Challenges in the Manufacture of Subassemblies for the Indian Fast Reactors

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1 Challenges in the Manufacture of Subassemblies for the Indian Fast Reactors A. Venugopal Reddy Fast Reactor Facility Nuclear Fuel Complex Department of Atomic Energy, India

2 Three stage Indian Nuclear Power Programme Natural Uranium PHWR 10 GWe ELECTRICITY Th Depleted U 530 GWe Th Pu FUELLED ELECTRICITY Pu FAST BREEDERS Pu U U FUELLED BREEDERS Very Large ELECTRICITY U STAGE 1 STAGE 2 STAGE 3

3 FBR Programme in India India started FBR programme with the construction of FBTR FBTR is a 40 MWt (13.5 MWe) loop type reactor. The design is same as that of Rapsodie-Fortissimo except for incorporation of SG and TG. FBTR is in operation since MWe Fast Breeder Reactor Project (PFBR) through Indigenous design and construction

4 FBR Programme in India Construction of PFBR has been undertaken by BHAVINI. PFBR will be commissioned by Beyond PFBR: 4 units of 500 MWe FBR (twin unit concept) similar to PFBR with improved economy and enhanced safety by Subsequent reactors would be 1000 MWe units with metallic fuel

5 Approach To Big Leap In FBR Programme

6 TUBES FOR CORE STRUCTURALS FUEL CLAD TUBES (6.6 x 0.45 x 2555 mm) BLANKET CLAD TUBES (14.33 x 0.56 x 2350 mm) CSR CLAD TUBES (22.4 x 1 x 1260 mm) DSR CLAD TUBES (21.4 x 0.7 x 1110 mm) REFLECTOR CLAD TUBES (44 x 1 x 3325 mm) IBC CLAD TUBES (44 x 1 x 3325 mm)

7 SPECIAL SUBASSEMBLIES MANUFACTURED FOR FBTR S.No. TYPE OF SUBASSEMBLY QTY (Nos) 1 Carrier SA with capsule for Irradiation Experiments Special SA ISZ Special SA IBZ Special SA IFZ Special SA INZ Special SA IF CIPTEX 2 8. Source Carrier SA 1 9. SA for Sodium Void Coefficient Measurement SA for Delayed Neutron Detection SA for Sodium Filter SA for Flow Blockage Experiments 2

8 PFBR-TYPE TESTING SUBASSEMBLIES MANUFACTURED FOR VALIDATING THE DESIGN S.No TYPE OF SUBASSEMBLY QTY (Nos) 1 Fuel Sub assembly for Pressure (Hydraulic) Drop Test 1 2 Fuel Sub assembly for Flow Induced Vibration Test 1 3 Blanket Sub assembly for Pressure (Hydraulic) Drop Test 1 4 CSR Sub assembly for Drive Mechanism Testing 2 5 CSR Sub assembly for Pressure (Hydraulic) Drop Test 2 6 DSR Sub assembly for Drive Mechanism Testing 1 7 DSR Sub assembly for Pressure (Hydraulic) Drop Test 1 8 Reflector Sub assembly for Pressure (Hydraulic) Drop Test 1 9 Inner B4C Shielding Sub assembly for Pressure (Hydraulic) Drop Test 1 10 Deformed & Straight SA for Handling Equipment Testing Element Fuel Sub assembly

9 Challenges in manufacture of SAs Special grade raw materials to suit requirement of high temperature nuclear service were manufactured with certain modifications to the standard grade Manufacture of thin wall clad tubes and hexagonal wrapper tubes with stringent specifications and cold work condition. Bur free end facing of clad tube was possible with double tool technique and a specially made fixture for holding clad tube on conventional lathe Machining/fabrication of components with intricate shape & very narrow tolerances.

10 Challenges in manufacture of SAs - Contd For obtaining the high degree of accuracy and consistent quality, Jigs, Fixtures & Special purpose machines were developed indigenously. Crimping of clad tube at Middle plug. Using conventional lathe. Special purpose machine with PLC Hard Chromium plating was developed, set up and produced the components required. Autogenous welding (GTAW) for thin wall/ section components. First end plug welding in Ar gas environment. Second end plug welding in closed chamber He gas environment

11 Challenges in manufacture of SAs - Contd Button forming on Outer Hexagonal tube (OHT) and Hexcan for FBTR & PFBR respectively. Tube dimension variation (tube manufacturing process constraints) Localized grinding on button surface for flat surface. For maintaining A/F of button dimension with minimum wall, A/F of tube shall be taken in to account and forming was done accordingly. Spacer Wire Bead Forming by Electro-fusion followed by Cold forming. Assembly of Pins (bundle) and Hexcan with a fixture having Radiation Shieldings for Pin magazine & Subassembly.

12 Challenges in manufacture of SAs - Contd Manual GTAW welding of hexagonal tube with fixture for maintaining the straightness of subassembly. Special purpose machine for GTA Welding process with filler addition, arc distance control. Development of Thoria & Deeply depleted UO2 pellets manufacture. Development of Low temperature Oxidative Sintering process in air at 1150 deg. C with addition of Nb2O5 as Sintering aid. Deeply Depleted UO2 pellets required for PFBR SAs have been manufactured. Spacer Wire Wrapping and spot welding at every quarter pitch.

13 Challenges in manufacture of SAs - Contd Inspection Techniques adopted for confirming the quality of the Subassemblies. Flourscent Die penetrant test Metallography X radiography Ultrasonic Testing (Pulsed echo & surface wave technique) Helium leak Testing Visual & Dimensional Specuial Purpose system for bend measurement of the subassembly.

