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Japan Earthquake: nuclear plants Fukushima part 2
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[QUOTE="Sotan, post: 6819723, member: 497173"] Some information from [URL='https://www.tepco.co.jp/decommission/information/committee/roadmap_progress/pdf/2022/d221027_08-j.pdf']this document[/URL] dated 27 Oct 2022. (Page numbers indicated below are as given in the top left corner by Adobe Reader for whole PDF file (total 57 pages). There are other page numbers too, for each section, and this can cause some confusion.) P4: They are planning to sample the water contained in the S/C chamber of Unit1 PCV. P5: One of the means to improve quake resistance of Unit 1 PCV is lowering the level of water in the PCV. They are therefore working on installing the necessary pipes, while making use of existing pipes too (like CUW – reactor water cleanup system?). Note 1* The needed pipes for removing such water in Unit 3 – making use of existing RHR, residual heat remover, pipes too – are already installed. As a first step they need to check the properties of the water in the S/C, and for this they plan an inspection/sampling operation, which has started these days and should end in Jan next year. There are some diagrams and a photo explaining the concerned are: first floor of Unit 1 reactor building with candidate spot for inserting new pipes (1-10mSv/h area); existing pipes; non-return valve on the CUW pipe. P11: Process planned for lowering the level of water in the PCV of Unit 1. The approximate goal, for now, is to bring water level around the “center” of the S/C pipes.P12~33 show the work being done in preparation for new inspections and, later on, sampling of debris from Unit 2 RPV. There is a lot of site preparation, robot testing and improving, and personnel training going on.P34~ : New data presented by IRID / JAEA regarding the characterization of the fuel debris situation inside the damaged RPVs. As they keep gathering information, they work on improving the degree of understanding regarding what exactly is in there. P36: refers to Unit 2. The new findings are at the bottom of the page. – As the fuel debris accumulated at the bottom of the RPV, a new rise in temperature greatly affected the course of the accident; the fuel debris containing a lot of metal melted first, at 1000-1300°C, then damaged the RPV wall in places, and then poured onto the pedestal floor. – The fuel debris that leaked/accumulated on the pedestal floor got cooler and did not succeed in “melting” the concrete; therefore, if right after the accident it was assumed that a MCCI (Molten core/Concrete Interaction?) happened, it is (now) assumed that the MCCI was almost absent. P37: refers to Unit 3. The new findings are at the bottom of the page. – As the fuel debris accumulated at the bottom of the RPV, a new rise in temperature greatly affected the course of the accident; the fuel debris containing a lot of metal melted first, at 1000-1300°C, but then, the fuel debris containing a lot of oxide compounds reached a high viscosity state (like a “hard liquid mixture”? sorry can’t find a good word), at 2000-2300°C, which damaged the RPV bottom on a rather large area and, over a few hours, fell on the pedestal floor. – The debris thus accumulated on the pedestal floor, due to its high viscosity, did not closely interact with the concrete; therefore, if right after the accident it was assumed that a MCCI (Molten core/Concrete Interaction?) happened, it is (now) assumed that the MCCI was almost absent. P38: new insights on the state of the fuel debris. They speak about results of analysis of some small grains/particle harvested in some previous investigation, results which are now added into a “debrisWiki” database. I think it is accessible here [URL]https://fdada-plus.info/wiki/index.php[/URL], English version here: [URL]https://fdada--plus-info.translate.goog/wiki/index.php?title=%E3%83%A1%E3%82%A4%E3%83%B3%E3%83%9A%E3%83%BC%E3%82%B8&_x_tr_sl=ja&_x_tr_tl=en&_x_tr_hl=ja&_x_tr_pto=wapp[/URL] P43~ : Report on the second part of the investigation into Unit 1 PCV. Interesting new images on P48-50, including a weird ball-shaped piece of debris found on the floor of the pedestal. Looks like a solidified bubble with holes in it. [/QUOTE]
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Japan Earthquake: nuclear plants Fukushima part 2
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