Example of method 2 "Retrieving fuel debris from the top (mobile platform)”

ⅰ) Challenges and reference information : (3) Remove shield plug

Task(s): Retrieval method, considering post processes and prevention of dose rate increase.

 

(3) Remove shield plug - Major challenges on the actual method

(1)Prior preparation (2)Install barrier (3)Remove shield plug (4)Remove PCV/RPV upper head (5)Install equipment and access (6)Dismantle and remove internal structures (7)Retrieve fuel debris (8)Collect fuel debris and Transfer canister (9)Clean-up equipment

Transport / install equipment

  • Places to assemble and install equipment for removing shield plug, if necessary
  • Equipment to be used for assembly
  • Maintenance of equipment and actions to trouble
Plant information
Assumptions and prerequisites
  • Allowable load of operation floor and passageway :1.2t/㎡
  • Size of equipment which should be transported through passageway : Width 1.2m, Height 3m or less
  • Overhead crane specification (Rated load 100t
  • Effective dose rate outside the PCV
    - Operation floor : 1mSv/h
    - Operation areas except for operation floor : 3mSv/h
    - Passageway inside the building : 5mSv/h

Removal

  • Method for removing shield plug, considering possible deformation, and sticking and biting of the shield plug
  • Preparation of temporary storage, and method for temporary placement of the removed shield plug
  • Method for transportation of shield plug to the temporary storage
  • Method for temporary placement of shield plug
  • Method for transporting removed shield plug to another temporary storage
Plant information

Countermeasures on dose increase

  • Management of dose rate increase when removing shield plug
  • Consideration of shielding substitutes for the shield plug