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Japan Does Not Face Another Chernobyl

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Re: Japan Does Not Face Another Chernobyl

#21

Post by rdtsc »

adsr wrote: post #11
ars wrote: post #6

Earlier quoted context omitted.

1.) Reactors aren't magic. They have very well defined properties. It's pretty easy to calculate if a containment vessel will hold. This type of engineering happens every day in every building you go in and every car you ride. 2.) The containment structure is quite large, and the residual heat is relatively low. There is a lot of water there, presumably too much for the residual heat to boil. (The water normally flow…

Three reactors are affected, and two plants, Fukushima and Onagawa. I would say that an earth quake and tsunami is outside the well defined.

> I would say that an earth quake and tsunami is outside the well defined.

But at the same time they are not completely independent events. Quite the opposite. It is likely that an earthquake will be followed by a tsunami.

If they engineered it so that 2 events: quake and flood are independent, then they made a mistake. Possibly there is nothing they could do but I doubt that.

This is somewhat similar to the birds and airplane engines. It is assumed that once in a while a bird will hit an engine and possibly take it out. No big deal, there are 1,2 or 3 more engines. But the problem is that birds fly in flocks. So chances are that the plane will fly into a flock of birds and all engines will go out. Which is what happened a year or two ago. Now there is probably not much they could do but hopefully at least they didn't assume that invidual engine failure due to bird hits would be completely independent failure events.

Re: Japan Does Not Face Another Chernobyl

#22

Post by adsr »

rdtsc wrote: post #21
adsr wrote: post #11

Earlier quoted context omitted.

Three reactors are affected, and two plants, Fukushima and Onagawa. I would say that an earth quake and tsunami is outside the well defined.

> I would say that an earth quake and tsunami is outside the well defined. But at the same time they are not completely independent events. Quite the opposite. It is likely that an earthquake will be followed by a tsunami. If they engineered it so that 2 events: quake and flood are independent, then they made a mistake. Possibly there is nothing they could do but I doubt that. This is somewhat similar to the birds an…

Completely agree with this. On the other hand, all their safety mechanisms so far have failed. Electric, diesel based and the automatic steam based. Which is why they now manually try to pump in sea water (according to what I have understood from the news). I'm not against science, but still, it seems that the situation is surrounded by a fair amount of uncertainty. So, to my way of thinking the most wise is to treat it as an uncertainty, until we know more from official sources.

Re: Japan Does Not Face Another Chernobyl

#23

Post by fxj »

do the math: http://edition.cnn.com/2011/WORLD/asiapcf/03/14/japan.us.nav... says the USS Ronald Reagan has been 100 miles away when "airborne radioactivity" was detected, and http://www.dailymail.co.uk/news/article-1366055/Japan-earthq... says that U.S. Navy crew in relief effort get a month's radiation in just one hour. From wikipedia: The worldwide average background dose for a human being is about 2.4 millisievert (mSv) per year, which is 0.2 mSv per month. i.e. 100 miles away they measured 0.2 mSv/h which, if we assume a r-squared dependency, 2 Sv/h within one mile at the reactor. Let's be conservative and assume linear dependence, then we still have 0.02 Sv/h which is a rather significant dose per hour. A dose greater than 0.5 sievert (Sv) is considered to be a high dose of radiation. With absorbed doses of 1 to 2 Sv and above, mortality is expected to be about 20%, according to radiation medicine specialists. Above a dose of 7 Sv the survival rate is zero.

Re: Japan Does Not Face Another Chernobyl

#24

Post by bhousel »

fxj wrote: post #23

do the math: http://edition.cnn.com/2011/WORLD/asiapcf/03/14/japan.us.nav... says the USS Ronald Reagan has been 100 miles away when "airborne radioactivity" was detected, and http://www.dailymail.co.uk/news/article-1366055/Japan-earthq... says that U.S. Navy crew in relief effort get a month's radiation in just one hour. From wikipedia: The worldwide average background dose for a human being is about 2.4 millisiever…

The pilots picked up the radiation while flying around the plant as it was venting steam. They didn't pick up that radiation at the aircraft carrier 100 miles away, so your assumptions about crazy high levels of radiation at the facility don't add up at all.

Re: Japan Does Not Face Another Chernobyl

#25

Post by pwim »

fxj wrote: post #23

do the math: http://edition.cnn.com/2011/WORLD/asiapcf/03/14/japan.us.nav... says the USS Ronald Reagan has been 100 miles away when "airborne radioactivity" was detected, and http://www.dailymail.co.uk/news/article-1366055/Japan-earthq... says that U.S. Navy crew in relief effort get a month's radiation in just one hour. From wikipedia: The worldwide average background dose for a human being is about 2.4 millisiever…

Tests detected low levels of radioactivity on 17 U.S. Navy helicopter crew members when they returned to the USS Ronald Reagan

These were members of a rescue crew, who were most likely far closer to the incident than the ship itself.

