Retrieval of Damaged Components form Experimental Fast Reactor Joyo Reactor Vessel

Transcription

1 Retrieval of Damaged Components form Experimental Fast Reactor Joyo Reactor Vessel June. 8 th, 2010 Yukimoto MAEDA Japan Atomic Energy Agency (JAEA)

2 Experimental fast reactor Joyo Joyo (Oarai R&D Center) Fuel Monitoring Facility Tokyo Spent fuel storage pool Joyo Irradiation Rig Assembling Facility Main cooling building Containment vessel 2

3 Role of To confirm the performance of sodium cooled FBR power plant Prototype fast breeder reactor power plant MONJU 280MWe (714MWt) Commercial power plant Experimental fast reactor 140MWt - To confirm the principle of sodium cooled FBR - To establish operation, maintenance technology - Irradiation for fuels and materials development using fast neutron field 3

4 Outline of Secondary pump Containment vessel Control room Dump heat exchanger Major specs Type : Loop type (2 loops) Rated power :140 MWt Fuel :MOX Core Structure : Stainless steel Coolant : Liquid sodium Core diameter : 80 cm Core height : 50 cm 4 IHX Primary pump Reactor vessel Start of construction :1970 Operation (breeding core:mk I) :1978 (irradiation core:mk-ii) :1982 Upgrading core ( MK-III) criticality :July 2003 Start of irradiation with MK-III core :May

5 heat transport system Loop A Loop B 470deg-c Secondary Loop 1200t/h Primary Pump Secondary Pump Reactor Vessel 500deg-c 300deg-c Primary Loop 1350t/h 350deg-c Intermediate Heat Exchanger Dump Heat Exchanger Cooling system type : Loop type Number of main cooling system : 2 Heat Removal : Air Cooling 5

6 History of Joyo Design Groundbreaking The first criticality achieved at Joyo Mark-Ⅰ Modification works Mark-Ⅱ Mark-Ⅲ The 1st criticality The 1st criticality 6

7 Upgrading of the Joyo cores MK-I core Breeder core MK-II core MK-III core Irradiation core Upgraded Irradiation core 50/75MWt 100MWt 140MWt Control rod Subassembly for irradiation Core fuel subassembly Shielding subassembly Reflector Inner core fuel subassembly Blanket fuel subassembly Outer core fuel subassembly Neutron Flux(>0.1MeV)(n/cm 2 s) MK-ⅢCore MK-ⅡCore Row 6 7

8 Installation of New Main IHX Transport from Warehouse to Maintenance Building Move from Maintenance Building to RCV Move inside RCV Stand-up Lift-down Installation Completed 8

9 Background On June 11th 2007, fuel handling machine was set up on the rotating plug (R/P) as a refueling preparation. The measured load of hold down shaft indicated abnormal decrease in the R/Ps jack down operation. It was suspected that there was an obstacle under the hold down shaft. The in-vessel storage rack under the hold down shaft stored an irradiation rig MARICO-2. As a result of visual inspection, an obstacle around in-vessel storage rack was identified as the MARICO-2 test subassembly. In-vessel Inspection Hole(B) Large Rotating Plug Sodium Level Upper Core Structure Reactor Vessel In-vessel Inspection Hole(A) Fuel Handling Machine Door Valve for Fuel Handling Transfer Pot Small Rotating Plug Hold Down Shaft 9

10 Structure of MARICO-2 MARICO : MAterial testing RIg with temperature COntrol 10

11 In-Vessel Inspection of Sodium cooled Fast Reactor In-Vessel inspection Hole(B) Small Rotating Plug Fuel Handling Hole 1 Access route is limited In-Vessel inspection Hole(A),(B) : Φ110 Fuel Handling Hole : Φ164 Auxiliary Hole for C/R : Φ150 Auxiliary Hole for C/R Large Rotating Plug In-Vessel inspection Hole(A) Top view of Rotating Plug 2 Inert Atmosphere: Ar gas Maintain the boundary 3 High Radiation (200~300 Gy/h) 4 High Temperature (~200deg-C) 5 Opacity : Sodium Lower level of sodium It is necessary to employ the appropriate inspection technology for fast reactor. 11

12 In-vessel visual observation by camera - Bent MARICO-2 on in-vessel storage rack - Camera Grasp the conditions of the transfer pot and the bent MARICO-2. Transfer pot Wrapper tube In-vessel Storage Rack 12

