Unit 2 Decommissioning

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Unit 2 Spent Fuel Removal: Second half of FY2017

Unit 2 Reactor Fuel Removal: First half of FY2020

Unit 2 July 2014 (METI)

Containment Structure
1. approx.34m
2. approx.11m
3. approx.20m
4. approx.9m
5. approx.2m
6. approx.17-34mm
Carbon steel liner

Reactor Vessel
1. approx.21m
2. approx.5.5m
3. approx.14cm
4, approx.18.4m
Carbon steel (with stainless steel lining)
Weight of UO2: 107t

Temperature at the bottom of RPV: latest data
Temperature in PCV: latest data
Temperature in reactor building As of 11/14, 2013: 21.1℃ (around south east corner on 1st floor) (reference) Outdoor air temperature 12.0℃
Temperature of accumulated water in torus room: 30.2-32.1℃ (As of 6.28,2012)
Humidity in PCV: 100％(dripping as of 7,2013)
Humidity in RPV: Unidentified
Flow rate of nitrogen injection:  latest here
Hydrogen concentration in PCV:  latest here
Pressure in PCV:  latest here
Dose rate in PCV: approx. approx. 72.9Sv/h (As of 3.27,2012)
Dose rate in RPV: Unidentified
Dose rate in the building: Most recent survey 2013
Dose rate in torus room: 4.3-137mSv/h (As of 4.12,2013)
Radioactive concentration: latest here
Water level of accumulated water in PCV: Approx. 0.3m from bottom part (As of 6.6,2014)
Water level of accumulated water in torus room: OP3160mm (As of 1.16,2014)
Water level of accumulated water in triangle corner: OP3050-3190mm (As of 6.28,2012)
Mass of fuel debris: Unidentified
Distribution of fuel debris (assumption): Existing the core part, lower plenum and PCV, but the ratio among those locations is unknown
Fuel debris MCCI products: Unidentified
Fuel debris dose rate: Unidentified
Fuel debris hardness: Unidentified
Fuel debris density: Unidentified (experiments to estimate fuel debris density here)
Weight ratio of fuel debris remaining in RPV: TEPCO 43% JAEA 30%
Percentage of fuel debris not in the RPV: TEPCO 57% JAEA 70%
Diagram of reactor vessel internal structures along with weights and dimensions located here: reactor_internals_id09_e.

Unit 2’s plan involves one of three strategies. These depend on the ability to decontaminate the refueling floor and return the overhead crane to service. If these two things can not be done the top of the building will be demolished. Then one of two building cover options would be installed based on the seismic soundness of the remaining building. Unit 2 didn’t suffer the types of structural damage units 3 and 4 did but would still need to be inspected before any cover building could be installed.

IRID cites the current nitrogen injection system as the starting point for plans to be developed to manage hydrogen gasses during decommissioning and fuel debris retrieval.