Japanese Tsunami

[DarkFish]

Originally Posted by Type941

Here's another question - in worst case (being 4-6 reactors melting fully down) - and with fallout partially into water, what happens then? How is water affected by radiation? Will it all get mixed up to a point where EVERYTHING will be just that much more contaminated and say our globabal normal radiation level average will incrase by say 0.002% (made up number)

you'd better add some zeroes to that number. On a global scale it will matter about as much as my decision to reply to your post. Everything from outside of Japan should be perfectly safe to eat. For food produced in Japan, it'll depend on the exact location it comes from, and where the local water supply is coming from.

[DarkFish]

Originally Posted by Type941

everyone is a goddamn pxssy it seems in there.

Until you go there yourself with a firehose in your hands you've got no right to speak.

Besides, we live in the 21st century. There do exist some things like "remotely controlled" and "automatically".

[Nicolas]

I'm a ignorant of these things, someone explain me, seems the way is to get water in these reactors what the problem with that, there is not enough water pressure, not enough pumps? they can't transport pumps to the place?

[TLAM Strike]

Originally Posted by Nicolas

I'm a ignorant of these things, someone explain me, seems the way is to get water in these reactors what the problem with that, there is not enough water pressure, not enough pumps? they can't transport pumps to the place?

OK the way I understand it the pumps have a diesel backup power supply to keep them going if the reactor is shut down. When the Earthquake happened the reactors shut down automatically causing the diesels to kick in to keep the reactors cool but the tsunami damaged the backup generators (they have batteries as back up for that and those were put to use for a while). The tsunami also flooded the building(s) where the generators connect to the pumps. It was then decided to pump in sea water followed by boric acid to cool the reactor though the fire suppression piping (echos of K-19 here), this will ruin the reactor. Then an aftershock happened and they had to stop pumping in sea water, and then they ran out of sea water in their reservoirs.

[Nicolas]

I would like to read more details about that, being the main issue, that must be the engineers focus now.

[Freiwillige]

Seems to me like Japan is being very hush hush about the goings ons with their reactors.

[Growler]

Originally Posted by Freiwillige

Seems to me like Japan is being very hush hush about the goings ons with their reactors.

Looking at the levels of headless-chicken panic in the rest of the world, I can understand why. This is a culture where an elderly woman being pulled from the wreckage of her home apologized for inconveniencing her rescuers.

On the global stage, Japan better than all nations (with the possible exception of Ukraine), understands the nature and consequences of radiation, fallout, and nuclear/atomic catastrophe. In Europe and the US, the anti-nuke crowd tends to have a lot of followers who only care to understand that "nuclear is bad" and will seize any and all opportunities to "prove it" when things like this happen.

I wonder where are the "aviation is bad" people are when a plane crashes? Or "autos are bad" when there's a bad wreck on the Beltway? Exactly. They don't exists, and accidents with those pieces of technology are far more common than nuclear reactor incidents - three major ones in some 30-odd years (Three Mile Island, Chernobyl, and now Fukushima). And in the last case, it took a severe earthquake, severe aftershocks, and major tsunami (all in the realm of 1000 year events, according to the BBC) to effect the nuclear disaster on top of it.

The situation is bad entirely due to the initial cause - the natural disasters - and the resulting disruptions that followed due to those initial causes.

People are doing everything they can to contain and resolve this issue - why wouldn't they? It's THEIR homes directly effected - yet California is about out of potassium iodide tabs while people freak out.

The resulting effects of this won't bother much of the world too much - this planet is a BIG place, and we're talking about a relatively inconsequential amount of radiation in comparison. Will people die of it? I hope not, but who can tell? Have lives changed already because of this? I would argue that the life changing events are the ones than led up to this, but that doesn't diminish the consequences of this, either.

What Japan needs, and what the rest of the world needs most right now is for people to stop being afraid, stop pointing fingers, and help. This is a bad situation - panic and blame won't fix it.

[MaddogK]

Originally Posted by Nicolas

I'm a ignorant of these things, someone explain me, seems the way is to get water in these reactors what the problem with that, there is not enough water pressure, not enough pumps? they can't transport pumps to the place?

There are 2 sets of pumps involved, 1 set for the primary side which evacuates the heat directly from the reactor and moves the heated coolant to the heat exchanger, and the secondary pumps which evacuate heat from the heat exchanger thru the secondary cooling system. The 2 cooling systems are independent from each other but work together. Pumping water into the reactor does nothing much to cool the reactor as the water isn't being drawn thru the heat exchanger, and the reactor water is radioactive so it must remain contained within the reactor, and the reactor can only hold so much water. Also the steam generated within the reactor cannot be allowed to escape to the open atmosphere as it also is radioactive.