13 In-vessel visual observation by camera - Top of the subassemblies and in-vessel storage rack- No damage to each handling head of subassembly and in-vessel storage rack 3 mm in width Handling Head Composite photograph 13

14 In-vessel Inspection Hole (A) In-vessel Inspection Hole (B) In-vessel visual inspection by fiberscope Visual Inspection Device (Fiberscope) Visual inspection device Sodium level during obs. Fiberscope Side View Light guide fiber Image fiber Observation Region Downward View SUS flexible and braided tube Radiation resistant fiberscope was applied to observation. Fiberscope was inserted in the reactor vessel through the in-vessel inspection holes. 14

15 Results of observation by fiberscope Clear image was obtained by radiation resistant fiberscope. Grasp the condition of the bent MARICO-2. Wrapper tube UCS MARICO-2 test subassembly Approx.200 mm Approx.90 mm In-vessel Inspection hole(a) MARICO-2 15

16 In-vessel inspection hole (B) Visual inspection device for UCS bottom Remote handling device Large rotating-plug Small rotating-plug 100 mm Structure of the tip Upward view - Visual field angle : 60 degree - Depth of focus : 30 ~ 400 mm 11m UCS subassemblies Side view - Visual field angle : 15 degree - Depth of focus : 100 ~ 2,000 mm Insert method Inspection device Tip 30mm UCS 70mm 2 m 16

17 Results of UCS bottom face observation MARICO-2 upper guide tube Sodium flow regulating grid UCS bottom face MARICO-2 upper guide tube Thermocouple Handling head Handling head connected with holding mechanism Deformed regulating grid 17

18 3-D image of bent MARICO-2 test assembly Upper Core Structure (UCS) Hold Down Shaft MARICO-2 Test S/A In-vessel Storage Rack 18

19 Replace UCS and retrieve MARICO-2 test S/A 1. Remove the existing UCS 2. Retrieve the MARICO-2 through the hole from which UCS is removed 3. Insert new UCS UCS retrieval device (cask) MARICO-2 test S/A retrieval device MARICO-2 Gripper Grip MARICO-2 wrapper tube Basket Wedge UCS Finger MARICO-2 Transfer Pot Replace UCS Retrieve MARICO-2 Grip transfer pot 19

20 Major subjects of UCS replacement (1) High radioactivity of UCS - UCS cask weight (preliminary evaluation) : >110 ton - Allowable load of C/V crane : 100 ton Reducing UCS cask weight UCS Cask (2) Sodium deposition between UCS and small-r/p - Overload during UCS removal Deformation of UCS and small-r/p Proper evaluation of sodium deposition Small R/P (3) UCS inclination control - Minimum gap between UCS and small-r/p : 5 mm UCS jack-up device with severe inclination control (4) Prevent impurity ingress to the sodium system Control of cover gas pressure, impurity concentration monitoring etc. ( Experience of cooling system renovation in MK-III modification work ) UCS R/V 20

21 Measure for reducing UCS cask weight Cask design target - UCS cask weight : <100 ton (including UCS 16.5 ton) - Surface dose rate of cask : <1 msv/h (1) In-vessel gamma dose measurement - Optimization of cask thickness based on dose rate distribution of UCS measured value Fuel handling hole (FHH) Hold down shaft Upper core structure (UCS) CRDM hole (CH) Inspection hole (A) (IH(A)) Inspection hole (B) (IH(B)) (2) Optimization of UCS cask structure - Variations of thickness : 2 4 * From a manufacturing standpoint, two kind of thickness is better. UCS Cask Multi-thickness structure Bent MARICO-2 Detector Type :Ionization chamber (IC) Range:0.1~1000 Gy/h 21

22 Dose rate on UCS surface - Evaluation Method - Neutron flux calculation 2-D transport code DORT Neutron flux, σ Gamma-ray source calculation ORIGEN2 CH IH(A) Gamma-ray source Gamma-ray flux calculation QAD-CGGP2 R/P Axial Position(mm) 1000 Conversion to dose : ICRP74 Calculated gamma dose rate UCS Inspection Hole(A) CRDM Hole (CH) Dose rate (Gy/h) Corrected by measured value Gamma dose rate measurement Dose rate distribution on UCS 22

23 Dose rate on UCS surface - Evaluation results - 90 UCS 450mm Sodium flow regulating grid Axial position from UCS bottom (mm) ~0.1 Sv/h 2500 ~1 Sv/h Max. : 43 Sv/h Dose rate (Sv/h) Sodium flow regulating grid 0 C/R sleeve Dose rate (Sv/h) Flange UCS Bottom Max. : 99 Sv/h Radial position (mm) 23

