(UPDATE 2) TEPCO restarted the cooling after 6PM on June 6, using the backup system (which was not broken by the way). The SFP water temperature had risen to 42 degrees Celsius.
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(UPDATE) It may take 3 days before TEPCO can fix the problem (wires not insulated well) in the backup motor. The rise in temperature of the SFP water is expected to be 0.3 degrees Celsius per hour, so in 3 days the temperature of the SFP water may rise by 21.6 degrees to 56.6 degrees Celsius (as the current temperature is 35 degrees Celsius, as tweeted by Councilwoman Kuniko Tanioka, who obtained the information by calling the NISA).
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Cause unknown so far. This is the motor for the secondary cooling system for the Reactor 4 spent fuel pool (see the diagram below, circled in red), installed outdoors:
From TEPCO's photo for the press, 6/5/2012 (Photos were taken on 6/4/2012):
As of 5AM on June 6, the temperature of the Reactor 4 Spent Fuel Pool is 38 degrees Celsius.
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27 comments:
Welp. Looks like insulation failure.
I thought it was the Primary coolant motor that 'burnt-out', not the Secondary.
There may be more to this than meets the eye, so to speak. How does a minor job of rewiring take three days? I can see it taking longer to replace the motor on the Primary and rewiring it. Are they not both on the same pallet? I can see that the secondary heat exchanger is outside.
I still wish that Hitachi tag could be clearly read.
Oh, perhaps it was said that they have up to three days to complete the repairs with a margin of safety.
The failure of the motor is very likely inaccurate. When a pump begins to fail it typically places an overload on the electrical circuit and trips the feed breaker to protect extensive damage. If the motor section of the motor-pump combination has a failure in he windings the feeder breaker will trip. The likely and visible problem appears to be faulty splicing of the electrical wire in the connection box leading to a short and the resultant insulation fire and melt through. The melt through is indicative of the high voltage (usually 480 volts) short to the case which acts to weld to the case until it melts.
Its hard to believe that there are not spare pumps and hardware to complete a very minor repair like this, I smell a rat.
"Tokyo Electric Power Company, or TEPCO, used a backup pump, but on Tuesday, it also broke."
http://www3.nhk.or.jp/daily/english/20120606_31.html
It's the secondary system. TEPCO stopped the backup because it was identical to the one that burned out, and found the same problem (cable insulation). They restarted the cooling.
I am curious whether Tepco will release their findings why this connection fumed off.
Personally, I don't believe that the original cause was an insulating problem.
Explanation:
This connection looks like a crimped connection.
Even crimped connections suffer of the thermal expansion/contraction problem, especially if cables of different diameter are being crimped together, as seems the case here. It is very difficult and requires much sensitiveness to crimp such correctly. I doubt this is easy if one is in protective gear.
If the connection is not well-done, it will be very prone to heat-cycling.
Heat-cycling happens continuously, for various reasons. (day/night change, electric load changes, etc)
But, every heat-cycling loosens the connection a bit more.
So, when the wires get looser and looser and the electric resistance at the connection increases, increasingly heating up the cables.
The shrinking tubing begins to smolder off, as seen at the cable connection in the upper-left of the picture.
It often doesn't directly burst into flames because of the (usually very poisonous) flame inhibitors, bromides etc.
But, if it bursts into fires (what didn't happen here), the resulting fire is usually incorrectly called a fire caused of "insulation failure".
Anyway, the heat-cycling extremely embrittles the wires over time.
Copper wires found in such degraded installations are often almost as brittle as gypsum.
At some time these wires break because of the thermal cycling only.
Look at the broken wire in the left. Note the pinkish color of its copper. This color is typical of overheated brittled copper.
The wire eventually broke, putting the pump out of operation after nobody noticed the fumes from the smoldering in the over-heated junction box for long time.
So, probable cause was just sloppy electrical connection.
Actually, I'd have expected some more thoroughness, but remember, it's just spent fuel. So, who cares? :)
Still, the intensity of the copper spray amazes me.