[Catfish]

As far as i read they do not have two separated water circuits, in all japanese reactors. They are said to be one-circuit heat exchange systems (?)
I have wondered how this is supposed to work, radiation-wise ?

[Oberon]

The US is going to throw a drone over the reactors and take a look with IR and see what's going on down there. That might shed some light on the situation a bit clearer than is being put forward by Tepco now...and/or lead to another round of the new game of global panic where you too can have a panic attack over an incident happening on the other side of the globe!

[MaddogK]

http://en.wikipedia.org/wiki/BWR

The condenser would be the heat exchanger.

[ASWnut101]

Originally Posted by Catfish

As far as i read they do not have two separated water circuits, in all japanese reactors. They are said to be one-circuit heat exchange systems (?)
I have wondered how this is supposed to work, radiation-wise ?

Like Maddog showed above, BWR's use one circuit to take the energy from the reactor and power the turbines. The high pressure steam leaves the reactor core, exits the pressure vessel, goes through the turbines, and then cooled back to a liquid in the condenser before being pumped through the reactor again. It's considered one of the primary safety disadvantages of a BWR, as the radioactive steam is allowed to escape primary containment.

[UnderseaLcpl]

Originally Posted by TLAM Strike

OK the way I understand it the pumps have a diesel backup power supply to keep them going if the reactor is shut down. When the Earthquake happened the reactors shut down automatically causing the diesels to kick in to keep the reactors cool but the tsunami damaged the backup generators (they have batteries as back up for that and those were put to use for a while). The tsunami also flooded the building(s) where the generators connect to the pumps. It was then decided to pump in sea water followed by boric acid to cool the reactor though the fire suppression piping (echos of K-19 here), this will ruin the reactor. Then an aftershock happened and they had to stop pumping in sea water, and then they ran out of sea water in their reservoirs.

Here's a question: Why weren't the control rods designed to simply drop into the core in the event of a power failure to stop the reaction?

I'm not an expert on this stuff, but I have what would probably be best described as a casual interest in nuclear power-generation technology. From what I understand, a full application of control rods should be enough to stop any reaction the plant is capable of generating. If that is correct, why weren't the control rods released the moment the power failed? Feel free to stop me right here if I've got something wrong.

In any case, I spoke to a friend of mine who works in the BNSF corporate office the other day and she said she wasn't surprised by what happened to the Japanese reactors because many of their systems were designed by General Electric. To clarify, BNSF Railways Inc. does a lot of business with GE. She told me that GE has a history, in recent years, of designing failsafes that aren't really failsafes because they like to cut corners at the expense of quality.

Her assumption was that the Japanese reactor failsafes were probably a lot like the failsafes they installed on the engines of our DASH-9 CE-44W locomotives to prevent plasma arcing in the event of a current reversal; which is to say that they rely upon the other systems in the cheapest, most basic system they could design to power the failsafes, which seem to have been "tacked-on" after the original design was completed.

In our case, we've suffered some damage to locomotive engines because the computer that is supposed to prevent the electronically-relayed command to the generators to reverse direction, and therefore current flow (locos use DC power), doesn't always function properly. Under some emergency circumstances, it will allow a sudden reversal of current, which fries the hell out of the motors.

I wonder if this situation with the Japanese nukes is indicative of faulty GE engineering to cut corners in the same way - utilizing existing systems to power failsafes. It seems to me that a simple pneumatic or hydraulic system that would activate in the absence of current would be sufficient to propel the control rods into the reaction chamber, much as airbrakes on trains will apply in the absence of air pressure.

Thoughts?

[Biggles]

Originally Posted by Growler

What Japan needs, and what the rest of the world needs most right now is for people to stop being afraid, stop pointing fingers, and help. This is a bad situation - panic and blame won't fix it.

I agree. I couldn't withheld an audible snort when I saw the frontpage of one of the Swedish newspapers, which took up the "news" that a handful of Swedish nationalities in Japan are afraid and want to get out of there, and are complaining that the Japanese gov. doesn't help that much. I'm sorry, but to quote Peter Griffin: "That just grinds my gears!"

[Platapus]

Originally Posted by UnderseaLcpl

Here's a question: Why weren't the control rods designed to simply drop into the core in the event of a power failure to stop the reaction?

In a BWR the control rods are raised from the bottom instead of dropping from the top.

a full application of control rods should be enough to stop any reaction the plant is capable of generating.

Under normal circumstances, yes, the application of the control rods will prevent further fission. However, it will have no affect on the heat being present or even continuing after the fission is stopped. The problem is that if the reactor has a large void (negitive) coefficient , the increased heat (when the cooling system fails), may overcome the absorption effects of the control rod.

http://en.wikipedia.org/wiki/Void_coefficient

In plain words, the hotter the reactor gets, the less effective the moderator will be. Given enough heat, the control rods may be of minimal use.