Total Fukushima radiation releases compared to total core inventories

  • Fukushima
  • Thread starter clancy688
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  • #26
NUCENG
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Preemptive strike in case of Dmytry finding this thread, huh?
<];-))

No, not really, Dmytry and I have been trading PMs. If he could be preempted, it would surprise me. He has a common and understandable set of beliefs and opinions. If I was reluctant to engage him on our disagreements it would really mean I'm not able to defend my beliefs. It can be hard to face a real challenge from an intelligent adversary, but that also makes the exchange worthwhile. I doubt that either of us will surrender, but I'm pretty sure that we won't set fire to the internet.
 
  • #27
Astronuc
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A daunting task indeed! If your task is to eat an elephant it is best to start with a single bite.

Don't dispair. PhD candididates willl be writing dissertations and computer models will be chewing on this event for years. You can work at this with simplifying assumptions and reasonable guestimates. Your numbers will be as good as anyone's. But I think you see why it doesn't make sense to use more than 1 significant digit in your calculations.

And just to add insult to injury, none of this will satisfy those who believe there has been recriticality.
Yes. I expect much research in what happened as was the case with TMI-2 and Chernobyl.

The source term really depends on the number of fuel rods breached and when. I've been reading some papers on fission products, particularly I and Cs yield. I'll post some references later.

With repect to recriticality, it has been mentioned (by Gunderson, or at least attributed to him) that I-131 should not be found in the SFP of Unit 4, based on the fact that it shutdown on Nov 30. However, of one considers about 13 half-lives of I-131 (t1/2 ~ 8 d), then the I-131 activity only decreases by four order of magnitude (104), so it should still be possible to detect I-131. It's precurors are Te-131 and Sb-131, but their half-lives are quite short (25 and 23 min, respectively), so they rapidly decay to I-131 at shutdown. Otherwise, they are transmuted to Te-132, Sb-132 in a neutron flux.

Cs has very limited solubility in UO2, but it requires temperatures of several hundred C to migrate out of the fuel matrix and into the gap (void volume between fuel and cladding, or plenum). However, if the fuel is breached and water/steam oxidize the UO2, Cs and other volatiles are more mobile. Then again, Cs forms uranates and zirconates.

At this point, one would want to calculate a source term assuming 30%, 50%, 70%, 90% of fuel rods failed to see what the source terms would contribute to released activity. The spent fuel pool would likely be less given the decay times. The available I in SFPs of Units 1, 2, and 3 would be much less than that of Unit 4.
 
  • #28
NUCENG
Science Advisor
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Yes. I expect much research in what happened as was the case with TMI-2 and Chernobyl.

The source term really depends on the number of fuel rods breached and when. I've been reading some papers on fission products, particularly I and Cs yield. I'll post some references later.

With repect to recriticality, it has been mentioned (by Gunderson, or at least attributed to him) that I-131 should not be found in the SFP of Unit 4, based on the fact that it shutdown on Nov 30. However, of one considers about 13 half-lives of I-131 (t1/2 ~ 8 d), then the I-131 activity only decreases by four order of magnitude (104), so it should still be possible to detect I-131. It's precurors are Te-131 and Sb-131, but their half-lives are quite short (25 and 23 min, respectively), so they rapidly decay to I-131 at shutdown. Otherwise, they are transmuted to Te-132, Sb-132 in a neutron flux.

Cs has very limited solubility in UO2, but it requires temperatures of several hundred C to migrate out of the fuel matrix and into the gap (void volume between fuel and cladding, or plenum). However, if the fuel is breached and water/steam oxidize the UO2, Cs and other volatiles are more mobile. Then again, Cs forms uranates and zirconates.

At this point, one would want to calculate a source term assuming 30%, 50%, 70%, 90% of fuel rods failed to see what the source terms would contribute to released activity. The spent fuel pool would likely be less given the decay times. The available I in SFPs of Units 1, 2, and 3 would be much less than that of Unit 4.
I just saw posts of instrument readings of 5000 Sv/hr in the suppression chamber of unit 4. Nothing about that reactor is making any sense. It is like we have entered the Twilight Zone.
 
  • #29
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I just saw posts of instrument readings of 5000 Sv/hr in the suppression chamber of unit 4. Nothing about that reactor is making any sense. It is like we have entered the Twilight Zone.
"follow the money" . You don't really think you are being fed accurate figures/values ,do you?Just review it from day one :-0
 
  • #30
546
1
Something interesting:

81 million tera-becquerels of iodine-131 are believed to have existed at the plant.
The utility says the amount of iodine-131 released outside the plant is about one
percent of the total with a margin of error included.
http://www.webcitation.org/5xunDms1r

81 million TBq... that's more then ten times the 6 million TBq I have estimated with NUCENGs methods.
 
  • #31
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Hmm, do you think the SFP's were designed to cope with the impact of 175 tons of RSJ falling from a height of 10 m. :-(
 
  • #32
NUCENG
Science Advisor
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Something interesting:



http://www.webcitation.org/5xunDms1r

81 million TBq... that's more then ten times the 6 million TBq I have estimated with NUCENGs methods.
My numbers were based on conservative cycle lengths, exposure, enrichment and fuel design. The nubers they are quoting are even more conservative estimate of I-131 at shutdown, but they are using that big number to say less than 1% was released which then sounds like an artificially low number to make a point.
 
  • #33
3
0
"We could say all the I-131 was gone." Well, we could say that except that TEPCO reports increasing amounts of I-131. If intermittent criticality is still producing I-131, you may be calculating total inventory loss for some time to come.


Thanks for your answer.

Interest: Yes, mainly I131 and C137. Other isotopes are not of concern. I played a little with the Chernobyl radioactive materials and IAEOs I131 conversion table. In Chernobyl, I131 and C137 alone were responsible for over 80% of the converted I131 activity. Other isotopes won't change the "danger"-math.

Ignoring: Yeah, of course.

Core retaining: I skimmed through your documents but didn't find charts for core releases based on partial meltdowns and containment venting. I have to admit that I was hoping for your response when I created this thread. There's only a german source which calculated core releases based on different accident scenarios:
http://www.biu-hannover.de/atom/unsicher/teil2.htm#4
I think in our case it's something between "Heizrohrleck im Dampferzeuger" (don't know how to translate this - probably a leak in the condenser) and "Kleines Leck im Sicherheitsbehälter (Niederdruckpfad)" (Containment leakage)
Overall I'd think that 1-10% of the core inventory of I131 and C137 has escaped.

Airborne release: Well, that's the only thing we know for sure, since there are the NISA numbers they used for INES-7

Liquid release: That's a good question... I think all damaged or broken fuel rods have probably released most of their fission products into the basement. The constant waterflow should have washed it out.

Age for spent fuel: I think if we're only concentrating on C137 then age should be of no concern. We could say that all iodine is effectively gone, but that nearly all of the original C137 is still there. I don't think that the rods are older than five years.
 

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