24 Shielding design result of UCS cask UCS cask 1mSv/h UCS Position Side Thickness (cm) (Carbon steel) Dose rate on cask surface (μsv/h) Top 6 10 <50 * Bottom * : The top of the cask (6) satisfies allowable dose rate (1mSv/h) with 0mm in thickness. Taking account of cask strength, 6 has same thickness as Total weight of UCS cask : ~93.4ton ( with UCS (16.5 ton)) below allowable load of crane (100ton) 24

25 Retrieval procedure of bent MARICO-2 Large R/P Small R/P Access route Fuel handling hole (Φ164mm) In-vessel inspection hole (B) (Φ110mm) Geometric condition UCS can not be positioned right above the bent MARICO-2 to avoid a contact with it. UCS 70mm Approx. 90mm 1m MARICO-2 UCS MARICO-2 In-vessel inspection hole (A) (Φ110mm) The retrieval device employs offset configuration 25

26 Lifting-up test device of bent MARICO-2 (1) Lifting-up test was planned to confirm: - bent MARICO-2 can be lifted-up - stuck of bent MARICO-2 with pot or not Drive shaft Drive mechanism Rotating mechanism Rack Pot Finger Seal ring MARICO-2 In-vessel inspection hole (A) Approx. 8600mm Upper face of R/P Simple handling device Lifting-up test device Upper face of pot Φ100mm 26

27 Lifting-up test device of bent MARICO-2 (2) 1 Lift-down 2 Rotate to open fingers 4 Rotate to close fingers Lifting-up simulation test was conducted to confirm : 3 Lift-down Holding function of bent part of wrapper tube Adjustment against position difference etc. Visual condition by optical fiber 5 Lift-up Lifting device Bent wrapper tube Rack Pot 27

28 Lifting-up test Fiberscope (Fuel handling hole) Large R/P UCS Adjusting angle of fingers Lifting-up device ( In-vessel inspection hole (A) ) Insertion of device MARICO-2 Small R/P 28

29 Lifting-up test of bent MARICO-2 Nov. 18 th 11:00 Insertion of fingers 12:47 Finger position adjustment 14:15 Bent MARICO-2 lifting-up The picture was obtained by fiberscope during lifting-up operation. 29

30 Measured load during lifting-up test (a)(b)(c) (d) (e) Weight Drive shaft 620N MARICO-2 200N Pot 850N Friction between pot and rack 130N Total 1800N 3 2 (a) Increasing load for lifting-up drive shaft (0mm) (b) Lifting-up drive shaft only (0-5.5mm) (c) Increasing load for lifting-up MARICO-2 with pot ( mm) (d) Lifting-up MARICO-2 with pot ( mm) (e) Lifting down This result indicated that bent MARICO-2 was lifted-up together with pot, but the rack was not stuck with pot. 30

31 Master Schedule for Joyo Resumption JFY ~ 15 th Periodical Inspection 7 th cy~ Disassembly and inspection of R/P Operati on Visual Inspection Function Test Gamma dose rate measurement Planning of UCS Replacement Work Manufacturing of New UCS UCS replacement MARICO-2 Retrieval Lifting-up test of MARICO-2 Design of MARICO-2 Retrieval Device Manufacturing of MARICO-2 Retrieval Device Mock-up test 31

32 Joyo s Roles for FBR Fuel Cycle Development Joyo Operation MK-III 1~6 cy 7cy~ 1. Fuel and Materials Tests (1) Development of High Burn-up Fuel using ODS* Cladding (2) Run to Cladding Breach (RTCB) (3) Development of Fuel Fabrication Short Process, Metal, Annular Pellet (4) Long Life Control Rod (Sodium Bond Type) (5) Test for External Users (University, fusion, etc.) 2. Irradiation Tests on MA (1) MA Bearing Fuel Irradiation Test 3. FBR Safety Tests (1) SASS(Self Actuated Shut Down System) (2) ISI&R Material Irradiation Fuel Pin Irradiation * ODS: Oxide Dispersion Strengthened Ferritic Steel 32

33 Summary In-vessel visual inspections were successfully conducted by fiberscope and video camera. These results are reflected to the restoration work of Joyo. The design of retrieval device of damaged UCS and bent MARICO-2 has been almost finished based on the radioactivity evaluation of UCS and lifting test of bent MARICO-2. Valuable experience and data are obtained through restoration work. 33