Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff
Speaker 1: Lauren Vogelbaum here. April of nineteen eighty six saw the
Speaker 1: accident at the Chernobyl nuclear power plant in Ukraine. Eight
Speaker 1: months later, workers who entered a corridor beneath the damaged
Speaker 1: Number four reactor discovered a startling phenomenon. Some sort of
Speaker 1: black lava had flowed out from the reactor core, as
Speaker 1: if it had been some kind of human made volcano.
Speaker 1: One of the hardened masses was particularly startling, and the
Speaker 1: crew nicknamed it the elephant's foot because it had flowed
Speaker 1: into a massive, wrinkled shape resembling an elephant's foot. Sensors
Speaker 1: told the workers that the lava formation was so highly
Speaker 1: radioactive that it would take just five minutes for a
Speaker 1: person to get a lethal amount of exposure from it.
Speaker 1: A decade later, the US Department of Energy's International Nuclear
Speaker 1: Safety Project, which elected hundreds of pictures of Chernobyl, obtained
Speaker 1: several images of the elephant's foot, which was estimated to
Speaker 1: weigh about two tons. Since then, the elephant's foot, which
Speaker 1: is known as a lava like fuel containing material or LFCM,
Speaker 1: has remained macabre object of fascination, but what is it?
Speaker 1: Because the elephant's foot was so radioactive, scientists at the
Speaker 1: time used a camera on a wheel to photograph it.
Speaker 1: A few researchers got close enough to take samples for analysis.
Speaker 1: What they found was that the elephant's foot was not
Speaker 1: the remnants of nuclear fuel, or not nuclear fuel alone.
Speaker 1: Experts explained that the elephant's foot is composed of a
Speaker 1: rare substance called korium, which is produced in a nuclear
Speaker 1: accident when the nuclear fuel and parts of the reactor
Speaker 1: core structures overheat and melt together, forming a mixture. A
Speaker 1: Quorium has only formed on its own five times in history,
Speaker 1: a once during a three mile island accident in Pennsylvania
Speaker 1: in nineteen seventy nine, once at Chernobyl, and three times
Speaker 1: at the Fukushima plant disaster in Japan in twenty eleven.
Speaker 1: For the article this episode is based on How Stuff Works,
Speaker 1: spoke by email with Edwin Lyman, director of Nuclear power
Speaker 1: Safety for the Union of Concerned Scientists. He said, if
Speaker 1: a core melt cannot be terminated, then eventually the molten
Speaker 1: mass will flow downward to the bottom of the reactor
Speaker 1: vessel and melt through with a contribution of additional molten
Speaker 1: materials dropping to the floor of the containment. The hot
Speaker 1: molten mass will then react with the concrete floor of
Speaker 1: the containment if there is one, again changing the composition
Speaker 1: of the melt. Depending on the type of reactor, the
Speaker 1: melt can spread and melt through the containment walls, or
Speaker 1: continue to melt through the floor, eventually infiltrating groundwater. This
Speaker 1: is what happened at Fukushima. When the melt cools sufficiently,
Speaker 1: it will harden into a hard rock like material. How
Speaker 1: stuff works also spoke by email with Mitchell T. Farmer,
Speaker 1: a veteran nuclear engineer and program manager at the Argonne
Speaker 1: National Laboratory. He explained the quorium looks quote a lot
Speaker 1: like lava, a blackish oxide material that gets very viscous
Speaker 1: as it cools down, flowing like sticky molten glass. The
Speaker 1: composition of a particular quorium flow and thus its appearance,
Speaker 1: will vary based on what materials melt together to make it.
Speaker 1: For example, the elephant's foot has a brownish hue that
Speaker 1: comes from concrete made with a lot of silica, basically glass.
Speaker 1: A part of it is always going to be uranium oxide. Fuel.
Speaker 1: Other ingredients include the fuel's coating, typically an alloy of
Speaker 1: zirconium called circuloi, and structural materials, which are mostly stainless
Speaker 1: steel composed of iron. A farmer said, depending on when
Speaker 1: water is resupplied to cool the quorium, the quorium composition
Speaker 1: can evolve in time As steam boils off. The steam
Speaker 1: can react with metals in the quorium, azirconium and steel
Speaker 1: to produce hydrogen gas, the effects of which you saw
Speaker 1: during the reactor accidents at Houkshima. The oxidized materials in
Speaker 1: the quorium are converted to oxides, causing the composition to change.
