8.9 earthquake in Japan: tsunami warnings

Astronuc

Basically one would have to make fuel elements out of carbides or graphite (carbon), and probably not use water for cooling, but rather use an inert gas. There is a program looking at Si carbide fuel cladding. The pebble bed modular reactor (PBMR) is one such concept.

Decay heat has to be removed from a reactor core following shutdown, so there needs to be a reliable cooling system for shutdown and emergencies, in addition to a reliable power generation system.

The current system at Fukushima Daiichi unit 1 failed, and we have to understand what failed and why in order to prevent future occurrences.

DevilsAvocado

Does this have any effect on the overall security?

It was a joke.

rhody

Astro,

See the PS edit I just added from my previous post, site map of reactor plant 1 circa 1975, I believe.

Rhody...

Astronuc

From the overhead picture, I believe the orientation of the units is from south to north (left to right) is 4, 3, 2, 1 and 5, 6. The picture would be made while unit 6 was being built. Unit 1 is the smallest and oldest of the units. I believe units 1 and 2 share a turbine building, and units 3 and 4 also share a turbine building.

From the hill west of the plant.
http://d.yimg.com/a/p/ap/20110312/ca...6lhMSjmMdP3Q--

Leftmost would be unit 1.

Lacy33

It would be interesting to go if one had the qualifications. But like any professional, you know that resources in the area are limited and will only hold essential personnel.
One can only hope they build that plant on property high enough and out of the way of flooding.
I was wondering, considering the limited resources, what would happen if they used sea water to cool the core.
You answered that. Thank you.
My two remaining questions are, can the plant be near completly shaken down and containment structures release dangerous components? And what would happen if the plant were to be totally submerged? Or both?
G-d forbid.

Also did Ben Vereen get his start in show business on the Lawrence Welk Show? JK

DevilsAvocado

Fukushima before and after:



Still photos from NHK World News broadcasts

Astronuc

The Mark I containment is designed to use water available in containment, in the torus for emergency cooling. As water is boiled off, it has to be supplemented from the outside. That continues until the core is cooled off.

Ideally, the fission products and unused fuel remain contained in containment. However, the fission gases, Xe and Kr will leak out with the steam that is released to keep pressure down. Other fission products like I and Cs will dissolve in the water, and if that water leaks out of containment, then the fission products will escape in the water. The water could then be diluted in the sea. While unfortunate, it's not the end of the world.

They will try to get sufficient cooling water into containment to minimize damage to the core and pressure vessel. They might flood containment, but not submerge the plant.

Beyond that, it is difficult to give a reasonable or informed explanation because I/we don't know the specific details regarding that status of the core, fuel, containment, or the specifics of how they are cooling the reactor. I don't see any value in speculation.

DevilsAvocado

DevilsAvocado

2011 03 12 Breaking News, Fears of nuclear meltdown after plant blast in Japan, Fukushima.

Cham Dallas, Professor, University of Georgia
http://www.youtube.com/watch?v=YOnZHny4d64

Lacy33

I understand your not wanting to speculate. This is not a news station and you have that luxury.
I did not mean that anyone should submerge the plant, I meant what if it was hit with a wall of water hence submerged and can that plant be shaken down and and if so what mag earthquake would it take to shake down that or any new plant? Thank you.

Astronuc

As far as we know, the plant was not damaged, and the other units (2-6) at the site are intact.

The inner containment (dry well) of unit 1 seems to be mostly intact. The question is what is going on inside the pressure vessel which holds the core. The pressure vessel is enclosed in the dry well.

If there was a hydrogen explosion, then it had to come from hydrogen generated in the core, and that indicates damage (significant oxidation/corrosion) to the Zr alloys (fuel cladding and channels) of the fuel. That could be considered a partial meltdown similar to TMI-2 core damage accident. Then one has to determine how much of the core is damaged.

Also in the core are the control rods which are inserted to keep the reactor shutdown, or subcritical. The control rods are made of stainless steel and contain boron (in form of boron carbide) and possibly hafnium. Boron (B-10) and hafnium are neutron absorbers and the absorb neutrons instead of the fuel. The plant personnel can also add borated water to the core in order to ensure that the damaged core remains subcritical. If there is a partial core meltdown, then that could also displace water such that criticality is not necessarily acheiveable.

At the moment, we have to wait for accurate and reliable information regarding the status of the core and cooling program.

rhody

Devils,

Nothing personal here, but that CNN news account bugs me in so many ways I won't even begin to list them all, and nothing against you for posting it. I personally don't care for fear mongering without facts to substantiate.

Rhody...

Lacy33

Thank you Astro, This has been very interesting and thank you for explaining this to us. We will just continue to watch with you, but now we understand what is going on. ... More than we did.

DevilsAvocado

Did you watch the video??

Lacy33

DA, I want to share some of my yummy medicine with you.
Then we can both be more calm. Aww,

nismaratwork

I did DA... I saw a hydrogen explosion, and then some dirty steam and smoke. You have to understand, if the fuel had become exposed we'd be talking Grays and Sieverts (or REMs it seems), not milliREMS. This isn't a good thing, because by some account (not verified) the concrete casing around the #2 reactor was compromised, but it doesn't sound like the... oh hell, what's the word, not sleeve... the inner layer is still intact.

The government is handing out Iodine tabs, and has established a reasonable exclusion zone. This isn't good, but I'm not seeing anything to be hysterical about. Lacy's right... deep breaths man, remember, even if this WERE Chernobyl 2.0, what could you do? Keep your mind clear, your emotions tamped down, and focus on the events as they evolve.

Maybe cesium is leaking, maybe not... we're not going to know much of this right now, unless you're Astronuc or have friend with NEST. We can only hope that Astronuc is wrong, and we're not seing oxidization of the fuel cladding, although I wouldn't bet against him for anything. If this is a TMI-2... it's not going to change because of our fear... even if you're personally at risk.

This is the time to be calm, even detatched, and rely on the most reliable info... nothing else.

rhody

Yes, and around 2:45 where the professor says it reach levels approaching three mile island but not Chernobyl may be a fair statement (I am no expert, we need Astro for that), and he didn't address a complete meltdown issue, skirted the question. I guess what bugged me the most was after thinking about it for awhile was, why wasn't CNN putting experts on the air to explain what could be done to contain the heat. Like progress on getting power restored to the cooling systems would have been more appropriate IMHO. This story makes for great ratings, however, this is not the time to try and capitalize on the situation. I broke a promise to myself about stating political views on this forum, which I intend not to repeat.

Rhody...