The industry has a strong vested interest in minimizing reported damage from the quake itself, because the implications for many nukes in earthquake zones would be expensive. We know that many accounts and reports indicate serious damage at Daichii from the quake, before the tsunami - here's a partial list: http://www.fukuleaks.org/web/?page_id=10166 - and we know that persistent leaks and problems from the plant have not been officially explained. We also know that a complete description and investigation of what happened to the meltdown reactors is still years away - no one yet knows where the melted core material ended up, for example. So claims of no serious quake damage are at the very best premature, and the evidence is against them. The willingness of official spokesmen to make such claims without the necessary qualifications casts more light on their credibility than it does on the status of the Daichii plants. I'm assuming you are talking about the reactors at Onagawa. According to reports, it escaped flooding and damage to its cooling systems because its seawall was more than twice as high as Daichi's or Daini's. Since its cooling systems remained fully functional, it could shut down without great trouble - but it has not been restarted, and the full extent of the quake damage is not known. I am unable to find the acceleration data for Onagawa's reactors, btw - the assumption that being closer to the epicenter means a stronger quake is likely but not certain. Notice that different reactors at Daichi took much different amounts of shake acceleration, despite being right next to each other and all the same distance from the epicenter. That would be the claim, yes. And it will be made in the wake of the mess we will face if the Prairie Island nuke up near the top of the Mississippi River is taken out by one of the nearby midcontinent faults, or the Diablo Canyon plant gets rocked and swamped in its turn, or whatever.
Uh oh, a conspirasist? All these data were available to the MANY independent groups that reviewed the situation. No one said there was NO damage, just not sufficient to cause the melt-downs. That required the lost of station power and the subsequent loss of back-up power.
I don't know if it helps or not, but according to TEPCO it experienced 250 Gal horizontal acceleration in response to a magnitude 7.2 earthquake in 2005, and it took them 21 months to restart on that occasion. Aside from that, there is, it seems, a CDROM out there that has the acceleration data on it - I came across an explanatory PDF but not the data. Here's a paper that is an attempt "to simulate the observed ground motions at the Onagawa Nuclear Power Plant at a depth of 128 m very near the source fault, using a heterogeneous source model." It is, however, behind a paywall: ShortâPeriod Source Model of the 2011 M[sub]w[/sub] 9.0 Off the Pacific Coast of Tohoku Earthquake .
Tell this guy that: The degree of damage from the quake itself remains to be discovered. Right now they are dealing with the latest in along series of unanticipated leaks, they don't know where the cores went in a couple of the reactors, and their credibility is shot to hell after all the lying and coverup they engaged in during the battle to avoid catastrophe. So we wait for hard evidence. Yeah, we have to assume the data was recorded - I'm just wondering why it isn't public knowledge. Until it is, any bragging about earthquake resistance has to taken as provisional out here in cash short ignorance land. The differences in actually sustained acceleration were surprisingly (to me) large just between different plants at Daichi - it appears to be a sensitive number, much dependent on the specifics of everything.
My recollection/understanding is that ground acceleration is influenced by some of the same factors as the mercalli sale. To be more specific, there's a hill near the plant. The plant looks to be in a valley. The shorel,ine looks to be reclaimed, or partially so. I would hypothesize that the reactors that had the greatest accelerations were those that had a greater depth to bedrock, and so stood on a greater depth of loosely or less consolidated soils - they were probably the ones farthest from the hill. Also the earthquake waves arereflectec and refracted by bedrock and surface top?ography. This can l,ead to constructive interference (amplified shaking) in some areas and destructive interference (reduced shaking) in other areas.
I am sorry, but you use a nomenclature of which I am unaware. "Gal"? I presume it is some form of G value. None the less, without knowing how the data was measured and processed, I never get excited by G values. I can slap my hand on a table and get 250 Gs. I know, I did this in a more extreme case for a living (ship shock protection). Tell me what the sensitivity of the building and equipment is (frequency content) and show me data appropriately filtered for that sensitivity, then I'll see whether "250 Gal" is important.
1 gal = 1cm/s/s of acceleration. Gravity anomaly maps are typically calibrated in miligal. According to TEPCO the ground acceleration is measured near the base of the reactor. Automatic reactor shutdown occurs when horizontal acceleration exceeds 200 Gal or vertical acceleration exceeds 100 Gal. A class 5 "Check stage" is initiated at values greater than 250 Gal. According to Fukushima Daiichi nuclear Disaster on Wiki Reactor 1 was designed to withstand 174 Gal of acceleration, Reactors 2 and 3 were designed wo withstand 420 - 460 Gal of acceleration. They had both previously been exposed to 125 Gal of acceleration with no concerns. This data seems to suggest that Onagawa 2 was designed for 580 Gal PGA. It goes on to say that Daiichi and Daini were upgraded for horizontal accelerations of 441-489 Gal and 415-434 Gal respectively. It goes on to say that 550 Gal was recorded at Daiichi in the foundation of Unit 2 and 254 Gal was recorded at Daini. " Units 2, 3 and 5 exceeded their maximum response acceleration design basis in E-W direction by about 20%." Accelerations of 2000 Gal were recorded. Addendum: And this just in (I literaly only just found this and can't be bothered retyping this post). according to this Document which appears to be Chapter 3 of a report prepared for or by the Japanese Government, the maximum horizontal acceleration observed at Onagawa was 607 Gal in the north-south direction at Unit 2. Maybe you and Ice will have more luck deciphering that than I am. I've been on the go all day learning new GIS software while proofreading the tutorial that goes with it. It's also coming up on 1am here.