Speaker 1: But if the quorium isn't cooled, it will move down
Speaker 1: through the reactor vessel, melting more structural steel along the way,
Speaker 1: which causes even more changes in its composition. A farmer said.
Speaker 1: If still under cooled, the quorium can eventually melt through
Speaker 1: the steel reactor vessel and drop down onto the concrete
Speaker 1: floor of containment. This happened all three reactors of Fukushima.
Speaker 1: The concrete that comes in contact with the quorium will
Speaker 1: eventually heat up and begin to melt. Once the concrete melts, concrete,
Speaker 1: oxides typically known as slag, are introduced into the melt,
Speaker 1: which causes the composition to evolve even further. The melting
Speaker 1: the concrete also releases steam and carbon dioxide, which continue
Speaker 1: to react with metals in the melt to produce hydrogen
Speaker 1: and carbon monoxide, causing still more changes in the quorium's composition.
Speaker 1: The resulting mess that created Elephant's Foot is extremely dangerous. Generally,
Speaker 1: quorium is much more hazardous than undamaged spent fuel because
Speaker 1: it's in a potentially unstable state that's more difficult to handle, package,
Speaker 1: and store. A lineman said to the extent that quorium
Speaker 1: retains highly radioactive fission products plutonium and core materials that
Speaker 1: have become radioactive a quorium will have a high dose
Speaker 1: rate and remain extremely hazardous many decades or even centuries
Speaker 1: to come, and although it should be contained, doing so
Speaker 1: could be hazardous in itself. That's because very hard, solidified
Speaker 1: quorium like that of the elephant's foot would have to
Speaker 1: be broken up to remove it from damaged reactors. Lyman
Speaker 1: said that will generate radioactive dust and increase hazards to
Speaker 1: workers and possibly the environment, but what's even more worrisome
Speaker 1: is that scientists don't know how quorium might behave over
Speaker 1: the long term, of like when it's stored at a
Speaker 1: nuclear waste repository. What they do know is the quorium
Speaker 1: of the elephant's foot is likely not as active as
Speaker 1: it was, and that is cooling down on its own
Speaker 1: and will continue to cool but it is still melting
Speaker 1: down and remains highly radioactive. In twenty sixteen, the new
Speaker 1: safe confinement shield, a giant structure of steel and concrete,
Speaker 1: was slid over Chernobyl to prevent any more radiation leaks
Speaker 1: from the nuclear power plant. Another steel structure was built
Speaker 1: within this containment shield to support the decaying concrete sarcophagus
Speaker 1: in Chernobyl's reactor number four. The new safe confinement would
Speaker 1: ideally help prevent a massive cloud of uranium dust from
Speaker 1: dispersing into the air in the case of an explosion
Speaker 1: in room three oh five to two. Room three oh
Speaker 1: five to two was directly under the number four reactor
Speaker 1: core and has been showing signs of increased neutron emissions
Speaker 1: since twenty sixteen. It's totally inaccessible to humans because of
Speaker 1: the deadly radiation levels and as fascinating as it is,
Speaker 1: nobody wants to see another elephant's foot. A farmer has
Speaker 1: spent most of his career studying nuclear accidents and working
Speaker 1: with quorium in an effort to develop ways for plant
Speaker 1: operators to terminate an accident, how much water to inject
Speaker 1: and where to inject it, and how fast water can
Speaker 1: cool the quorium and stabilize it. He said, we do
Speaker 1: large experiments in which we produce quorium with the real materials,
Speaker 1: but we use electrical heating to simulate decay heat instead
Speaker 1: of decay heating itself. We focused most of our work
Speaker 1: on studying the efficiency of water addition in quenching and
Speaker 1: cooling quorum for various quoreum compositions. Thus, we are doing
Speaker 1: research on accident mitigation. The other end of it is
Speaker 1: accident prevention, and this is a principal focus area for
Speaker 1: the nuclear industry. Today's episode is based on the article
Speaker 1: Chernobyl's Elephant's foot is a toxic massive quorum on HowStuffWorks
Speaker 1: dot Com, written by Patrick J. Kiger. Brainstuff is production
Speaker 1: of My Heart Radio in partnership with how stuffworks dot Com,
Speaker 1: and it is produced by Tyler Klang. For more podcasts
Speaker 1: from my heart Radio, visit the iHeartRadio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows.