Japan Earthquake: nuclear plants

Astronuc

My understanding is that Mk I do not have hydrogen recombiners - and I don't know if any have been retrofitted. I believe Mk II and Mk III do.

warren_c

I just want to thank every one who has contributed to this thread especially the PF mentors and those who have worked in the industry. I have learned a lot from all of your knowledge and I appreciate that most of the discussion has been fact based.

Thank you all. I wish the best for Japan and hope they get the situation under control soon.

RealWing

I believe you are correct- The realtively small MK-I containment systems rely on nitrogen inerting to ensure there is a low risk of H2 explosions and the NRC accepted this in the 1980's. Powered H2 recombiners may still have been retrofitted, but withiout any power - they did nothing.

Astronuc

I think there is nitrogen in the drywell, but not on the reactor floor.

At Fukushima, it was not by design that the H₂ went into the volume above the reactor building floor. Apparently the venting system duct work (or somewhere else) ruptured/leaked. The H₂ and steam should have gone up the stack.

The point to be emphsized here is that the event is well BEYOND design basis - the combined effects of earthquake and tsunami (greater than design), the station blackout, and then the injection of seawater and boric acid.

You bet other plants are now looking at DBE and combined effects of natural phenomena, and their EOPs.

TVA is already looking at their units from a worst scenario.
http://www.bloomberg.com/news/2011-0...cial-says.html

Ivan Seeking

They were just hit by another quake, about a 6.5, with a [small] Tsunami warning that affects the plant. Hopefully this won't make things worse.

RealWing

Both the dry well and wet well are interted with N2 - but not the reactor floor.

Agree about DBE events and the already analyzed beyond DBE events- we need to rethink this whole issue - particularly for older reactors. The new "advanced" reactor designs have what appears to be several passive cooling systems that do not rely on any power.

Just like TMI and Chernobyl - unfortunately it takes an tragic event such as this one to make all us engineers and plant operators look hard at the lessons-learned and act on them.

TCups

You almost had to be there. It was the beginning of the analysis of the photos coming out of Fukushima, starting with this still photo of the north wall of Bldg 4 after a fire and explosion, and the interpretation that there was a tongue of "something" hanging out of the side of Bldg 4 somewhere around post #500-600. There was debate regarding whether this was insulation or corium. The annotations in black letters were my own observations, added to the photo, and at that point in time there was speculation on my part that the SFP was on the north side of the Bldg. It wasn't

see:

http://i306.photobucket.com/albums/n...27_5964756.jpg

The new video is interesting. Notice the drywell cap in the northeast corner of Bldg 4 in the new video?

Texan99

This "Brave New Climate" article claims that the replacement generators couldn't be made to connect to the existing system in time:

Astronuc

I the drywell cap is on the NE side, I would expect that the SFP is on the south side of the building.

AtomicWombat

Thanks Joe,

I've posted photos of "corium" before:
http://www.physicsforums.com/showpos...&postcount=580

Five different types of corium were discovered at Chernobyl, perhaps emphasising its tendency to separate into phases:
Chernobyl Corium

My impression was that at Chernobyl, with the exception of the initial firefighting, water was not heavily used to contain the situation, mainly due to fears of a steam explosion when the corium melted through to the basement.
Steam explosion risk

Astronuc

That's one problem I heard about with someone with connections to Japan.

I wonder it they couldn't splice cables - or does that imply the wrong voltage?

Next time - have compatible backup generators, and don't put EDGs and fuel supply oceanside - especially not when the coast is near a major subduction zone.

And apparently, since 1990, there has been one mag 7+ earthquake between Iwaki and Tokyo, near the coast.

TCups

In medicine, after a major traumatic injury, the first hour is called "the golden hour". It is the critical time when heroic efforts to stabilize the patient, maintain an airway, replace lost blood, etc. are most effective -- before body functions start to shut down. After the disasters, the quake and the flood, it sounds like Fukushima may have had a "golden hour" -- a very short interval where the right intervention might have dramatically changed the course of events. How sad it would be if it was technology as basic as "a different type of plug" that was the "nail", as the child's story goes -- "for want of a nail the horse was lost", etc.

It would be hard for me to imagine those first minutes and hours. Power failing. No phone service. The tsunami hit. The generators go and the operators look on in horror as things go horribly wrong.

As I posted earlier -- a helicopter pad and a universal emergency power connection interface might have made for a very different outcome.

I also remember the story of TMI having only one phone line in the control room and the operators desperately trying to call for assistance, but the line was busy much of the time by people calling in to see what was going on.

Hindsight is usually 20/20, and often, it is the simple stuff that leads to failures.

Rational Deb8

Hi folks,

I'm new here, first post. I'm hoping that RealWing or other experts here might be able to help with a few questions.

First, it seems that they've recovered CAMS readings on the drywell and suppression chamber. I'm interested in the significance, if any, but have no idea what normal operating CAM rad levels would be on BWR drywell, or what levels would be expected 15 days post scram (or even 15 days post normal coast down). I feel like an idiot, because I've lost the link (still have the pdf page up) to provide to you all - would have been probably either NISA, TEPCO, METI, or JAIF pdf status report... They're showing:

CAMS

Unit 1 D/W: 3.46 ×10e1Sv/h
S/C: 2.22×10e1Sv/h
(As of 9:00, March 27th)

Unit 2
D/W: 4.16×10e1Sv/h
S/C: 1.41×10e0Sv/h
( As of 9:00, March 27th )

Unit 3
D/W: 3.37×10e1Sv/h
S/C: 1.31×10e0Sv/h
(As of 10:10, March 27th)

I don't suppose anyone here knows of a good source for BWR typical instrumentation normal operating ranges, and charts or spot tables of what would be expected for the for a few days/weeks after scram (ideally), or even after normal shut down?

Thanks in advance!

83729780

days earlier (page 26 or so) there was discussion as to what the molten material here was (insulation? corium?):



in the new video you can see a similar formation oozing over a wall (3:45 to 3:47)



looks rather innocuous IMHO

Joe Neubarth

At Chernobyl they found (or so I read years ago) that the water only seemed to accelerate the burning process in the pile. Could be the water was dissociating and providing oxygen to the burning Uranium and Graphite.

RealWing

Good question!!!!

I've been watching the Suppression Chamber or S/C (Torus area) for some time since it gives you some indication of fuel damage. When the reactor vessel was vented to relieve pressure (and allow water injection), it vents into the S/C under water. If it was just steam, the radiation levels would be quite low. - but the levels are quite high instead.

eg Unit 1 is now 22.2 Sv/hr or 2220 rem/hr or ~36rem/min. In other words , in less than 1 minute, a worker would recieve their emergency dose for a year (assuming my calcs are correct)

AtomicWombat

The are at least a couple of reasons I can think of. If the pile is superheated there will always be a steam interface between it and any water layer - so heat transfer will be poor. At the interface the steam temperature will approach the pile temperature.

This steam will react with
1) Zircon - producing hydrogen gas in an exothermic reaction:
Zr + 2H2O -> ZrO2 + 2H2.
2) Graphite:
C + H2O -> CO + H2
See:
The Rate of Oxidation of Graphite by Steam
The 2nd reaction is likely to be restricted to Chernobyl.