Ancient natural fission reactor offers clues on how to store modern nuclear waste

August 14, 2018 by Bob Yirka, Phys.org report
A scanning electron microscope image of uranium ore from the Oklo natural nuclear reactor. Insets show fissionogenic Cs and Ba hotspots. Credit: PNAS

A team of researchers from the U.S. Naval Research Laboratory and Washington University has learned more about possible ways to store modern nuclear waste by studying an ancient natural fission reactor. In their paper published in Proceedings of the National Academy of Sciences, the group describes their study of cores taken from the natural Oklo nuclear reactor and what they found.

As scientists continue to search for new more environmentally friendly ways to produce power, the old ways continue to generate waste. One such source is waste from . Various options regarding how to store it long term have been discussed, but few have panned out, leaving waste to be temporarily stored onsite. In this new effort, the researchers sought to learn more about what actually happens as nuclear waste decays over its active lifetime. To learn more, they traveled to Gabon, located in West Africa. At a location known as Oklo, there exists the remains of a natural nuclear . Due to a variety of events, the site was the scene of naturally occurring fission approximately 2 billion years ago. The uranium-235 that drove the reactions has long since decayed, but the history of how that occurred remains.

To learn more about what happened as the fissionable material decayed, the researchers took core samples and brought them back to their lab, which houses the Naval Ultra Trace Isotope Laboratory's Universal Spectrometer. There, they were able to piece together the history of the radioactive material as it moved through its elemental states, some of which included isotopes. Of utmost concern was what became of the cesium that was produced as a byproduct of uranium fission. Cesium has been found to be particularly hazardous due to its high degree of radioactivity—it was released into the environment after both the Fukushima and Chernobyl accidents. The researchers found that it was absorbed by an element called ruthenium, approximately five years after the reactor ceased. It was held there in place for almost 2 billion years.

The researchers suggest that discovering that cesium had been contained by ruthenium offers some ideas on possible ways to deal with produced in modern reactors. They further note that ruthenium is too rare to use, but something like it might do the trick. They plan to investigate further.

Explore further: Trace amounts of isotope from Fukushima disaster found in California wine

More information: Evan E. Groopman et al. Discovery of fissionogenic Cs and Ba capture five years after Oklo reactor shutdown, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1807267115

Abstract
Understanding the release and sequestration of specific radioactive signatures into the environment is of extreme importance for long-term nuclear waste storage and reactor accident mitigation. Recent accidents at the Fukushima and Chernobyl nuclear reactors released radioactive 137Cs and 134Cs into the environment, the former of which is still live today. We have studied the migration of fission products in the Oklo natural nuclear reactor using an isotope imaging capability, the NAval Ultra-Trace Isotope Laboratory's Universal Spectrometer (NAUTILUS) at the US Naval Research Laboratory. In Oklo reactor zone (RZ) 13, we have identified the most depleted natural U of any known material with a 235U/238U ratio of 0.3655 ± 0.0007% (2σ). This sample contains the most extreme natural burnup in 149Sm, 151Eu, 155Gd, and 157Gd, which demonstrates that it was sourced from the most active Oklo reactor region. We have discovered that fissionogenic Cs and Ba were captured by Ru metal/sulfide aggregates shortly following reactor shutdown. Isochrons from the Ru aggregates place their closure time at 4.98 ± 0.56 y after the end of criticality. Most fissionogenic 135Ba and 137Ba in the Ru migrated and was incorporated as Cs over this period. Excesses in 134Ba in the Ru point to the burnup of 133Cs. Cesium and Ba were retained in the Ru despite local volcanic activity since the reactor shutdown and the high level of activity during reactor operation.

