Toward safer, long-life nuclear reactors—metal design could raise radiation resistance by 100 times

December 16, 2016 by Katherine Mcalpine
An electron microscope reveals the radiation-induced cavities inside samples of pure nickel and alloys. The cavities in nickel-cobalt-iron and nickel-cobalt-iron-chromium-manganese alloys are 100 times smaller than those in pure nickel. Credit: Wang Group, University of Michigan

In findings that could change the way industries like nuclear energy and aerospace look for materials that can stand up to radiation exposure, University of Michigan researchers have discovered that metal alloys with three or more elements in equal concentrations can be remarkably resistant to radiation-induced swelling.

The big problem faced by metals bombarded with radiation at high temperatures—such as the metals that make up nuclear fuel cladding—is that they have a tendency to swell up significantly. They can even double in size.

"First, it may interfere with other parts in the structure, but also when it swells, the strength of the material changes. The material density drops," said Lumin Wang, U-M professor of and radiological sciences. "It may become soft at high temperatures or harden at low temperatures."

This happens because when a particle flies into the metal and knocks an atom out of the , that displaced atom can travel quickly through the metallic crystal. Meanwhile, the empty space left behind doesn't move very fast. If many atoms are ousted from the same area, those empty spaces can coalesce into sizable cavities.

To control the formation of these cavities, and the attendant swelling, most recent research has focused on creating micro- and nano-structures inside the metal as specially designed "sinks" to absorb small defects in a way that preserves the integrity of the material. But Wang and his colleagues are kicking it old school, looking at that don't have breaks in the crystal structure of the atoms.

An electron microscope reveals the radiation-induced cavities inside a sample of pure nickel. The cavities in nickel-cobalt-iron and nickel-cobalt-iron-chromium-manganese alloys are 100 times smaller. Credit: Wang Group, University of Michigan

Colleagues at Oak Ridge National Laboratory in Tennessee created samples of a variety of nickel-based alloys. These were then exposed to radiation in a facility at the University of Tennessee. The most successful alloys were concentrated solid solutions—crystals made of equal parts nickel, cobalt and iron; or nickel, cobalt, iron, chromium and manganese.

"These materials have many good properties such as strength and ductility, and now we can add radiation tolerance," said Chenyang Lu, a U-M postdoctoral research fellow in nuclear engineering and radiological sciences and the leading author of the report in Nature Communications.

In an experiment proposed by Wang, UT researchers exposed the samples to beams of radiation that created two levels of damage, similar to what may accumulate in a reactor core over several years and over several decades. These experiments were done at a temperature of 500 Celsius or 932 Fahrenheit—a temperature at which nickel-based alloys are usually prone to swelling.

These samples were analyzed at U-M's Center for Material Characterization with a transmission electron microscope. The team found that compared to pure nickel, the best alloys had more than 100 times less radiation damage.

To explain what was special about these alloys, the team worked closely with the group of Fei Gao, a theoretician and U-M professor of nuclear engineering and radiological sciences. Gao's group performed computer simulations at the level of individual atoms and showed that the radiation tolerance in this group of alloys can be attributed to the way that the displaced atoms travel within the material. The explanation was further confirmed by another set of experiments conducted by the team at the University of Wisconsin.

An electron microscope reveals the radiation-induced cavities inside a sample of nickel-cobalt-iron-chromium-manganese alloy. The cavities in pure nickel are 100 times larger. Credit: Wang Group, University of Michigan

"In simplified terms, if there are a lot of atoms of different sizes, you can consider them bumps or potholes," Wang said. "So this defect won't travel so smoothly. It will bounce around and slow down."

Because the displaced atoms and the holes in the crystal structure stayed near one another, they were much more likely to find one another. In effect, this repaired many of the vacancies in the complicated alloys before they could join together into larger cavities.

"Based on this study, we now understand how to develop a radiation-tolerant matrix of an alloy," Wang said.

