https://www.sciencenews.org/article/containers-u-s-plans-use-nuclear-waste-storage-may-corrode
[Sigh. We know this stuff is going to take tens to hundreds of
thousands of years to decay to 'safe' levels. Longer than we have a
recorded history for our species. We really need to make an effort to
make containment that works for more than a few decades.
Personally, given that we have the problem and have not come up with a
process for making long-lived radioactive materials not radioactive
other than waiting them out for the natural decay time, I'm a fan of
vitrification at low density of waste to glass. We have plenty of waste
glass in western society and it's relatively cheap to make more -
basically sand and heat. If the radioactive material is diffused enough
in the glass, it will be unattractive for future use. The glass blocks
would generate heat for a long time, so I would want them placed with
some space between to allow for heat dissipation. I like the idea of
putting the blocks into defunct underground uranium mines, which are
already naturally radioactive (though this will make them more so).
Fill the mine shafts with large rocks and fill to make excavation
challenging. Build in passive defence mechanisms and warning markings
and devices to discourage 'tourism'. For a few hundred years, people
are likely to still have some sense of our written languages and some
icons on signage. Better minds should bring better ideas, recognizing
we aren't trying to 'store' this waste, we want to dispose of it
permanently.]
The containers the U.S. plans to use for nuclear waste storage may corrode
Groundwater exposure could cause the metal and glass binding the waste
to break down
By Maria Temming
February 3, 2020 at 6:00 am
Containers that the U.S. government plans to use to store dangerous
nuclear waste underground may be more vulnerable to water damage than
previously thought.
Millions of liters of highly radioactive waste from the U.S. nuclear
weapons program are currently held in temporary storage units across the
country. The government’s game plan for permanently disposing of this
material is to mix radioactive waste into glass or ceramic, seal it in
stainless steel canisters and bury it deep underground. Such a nuclear
waste dump may be constructed under Yucca Mountain in Nevada, but local
opposition has stalled the project (SN: 1/16/02).
Now, new lab experiments reveal another potential snafu in the scheme.
When a nuclear waste package is exposed to groundwater, chemical
interactions between a stainless steel canister and its glass or ceramic
contents may cause the materials to corrode slightly faster than
expected, researchers report online January 27 in Nature Materials. That
corrosion risks exposing the radioactive waste stored in the container.
Xiaolei Guo, a materials scientist at Ohio State University in Columbus,
and colleagues discovered this problem by pressing pieces of stainless
steel against glass or ceramic and submerging the materials in a
saltwater solution, simulating groundwater exposure. When water seeped
into the boundary between the stainless steel and ceramic or glass, the
steel released ferrous iron, ferric iron and other components that
created an acidic environment at the metal’s surface. That acidity
corroded the neighboring ceramic or glass.
Some water exposure is considered inevitable while nuclear waste is
entombed, says William Ebert, a nuclear materials researcher at Argonne
National Laboratory in Lemont, Ill., not involved in the work. An
underground nuclear waste dump is, after all, supposed to store waste
securely for thousands of years. But Ebert cautions that submerging
metal, glass and ceramic in saltwater in the lab is quite different from
a very small amount of groundwater seeping into a steel canister. So
it’s not entirely clear how much the newly identified corrosion process
would jeopardize buried nuclear waste.
Guo and colleagues are investigating materials to coat the inside of a
steel canister that could act as a buffer between the metal and ceramic
or glass components, just in case.
--
Darryl McMahon
Freelance Project Manager (sustainable systems)
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