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Satellite image on 16 March 2011 of the four damaged reactor buildings at Fukushima.
New research shows that corrosion of reactor pipes currently being used to pump water into the reactors in an attempt to cool the melted fuel may compromise those pipes long before TEPCO plans to stop injecting water. This same corrosion may be doing considerable damage to metal parts in the spent fuel pools.
TEPCO injected seawater early in the disaster in a last ditch attempt to cool the reactors. This introduced large amounts of salt into the pipes and the spent fuel pool. TEPCO currently uses a portion of the existing reactor pipes and spray rings to pump in water. If those fail there is no replacing them, humans can not enter those portions of the reactor and robots capable of such work do not exist.
The spent fuel pools also are at risk. TEPCO pulled two unused fuel assemblies out of unit 4′s spent fuel pool. They had moderate corrosion, older used fuel assemblies and other sections of the pool may not be faring so well. The pools have considerable sediment.
TEPCO has made some efforts to clean and remove salt from the water being used to cool the reactors. Salt remained in these systems for an extended period of time and salt deposits may still remain in places with limited water flow. Other out of spec water chemistry continues to corrode pipes and other metals involved.
The worst case scenario gives as little as 3 years before pipe failure, even using the worst corrosion factor on a new pipe (Daiichi’s are 34-42 years old) only gave it up to 7 years before failure. More investigation is needed to establish more exact failure ranges and those are ongoing. What this does highlight is the drastic failure potential currently going on and as usual TEPCO is mostly ignoring the issue.
The SimplyInfo.org research team has issued a new set of papers on corrosion factors at Fukushima Daiichi.
The main paper “Spent Fuel Pools At Fukushima; Follow On Report – Corrosion“ looks at corrosion factors in the spent fuel pools at Fukushima Daiichi, it also looks into the ongoing corrosion of pipes still in use to cool the melted down reactors. This paper also looks at the factors such as the long term impact of sea water injection at the plant and the ongoing uncontrolled water chemistry. For a more basic overview of how corrosion happens within the systems at Fukushima Daiichi, the companion paper “Corrosion At Fukushima Daiichi Explained” is included.
The corrosion issues at Fukushima Daiichi are concerning and merit more immediate action to mitigate the potential consequences.
Both papers can be found at the links provided or a complete PDF of both papers can be downloaded here
SimplyInfo.org Corrosion At Fukushima Daiichi PDF
Photo by Digital Globe under Creative Commons license.
27 Comments
http://www.marinecorrosionforum.org/explain.htm
I am quite sure the firehoses they used to spray the sea water in caused Cavitation.
http://en.wikipedia.org/wiki/Concrete_degradation#Sea_water
The concrete walls of the reactor that keep the radiation inside are reinforced with metal rods and now that those walls are cracked the metal rods are now exposed to sea water.
What will go first the pipes or the walls is my question.
What is the state of pipes and concrete corrosion in similar plants about the same age?
This was not a new plant some corrosion has already happened. Also what did the nuke plants maintance records say about corrosion at the plant before the accident?
If the plant was lax on fixing corrosion problems before the accident then any estimates are wishful thinking.
It might be time to bury the nuke plant in concrete.
I recall people worrying about this at the time of sea water being used. Thanks for the heads up.
I’m sure the fires hoses did not cause cavitation.
Who is going into the fuel ponds to paint them to protect them from corrosion?
Which require them to be dried out before painting (I know of no paint which can be applied underwater, especially moving seawater).
This has been an ongoing crisis and cold shutdown is years away if not impossible and with the threat of another Great Earthquake even the encasing in concrete (Chernobyl) solution may not work. The Japanese people are officially on the hook for all the risk cost and personal suffering from this predictable disaster and GE and all the other profiteers from the Nuclear Industry keep pushing for more plants.
TEPCO made very few pre-accident records public. Those that were, were mostly as punishment by NISA when TEPCO was caught faking safety testing. We we do know is many pre-accident photos showed considerable rusting of metal surfaces both inside the reactor systems and inside the buildings in general. At US reactors of similar age and design such as Oyster Creek and Brunswick both have massive corrosion problems and have for a long time. So they can give some hints about how Fukushima may have fared over the years.