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tpb
4.3 / 5 (6) Aug 14, 2018
Storing the waste is a idea whose time has come and gone.
We need to reprocess the waste and burn up what we can't reprocess in reactors designed for this purpose.
The next step is to use newer reactor designs that inherently burn up the waste to make energy.
lokay5
1.5 / 5 (8) Aug 14, 2018
Nuclear-generated electricity is an idea that has come and gone.
The three melted-out reactor cores at Fukushima Daiichi are the last three nails in nuclear'-generated electricity's coffin.
WillieWard
3.8 / 5 (8) Aug 15, 2018
The three melted-out reactor cores at Fukushima Daiichi...
Zero deaths from radiation exposure, meanwhile air pollution from fossil fuels(backup for intermittent renewables) respects no border and kills millions of people every year.
Wind/solar, even with a terawatt(1000 gigawatts) of installed-capacity at cost of trillions of dollars and huge ecological impacts, have failed miserably at reducing emissions and displacing fossil fuels. As general rule: natural gas(methane(CH₄): 70x worse than CO₂) has replaced coal and halved CO₂ emissions while wind/solar took the credits, providing an expensive form (economically/ecologically) of "greenwashing" for the gas/fracking industry.
Carbon-free nuclear power is the only scalable way to stop Climate Change, as hydro/geothermal are site-specific(geographically limited) and biomass is worse than coal in terms of greenhouse effect and competes with agriculture; solar/wind only exists to provide a decorative facade for coal/oil/gas.
Anonym642864
1 / 5 (3) Aug 15, 2018
In the beginning of the universe only radioactive element was formed. Each radioactive element was absorbed by other thus radioactivity becomes zero and formation of compound took place.
lokay5
1 / 5 (4) Aug 16, 2018
And you're comfortable burdening hundreds of future generations with the radioactive waste?
lokay5
1.8 / 5 (5) Aug 16, 2018
Japan's National Institute of Advanced Industrial Science and Technology have estimated the cost of decontamination and cleanup to be more than $50 billion and will take at least 40 years.
ShotmanMaslo
3.7 / 5 (3) Aug 16, 2018
And you're comfortable burdening hundreds of future generations with the radioactive waste?


Much more comfortable than burdening them with climate change. And it is not hundreds of generations either.
WillieWard
4 / 5 (4) Aug 16, 2018
And you're comfortable burdening hundreds of future generations with the radioactive waste?
Bury it in my backyard. Commercial nuclear waste has neither killed nor injured anyone, it is tiny is and safely stored in dry casks and emits less radiation than a bunch of bananas.
It's safer than mercury(teratogen) present in coal ashes and arsenides and other chemical carcinogens present in solar panels that never lose their toxicity with time.
https://pbs.twimg...XC-4.jpg
https://pbs.twimg...NTAV.jpg
https://pbs.twimg...jmtY.jpg
https://pbs.twimg...zrxW.jpg
"Nuclear Waste: Ideas vs Reality"
https://thoughtsc...reality/
https://thoughtsc...r-waste/
"Used Nuclear Fuel"
https://www.youtu...vIzH2W6g
https://www.youtu...dQQsxiq0
https://www.youtu...ZMxf_kZg
WillieWard
3.7 / 5 (3) Aug 16, 2018
Japan's National Institute of Advanced Industrial Science and Technology have estimated the cost of decontamination and cleanup to be more than $50 billion and will take at least 40 years.
People receive more radiation during a commercial flight(up to 65mSv), or in Kerala/Ramsar/Guarapari(up to 800mSv), than visiting Chernobyl(5mSv) or Fukushima(20mSv).
https://pbs.twimg...ccDq.jpg
https://pbs.twimg...PLQp.jpg

"...Fukushima ... radioactivity down to levels that are comparable with other major cities, including New York and Singapore."
https://www.vnews...19113765
"Fukushima Diaries The picture painted by anti-nuclear fear mongers does not match reality. Visit Fukushima with these three witnesses."
https://www.youtu...l_MaRngI
https://www.youtu...gLGA5TpM
dhcasti
3 / 5 (2) Aug 16, 2018
Iokay5, your position is based on good reason; current uranium based nuclear energy production is inefficient, that's why the waste products remain radioactive for tens of thousands of years. However, as a reasonable human, you should consider that uranium is NOT the only source of nuclear energy, thorium is four times as abundant and promises to be significantly more efficient resulting in far less waste with a half life measured in hundreds of years. Yes there are technical challenges to realizing it, but it will require acceptance by a majority of the population, especially those that want all the benefits of energy for humankind, but are equally concerned for the environment.
antialias_physorg
3.7 / 5 (7) Aug 16, 2018
Much more comfortable than burdening them with climate change.

