sounds interesting.
I prefer the "u" in honour as it seems to be missing these days.
The only problem with nuclear waste storage is politicians. Radioactive waste storage is a proven, safe technology. Even so, long-term geological storage is not the right solution, since we would be throwing away a lot of good, fissionable material that can be recycled for energy production in, e.g., fast reactors.
I had but a simple dream, to destroy all humans.
I'm wondering if this might have implications beyond use in nuclear reactors. One of the big concerns with a manned trip to Mars is long-term exposure to radiation while en-route. This means that any spacecraft you use will have to be shielded, or at least have a shielded compartment for use during periods of high solar activity.
Ceramics make good radiation shields, and could be great for low(er)-weight shielding for spacecraft, especially if you can use a method like this to extend the lifetime of the shielding to put it in line with the lifetime of the craft. The potential problem I can see is that ceramics are generally brittle, so you would probably need some sort of exterior shell to provide both structural rigidity and impact resistance. But considering all current spacecraft are metal-skinned anyway, this shouldn't be a huge issue.
Plus, if you're using a nuclear rocket for your ship, these things can pull double-duty! It's like a spaceflight magic bullet.
Out of the generation IV proposals it is probably the gas cooled fast reactor that will benefit the most from this.
http://en.wikipedia.org/wiki/Gas_cooled_fast_reactor
One of the major issues with global warming is that the hydrogen used to produce amonia and subsequently artificial fertilizer, is currently derived from natural gas. The process emits a lot of CO2 , and it isn't really feasible to
stop producing hydrogen as it could result in a collapse of agriculture due to drastically increased fertilizer prices.
Two generation IV reactors, the very high temperature reactor, and the gas cooled fast reactor, are aimed to resolve this by dramatically improving the efficiency of electrolysis of water. This can be achieved through so called thermochemical hydrogen production ( http://en.wikipedia.org/wiki/Sulfur-iodine_cycle), but it requires temperatures exceeding 800 C.
While it is likely that thermal reactors with helium coolant ( such as the pebble bed reactor ) could achieve this, it gets more tricky for fast reactors. Fast reactors have about 100 times less waste, better uranium utilization and the waste decays to safe levels between 100 and 1000 times quicker than for thermal reactors. The main catch is that the MUCH higher power density and neutron flux makes it difficult to find suitable materials. Sodium coolant doesn't work for hydrogen production since it boils before reaching the necessary temperatures, lead has corrosion issues especially at high temperatures and its high mass density makes it difficult to find materials that are strong enough at the temperatures required. Helium works, but because it has a much lower heat capacity than molten metals the reactor would likely reach higher temperatures under accident scenarios, and thus materials that can withstand a very strong neutron flux at high temperatures is absolutely necessary for a gas cooled fast reactor to be feasible.
You suggest that recycling the fissionable material will eliminate, or greatly reduce, waste. Not so. The problem is that the fissionable material is only a very small percentage of the waste stream. Almost verything that has been through a plant is treated as waste. The bulk of this is low level waste with no recycling potential.
Engineering is the art of compromise.
The most common ceramic of this type to be used for the past few decades is known as "partially stablised zirconia". Engineering students generally find out about it in the first year of their course if they have been educated in the last twenty years. It's cool and interesting stuff with some applications like the above but sometimes other stuff is more useful - metal tubes can flex more than even a tough ceramic like PSZ, low conductivity can be a drawback etc etc.