News of Explosion at Japanese Nuclear Plant

Yeah, the reactor building walls are crumbling (just now on BBC via AP news feed).

http://www.foxnews.com/world/2011/03/12/shaking-smoke-seen-japanese-nuclear-plant-facing-possible-meltdown/

Another Chernobyl in the making? Really sad news-

My sympathesis to Japanese people. May they the strength to overcome this calamity.

Not really. The two reactors are completely different.

There does appear to be, at least, a partial meltdown of the core, but the term melt down is not necessarily a useful way to describe the situation.

Estimates are that about about 1.5 meters of reactor fuel has been exposed. The coolant system is probably destroyed or further damaged.

The real question is if the floor of the reactor vessel compromised? As long as the floor is not breached they can still contain the mess. It is not going to be easy, but it is far easier than if the floor were to be breached, which would allow the fuel to melt through and contaminate the bedrock beneath the reactor - the so called China Syndrome.

Japan did their homework when they built these reactors. Each is built on bedrock to minimize earth quake damage and they are located on the eastern side where prevailing winds will blow to the sea.

Last I heard was that radiation levels outside the plant were at about 600 millirems/hr. That is pretty high considering most of us get that much in a year from natural and manmade sources.

However, that is nothing compared to Chernobyl, where workers and emergency crew were exposed to levels in excess of 1 million millirems or about 2 to 3 times that required to cause death.

Hopefully, we will see good news from Japan. However, this will deal a severe blow to the nuclear industry in general, so the idea of using more nuclear energy plants to help with our own energy needs looks grim.

Latest news suggests that the reactor vessel was not breached in the explosion. Radiation levels support that claim, so this is a good sign.

Nevertheless, the crises is still ongoing and there are still potential for things to turn for the worse. So it ain't over yet as the Fat Lady has not sung her song.

Last I heard (6 hours ago) was that the reactor is in a steel shell, with a (now compromised) concrete casing. Reported plan was to flood it with seawater for cooling, and to lace the water with boron tp soak up protons. Even if the reactor itself was 'OK', this would leave it stable but beyond recovery due to corrosion etc. Presumably they would give it a nice thick concrete jacket if persuing that plan, and leave it till gawd knows when.

The above is just regurgitated news, rather than expert knowledge.

It appears that the reactor situation is less of a problem than the general devestation caused by the tsunami.

The reactor vessel is contained within a containment building. The containment building consists of a seal welded steel inner skin with a thick concrete outer layer, in the order of four feet thick. The steel is to seal the inside and the concrete is massive so as to absorb radiation.

As I understand it, some of the outer concrete has broken off but the steel shell is still intact. I'm guessing that they have had to open some hatches to get water in there to cool the reactor, thus releasing a small amount of contamination. The fuel continues to radiate even when the reaction is shut down; this radiation produces heat that must be removed but the built in cooling system is not working because there is no electricity to run it. The back-up diesels were flooded by the tsunami.

This is what I have gleaned from various reports combined with experience designing structures for some of these nukes.

boron to soak up protons

But doesn't boron soak up neutrons instead of protons?

Yes, boron is used as a moderator to slow down fast neutrons.

As far as absorbing protons go, anything will do that. In fact skin will absorb protons before they get through a few layers of epithelia cells.

Actually boron is not a moderator, it is a poison.

Boron has a large cross section for absorption, so it acts to reduce the population of thermal neutron. This quality is what makes it a poison, and why boron can be used for things like control rods and neutron shields. Or in this case as an additive to reduce reactivity.

Moderators increase the population of thermal neutrons by being effective at slowing down fast neutrons, without absorbing too many in the process. For this reason, a good moderator necessarily lacks poisons, like boron.

The seawater being added for cooling is a good moderator, due in large part to the atoms of which it is comprised are mostly hydrogen...the low mass (similar to the neutron) allows largest transfer of energy per incident, and hydrogen does not absorb an excessive amount of the neutrons.

Adding a good moderator is a bad thing when trying to keep things cool, so the boron is added to offset the positive reactivity of the cold dense seawater.

Thanks. Makes sense to me.

Don't confuse me with the facts !

