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Engineering
Nuclear Engineering
Japan Earthquake: nuclear plants Fukushima part 2
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[QUOTE="Sotan, post: 6820887, member: 497173"] The Nuclear Regulatory Authority (NRA) of Japan also has periodic meetings in which experts from various institutions and organizations discuss recent reports coming from Fukushima Daiichi, as well as additional studies and results. Unfortunately they are mostly in Japanese, but exploring the English version can also provide some data. - The list of NRA meetings dedicated on the analysis of the Fukushima Daiichi accident is on [URL='https://www.nra.go.jp/disclosure/committee/yuushikisya/jiko_bunseki01/']this page[/URL]. Most recent was on Oct 31. The blue rectangle named 会議資料 leads to the written materials used in that particular meeting. Lower on the page there is a link named 会議映像 which leads to the recording of the meeting on youtube. The recording for the meeting of Oct 31 is [URL='https://www.youtube.com/watch?v=A9H9EL9PH34']here[/URL], it is over 4h long, and one of the subjects discussed (among many) is the matter of the missing concrete and exposed rebar. At around 38:19 an associate professor from Osaka University (mr. Oishi) presents a study carried out by his team, discussing this subject. They make some theoretical analysis of the factors that might have led to that state of the bottom of the RPV and in the second part they present some experimental results on concrete and rebar behavior at high temperatures. I am picking to report this not because there is something extraordinarily new or significant to report but because in their analysis they mention a second factor, besides MCCI, that might have contributed significantly to the disappearance of the concrete. At 42:04 they list the possible factors and two of them (marked with A in the rightmost column) are considered significant, one (B) is so-so, and 4 others (marked with C are considered less likely to have contributed. A-factors are MCCI and "dissolution in water": some components of concrete can get dissolved in water, especially SiO[SUB]2[/SUB]. The reaction obviously needs the presence of water and can happen even at temperature as low as 200[SUP]o[/SUP]C. (The B-factor is mechanical erosion.) The chief of NRA at 1:22:19 considers this as significant. The hot molten fuel falling in the water at the bottom of the PCV inevitably raises the water temperature and the creates conditions for the dissolving of the concrete, while leaving the steel bars relatively unaffected - even without actual MCCI taking place. Or at least this possibility too should be taken into consideration and further investigated through actual experiments in the lab. Of course this is just a very little snippet taken from a 4h meeting. So much to see and read... [/QUOTE]
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Japan Earthquake: nuclear plants Fukushima part 2
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