Emergency Cooling Effort Failing at Japanese Reactor, Deepening Crisis - NYT

[flamingdem]

http://www.nytimes.com/2011/03/15/world/asia/15nuclear.html?_r=2&hp

* The issue is especially number two which uses MOX that has 7% plutonium, apparently an error was made that shut off the vents in that reactor, yow

see below:
“They’re basically in a full-scale panic”

-snip
The plant’s operator, Tokyo Electric Power, said late Monday that repeated efforts to inject seawater into the reactor had failed, causing water levels inside the reactor’s containment vessel to fall and exposing its fuel rods. After what at first appeared to be a successful bid to refill the vessel, water levels again dwindled, this time to critical levels, exposing the rods almost completely, company executives said.

Workers were having difficulty injecting seawater into the reactor because its vents — necessary to release pressure in the containment vessel by allowing radioactive steam to escape — had stopped working properly, they said.

The more time that passes with fuel rods uncovered by water and the pressure inside the containment vessel unvented, the greater the risk that the containment vessel will crack or explode, creating a potentially catastrophic release of radioactive material into the atmosphere — an accident that would be by far the worst to confront the nuclear power industry since the explosion of the Chernobyl nuclear power plant 25 years ago.

In reactor No. 2, which is now the most damaged of the three at the Daiichi plant, at least parts of the fuel rods have been exposed for several hours, which also suggests that some of the fuel has begun to melt. If more of the fuel melts before water can be injected in the vessel, the fuel pellets could burn through the bottom of the containment vessel and radioactive material could pour out that way — often referred to as a full meltdown.

“They’re basically in a full-scale panic” among Japanese power industry managers, said a senior nuclear industry executive late Monday night. The executive is not involved in managing the response to the reactors’ difficulties but has many contacts in Japan. “They’re in total disarray, they don’t know what to do.”

[Poll_Blind]

1. So basically the core's container becomes an out-of-control pressure cooker?

Obviously, the thing is meant to contain an enormous amount of pressure. Which would make the moment of failure, if that should occur, spectacular and devastating.

PB

[flamingdem]

2. Especially in the #3 reactor where fuel contains plutonium

I'm trying to find out just what that means!

[Poll_Blind]

5. Because of the reactor's multi-container design there is hopeful speculation that...

...the absolute worst case scenario would involve a catastrophic explosion which would spread highly radioactive material as far as 500 meters. The nuclear reactors in Japan were designed with avoiding another Chernobyl in mind, even in a hopeless situation like this one appears to be.

For instance, under the nuclear assembly is what is called a "core catcher" which is designed, as an absolute last resort, to catch and spread out the molten core to prevent it from hitting the water table. That alone, assuming it hasn't been damaged by the earthquake, would be a huge help if such a worst-case scenario should happen.

OnEdit: That 500 meter figure was from the BBC with UK govt's top nuclear expert pondering "worst case scanrio", given the design of the plant, etc.

PB

[nadinbrzezinski]

14. This design is from the 1960s

it is a G-1 from GE.

Chernobyl happened in the 1980s

The design are different.

This is a LW reactor with rods that go up and down to control the reaction

Russian reactors were pile reactors, where you got your rods down, pile the crap, remove rods, good luck.

Here is a happy thought, and why the Russians have had a few more Naval Reactor accidents than the west... their naval reactors are also pile reactors.

[Marblehead]

8. plutonium

highly deadly if inhaled.

[pokerfan]

13. It makes it somewhat worse

From the Union of Concerned Scientists:

One particular concern with Unit 3 is the presence of mixed-oxide (MOX) fuel in the core. MOX is a mixture of plutonium and uranium oxides. In September 2010, 32 fuel assemblies containing MOX fuel were loaded into this reactor. This is about 6% of the core.

I have done considerable analysis on the safety risks associated with using MOX fuel in light-water reactors. The use of MOX generally increases the consequences of severe accidents in which large amounts of radioactive gas and aerosol are released compared to the same accident in a reactor using non-MOX fuel, because MOX fuel contains greater amounts of plutonium and other actinides, such as americium and curium, which have high radio-toxicities.