You wrote, ""

I would tend to agree. However, which of the two stories will be making the headlines first?

Most news organizations tend to hype stories so that they have more drama than they actually contain and pick stories that they know will best grab attention.

Now the Japanese government has acknowledged there has been a meltdown. I don't know what that will translate to as far as damage environmentally, but this whole thing has not played out yet.

Sources state that iodine and cesium have now been detected outside the nuclear plant, which are considered as indicators that the containment vessel has indeed been breached.

All of this means that there is a greater potential for a core meltdown through the reactor floor. I read this as a very serious situation that appears to be growing worse as more news is made available and the plant teams continue to work to discover the true extent of the damage.

Could be that the I and Cs were released in a controlled venting operation - does indicate fuel rod(s) ruptured, tho'.

We don't know, but the Japanese government is confirming a reactor meltdown has occurred at Fukushima Daiichi No. 1.

We will just have to wait to see if the containment vessel has ruptured and where.

That and how they can cool the reaction, which may not be possible now.

Got a link for the meltdown confirmation? Can't find it.

No, I get intelligence reports, but I was not able to confirm that on the public consumption news. The release was supposed to be from the Japanese daily Nikkei.

That doesn't mean that the intel is right. Could be a translation error, who knows? Maybe, maybe not. I do know that there have been conflicting statements among Chief Cabinet Secretary Yukio Edano, Nikkei, and NISA.

However, as I said before, the word meltdown is not what most people think of. Just because there is a meltdown does not mean the core is on a runaway death journey to the Earth's core.

The more critical question is the state of the reactor vessel, if that has been breached, and where. I am getting conflicting reports, but even the on-site team may not know that answer.

The worst case scenario is a breach through the floor. I understand that breaches elsewhere are easier to manage than one in the floor.

A second reactor in the same plant is also experiencing trouble, but I have not seen any intel on the nature of that problem.

Thanks.

Got a feeling this is going to end with a concrete tomb. No harm done, just loss of a few G¥, some generating capacity and some land.

Well said.

NISA status reports:

http://www.nisa.meti.go.jp/english/index.html

No mention of the explosion in the latest release:

Seismic Damage Information (the 13th Release) (As of 11:00 March 12, 2011)

- It's not clear whether that timestamp is UTC or local. Either way, it's been some time since the last news release (previous ones were at 1:30 intervals).

We probably won't know what's actually happening until after the fact. Governments have a knack for obfuscating bad news. Here they're saying that the Tokyo stock exchange will resume business as usual on Monday. WTF!

http://www.marketwatch.com/story/radiation-leaks-at-japan-quake-hit-nuclear-plant-2011-03-12?pagenumber=1

any radiation has leaked ?

The wall of water, triggered by Japan's massive earthquake, destroyed docks, boats and harbor equipment up and down the coast. Strong currents continue in Crescent City and Santa Monica Bay

Yes. Read my earlier posts. I don't know of any changes. It was about 600 millirems per hour outside the plant and much higher inside the control room.

"Loss of power..."

One thing a nuclear reactor has enough of is power. I have no expertise on this, but it seems wrong that a nuclear-powered electricity generating plant is destroying itself because of a lack of electricity.

Did the quake and/or tsunami break enough machinery that the plant can't convert any of that heat into its own power? Or was it not foreseen to make that possible?

More generally, can a self-powered failsafe be designed into a nuclear reactor to make it SCRAM itself if it gets above a critical temperature, like a switch on a gravity-driven deuterium reservoir above the reactor?

Lynn,

It may not be reasonable to expect the system to be functional enoughto generate electricity after a significant accident has occurred. In fact it would probably be irresponsible for the operators to attempt such a thing without adequately verifying that the benefit of attempting to do so would outweigh the risks.

I'm not saying it would be impossible, but such a determination would need to be assessed prior to over-riding any safety measures in place which shut off power generation while certain parameters are not nominal.

While it initially seems wrong for, as you put it, a nuclear-powered electricity generating plant is destroying itself because of a lack of electricity, at the moment it is no longer a nuclear-powered electricity generating plant. It's a damaged piece of equipment that is not producing electricity and may or may not be able to do so in it's current condition.