The study, titled "Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single phase alloys," appears in Nature Communications.

Explore further: Physicists create a high-strength material for the aerospace and engineering industries

More information: Chenyang Lu et al. Enhancing radiation tolerance by controlling defect mobility and migration pathways in multicomponent single-phase alloys, Nature Communications (2016). DOI: 10.1038/ncomms13564

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gkam
1.7 / 5 (12) Dec 16, 2016
How about just using less-dangerous solar and wind?

BTW,the reactor vessels for the new European reactors have metal flaws and they do not know if they can be used. They will use them anyway and just pray.
Zzzzzzzz
4.6 / 5 (10) Dec 16, 2016
gkam, the article is about radiation resistance in alloys of certain structures. I doubt there is anyone who frequents these comment sections that is not already aware of your agenda when it comes to the subject of power generation technologies. It does get a bit tiresome at times.
WillieWard
4 / 5 (4) Dec 16, 2016
Who but george kamburoff takes george kamburoff seriously?

Nobody here.

Nobody out there, which is why he spends all his time here (wasting ours).
Roderick
5 / 5 (4) Dec 16, 2016
Gkam,

Try to keep your mind open. Without economic storage, wind and solar power are only useful to satisfy peak demand. Any glance at the World Bank estimates on per capita CO2 emissions shows that nuclear intensive countries have much lower per capita emissions that Green Germany and Denmark.
Caliban
Dec 16, 2016
This comment has been removed by a moderator.
syndicate_51
4 / 5 (4) Dec 17, 2016
Caliban, please refer yourself to a reactor at Argonne national laboratory called EBR II and see your ignorance.

Solar and wind, cannot hope to take the base load anytime soon. What are they 1% of 1% of current energy generation or something like that compared to world needs. Also they are hybrid technologies. You need backup for when there is no sun or wind and no, battery power is not feasible as of yet. Although these could become a goal in the future. Not soon enough.

Gkam and Caliban, I will put you two in the control room of say any Advanced Integral Fast Reactor, (of which all its's technologies are proven), and say GO NUTS! Turn any nobs you want, any number of times as long as you want. Just try and melt it down! Unfortunately for you two, you're fighting physics. You know (if you know anything about science) how that turns out.
syndicate_51
4 / 5 (4) Dec 17, 2016
EBR II for the record, was shut down just as it was entering the last phase of development. Economic feasibility.

Who shut it down, the Clinton administration.

Who lobbied them? Oil and gas. Hmmmmmmmmmmmmmm.................. Hmmmmmmmmm.................

Who funds Helen Caldicot? Oil and gas. Hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm........

Wait! It cost more money to shut down than if they had kept the program going highlighting the political agenda in place against it? Hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm........

Wait the Oil and Gas industry knows that Solar and Wind will still rely upon them for down time? Hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm...
syndicate_51
4.2 / 5 (5) Dec 17, 2016
Solar and Wind cannot provide alternative power fast enough, this doesn't mean they should be abandoned. No. However something will be needed to bridge the gap and I get this feeling that it may already be too late for all of this anyways.

AIFR's, can fix the problem but either option will require trillions worldwide in infrastructure investment. So should we spend that on a technology that still requires full support from oil and gas (which they love) or should we move to a truly independent form of energy while transitioning to renewables?
ab3a
not rated yet Dec 17, 2016
Building safer alloys for high neutron exposure is a big deal, not just for fission reactors, but also for those fusion systems that so many think are so "clean." It is also helpful for nuclear batteries on exploratory spacecraft.

Please save the vitriol for actual construction projects, not the research that might or might not be included in it.
Eikka
3.7 / 5 (3) Dec 17, 2016
BTW,the reactor vessels for the new European reactors have metal flaws and they do not know if they can be used. They will use them anyway and just pray.


That is a flat out lie.
MarsBars
1 / 5 (2) Dec 18, 2016
That is a flat out lie.