The spent fuel pools are concrete with a stainless steel liner, they are not painted. Normally proper water chemistry keeps them from corroding and there is a check system in place to try to catch the early signs of a leaking pool liner.
The US nuclear industry wants this to be forgotten about. I routinely catch them lying about well documented incidents and risk factors or missing obvious technical aspects because they really do not pay attention to what is going on at Daiichi, For them it is a PR game and someone else’s problem.
We looked at the potential to entomb the whole mess in concrete but due to the location and high quake incidence concrete likely wouldn’t work. TEPCO has also done nothing to attempt to find the location of the melted fuel. Investigative work like scoping containment gives some hints as does the combination of radiation readings around the reactor buildings. By this time at both TMI and Chernobyl they had been able to do something to locate where the fuel was and what condition. At Chernobyl they managed to do so with 1980′s technology. The DOE proposed the Muon scanning but it may not happen and it may not be able to “view” enough area to find the melted fuel if it is outside of containment.
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Sea Water corrodes stainless steel.
The highest water velocities, at the tips of propellers or in pumps can result in bubbles of entrained air imploding with sufficient energy to remove metal or break up composites. Called cavitation, this noisy and aggressive mechanical destruction must be corrected by design, or if it cannot be eliminated, countered by the selection of suitably resistant alloys.
Are high pressure firehoses enough to cause cavitation is the question.
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I agree it might not work and would not stop contamination of the water table at all. But what else can they do cover it in molten lead?
Firehoses were hooked to exterior building fire lines or used to spray water from a distance into the fuel pools. The attempts to spray water into the pools using watering booms could potentially cause some sort of movement or mechanical wear if the water velocity was hard enough and the hose was close enough to the pool. Knocking debris around the pool would be more likely than actually damaging metal structures in the pool through corrosion I would think
Cavitation ain’t the issue at Fukushima. The cavitation would occur at the pump impellers or under higher pressures (100 psi or greater).
Sea water does not corrode stainless steel. However at temperatures over 140 F, the chlorides will crack (but not corrode) the stainless steel.
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Cavitation can occur at any pump. The easy way to cause cavitation is to cut the feed to a pump. When the pump becomes REALLY noisy, the pump is cavitating. If the fire department was sucking air in the inlet of their pump, their pump would be damaged.
Wow, I’m impressed at the expertise expressed in these comments.
Bit of a whiplash from “sexy baby,” though~!
From the way back machine.
Corbett is a Canadian who has lived in Japan for a decade or so.
Thinking back to my fluid dynamic days in college. I’m kind of leaning towards the notion that sprayed water from fire hoses is not laminar, its a turbulent flow (except for several feet beyond the nozzle. That being said, would fire hose water jets have the hydrodynmic properties, such as surface tension, pressure,, velocity, temperature, viscosity, etc. to cause cavitation on sprayed surfaces? Don’t know just asking the question. My hunch is water sprayed from fire hoses over the likely distances makes the idea of cavitation, hard to swallow. Still, I suppose we can’t rule it out. I’m inclined to follow Nancy’s line of thought in #16 – things moving around from the water jets is a more likely problem.
http://en.wikipedia.org/wiki/Fire_hose
If you are right about 100 psi being needed then a firehose could do this. Thanks without your number I would not have had any idea to look for the psi of a firehose.
Cavitation is a trailing edge phenomenon in high relative fluid movement (i.e a fast moving impeller in stationary water or a stationary object in a high speed fluid flow). Higher static pressure actually makes cavitation less likely.
It is similar to the separation of the air behind a wing at supersonic speed. That recombination is what makes the sonic boom. A more scaled down example would be the crack of a whip as the tip exceeds the speed of sound. The math is at the other end of the scale when it’s in a liquid.
I don’t think this is very pertinent to the situation unless you are talking about the pumps or the pipes currently moving fluid at high speeds. I know nothing about Nuclear Power Plants, but normally cooling uses high volume, low speed circulation.
Water flying through the air will do mechanical damage to what it is hitting (mass*velocity), but cavitation would only be a threat to the firefighting water pump or plumbing.
An extra ordinary thank you for your thoroughness and persistence with this issue. Ever grateful.
Your perspective is always appreciated Things, you have continually set an example for me to at least attempt to think out of the box, and, I also hope you are satisfactorily situated for the winter.
Peace and Resolve.