http://www.tepco.co.jp/decommision/planaction/roadmap/index-j.html
There’s an update on Tepco’s site regarding the medium-long term roadmap for decommissioning, dated October 1st.
One PDF files posted there has information on several investigations on the damaged reactors:
http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/d151001_08-j.pdf
Starting on page 1 (I’m using the page numbers as they are in the PDF file, not what the browser or Adobe Reader displays) there’s info on the investigation of “TIP room”, main steam valves room and “airlock room” of Reactor 1.
Page 2: General info
- because in the area of the entrance of TIP room and main steam valves room the radiation level is high, access will be made by opening a hole in the corridor of the turbine building (where the radiation level is low).
- the SHC room is yet to be investigated too, but radiation is high in this case even in the corridor of the turbine building. Therefore they will study the possibility of accessing the SHC room from the main steam valves room.
- there’s a drawing with the first floor of reactor 1 and the radiation values. The turbine building is at the right side (the gray band is the corridor). SHC and TIP rooms are adjacent to that corridor. Airlock room is on the other side of the PCV. Sorry but at the moment I don’t know the meaning of TIP and SFC.
Page 3: Purpose of the investigation (1)
- TIP room:
- reduction of the radiation level around X-6 penetration (study of the possibility of accessing the AC pipes). X-6 penetration offers a way inside the PCV, but radiation levels in the area must be decreased. For this reason the decontamination of the highly radioactive AC pipes (ducts?) is necessary.
This requires setting an installation for removing radioactive contamination on one side of the AC ducts, at first floor – which means right near the TIP room. The investigation should indicate if access is possible from the TIP room to the highly radioactive AC ducts (they measured more than 1000 mSv/h);
- stopping the water leak of the lower PCV: study of the possibility of sealing the leak in the “vacuum destruction line”, leak discovered right below the TIP room;
- repairs of some electrical connections/cables in the PCV penetrations (these require human operators, so again a reduction in radioactivity of the area is strictly required);
- studying the possibility of accessing the SHC room and the main steam valves room.
Page 4: Purpose of the investigation (2)
- Main steam valves room:
- study of the possibility of repairs in the PCV; study of the access to PCV penetrations. Welding and filling are the the two methods envisaged for “repairing” some of these penetrations; if human access will be deemed impossible, filling will be the only method left.
- Airlock room:
- examination of the area around the X-53 penetration, especially of the traces/leaks of highly radioactive water observed on the floor of the Airlock room, leading to the funnel on the floor; also study the possibility of doing some repairs in the area of the penetration if needed.
Page 5: Drawing of the areas targeted for investigation
Page 6: The devices to be used. A visible light camera on wheels, a 3D scanner, a gamma camera and a radiation level detector.
Page 7: Schedule.
Seems that the TIP room and main steam valve room investigation is actually on the way.
The decontamination of the various rooms should begin during 2016.
Repairs to the PCV – probably to start in 2018.
Pag. 8: Additional info
The aimed radiation level, after decontamination, is 3 mSv/h for the working areas and 5 mSv/h for access routes. The main sources of radiation are the inside surfaces of the AC and DHC pipes/ducts, but also walls, floors and machinery surfaces. Shielding of some surfaces – insufficiently decontaminated – might also be required in the end.
The gamma camera images in the right suggest 300-500 mSv/h for DHC pipes and 1000-1200 mSv/h for AC ducts.
Pag 9: Additional info on the decontamination plans for the AC ducts
Pag 10: Additional info on the decontamination plans for the DHC pipes
- It is known that the DHC pipes and the adjacent RCW pipes are all highly contaminated. The first step would be emptying the pipes through the existing valves; removing the contaminated water should decrease the radiation level. Washing/rinsing/drying the pipes could help too (the main contaminant, Cs, is soluble in water). The removal of water should be done through the existing structures: drainage pipes -> gathering funnel -> floor funnel -> reactor building torus room sump pit) if it is deemed usable. Complete removal of the DHC pipes will be considered in the end.(…the document continues with the progress of investigations on R2 and R3. Will have to post later about those, ran out of time for now.)