Tepco: Bent rod found in spent fuel pool — Nuclear fuel rods touching — “Serious fuel failure accident” risked at Japan plant

Published: December 13th, 2012 at 10:04 am ET


Title: Bent rod found at TEPCO’s Niigata reactor
Date: December 13, 2012

Tokyo Electric Power Co. said Dec. 12 a bent water rod caused two fuel rods to come into contact inside a fuel rod assembly stored in a spent fuel storage pool for the No. 5 reactor of the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture.

No damage to nuclear fuel or other anomalies have been reported, but the two fuel rods may have been in contact with each other when they were burning inside the reactor.

The situation had the potential to cause a serious fuel failure accident. […]

Water rods [a passage for coolant water that runs through the center of a fuel assembly] were found to be bending in 18 fuel rod assemblies in the storage pool. Closer studies found that in one fuel rod assembly, the bending water rod pushed one nearby fuel rod into contact with another. […]

See also: [intlink id=”gundersen-im-sure-lot-damaged-nuclear-fuel-fukushima-spent-fuel-pools-tubes-cracked-be-completely-severed-video” type=”post”]{{empty}}[/intlink]

Published: December 13th, 2012 at 10:04 am ET


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  2. Photo: Cracks found in spent fuel rods at Japan nuclear plant January 12, 2013
  3. Kyodo: Level 1 incident at Japan nuclear plant — Deformed fuel rods stuck together in pool December 19, 2012
  4. Nuclear Engineer: Fuel assembly damaged at Fukushima Unit 4 — It’s bent in shape of banana — Unknown if pellets poured into pool during removal — Tepco stopped English translations (AUDIO) December 19, 2013
  5. Accident in Reactor 3 fuel pool at Fukushima — Large piece of wreckage falls nearby spent uranium rods — M5 quake hits plant soon after — Official: “Unable to say” whether any are damaged (PHOTOS & VIDEO) August 29, 2014

27 comments to Tepco: Bent rod found in spent fuel pool — Nuclear fuel rods touching — “Serious fuel failure accident” risked at Japan plant

  • Sickputer

    It's the Goliath of nuclear plants, the largest in the world and located in central Japan on the opposite coast from Fukushima.

    Had a bad experience with an earthquake in 2007 and I don't think it has ever recovered despite massive retrofits. After 20+ years of operation lots of spent fuel rods.

    • lam335 lam335

      I wonder if this bending occurred as a result of the earthquake you mention. That would raise still more questions about the ability of nuclear reactors to safely withstand earthquakes.

      • PavewayIII PavewayIII

        Kashiwazaki was Japan's first example of flawed seismic design based on underestimating a future earthquake's magnitude. I'm getting the idea that they're either not very good at estimates or they only leave a 2% safety margin on their designs.

        The seismic-qualified parts of the plant withstood the 'extra' shaking they were not designed for. They bolted on some extra pipe support and claim the entire plant has magically been uprated to the new, known extreme plus 10%.

        No idea if the 2007 quake had anything to do with the bent fuel pellet dispensers (think 'Plutonium Pez').

        Count on the next earthquake near Kashiwazaki to be 15% – 20% larger. TEPCO: "Gee… we never expected that"

    • Johnny Blade Johnny Blade

      @S.P., You've ALWAYS got more interesting footnotes to contribute and it's ALWAYS appreciated even though your info rarely holds any room for optimism! I'll leave that dept. to TEPCO/GE "spin Dr.'s" or Big Nuke's P.R. MAD men when I feel the need to sugar-coat reality.LOL! I dug around a bit after your "Goliath" of nuke plants post and found this too(?)!
      http://english.ruvr.ru/2012_02_26/66913971/ wonder if it's related? and #2;"how come they didn't find this issue SOONER"?!!(they probably knew "something" was awry but "chose" not to deal with it until it too became a MAJOR problem?!!) TEPCO SUCKS!!

    • AGreenRoad AGreenRoad

      SLLOOOOOWWWWLLLLYYYYY, the truth comes peaking it's head out..

      On 3/11; 15-24 Nuclear Reactors/SFP’s In Japan Were Damaged, Not 3 or 4; via A Green Road http://agreenroad.blogspot.com/2012/03/14-nuclear-reactors-at-4-japan-sites.html

      Atucha Nuclear Reactor Taken Over By Terrorists; via A Green Road

  • lam335 lam335

    Can someone explain what a "water rod" is/what it does in a reactor?