I'll call 'false dichotomy' on that one.

However, as a reasonable human, you should consider that uranium is NOT the only source of nuclear energy, thorium is four times as abundant and promises to be significantly more efficient resulting in far less waste

Look at the timeline that would be needed to make any significant headway using nuclear. There's only a handful companies in the world that can build fission powerplants (and they can't build hundreds in parallel). Using wind and solar the world could be on full renewable by 2050. With nuclear? You'd have be starting to experiment with a handful of second generation thorium reactors by then. Maybe.

Nuclear is just detracting (huge amounts) of funds for a very expensive and unnecessary energy source. And that isn't even considering the waste issue.

ShotmanMaslo
3 / 5 (3) Aug 16, 2018

I'll call 'false dichotomy' on that one.


It is not a false dichotomy. France was mostly powered by nuclear back in the 80s, a feat that renewables are still far from matching, let alone exceeding. Anti-nuclear sentiment is the main factor for climate change being such an existential threat, instead of a mere inconvenience. Renewables are too little, too late.
dhcasti
5 / 5 (3) Aug 16, 2018
As the owner of a 2.1 kilowatt rooftop photovoltaic system, a home built solar heated outdoor shower, and efficient transportation, I am all for renewables and efficiency, but my love for the natural world includes NOT seeing wind turbines and concentrating solar towers covering the amount of land necessary to bring all of humankind the benefits of energy. As a old tree hugger, I used to reflexively reject nuclear without conscious and rational analysis. Future generations WILL look back on us like we look back on the ignorance of the past, and their standard of living could be worse, not better, than ours.
WillieWard
3.7 / 5 (3) Aug 16, 2018
Using wind and solar the world could be on full renewable by 2050.
https://pbs.twimg...blo5.jpg
Wind and solar have achieved an impressive milestone of a terawatt(1000 gigawatts) of installed-capacity at cost of trillions of dollars with almost nothing to show in terms of reducing emissions.
Intermittent renewables are just a distraction to keep the expansion of coal and gas/fracking industries.
"If you look around a little http://electricitymap.org, you will quickly notice that countries with low CO2 emissions create this with a lot of hydropower, with a lot of nuclear energy or with a lot of both."
"The ones that went with nuclear and hydro decarbonized. The ones that went with wind and solar failed and keep failing."
"While nuclear and hydro are strongly correlated with decarbonization of energy at aggregated national levels, solar and wind are not."
https://pbs.twimg...cQTY.jpg
Wind and solar are a fiasco even in small-scale.
Captain Stumpy
1 / 5 (1) Aug 16, 2018
@antialias_physorg
Nuclear is just detracting (huge amounts) of funds for a very expensive and unnecessary energy source. And that isn't even considering the waste issue
yes and no

IMHO, it will be absolutely necessary for future human exploration and survival

however, as with all things, there are drawbacks (like the waste)

I'm not saying that we should scrap solar or other green technology, mind you

antialias_physorg
1 / 5 (3) Aug 16, 2018
We're looking at huge cost overruns in terms of timeframe and cost in all nuclear facilities currently under construction. One part of Hinkley point nuclear powerplant (Hinkley Point C) in the UK will cost 20bn pounds to construct and 50bn in subsidies to the consumer over the next 30 years in guaranteed subsidies. The powerplant will produce 3.2 GW of electricity and double that in heat....in 2027...if all goes according to plan from now on (which, given its history, is unlikely)

Just for comparions. In 2017 China invested 132bn dollars in renewables and added 53 GW of solar. Instantly.
World total for 2017: 333bn dollars. 160GW added. Instantly.
https://www.green...-in-2017

