Aqueous release during Fukushima

Brian Sheron, Office Director of Nuclear Regulatory Commission’s Office of Nuclear Regulatory Research, NRC’s 2013 Regulatory Information Conference (emphasis added): Aqueous release occurred during Fukushima accident… Current models do not address aqueous release pathways… [NRC's Office of Nuclear Regulatory Research] is starting a program to assess: Containment failure modes that could lead to aqueous releases; Source term modeling for aqueous pathways; Transport of contaminated water and its radiological consequences…

http://www.nrc.gov/public-involve/conference-symposia/ric/past/2013/docs/abstracts/sheronb-rev1-hv-w15.pdf

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Research on Aqueous Pathways

Resulting from Severe Accidents

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Aqueous release occurred during Fukushima accident

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Current models do not address aqueous release

pathways

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RES is starting a program to assess:

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Containment failure modes that could lead to aqueous releases

–

Source term modeling for aqueous pathways

–

Transport of contaminated water and its radiological

consequences: surface water bodies, groundwater

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Expected outcome: whether potential aqueous releases

warrant further mitigating actio

Sheron, Part I (6:15 in): “Another area that we’re looking at — it’s not really part of the ‘Post-Fukushima Lessons Learned’ — it’s aqueous pathways. One of the things we saw — and it was because most likely perhaps containment failure and liner melt-through — that there was contaminated water that was released to the environment into the ground. And the question is, how does that water behave once it’s released? How does it find its way to other waterways? What kind of doses might be expected from that? We’re just starting right now to do some work in that area.”
Sheron, Part II (11:45 in): “There was actually aqueous releases at Fukushima… The question is: Where did it leak out? How did it leak out? We don’t know yet. Speculation is… the core melt probably went down into the drywell, spread, and perhaps burned through the liner, which will provide a release path… The question now is: if there are aqueous release paths during a severe accident, what are the consequences? What we’re planning on looking at, at least — we haven’t started — is to first look at containment failure modes: Did we miss anything? Are there containment failure modes — that could occur below grade, you might say [Below grade: The portion of a building that is below ground level] — where water could leak out? The source term modeling for the aqueous pathways. Then the transport of that contaminated water, and the radiological consequences. How does it get into surface water? Does it stay in ground water? And what are the radiological doses… downstream? The expectation is, we’ll get a better feel for what the safety concern is with that, and whether any further actions are needed.”