Total Fukushima radiation releases compared to total core inventories

  • Context: Fukushima 
  • Thread starter Thread starter clancy688
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Discussion Overview

The discussion focuses on the technical and numerical aspects of radiation releases from the Fukushima Daiichi nuclear disaster, specifically comparing the amounts of iodine and cesium released to their core and spent fuel pool inventories prior to the accident. Participants explore various factors influencing these releases, including the operational status of the reactors and the characteristics of the fuel.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about the pre-accident inventories of iodine and cesium in the core and spent fuel pools to compare with the released amounts.
  • Another participant suggests focusing on Cs-137 and I-131 as the primary isotopes of interest, given their relevance to Fukushima measurements.
  • Questions are raised about whether to ignore the spent fuel pools and reactors 5 and 6 due to the damage being limited to units 1, 2, 3, and 4.
  • Participants discuss the potential retention of core material in the reactor vessel and the expected airborne and liquid releases from containment.
  • One participant estimates that 1-10% of the core inventory of I-131 and Cs-137 may have escaped during the incident.
  • Another participant provides a ranking of source strength for the units, suggesting that unit 4 would have a higher Cs/I ratio due to its shutdown prior to the accident.
  • Discussions include calculations related to uranium mass in the cores and the percentage of fissionable material, as well as the implications for estimating isotope release.
  • Participants reference various sources and documents to support their claims and calculations regarding the radiation releases and core inventories.

Areas of Agreement / Disagreement

Participants express differing views on the significance of various units and isotopes, as well as the assumptions needed for calculations. There is no consensus on the exact amounts released or the methodologies for estimating them, indicating that multiple competing views remain.

Contextual Notes

Participants note limitations in available data and the need for assumptions regarding the age of spent fuel and the operational history of the reactors, which may affect the accuracy of their estimates.

  • #31
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. :-(
 
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  • #32
clancy688 said:
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
"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.


clancy688 said:
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 I am Dampferzeuger" (don't know how to translate this - probably a leak in the condenser) and "Kleines Leck I am 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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