  • Ace33

    I'm just guessing but im sure they mean control rod

  • Ace33

    I was wrong some more searching and I found this
    1. A water rod, usable for containing water in a substantially interior position in a nuclear fuel rod bundle, the bundle having a plurality of lattice positions spaced at a predetermined lattice pitch, comprising:

    a hollow longitudinally extending tube having a sidewall which defines a cross-sectional interior region of said tube, configured to substantially occupy a predetermined number of the lattice positions of the bundle;
    said cross-sectional interior region being configured to define two round-cornered, triangular regions continuously connected by a constricted region, said constricted region being defined by two inwardly extending longitudinal projections;
    wherein said predetermined number is greater than four lattice positions and less than nine lattice positions; and
    wherein said area of said cross-sectional region, said predetermined number, and said pitch define a water rod efficiency greater than about 0.7; and,
    at least one projection on an exterior portion of said sidewall; and
    wherein said sidewall has sufficient resiliency to permit inward flexing of said sidewall, at least in a portion substantially adjacent to said projection, to permit passage of said projection over an obstruction when said water rod is axially moved proximate to said obstruction.

    and here is the source http://www.google.com/patents/US5149495

    • aigeezer aigeezer

      Good find, Ace33. I wish it weren't in patent-law jargon but it is what it is.

      Among other things, it appears to anticipate the need for flexing and bending.

    • PhilipUpNorth PhilipUpNorth

      My take is: Fuel assemblies are designed such that in a reactor core, the fuel pellets are in close enough proximity to induce fission, but are spaced far enough apart to allow the fission to be moderated by the water between the tubes, thereby assuring the continuation of the chain reaction.

  • bwoodfield bwoodfield

    Here is the general idea behind water rods:

    In a boiling water reactor (BWR), the water that flows through the fuel rods (in the flow chamber) will quickly turn to steam. This reduces the ability to remove heat from the fuel rods. Therefor they have special chambers within the flow chamber were the water is under pressure and stays liquid, allowing for proper fuel moderation.

    • patb2009

      no way man, the reactor runs at one constant pressure, a BWR is running at say 50 -200 PSI just enough to raise the operating temp to say 600-800 F. A PWR is running at close to 2000 PSI
      to ramp up the operating temps.

      No Way, they maintain pressure differential. you'd be crushing thin wall pipes, the fuel rods must be either liquid filled and have that spring serve as a pressure damper or the fuel rods let a little pressure in or out to equalize with a diagphram.

      that water tube is just to keep water flowing up the center and help maintain nuetron flux and cooling.

  • bwoodfield bwoodfield


    <cite>Boiling Water Reactor (BWR) fuel assemblies include fuel rods and water rods within a flow channel. Water flowing through the many fuel bundles within respective channels provide both coolant and moderator to sustain the nuclear reaction. The moderator function is provided primarily by the higher density liquid. Energy addition along the fuel rods, however, converts some of the water to lower density steam so that its effectiveness as a moderator decreases as the fraction of liquid decreases along the length of the fuel rods. The resultant steam-water flows, referred to as two-phase flows, have higher velocities and cause significant pressure drop along the length of the fuel during typical operation. To reduce this variation in liquid moderator, modem BWR fuel designs include separate flow paths within the fuel bundles which remain filled with liquid (water) over the length of the fuel bundles. These water paths can be configured as one or more round or square tubes (or as cruciform shaped flow passages) generally referred to as water rods. For normal operating conditions, these water rods provide 15% to 20% of the available moderator liquid in BWR fuel bundles.</cite>

  • PhilipUpNorth PhilipUpNorth

    "Closer studies found that in one fuel rod assembly, the bending water rod pushed one nearby fuel rod into contact with another…"
    The question for ENEnews is: "What happens when two or more fuel rods come into contact with each other?"
    And in the case of Fukushima Unit4 SFP, the question becomes:
    "What happens when many FUEL PELLETS come into contact with each other?" Because as they attampt to empty SFP4 (and SFP3,2,&1), they will be spilling fuel pellets from burned, damaged, and compromised leaker spent fuel assemblies onto the floor of the SFP. What then?

    • weeman

      I wouldn't be surprised if this was the cause of the fuel pool explosions at Fukushima or at least a factor.

      • patb2009

        i'd be surprised if one rod touching another causes a criticality.

        We've had meltdowns at TMI where the top 18 inches of the core melted and slumped and we didn't see Transient criticality.

        Now if you have more touching and loss of coolant, then you have an issue.

        we definitely saw something in SFP 4 at Fukushima
        but much bigger event.

        I suspect in a lot of racs we've had fuel assembly failure, water rod torsion, fuel rod failure.

        the systems are sensitive but usually it takes a bit more like at Snap-7

  • Flapdoodle Flapdoodle

    I figure searching for bent rods is like looking for dirt. You just step outside and there it is.

  • Sol Man

    Flap, you're right. I did not locate what the weight range is for a particle of dust, and how much atomized fuel rods have gone missing, exactly. But, no matter, there it is, in every film of dust dispersed nearly everywhere around the world.

  • The point is simple, nuke is not safe on our HOME PLANET

    Not in the first 6 decades where nuke failed and poisoned us again and again, look at this list of 99 accidents.


    And look at the mismanagement of risk, which can only be attributed to lack of political ability to deal with nuke, and greed, a manifesto


  • Sickputer

    Those pictures and schematics of nuclear components just show how the technology is so complex and full of potential for failure.

    As Einstein supposedly once said: "Nuclear power is one hell of a way to boil water."

    He also said this: "Two things are infinite: the universe and human stupidity, and I'm not sure about the universe."

  • Fukslow