My guess is that it must have failed to be able to supply its own electricity.

The rational for that is that they attempted to use a backup generator that turned out to also be destroyed in the tsunami and that was why they named it backup generator.

My response was aimed at designing safer things, not criticizing people who know a lot more about something than I do.

Why not have an emergency reservoir of coolant behind a properly-designed plug that melts or opens at a certain temperature? (For all I know, that could be the mechanism they're using to flood the cores with sea water, but I don't think that's it.)

As I understand it:

• The (electrical) power which should have driven the pumps to supply cooling water failed, when this reactor (and the rest of the local power generation system) shut down following the earthquake.
• The diesel generators that were the primary back-up were damaged by the earthquake/tsunami, and failed.
• The secondary backup was supposed to have been provided by batteries, but these had insufficient capacity.

There are obviously lessons to be learnt here.

This blog gives some useful insight.

A.H. just borrowing your post to get this additional info into the discussion.

The reactors are shut down in a seismic event, so they stop generating electricity. The fuel continues to radiate particles and heat when the reactor is shut down, continued cooling water circulation is required to remove this heat. The power to move the coolant is then usually provided by the grid but failing that, by back up diesel generators, and failing that, by batteries. Unfortunately, the diesels are on low ground and were swamped by the tsunami. They switched to batteries, but they have a limited time of availability. so now they are trying to pump sea water into the drywell to cool the vessel.

The plants survived the earthquake, intact; it was the tsunami that did the damage.

So people, what's the bottom line? Worst case scenario...

I have read news articles and seen fallout maps covering the Pacific ocean and threatening the western half of the US with 750 RAD within 10 days...

Isn't there a way to better way to stop the reactor in these emergencies? Seems like an oxymoron... "Control rod"! How was control lost?

"How was control lost?"

Did you miss the part about the tsunami?

Just got word that there was a second explosion, this time at Fukushima Daiichi nuclear reactor No. 3 due to hydrogen buildup. Six employees missing.

Too early to tell what it really means, but they claim the #3 reactor vessel was not damaged.

Fukushima reactor #2 has just had a coolant failure and is now being pumped with seawater to keep that core cool.

This raises the prospect for that building to explode, too, just like units 1 and 3 did.

All in all, there are 6 Fukushima reactors that are listed as in a state of emergency. Three are part of the Dai-ichi complex and the other three are part of the Daini complex.

Still an ongoing situation that is very serious.

In the extremely long telephoto shot of the "first explosion" I noticed what appeared to be a visible shock/compression wave ascend rapidly upwards, much like that seen at the muzzle of a large caliber gun. There were no debris visible in the explosion, although this could be due to the distance.

Does anyone know what this shock wave might indicate?

Explosion at the third reactor (number 2) being reported.

965 μSv/hr reported (not sure where). Buildings #1 and #3 being evacuated. Situation not clear.

http://interactive.foxnews.com/livestream/live.html?chanId=5

Sorry, the link's just been disconnected in mid-statement.

The new reigniting/explosion of the #4 reactor fire is in the spent fuel cooling pool that holds the spent fuel rods OUTSIDE the reactor vessel containment. This is very bad, jkj, on nukeworker [http://www.nukeworker.com/forum/index.php/topic,26998.0/all.html] joked about it yesterday: "One thing I've always wondered about the design of the Mark I reactors---- with secondary containment exposed with the " blow-out" panels blown-off-----how's the spent fuel pool doing? Can they cool and maintain the pool? Do you have rad ducks and sea-gull mutants swimming around in the pool? Maybe they ran down to home-depot for a pool tarp and a garden hose."

There's been a lot of talk about the vessels integrity being compromised because of the torus designing of these GE Mark 1 BWR's but that would have been just cracks and small holes. This is fuel burning with no possible of containment. Everything that burns goes up and out, its not the greese on the crane burning: its FUEL i think. Not my field but no blow-outs in the GOM and i can't connect it to Stuxnet I'll just leave this for others to correct. For sure the brave RP's working on site to try and control this need our prayers and respect.