Unit 1
Status of Progress Points
(*5) RPV (Reactor Pressure Vessel)
(*6) PCV (Primary Containment Vessel)
Investigation into TIP Room of the Unit 1 Reactor Building
- To improve the environment for future investigations inside the PCV, etc., an ivestigation was conducted from September 24 to October 2, 2015 at the TIP(*1) Room. (Due to high dose around the entrance in to the TIP Room, the investigation of dose rate and contamination distribution was conducted through a hole drilled from the walkway of the Turbine Building, where the dose was low).
- The investigative results identified high dose at X-31 to 33 penetrations(*2) (instrumentation penetration) and low dose at other parts.
- As it was confirmed that work inside the TIP room would be available, the next step will include identification of obstacles which will interfere the work inside the TIP Room and formulation of a plan for dose reduction. (*1) TIP (Traversing In-core Probe)
(*2) Penetration: Through-hole of the PCV
3D laser scan inside the Unit 1 R/B underground floor
- The upper part of the underground floor (torus room) of Unit 1 R/B was investigated with a laser scan using a remote-controlled robot, and collected 3D data.
- 3D data, which allows examination based on actual measurements, can be used to examine more detailed accessibility and allocation of equipment.
- Combining it with 3D data on the R/B 1st floor allows obstacles on both 1st and underground floors to be checked simultaneously. This allows efficient examination of positions to install repair equipment for PCVs and vacuum break lines.
Investigation in the leak point detected in the upper part of Unit 1 Suppression Chamber (S/C(*3))
(*3) S/C (Suppression Chamber): Suppression pool, used as the water source for the emergent core cooling system.
- Investigation in the leak point detected in the upper part of Unit 1 S/C from May 27, 2014 from one expansion joint cover among the lines installed there. As no leakage was identified from other parts, specific methods will be examined to halt the flow of water and repair the PCV.
Status of investigation inside the PCV
Prior to fuel debris removal, an investigation inside the PCV will be conducted to inspect the status there including the location of fuel debris.
[Investigative outline]
- In April 2015, an device, which entered the inside of the PCV through a narrow access opening (bore: ﾏ100 mm), collected information such as images and airborne dose inside the PCV 1st floor.
- Based on the knowledge obtained from the above investigation in April 2015, another investigation will be conducted in March 2017, in which a dosimeter and a camera mounted on a self-propelled investigation device will be suspended from the 1st floor grating to inspect the status on the basement floor outside the pedestal and around the workers access opening.