Eikka - enter "epr reactor problems" into Google, view the results, and then come back and tell us that Reuters, the BBC, The Guardian, Telegraph, Independent, World Nuclear News, Wikipedia, etc., etc. are all lying.
Eikka
5 / 5 (2) Dec 18, 2016
That is a flat out lie.

Eikka - enter "epr reactor problems" into Google, view the results, and then come back and tell us that Reuters, the BBC, The Guardian, Telegraph, Independent, World Nuclear News, Wikipedia, etc., etc. are all lying.


That's not the point. Material defects have been detected - to claim that they don't know if it's safe, aren't doing anything about it, and are "praying" for it to work is a flat out lie.

https://safeenerg...anamoly/
The pieces are all made of 16MND5 steel. The defect consists in carbon segregation in a certain area of the partly spherical upper and lower heads. It occurs due to insufficient elimination during the forging process of the higher part of the ingot, where carbon tends to concentrate, in the fabricated piece.


I.e. carbon has clumped up inside the steel which causes steel to become less ductile and more prone to fracture.
Eikka
5 / 5 (3) Dec 18, 2016
continued quote

Major defects in the vessel closure head were found by Areva in the Autumn of 2010 and in June 2011. One concerned the welding of adaptor tubes, the other concerned the welding of more than 50 penetrating tubes (out of 107 in total). In October 2011 ASN allowed Areva to carry out deep repair work instead of fabricating a new head.


The carbon deposits can be broken down by heat treatment - annealing the steel to diffuse the carbon around and make it more ductile again. The impact resistance of the affected steel was measured to be on average 54 J where the regulation minimum was 60 J and so Areva could repair the work instead or replacing it.

Here's the thing: if Areva can't show that the repair work is done correctly, that it puts the material within the regulation specs, the reactor will never start.

They're not simply crossing their fingers and hoping for the best - if the work doesn't pass regulation it is actually illegal to turn it on.
Eikka
5 / 5 (2) Dec 18, 2016
The main complaint about the material defects issue is that Areva went ahead and put the reactor vessel in place and allowed construction to continue on around it for months before they even got the test results on the steel.

The materials test was part of the offical qualification process for the reactor. They were just too cock sure that they'd pass the test and save couple months of construction time - and they didn't - so they ended up losing months.

This is why the EPRs in Flamanville and Finland have turned out so much behind schedule and so much over budget. Areva sucks at project management.
RealScience
5 / 5 (3) Dec 18, 2016
Areva sucks at project management

Which raises a question - should a company that "sucks at project management" be building nuclear reactors?"

Building safer alloys for high neutron exposure is a big deal, not just for fission reactors, but also for those fusion systems that so many think are so "clean." It is also helpful for nuclear batteries on exploratory spacecraft.


Agreed. If we build new nukes of any kind they'll be safer, and such alloys would also be useful for storing the radioactive waste that we already have. Regardless of whether one is pro-nuke or anti-nuke, this is useful research.

Eikka
5 / 5 (1) Dec 19, 2016
Which raises a question - should a company that "sucks at project management" be building nuclear reactors?"


Simple answer to a simple question: No.

However, since nobody's built one Europe in over 20 years, it's more or less expected that the first to try is going to bungle it up somehow - out of plain lack of experience - hence why the quality and safety regulations are in place.

Regardless of whether one is pro-nuke or anti-nuke, this is useful research.


In my observation the anti-nuclear people oppose both nuclear power AND the waste disposal - which seems contradictory at first but it's really logical if you consider that disposing of the waste robs them of their main argument against nuclear power in general.

That's becuse the opposition to nuclear power has become a political dogma and a matter of personal faith rather than a rational argument against a problem.
MarsBars
1 / 5 (2) Dec 21, 2016
BTW,the reactor vessels for the new European reactors have metal flaws and they do not know if they can be used. They will use them anyway and just pray.


That is a flat out lie.


