Fukushima Daiichi Unit 2 Spent Fuel Pool Inspected

An inspection of unit 2’s spent fuel pool has been completed. This is what they found.

The work was completed in early June and appears to have been conducted without any unexpected problems. A small underwater ROV was used to do the work. Due to the high radiation levels on the refueling floor, remote operated heavy equipment carried the ROV from the access platform to the spent fuel pool.

They looked for a group of specific conditions in the pool:

1. Condition of the control rods stored in the pool and the hangers they are stored on.
2. Fallen objects or similar problems in the base of the cask pit.
3. Fuel channel boxes stored in the pool and their current condition.
4. Surge skimmer filter system as part of the spent fuel pool.
5. Look for interfering objects that may hinder future spent fuel removal.
6. Check the pool gate bolts to assure the gate is safely intact.

Before the work was done at unit 2, a mock up was prepared at the Fukushima Robot Test Field in Minamisoma. Workers tested the ROV and inspection routine.

 

TEPCO plans to review the captured video in more detail. At this point they consider the conditions in the pool to be favorable for the future fuel removal. No severe damage or problems were found. Unit 2 did not have a major explosive event on the refueling floor like units 1 and 3 did, this likely spared the spent fuel pool the kinds of damage seen at other units. The fuel racks did show what appears to be some form of residue growing on the racks. This is distinctly different in form vs. substances found on the fuel racks at unit 3.

 
Key for graphic above:
1. fuel racks  2. cask pit  3. control rod hangers  4. fuel gate  5. skimmer filter

 

Diagram above shows equipment used to put ROV into pool and the route used on the refueling floor.

Image above, fuel racks with residues.

Image above of fuel gate

Image above shows control rods stored in spent fuel pool.

The removal of spent fuel from the pool is currently planned for fiscal year 2024-2026. Details about the plans for spent fuel removal at unit 2 can be found here.
Our prior report on this inspection can be found here.

https://www.tepco.co.jp/decommission/information/newsrelease/reference/pdf/2020/1h/rf_20200610_1.pdf

https://www.tepco.co.jp/decommission/information/newsrelease/reference/pdf/2020/1h/rf_20200611_5.pdf

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