Japan Quake: Fukushima Reactor Must Be Shut Down, Core Cooled

[FourScore]

Japan Quake: Fukushima Reactor Must Be Shut Down, Core Cooled
Posted March 11, 2011 by Nathan Temple

I’ve worked in the US nuclear industry for 30+ years and for 18 years I was a licensed senior reactor operator/control room supervisor on a boiling water reactor (BWR) similar to the Fukushima plant. I helped write the emergency procedure guidelines that are used at US BWRs. There is a great deal of information flying around that just does not make sense. There just seems to be no detailed technical information getting out to the public on this. At the risk of over simplifying the system, a BWR is like a giant pot of boiling water. Regular light water, not heavy water, goes through the reactor, is heated by the splitting of uranium atoms, turns to steam and spins a turbine-generator to make electricity. The steam is condensed back to water and pumped back into the reactor to continue the cycle.

There are 3 basic barriers to the release of radiation: the metal clad that encases the uranium fuel, the reactor pressure vessel, and the containment. If 2 of these 3 are compromised, and the third is in jeopardy, US plants will advise shelter or evacuation of nearby residents.

The reactor operates at a normal pressure of about 1000 psig. During an earthquake of this magnitude, the reactor would be expected to automatically shut down (called a reactor scram). Control rods are hydraulically driven into the core in less than 7 seconds. I do not know if this took place but if it did not, we’d probably hear about it because it would be such a big deal. Even with rods inserted, the reactor continues to produce heat equivalent to about 3% of its full power level. This is not the same as taking a pot off the stove and letting it cool. There are still some atoms splitting and fission products decaying that produce heat. This drops off slowly and is why there needs to be layers of redundant cooling with backup power. During such an earthquake, power from outside the plant would not be expected to be available.

The plants have several back up diesel generators (locomotive style engines) that supply power to motor driven cooling systems that will supply high flow of water up to about 300 psig.. There are also steam driven systems to supply cooling water up to 1100 psig. There are also pressure relief systems that active at about 1100 psig. If reactor pressure gets too high, relief valves open and discharge steam to a water filled pool inside the containment...

http://theenergycollective.com/nathantemple/53384/how-shutdown-and-core-cooling-japanese-reactors-likely-functions

[krawhitham]

1. Fukushima plant no. 2 now having issues too

TEPCO reports Fukushima No.2 plant sees 3 reactors lose cooling function


They have 4 reactors and plant no. 2 and 6 and planet no. 1

[PA Democrat]

2. Cenk is interviewing a CNBC reporter in Japan. She says there are TWO

reactors in which they are unable to control pressure.

[rhett o rick]

3. There is a lot of misleading info out there. Thanks for this. nm

[riverwalker]

4. What was the statement about this "coolant'

being flown in by the Air Force, from Hilary Clinton earlier today? Every story I've read there is no "special coolant" magic nuclear antifreeze being flown in by anyone. That is just bad reporting by the media.

[FourScore]

6. Exactly. n/t

[riverwalker]

5. update from Reuters: There was no "coolant"

http://www.reuters.com/article/2011/03/11/japan-quake-nuclear-coolant-idUSN1125270120110311

UPDATE 1-US did not deliver coolant to Japan nuclear reactor

[KittyWampus]

9. this actually makes me laugh (in a crazed sort of way) like its coolant for our radiator.

But it's not funny. Not if it's an emergency situation in Japan nor if it indicates to crappy reporting we have.

[AtheistCrusader]

10. It would probably be Boric Acid

or a cadmium solution to help scram the core.

But they probably have plenty on-site.


One correction to the OP above, the electrical generators for the pumps are inoperative. Two things I haven't been able to find out:

does the site have 3 or 4 of these backup generators and
what the hell happened to them?

Did they fall over? I saw people claim they were flooded out, but the site of the reactor isn't inundated, so what the hell...

[kristopher]

12. They just went through a 30 foot tsunami, what the hell do you THINK happened?

[AtheistCrusader]

13. Aerial footage of the reactor shows the site is pretty much ok, physically.

Unless the news crew was confused and it wasn't Fukushima.

Edit: Other articles indicated the diesel systems ran for at least an hour before breaking down. Long after the initial tsunami was gone.

[kristopher]

16. You think you can determine the damage to the reactors from a distant shot of video?

Right. Sure you can.

That must be why they just extended the evacuation zone.

[AtheistCrusader]

17. I ASKED WHAT HAPPENED TO THE DIESEL GENERATORS

SPECIFICALLY WHETHER THEY ACTUALLY WERE FLOODED OR DID THEY FALL OVER


DOES THE BIG FONT HELP YOU AT ALL?

[Hannah Bell]

7. both fukushima 1 & 2 were reported shut down this am. but cooling is still needed for 24 hours.

this is the problem as i understand it.

they were cooling on special power but not powerful enough.

[KittyWampus]

8. So, you worked in a job like Homer Simpson?

KIDDING!

[roamer65]

11. Tell me if this is true or not....

The control rods are cadmium, correct? Once fully dropped into a reactor running at full bore, the rods swell due to absorption of neutrons and they swell and cannot be retracted there after....Is that correct?

[kristopher]

14. These reactors do not have containment "domes"

They were built in the early 1970s (work began in 1966) and the photos and video makes clear there are no domes. They have containment buildings, but to assume that their containment structure and system are the same as where the OP author worked is unjustified.

This is a critical situation that IS NOT in control.

[AtheistCrusader]

18. There is a full containment inside the building.

It's a concrete shell, that contains the primary core, and the BW, and is shaped sort of like an upside down turnip.

[sce56]

15. The problem is that they will only tell you what they feel comfortable with be it the truth or a lie

I have worked around some nukes and have been into the control room and other rooms at SM1! Three Mile Island was nothing at first also but they did not tell the truth at first now did they! When they evacuate as they did it is really bad and all of the engineering in the world is only as good as the QC behind it. Look at Diablo Canyon they built the foundation backwards the blueprints were reversed and was not caught at first. Murphys law "Anything that can go wrong, will go wrong"n In Nukes Murphy was an Optimist!