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."

Re:Pretty Helpful

[Anonymous Coward]

I think it'd probably be more useful in plant operation than storage just because the fatigue mechanics are going to always be an unknown. When you're looking at a 10k year life span for some container it doesn't make much sense to use ceramics for anything structural. Like the actual container. Honestly, we should probably just burn all the fuel down even if Plutonium is a by product, and then just store the much smaller more inert waste left over. At least with a ceramic part in a plant you could get perhaps improved wear resistance, life, corrosian resistance, and monitor it, and perhaps saving on zirconium and weight should that prove important. When looking at long term storage the monitoring isn't going to be an option. Ceramics are brittle, they *will* crumble (smaller chips are stronger which has to do with certain statistical aspects of fracter mechanics. smaller pieces smaller largest cracks.) Ceramics are good at being chemically inert and hard. Sticking in one piece not so much. Steel (maybe not so much with hydrogen embrittlement), and especially bronze... well those will do a pretty good job of not crumbling.

You could probably sinter the ceramics in such a way that they were particularly porus, then perhaps coat them in teflon to confer some water resistance. Gas escapes, water generally stays out. But then you're really just using ceramics to protect the vessal and be chemically inert. (But you'd have the additional problem of accumulating water between your metal vessal and the ceramic defense, and possible catalytic reactions.

Other uses?

[Rocketman_Ryan]

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.

Gas Cooled Fast reactor

[BlueParrot]

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 [wikipedia.org]

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 [wikipedia.org]), 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.