Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How did this worker approach this fuel mass at Chernobyl?

  1. Feb 18, 2013 #1
    I accidentally happened upon this photo while researching some things about the 1986 Chernobyl nuclear disaster and I freaked out! How did this worker get so close to this mass of melted nuclear fuel in the basement of Chernobyl without receiving several lethal doses of radiation?

    This mass of corium located in the basement directly beneath the Chernobyl reactor is known as "the elephants foot" and it emits radiation at levels in excess of 10,000 roentgens per hour.

    Approaching it would mean certain death. The individual shown in the below image is either completely insane or outright suicidal.

    I am quite certain that this worker, as well as the person who took the photograph, are now both deceased. Probably from either cancer or acute radiation sickness.

    Last edited: Feb 18, 2013
  2. jcsd
  3. Feb 18, 2013 #2
    I don't think that the Soviet government really told those people about the dangers.
  4. Feb 18, 2013 #3
    I think that photo was taken in the 1990's, after the collapse of the USSR.
  5. Feb 18, 2013 #4
    Here is another photo of the "elephant's foot." You can see distortions and abnormalities in the photograph caused by EXTREME levels of radiation. This radiation (thousands of rads per hour) actually caused the lower half of the worker to appear transparent.

    Crazy... absolutely crazy....

  6. Feb 18, 2013 #5

    I like Serena

    User Avatar
    Homework Helper

    Just making a couple of calculations...

    This elephant's foot gives off 10000 R per hour at its surface.
    According to wiki 500 R during 5 hours is considered lethal.
    That is equivalent at sitting at a distance of 1.5 m for 5 hours.
    ... which appears to be what this guy is doing!
    Presumably doable with protective clothing but it does not look smart.
  7. Feb 18, 2013 #6


    User Avatar
    Science Advisor
    Gold Member

    10,000 R/hr is 2.8 R/second. Assuming the guy just ran up, took the picture, and then ran back, his dose would not be too extreme. More than I would volunteer to receive though.
  8. Feb 18, 2013 #7
    Yes, but enough to make you very ill and dramatically increase your risk of cancer and many other health ailments.

    Approaching a mass of corium is crazy regardless of the circumstances. This should have been done with robots and not people.

    Off-topic, but how do roentgens convert to rads? Which unit is greater? Why isn't this unit of measurement used in the United States?
    Last edited: Feb 18, 2013
  9. Feb 18, 2013 #8


    User Avatar
    Science Advisor
    Gold Member

    Not for 10-20 R. You don't start to see acute symptoms until around 100 R. As for increase risk of cancer, there is no way to know if there are long term risks associated with low exposure doses.

    Not as crazy as smoking, being overweight, or texting while driving.

    From: http://www.osha.gov/SLTC/radiationionizing/introtoionizing/ionizinghandout.html

    Quantifying Exposure and Dose

    Exposure: Roentgen

    1 Roentgen (R) = amount of X or gamma radiation that produces ionization resulting in 1 electrostatic unit (esu) of charge in 1 cm3 of dry air at STP. Instruments often measure exposure rate in mR/hr.

    Absorbed Dose: rad

    1 rad (Roentgen absorbed dose) = absorption of 100 ergs of energy from any radiation in 1 gram of any material; 1 Gray (Gy) = 100 rads = 1 Joule/kg; Exposure to 1 Roentgen approximates 0.9 rad in air.

    Dose (in rads) = 0.869(f)(Roentgens) where the f-factor is the ratio of mass energy-absorption coefficient of medium, such as bone, compared to air.

    Biologically Equivalent Dose: rem

    Rem (Roentgen equivalent man) = dose in rads x QF, where QF = quality factor. 1 Sievert (Sv) = 100 rems.
  10. Feb 18, 2013 #9

    jim hardy

    User Avatar
    Science Advisor
    Gold Member
    2018 Award

    The elephant's foot is largely silica glass from the sand that surrounded the vessel.
    While it contains fuel fragments, it's not like it was pure corium. It's a few percent uranium.

    http://www.tesec-int.org/chernobyl/Radioactive waste in the Sarcophagus.htm

    Not to minimize the danger at all.
    As somebody else pointed out - in a 10,000 R field one could have a few second stay time.
    I'd wager the field there was on order of a few hundred R. But that's just a guess. Lack of fogging on the film supports it...
    Last edited: Jan 17, 2016
  11. Feb 18, 2013 #10
    At the time when they made this picture there were already 100 - 700 Roentgen
  12. Feb 18, 2013 #11
    So the "elephants foot" was only a few % uranium and was made largely of sand/concrete/zirconium and other materials which the molten corium mixed in with after melting?
  13. Feb 18, 2013 #12
    What we don't know, was the mass 10000R/hr on contact or at some distance away?

    Typically dose rates are reported as on contact and at 3 feet. 10000R/hr on contact means less a few feet away, which gives him just enough time to safely get in and take a picture. Or he could have just not cared.

    Because there was other materials in the mass, it's likely the dose rates were only internal or on contact to the mass. The other materials mixed in the glass type mass would also provide some level of shielding.
  14. Feb 25, 2013 #13
    BTW, uranium per se is _not_ a significant source of radiation here. Fission products are.

    The worker in this photo is reckless, but not too much.

    You know, some people in fact had to *collect* material with comparable levels of radiation in the first weeks and months after accident, when chunks of fuel and graphite from reactor were lying bare of the ground around the destroyed Unit 4 and were making any sort of accident response very dangerous. THAT was crazy.
  15. Feb 25, 2013 #14

    I like Serena

    User Avatar
    Homework Helper

    If I were say 70 years old and had kids and grand kids living nearby, I'd be motivated not to wait for the proper equipment.
  16. Feb 25, 2013 #15
    In this particular situation "kids and grand kids" already got their dose of Iodine-131 etc from the aerosols in the air.

    The cold debris around reactor was not producing much of a contamination any more - at least compared to still burning open-air graphite fire in the ruined reactor core it is miniscule.

    Yes, debris was very radioactive per se, but IIRC gammas are attenuated in half by ~150 meters of air. Nearest housing is no closer than 3 kilometers - attenuation of gammas by 2^20 = ~million times, even discounting attenuation due to inverse square law.

    Clean-up was necessary because otherwise it was impossible to approach the Unit 4 building and do anything. Thousands of R/h.
  17. Feb 25, 2013 #16

    jim hardy

    User Avatar
    Science Advisor
    Gold Member
    2018 Award

    There are motion pictures from days after the accident of people atop the building tossing pieces of reactor back down into the pit. They'd get a very high dose in just one few second run.

    That was self sacrifice.
  18. Feb 25, 2013 #17
    Is that the actual elephants foot? I don't think so that kind of looks like it might be a turbine or something, and I thought no one EVER got that close to the "elephants foot" in person... I thought the only photo(s) they got of it was with a robot.
  19. Feb 26, 2013 #18
    ONLY robots should be used to approach areas of the Chernobyl reactor that are too radioactive for people.

    The workers who entered areas of the reactor where there was literally melted nuclear fuel laying about on the ground are likely at extremely high risk of cancer.
  20. Feb 26, 2013 #19
    That's the movie

  21. Feb 26, 2013 #20
    not necessarily true.

    for accute exposure cases, you can linearly assume something like a .04% increase in chance of cancer over your lifetime per 10 Rem. A single chronic case shouldn't have a very large increase over the chance you already have to get cancer over all sorts of other stuff.

    It's usually in long term chronic exposure that cancer rates start to rise greatly.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?