Example of operation steps where “prerequisites” (Table a-1 of the RFP) should be taken in consideration
(Please refer to this list these prerequisites written in the RFP)
Prerequisites of? |
Related operation steps |
|---|---|
Assume that the rubbles are removed and decontamination work proceeds in 2020 when fuel debris retrieval starts. |
Install barrier (Example(1), Example(2), Example(3)) |
Condition inside the PCV/RPV is under high radioactivity and high humidity. Water is dripping due to the continuous water injection.
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Steps based on "Atmospheric environment inside PCV (temp, dose rate, etc.)” in reference information |
Water level inside PCV is the same as current measured or estimated one as of 2014.
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Steps based on "Atmospheric environment inside PCV (temp, dose rate, etc.)” in reference information |
No radiation shielding effect by water is counted.
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Steps based on "Atmospheric environment inside PCV (temp, dose rate, etc.)” in reference information |
| Acceptable maximum load for floor of 1.2t/m2 shall be considered when installing and transferring heavy weight objects inside the building. < Evidence of prerequisite > Set by METI’s “Integrated Dose Reduction Planning” Project . |
Install barrier (Example(1), Example(2), Example(3)) Remove shield plug (Example(1), Example (2)) Create opening on the side of PCV (Example(3)) Install equipment and access (Example(1), Example(2), Example(3)) Dismantle and remove internal structures (Example(1), Example(2), Example(3)) Collect fuel debris and Collect fuel debris and transfer canisters (Example(1), Example(2), Example(3)) Clean-up equipment (Example(1), Example(2), Example(3)) |
Visibility inside PCV/RPV is very low due to no lighting provided.
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Retrieving fuel debris (Example(1), Example(2), Example(3)) |
Inside PCV/RPV are densely installed internal structures.
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Step based on "Schematic diagram for internal structures" |
| Assume that air dose rate is 100Gy/h inside PCV, and 1kGy/h inside RPV. < Evidence of prerequisite: > 100Gy/h was set for the radiation dose rate of atmospheric environment inside PCV based on the value , 72.9Sv/h (max) which was measured at Unit2 on March 27, 2014. For RPV, set 1kGy/h that 10 times the dose rate inside PCV in consideration of internal structures and fuel debris inside RPV. |
Prior preparation (Example(1), Example(2), Example(3)) Remove PCV/RPV upper head (Example(1), Example(2)) Create opening on the side of PCV (Example(3)) Install equipment and access (Example(1), Example(2), Example(3)) Dismantle and remove internal structures (Example(1), Example(2), Example(3)) Retrieving fuel debris (Example(1), Example(2), Example(3)) |
For effective air dose rate outside PCV, assume that, after the start of the fuel debris retrieval, effective dose rate on the operation floor is 1mSv/h, 3mSv/h in operation area other than operation floor; and 5mSv/h in a passageway inside the building.
< Evidence of prerequisite > Set prerequisite that rubbles are removed and decontamination work proceeds when Retrieving fuel debris starts. |
Prior preparation (Example(1), Example(2), Example(3)) Install barrier (Example(1), Example(2), Example(3)) Remove shield plug (Example(1), Example(2)) Remove PCV/RPV upper head (Example(1), Example(2)) Create opening on the side of PCV (Example(3)) Install equipment and access (Example(1), Example(2), Example(3)) Dismantle and remove internal structures (Example(1), Example(2), Example(3)) |
Use existing opening, hatch, and stairs inside the reactor building for accessing each floor and delivering the equipment to each floor. No new openings, in principle, shall be created on the outer wall of the building. （Seismic safety and prevention of radioactive substance leakage shall be considered if installation of new openings necessary.） |
Install barrier (Example(1), Example(2), Example(3)) |
Dimension of equipment to be brought in, in principle, shall meet with the passageway width of 1.2m and height of 3m. |
Install barrier (Example(1), Example(2), Example(3)) Remove shield plug (Example(1), Example(2)) Create opening on the side of PCV (Example(3)) Install equipment and access (Example(1), Example(2), Example(3)) Dismantle and remove internal structures (Example(1), Example(2), Example(3)) Collect fuel debris and Collect fuel debris and transfer canisters (Example(1), Example(2), Example(3)) Clean-up equipment (Example(1), Example(2), Example(3)) |
| Give consideration to the possibility of the accumulation of hydrogen gas inside PCV/RPV when cutting fuel debris or internal structures. |
Prior preparation (Example(1), Example(2), Example(3)) Retrieving fuel debris (Example(3)) |
| By the start of fuel debris retrieval, 100-ton class overhead crane is installed and available, and spent fuels in SFP and the equipment in DSP are all cleared off. < Evidence of prerequisite > Set rated weight correspond to existing overhead crane’s weight. |
Install barrier (Example(1), Example(2)) Remove shield plug (Example(1), Example(2)) Remove PCV/RPV upper head (Example(1), Example(2)) Install equipment and access (Example(1), Example(2)) Dismantle and remove internal structures (Example(1), Example(2)) Collect fuel debris and Transfer canisters (Example(1), Example(2), Example(3)) |
Total weight of equipment installed on the operation floor shall be minimized in consideration of seismic safety. |
Install barrier (Example(1), Example(2), Example(3)) Install equipment and access (Example(1), Example(2), Example(3)) |
No shielding function or air tight function is counted to the container covering operation floor.
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Install barrier (Example(1), Example(2), Example(3)) |
※SFP：Spent Fuel Pool
※DSP：Dryer Separator Pool