Re: Japan Does Not Face Another Chernobyl

#26

Post by fxj »

pwim wrote: post #25
fxj wrote: post #23

do the math: http://edition.cnn.com/2011/WORLD/asiapcf/03/14/japan.us.nav... says the USS Ronald Reagan has been 100 miles away when "airborne radioactivity" was detected, and http://www.dailymail.co.uk/news/article-1366055/Japan-earthq... says that U.S. Navy crew in relief effort get a month's radiation in just one hour. From wikipedia: The worldwide average background dose for a human being is about 2.4 millisiever…

Tests detected low levels of radioactivity on 17 U.S. Navy helicopter crew members when they returned to the USS Ronald Reagan These were members of a rescue crew, who were most likely far closer to the incident than the ship itself.

http://www.dailymail.co.uk/news/article-1366055/Japan-earthq...:

"The helicopters sounded the alert around 60 miles from the coast and the ship’s sensors also sounded when it was 100 miles north east of the plant."

Re: Japan Does Not Face Another Chernobyl

#27

Post by dicemoose »

adsr wrote: post #11
ars wrote: post #6

Earlier quoted context omitted.

1.) Reactors aren't magic. They have very well defined properties. It's pretty easy to calculate if a containment vessel will hold. This type of engineering happens every day in every building you go in and every car you ride. 2.) The containment structure is quite large, and the residual heat is relatively low. There is a lot of water there, presumably too much for the residual heat to boil. (The water normally flow…

Three reactors are affected, and two plants, Fukushima and Onagawa. I would say that an earth quake and tsunami is outside the well defined.

Actually, two plants in Fukushima. Onagawa is in Miyagi and is not affected, though they did detect heightened radiation readings probably from Fukushima.

Re: Japan Does Not Face Another Chernobyl

#28

Post by _delirium »

ars wrote: post #6
btmorex wrote: post #5

This is a bad article. 1.) He argues that the three mile island accident means that the containment vessel will hold now. Even if they were the exact same reactor design, that doesn't logically follow, but they aren't the same design which gives even less credence to this argument. 2.) He says that once the reactor is flooded with water they won't have to do any more pressure releases. Again, I don't see how that fol…

1.) Reactors aren't magic. They have very well defined properties. It's pretty easy to calculate if a containment vessel will hold. This type of engineering happens every day in every building you go in and every car you ride. 2.) The containment structure is quite large, and the residual heat is relatively low. There is a lot of water there, presumably too much for the residual heat to boil. (The water normally flow…

On #1, it's specifically the TMI comparison in the article that isn't very convincing, because many of the postmortems (though there is some disagreement) conclude that it was somewhat luck that the corium didn't melt through the containment at TMI, due to the specific pattern of melting and cooling. So the fact that it held doesn't tell you what would happen in another incident with much confidence (even if the two designs were the same, which they aren't). There may be other reasons to conclude that breaching containment is unlikely, but the particular argument the article presents isn't a great one.

Re: Japan Does Not Face Another Chernobyl

#29

Post by mistermann »

adsr wrote: post #22
rdtsc wrote: post #21

Earlier quoted context omitted.

> I would say that an earth quake and tsunami is outside the well defined. But at the same time they are not completely independent events. Quite the opposite. It is likely that an earthquake will be followed by a tsunami. If they engineered it so that 2 events: quake and flood are independent, then they made a mistake. Possibly there is nothing they could do but I doubt that. This is somewhat similar to the birds an…

Completely agree with this. On the other hand, all their safety mechanisms so far have failed. Electric, diesel based and the automatic steam based. Which is why they now manually try to pump in sea water (according to what I have understood from the news). I'm not against science, but still, it seems that the situation is surrounded by a fair amount of uncertainty. So, to my way of thinking the most wise is to treat…

>On the other hand, all their safety mechanisms so far have failed. Electric, diesel based and the automatic steam based.

Wrong and wrong. Some backup cooling mechanisms have failed, not all safety mechanisms.

The electric backup worked as designed. The diesel backup did not, as I understand it, because it was affected by the tsunami (which is inexcusable in my opinion). And the backup diesel generators brought in from off-site, from what I've read, could not be attached due to incompatible connectors (which if true, is also inexcusable).

Re: Japan Does Not Face Another Chernobyl

#30

Post by _delirium »

tea3 wrote: post #16

If there is no risk of the second containment level being breached why do newer reactors have a third level containment (which is missing from these older reactors)? I'm just curious.

One reason is "the last level of containment held" doesn't give engineers the safety margin they want, or the public-reassuring PR they'd want. Much better to be able to say that the last level of containment is never even relied on, but is purely insurance.
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