Because of this, the number of latent cancer fatalities resulting from an accident could increase by as much as a factor of five for a full core of MOX fuel compared to the same accident with no MOX. Fortunately, as noted above, the fraction of the fuel in this reactor that is MOX is small. Even so, I would estimate this could cause a roughly 10% increase in latent cancer fatalities if there were a severe accident with core melt and containment breach, which has not happened at this point and hopefully will not.

http://allthingsnuclear.org/tagged/Japan_nuclear

[Lone_Star_Dem]

3. I just read the exact same article in the Times of India

I wish they'd expound on what exactly is wrong with the vents and if they have any hopes of being able to get them working enough to again begin the cooling process.

[flamingdem]

7. It looks like operator error, it was shut accidentally + they cannot reopen it nt

[RUMMYisFROSTED]

4. k 4 more info

[wtmusic]

6. Update

"1918: Technicians have resumed injecting seawater into the stricken reactor 2 at Fukushima after a steam vent of the pressure container was opened, Kyodo news agency reports citing Tokyo Electric Power (Tepco)."

http://www.bbc.co.uk/news/world-middle-east-12307698

Beware of reports from those "not involved in managing the response to the reactors’ difficulties".

[Statistical]

10. Thanks for the update.

If they hadn't been able to open the vents they would have never been able to add water to the RPV.

[wtmusic]

11. What's the RPV? nt

[Lochloosa]

15. Reactor Pressure Vessel

[Statistical]

17. RPV - reactor pressure vessel.

Everything rests of the RPV.

If the RPV remains intact then eventually the reactor will cool. With no fission present all the heat is from nuclear decay and that will fall off exponentially, predictably, and based on the rate that shorter lived isotopes "burn off" (go inert).

This reactor produces about 500MWe (Megawatts of electricity). To do that a peak power it produces roughly 3x as much thermal energy (nuclear plants tend to be about 33% efficient) so say 1500MWt (Megawatts thermal). No most of that power is produced by fission not decay.

When the reactor scrammed thermal output droped to ~100MWt (or in the ballpark), a 1400MWt reduction. This is why SCRAM is the first and immediate step. It changes the heat problem by an order of magnitude. Without new fission that thermal output will never rise. About 1 hour after scram thermal output has declined to about 25MWt. After a day the output is down to "only" 6MWt. After a week output is down to only 3MWt. So as time goes on and on the heat output of the core falls. As long as they can keep the heat in reactor below the melting point of the RPV and the pressure below the bursting point eventually the reactor will go "cold".

[flamingdem]

12. The issue is now the #3 reactor which is shut off not the #2 reactor

the one of concern has the MOX fuel, I believe.

[flamingdem]

16. If you search you will see that the use of seawater is experimental, not a certain solution nt

[flamingdem]

9. Comments foreshadowing the incident when the MOX fuel was loaded

http://www.japantoday.com/category/technology/view/mox-fuel-loaded-into-tokyo-electrics-old-fukushima-reactor

MOX fuel loaded into Tokyo Electric's old Fukushima reactor

Sunday 22nd August, 05:36 AM JST

FUKUSHIMA —

Tokyo Electric Power Co loaded plutonium-uranium mixed oxide fuel Saturday into a reactor at its nuclear power plant in Fukushima Prefecture in preparation for the largest Japanese utility’s first plutonium-thermal power generation.

The No. 3 reactor at the Fukushima No. 1 plant would be the third in Japan to be used for the so-called pluthermal generation, but the only one among the three to have been subjected to antiaging treatment with 34 years since its launch. Pluthermal output has already begun at the No. 3 reactor of Kyushu Electric Power Co’s Genkai plant in Saga Prefecture and the No. 3 reactor of Shikoku Electric Power Co’s Ikata plant in Ehime Prefecture.
#

LIBERTAS at 04:32 PM JST - 22nd August

More than ANY plants in Iran, and given the recorded madness of both Donen and its predecessor Genden, incompetence at Japanese nookular plants makes this a way bigger danger to humanity. Definitely time to have a competent external authority supervise these idiots.
#

escape_artist at 02:39 PM JST - 23rd August

maybe they forgot to tell everyone how they've determined there will never be any more earthquakes. Idiots is indeed correct. Likely long-term pain for short term gain.