This was no simple broken wire.
The cable must have literally exploded.
And I cannot find any arc damage at the grounded casing.
It could have either been a short to the box cap or the other phase due to the smoldered-off (and thus ineffective) insulation.
It also could be possible that the insulation wore through because of vibration friction, but this should be uncommon if the cables were installed correctly.
However, things of this kind shouldn't be regular at nuclear installations.
I believe the fate of Japan shouldn't depend on such a simple motor.
Hook up an fn honda gas motor for christ sakes, are these guys that cheap?
So quick to criticize. Tsk. Tsk. Judging from the high quality standards of most ALL Japanese successfully applied technologies, why suspect irresponsiblity or negligence in the construction or design of components here? SHAME on you. The reason for this component of the pump's electrical service is intuitively obvious. What would be the easiest method of guaranteeing a failure exactly like this one? Hmm?
ANSWER: Insert a Stuxnet infected memory stick into a USB port accessing the Sieman's pump switching system to turn off the water or coolant flow through this pump, which would soon result in the pump's bearings overheating and failing. This failure would in turn cause the pump's impeller to make contact with the casing and make one loud-ass racket and considerable physical resistance to the spinning of the pump, thus causing a massive increase in resistance to the physical spinning of the motor causing an instantaneous overheating of the weakest link in the motor's power circuit, causing a fuse failure or failure in the motor's electrical feed opposite the fuse. And where would this other fusible link be located to maximize the safety of the motor? In the most easily accessible part of the motor's circuit, where this box is, as a matter of fact. Child's play diagnosis for one not given to sucking up to the freaks who blew this facility up. That mushroom cloud at MOX reactor #3 is most convincing. Also, Jay Rockefeller has a big mouth.
The photo shows that the failure is in the wiring connection junction box where the motor wires connect to the supply wiring from the breaker panel. the TAPED supply wire splice on the right must have vibrated against the inside of the metal junction box cover until it grounded and started the arcing melt down cycle and burnt a hole into the box cover.
stupid lack of quality installation failure.
9:02 PM, you are a stupid idiot. Stuxnet infected memory stick????????
Maybe it's Stuxnet like that conspiracy theory says?
Geez, of course, it is stuxnet. ;-((( Just disregard the obvious that the execs at TEPCO are criminal corner cutting liars, and that the nuke plant in question is an old piece of shit run way past its proper decommissioning date, and that it is located on the east coast of Japan which is the most seismically active, thus more tsunami prone, and that the east coast of Japan as a whole rests on a very active subduction zone called "the ring of fire". Yeah, ignore all this and it is stuxnet.
If Stuxnet is ever proven, Israel will be SOOOOO busted.
8:05 AM = Israeli paid shill apologist.
I would like to think that Siemen's Industrial implemented a fix for StuxNet long ago. Anyone have confirmation for Siemen's PLC's?
Micro$oft implemented a series of updates to put out flame recently.
The $64,000 question is:
Did TEPCO impliment such a fix if available?
I don't believe Fuku-I's computer system is advanced enough to accomodate Stuxnet.
They may have had an influx of Industrial free samples from Siemens, a competitor of Siemens &/or a distributor! :)
Now would be an astute time to start ordering as many "free samples" from vendors far and wide, if TEPCO is as financially strapped as their actions let on, to maintain spare equipment onsite. It may be a doable way to share some of the financial pain worldwide.
They have had their insurance revoked, i hear.
http://agreenroad.blogspot.ca/2012/03/tepco-loses-insurance-coverage-for-all.html
Is there any confirmation on that, anyone?
I don't believe Fuku-I's computer system is advanced enough to accomodate Stuxnet.
10:29 AM, you are indeed correct. Their computer system had only the basic necessary upgrades. Oh, and, apeman2502, you are a complete fool.
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Fine method of telling, and enjoyable article to acquire factual statements.
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Oh it seems burned out extremely, I just hope that the wires get fixed on time again; I like to appreciate you for the pictures captured.
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There may be more to this than meets the eye, so to speak.
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