Eikka - enter "epr reactor problems" into Google, view the results, and then come back and tell us that Reuters, the BBC, The Guardian, Telegraph, Independent, World Nuclear News, Wikipedia, etc., etc. are all lying.


That's not the point. Material defects have been detected...

Your original post called ALL of gkam's statement a lie, which it clearly wasn't if major news media reported on those defects. That's my point. I grant you that the second sentence in gkam's statement can be considered hyperbole, but the EPR reactor vessel defects are real - as you now concede.
MarsBars
1 / 5 (2) Dec 21, 2016
the opposition to nuclear power has become a political dogma and a matter of personal faith rather than a rational argument against a problem.

I recently saw a TV report "Into the Zone, Fukushima", revisiting 5 years after the meltdown of the 3 reactors. Some quotes:

Naohiro Masuda, Chief Fukushima Decommissioning Officer: "We are currently working on a timetable to decommission the reactors over the next 30 to 40 years."
"It's estimated that 200 tonnes of debris lies within each unit so in total about 600 tonnes of melted debris fuel and a mixture of concrete and other metals are likely to be here."

Naoto Kan, former Prime Minister: "This is a major accident, which has never happened anywhere in the world. I think 40 years is an optimistic view."
"So far the government is paying $70 billion to support TEPCO. But that is not enough. It will probably cost more than $240 billion."
(continued)
MarsBars
1 / 5 (2) Dec 21, 2016
"It's become clear that nuclear power is more dangerous than other energy sources. In the past, they said it was cheap - but it was only cheap if the cost of accidents, or the cost of disposing of spent fuel and nuclear waste was not included."

Gregory Jaczko, former Chairman, US Nuclear Regulatory Commission: "Nobody really knows where the fuel is at this point, and this fuel is still very radioactive and will be for a long time."
"You have to now accept that in all nuclear power plants, wherever they are in the world, that there's a chance you can have this kind of a very catastrophic accident and you can release a significant amount of radiation and have a decade-long clean-up effort on your hands. And that's the reality of nuclear power."

It will be 2021 before they clear debris down to the fuel rods. There is no existing technology to then deal with removing the fuel; that technology still needs to be invented.
TheGhostofOtto1923
5 / 5 (3) Dec 21, 2016
It will be 2021 before they clear debris down to the fuel rods. There is no existing technology to then deal with removing the fuel; that technology still needs to be invented
Great - a learning experience. Seriously, nuclear will be the principal power source for space colonization. Developing tech and strategies to deal with such accidents is critical to this effort. And colonization is critical to the long term survival of our species.

Testing to failure is an integral component of product development, regardless of scale.
MarsBars
1 / 5 (2) Dec 23, 2016
Great - a learning experience. Seriously, nuclear will be the principal power source for space colonization. Developing tech and strategies to deal with such accidents is critical to this effort. And colonization is critical to the long term survival of our species.

Testing to failure is an integral component of product development, regardless of scale.

Otto, how many learning experiences must be endured before the industry gets it right, or the costs become prohibitive? 1100 square kilometres of Fukushima's forests, mountains and villages remain uninhabitable, 100,000 people cannot return, and the cleanup cost will be tens if not hundreds of billions. Testing to failure is no fun when the test site is a production power station in a populous area.

Space colonization will be critical to our species' long term survival due to us having comprehensively trashed, poisoned and over-exploited this planet. Will we even be around long enough for serious colonization to occur?
cortezz
3 / 5 (2) Dec 23, 2016
Nuclear power plants can be build to be safe even in cases like fukushima. The stupidity of japanese and their old safety standard plants does not mean that every power plant in the world is somehow dangereous. Same goes to tshernobyl. For example, finnish nuclear power plants are made to withstand tsunamis, airplane crashes, earthquakes etc. stuff that cannot even happen in Finland. All nuclear bomb test combained have done more harm to humans in general than all nuclear catastrophes but this is rarely mentioned.

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