Solar/wind/hydro seem a lot more bang for the buck (and a lot faster to get results) to me.
Captain Stumpy
1 / 5 (1) Aug 16, 2018
@antialias_physorg
Solar/wind/hydro seem a lot more bang for the buck (and a lot faster to get results) to me
not arguing that point at all, let alone the cost overruns

solar is a great idea, but not so much on Europa - so nuclear power is absolutely necessary if we're getting off this rock

batteries are improving, but ...
antialias_physorg
1 / 5 (2) Aug 16, 2018
solar is a great idea, but not so much on Europa

Sure, that's a different issue. Though on europa I'd go for hard radiation panels harvesting off of what's coming from Jupiter. If you want big power generation for a settlement the cryovolcanism would do the trick.
Uranium and Throium are likely not particularly abundant out there. Hydrogen is (which means fusion...which is an entirely different thing. Research into fusion is sensible...and it's nowehre near as expensive as going for dead-on-arrival fission tech)
Captain Stumpy
1 / 5 (1) Aug 16, 2018
@antialias_P
Sure, that's a different issue.
I don't think it is
we may well develop better tech once were on Europa, but getting there is going to be where Nuke energy (fission or fusion) is required, especially if the transport has any life support for a group larger than 2 people
Research into fusion is sensible...and it's nowehre near as expensive as going for dead-on-arrival fission tech)
I agree that fusion research is sensible
IMHO - fusion research is the Nuclear research that is of paramount importance at this point, but I am thinking we will require fission in conjunction to supply the requisite energy to kick sh*t into gear

WillieWard
3 / 5 (2) Aug 16, 2018
..(Hinkley Point C) in the UK will cost 20bn pounds..
"Battery storage needed to convert solar generation equal to a year of Hinkley nuclear generation to baseload: $700 billion, about 28 times the ~$25 billion cost of the Hinkley plant."
http://euanmearns...storage/

Meanwhile in China, one of world's largest manufacturers of windmills and solar panels:
"China is funding its nuclear power future by selling solar panels to those who don't know better."
"China weakness is foreign oil dependence but will they scale to building two nuclear reactors per week"
https://www.nextb...eek.html

"The Dark Side of China's Solar Boom" - Jul 2018
"Experts say that millions of aging panels could have significant environmental impacts..."
http://www.sixtht...ar-boom-
lokay5
1 / 5 (2) Aug 18, 2018

Japan's National Institute of Advanced Industrial Science and Technology have estimated the cost of decontamination and cleanup to be more than $50 billion and will take at least 40 years.

WillieWard
3 / 5 (2) Aug 18, 2018
It seems that South Koreans aren't listening to antinuclear fearmongers(fossil-fuel lobbyists), and definitively don't believe in sunshine&breeze unicorn energy.
"..as global warming intensifies, the trend against nuclear power that emerged in many countries after the Fukushima Daiichi Nuclear Power Plant accident in 2011 has reversed... Opposing nuclear energy is now an outdated trend." - 2018/07/31
http://focustaiwa...035.aspx
"7 in 10 Koreans approve of nuclear power" - Aug 16, 2018
https://www.korea...971.html
"Seven out of 10 Koreans surveyed want power to come primarily from nuclear reactors."
http://koreajoong...=3052035
"People in Taiwan have lost faith that government [can achieve] its nuclear-free goal without compromising the stable supply of electricity since the major power outage on August 15 last year."
http://m.koreatimes.co.kr/pages/article.asp?newsIdx=252025
Whart1984
Aug 19, 2018
This comment has been removed by a moderator.
24volts
3 / 5 (2) Aug 19, 2018
"We're looking at huge cost overruns in terms of timeframe and cost in all nuclear facilities currently under construction".

It wouldn't take 10 years or be anywhere near as expensive if every Tom, Dick, and Harry wasn't suing over every little thing that could possibly happen or simply because they don't want one close around. THAT'S what takes nuclear plants so long to get going. There are plenty of places on the planet where waste could be stored without a problem too but again we have every jerk around suing over it.
lokay5
1 / 5 (1) Aug 22, 2018
And "every jerk around" wins every lawsuit. Does that tell you anything?

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