Unit 2 Primary Containment Vessel Investigation At Fukushima

Transcript

Reference February 9, 2017 Tokyo Electric Power Company Holdings, Inc. Unit 2 Primary Containment Vessel Investigation at Fukushima Daiichi Nuclear Power Station (Results of deposit removal work) Tokyo Electric Power Company Holdings, Inc. 1. Unit 2 Primary Containment Vessel investigation The purpose of this investigation is to inspect the platform inside the pedestal, fuel debris fallen to the Control Rod Drive (CRD), and structures inside the pedestal. Today, preparatory investigation was conducted for X-6 penetration and CRD exchange rail which the self-propelled Scorpion robot will take to the pedestal. Control Rod Drive (CRD) exchange rail Pedestal opening Pedestal ＲＰＶ Primary Containment Vessel (PCV) Next investigation area Control Rod Drive (CRD) Platform About7.2m X-6 penetration Basement floor Investigation area inside the pedestal 1 2. Work steps for Unit 2 PCV investigation Step 2. Drilling device set up Step 1. Drilling device carried in Drilling device Isolation Shielding X-6 penetration Isolation unit* Drilling device X-6 penetration Step 3. Drilling on X-6 penetration Drilling device Hole saw X-6 penetration Clamp *Combination Step 4. Preinvestigation of X-6 penetration and CRD rail using guide pipe X-6 penetration CRD rail Pan-tilt camera Step 5. Pre-investigation inside pedestal using guide pipe Pedestal X-6 penetration CRD rail Pan-tilt camera of isolation and shielding Step 6. Obstacle removal device inserted* Step 7. Investigation using selfpropelled investigation device *The device may not be inserted depending on the obstacle conditions. Deposit removal device Self-propelled investigation device 2 3. Insertion of deposit removal device  Based on the analysis results of the digital images obtained from the previous investigations, a device was inserted in the Unit 2 PCV today to remove deposits on the CRD rail, which may pose obstacles to the self-propelled investigation device.  The height of the deposits were estimated and mock-up tests have been conducted to confirm the access to the pedestal area with the self-propelled investigation device. Isolation valve Isolation valve Guide pipe (Φ110mm) Long shot camera and lights Pedestal Sling X-6 penetration Pedestal opening Chamber Platform Control Rod Drive (CRD) Alternative shielding Inside of Primary Containment Vessel Deposit removal device Back camera and lights Front camera and lights Water injection nozzle （Water pressure: about 7.5MPa） Deposit removal device (image) Front camera and lights Scraper *No dosimeter attached The head of the guiding pipe opens to bring down the device on the CRD rail. The device washes off the deposits with water injection as well as push them off with a scraper based on the situation. 3 4-1. Results of deposit removal work (landing position of the guide pipe) Step 6 Isolation valve Isolation valve Guide pipe for pre-investigation (Φ110mm) 自走式調査装置による調査概要 Pedestal Deposit removal robot X-6 penetration Chamber unit Platform Control Rod Drive (CRD) Alternative shielding About 2000㎜ About 100㎜ Shooting range Inside of Primary Containment Vessel Images from guiding pipe camera Before the removal After the removal Images from front camera attached to the device Before the removal After the removal 4 4-2. Results of deposit removal work (position where deposits strongly adhered to the rail) Step 6 Isolation valve Isolation valve Guide pipe for pre-investigation (Φ110mm) 自走式調査装置による調査概要 Pedestal Deposit removal robot X-6 penetration Chamber unit Platform Alternative shielding Control Rod Drive (CRD) About 2000㎜ About 800㎜ Shooting range Inside of Primary Containment Vessel Images from guiding pipe camera Before the removal After the removal Images from front camera attached to the device Before the removal After the removal 5 4-3. Results of deposit removal work (position where the device run on deposits) Step 6 Isolation valve Isolation valve Guide pipe for pre-investigation (Φ110mm) 自走式調査装置による調査概要 Pedestal Deposit removal robot X-6 penetration Chamber unit Platform Alternative shielding Control Rod Drive (CRD) About 2000㎜ About 1000㎜ Inside of Primary Containment Vessel Shooting range Images from guiding pipe camera Images from front camera attached to the device 6 4. Summary  Today’s investigation results • The device removed the deposits in a part of the planned area (about 1m out of 5m from the landing point). • It took time to remove the deposits because they adhered stronger to the rail as it got closer to the pedestal area. • Today’s work was closed by retrieving the device before it prevents next investigation with a malfunction of the camera. • The device on the deposits could not run on some parts.  Based on today’s investigation results and mock-up testing, we will determine whether to conduct further investigation with the selfpropelled investigation device. 7 Reference: Work site scenes The deposit removal work was conducted by remotely operating the device in the remote operation room and by inserting/pulling out the guiding pipe at the field headquarters and inside the Unit 2 Reactor Building. Remote operation room in the main administrative office Inside the Unit 2 Reactor Building Work site scenes 8 Reference: Unit 2 Primary Containment Vessel (A2 investigation) Pre-investigation with guiding pipe, Radiation estimation  Radiation levels estimated from noise images on the camera screen*1: ① Around the scaffold on the CRD rail: about 30 Sv/h ② Outside the pedestal: about 530 Sv/h*2 ③ Inside the pedestal: about 20 Sv/h X-6 penetration ② ① Pedestal 2.3m ③ Scaffold Inside of Primary Containment Vessel ：Positions where radiation levels estimated *1 Reference values estimated from noise images on the camera screen by comparing them at the times of radiation testing and actual investigation (error margin of ±30%) *2 It cannot be simply compared, but we evaluate that the surface radiation of a fuel assembly is several ten 9 thousands Sv/h one day after the reactor stops. 9