Something does not compute here. We are talking about 1/4 of a G? Hell, CAST iron pipe should take 1/4 of a G!
The Document appears to recount a comparison of the accelerations actually experienced by the Onagawa complex with an a priori modeling of the range of accelerations anticipated from expected quake sources. That isn't quite what we need. The 4/11 quake, from an unexpected source, delivered a couple of accelerations greater than the ranges modeled, but the ranges actually prepared for would be our concern. Also, using acceleration alone seems to overlook some major issues - such as the total range of motion inflicted, and the dimensional combination effects (twisting etc), and the force involved. But I'm not sure what I'm reading there, actually.
I guess this is a part where I say that a journalist should not dwell into engineering world... Cost is the primary force behind all engineering projects.
Consider how much inertia a building has... Consider how flexible a building is... The problems arise, in part, because you apply 600 Gal at the base of the building and 0 Gal at the top.
It still seems absurdly low. I mean, if they can design floors with 1000 Gal on dead weight plus a set PSF for live weight with a safety factor of what, two? What is the issue with 0.6 G? I am used to designing things to 250 G not 250 Gal. As I said, something does not compute.
I don't know what to tell ya really. Buildings are designed to carry weight, not to sway, bounce and twist - that may be part of what you're struggling with, live load versus dead load. There's also the fact that buildings in an earthquake behave somewhat like simple harmonic oscillators - they vibrate in multiple modes at the same time. Aside from that, the only other points of reference I can give you are that the california building code specifies 0.4G acceleration (390 Gal) and that 1 Gal is noticeable by people, 20 Gal is enough to cause them to loose their balance, a well designed building will take 490 Gal for a short time. In Japan, Shindo 7 (the most sever class) starts at 400 Gal. In India Zone 5 is 353 Gal. Please Register or Log in to view the hidden image! Please Register or Log in to view the hidden image!
Dude, I've designed ships for underwater explosion shock loads using both transient and modal techniques. I am a world expert on the Dynamic Design Analysis Method. I KNOW dynamics and analysis. I'm just "shocked" that anyone could have a problem with .4G!
There's also duration to consider. Underwater explosions, you're dealing with transient loads, you've got to accomodate the initial impulse and the reaction forces. Earthquakes are hundreds of seconds of sustained shaking.
I smile because I made my career pointing out that the UNDEX loading was more than just the shock wave but the other phenomena too. It is the long duration (multi hundred MILLIsecond in my case) bubble effects that rule for many situations. It has always struck me that the PROPER analogy with earthquakes is the tsunami. Earthquake = shock wave effects, tsunami = bubble effects. Just a thought.
Well, I am still recommending a jello spray down, and freze. The simplist way to shut down all the problems from the begining was to freeze the whole plant with nitrogen. As for right now and anytime before now the simplist and cheapest way to shut down any fluid spread, or atmosphereic distribution is to freeze the the groundor facility, creating a iceberg that clean water has to flow around, at the same time traping contaminated water within the iceberg. Japan has enough nitrogen to freze the nuclear plant and every drop of water at the nuclear plant, nitrogen is one of their most abundant resources, mainly because the atmosphere is 78% nitrogen and can be accessed right away. seperating nitrogen from the air is not hard for a country like japan. it is very low cost to pump nitorgen, as well if nessacary any cooling rods that extend in to the dirt/soil can be fitted with automatic tanks that exstract nitrogen fron the air at the direct location of the cooling rods. makining freezing the ground at any location easy. It does not take long to drill wholes into the soil, 500, or 1,000 it shoud be easy. I know because i have done some pile driving work before in the past and we reach depth pretty fast, the machinery is also light. As far as tubing for the rods, Japan has plenty of aluminum for producing piping. Using Nitrogen to control the enviroment at the nuclear station was a good idea when this disaster started and it is a good idea right now in handleing the water flow issues. DwayneD.L.Rabon
Yeah, I get that - I only said they were transient, I didn't say they were instantaneous. You're still dealing with hundreds of milliseconds versus hundreds of seconds and that makes a difference. I also know that some of the improvements they made at Onagawa were things like bolting pipes to walls rather than leaving them hang freely.
Not much if the modes of interest in an NPP are in the 0.1 Hz range and the modes of interest in the ship are in the 100Hz range. The structural response of an upper deck looks quite like an scaled earthquake plot, at least the plots I have seen.