14 HEXCANS; PROCESS FLOW SHEET Machined Ingots Extrusion to Rods Deep Hole Drilling, Expansion Extrusion to Blanks First Pass Pilgering to intermediate circular tube Solution Annealing, Straightening, IDP/ODG, UT Second pass pilgering to pre final hexcan Solution Annealing, profile Straightening, IDP/ODG, Visual Third pass pilgering to final hexcan Finishing Operations, DP Testing, Visual & Dimensional Check QS & Documentation

15 Materials for FBTR Subassemblies Foot Assembly SS 316L Gripper Spring Nimonic 80A Axial Blanket Clad SS 316L Fuel Clad SS 316M OHT SS 316L IHT SS 316L Handling Head SS 316L Hard Chrome Plating on OHT Buttons

16 Flow Sheet for FBTR Fuel Subassembly I. AXIAL BLANKET PIN FABRICATION 1 ST END PLUG WELDING (GTAW) WITH CLAD TUBE LOAD THE ThO2 PELLET STACK IN THE 1 ST END PLUG WELDED CLAD TUBE 2 ND END PLUG WELDING IN CLOSED CHAMBER IN He GAS ATMOSPHERE SPACER WIRE WRAPPING & SPOT WELDING (RESISTANCE) AND WIRE END WELDING BY GTAW INSPECTION ACCEPTED AXIAL BLANEKT PINS II. LOWER INNER PORTION OF FUEL SA ASSEMBLE FUEL RAILS AND RIVETS WITH LOWER INNER HEXAGONAL TUBE ASSEMBLE AXIAL BLANKET PINS (7 NOS.), SPACERS, LOWER INNER HEXAGONAL TUBE AND RIVETS, FORM & FLARE THE RIVETS ASSEMBLE LOWER INNER HEXAGONAL TUBE WITH FOOT ASSEMBLY AND WELD BY GTAW

17 III. UPPER SA OF FUEL SUBASSEMBLY ASSEMBLE AXIAL BLANKET PINS (7 NOS.), SPACERS, UPPER INNER HEXAGONAL TUBE AND RIVETS, FORM & FLARE THE RIVETS ASSEMBLE UPPER INNER HEXAGONAL TUBE WITH LIFTING HEAD AND WELD BY GTAW ASSEMBLE UPPER INNER HEXAGONAL TUBE ALONGWITH LIFTING HEAD WITH OUTER HEXAGONAL TUBE AND WELD BY GTAW ASSEMBLE FUEL PINS (6 NOS.) OVER RAILS OF LOWER PART OF FUEL SUBASSEMBLY. ENVELOPING THE FUEL PINS AND LOWER INNER HEXAGONAL TUBE WITH OHT OF UPPER SUBASSEMBLY WELD OHT TO FOOT BY GTAW FINAL INSPECTION OF FINISHED FUEL SUBASSEMBLY ALCOHOL CLEANING OF FUEL SUBASSEMBLY PACKING AND DISPATCH/STORE

18 OHT to Foot & Head Portion Welding (GTAW) Bottom Plug Welding (GTAW) Top Plug Welding (GTAW) Welding Techniques Used for FBTR Subassembly Fabrication

19 Tubular Components of FBTR Subassemblies

20 Components of FBTR Subassemblies

21 Components of FBTR Subassemblies

22 Salient Details PFBR Fuel Subassembly Fuel : (Pu-U)O 2 Pellet OD/ID : 5.55/1.8 mm Pin OD/ID : 6.6/5.7 mm Peak Linear Power : 450 W/cm Active core height : 1000 mm Breeding Ratio : 1.05 Clad & Wrapper : 20 % CW D9 No.of Pins : 217 Width Across Flats : mm Peak target Burnup : 100 GWd/t Peak neutron dose : 85 dpa No of Fuel SA : 181 Total SA : 1758

23 Materials for PFBR Subassemblies Fuel Clad Tube - D9 Hexcan- D9 Components- SS 316LN Natural B 4 C Pellets Top Axial Shielding Clad Tube SS 316LN

24 Components for PFBR Subassemblies Handling Head Piston Foot Upper Part Dash Pot Cylinder Bottom Plug Coolant Entry Tube

25 Crimped tube & Sectioned crimped portion of clad tube

26 Crimping Machines

27 Button Forming Machine

28 Automatic Hexcan Welding Machine Both conventional and orbital techniques with GTAW cum Plasma were applied successfully for hexcan peripheral welding with filler addition. Automatic torch inclination with Torch oscillation axis provided for keeping it perpendicular to welding face in synchronization with tube rotation. Software based automatic control with feedback system for all critical parameters with recording facilities. Arc Distance Control

29 Automatic Pin Assembling Machine 1. Pin Magazine (127 Pins) 2. Foot Assembly 3. Hexcan assembled with Top Assembly 4. Shielding 5. Input Trolley 6. Material Transfer Robot Pin Assembling Robot 8. Pin Pushers 9. Special Grippers for Pin 10. Assembly Stn./Fixture 11. Lower Part Holding Stn. 12. Welding/Bead Grinding Robot 13. Finished Subasembly

30 Major Components of the Equipment Rail mounted predefined position mobile trolley with shielding for input components upper & lower parts, pins (217) in pin magazines (2). Specialized track mounted robots for components handling (R1), pins picking, orientation identifying and placing (inserting) over rails (R2) and hexcan to lower part welding(r3). Lower parts, pins & upper parts assembly fixture (customized lathe with specialized supports and shielding). Upper parts (hexcan & handling head) pin magazine support system with automatic hexcan inserting. Robotics & process controls with feedback system. Special end of the arm facility effectors for handling, pick and place, welding torch, excess bead grinding and inspection gadgets, tooling, if required. CCTV cameras (3nos.) for vision system.

31 Special Features of the Equipment Remotisation of radioactive pins assembling and fabrication processes (weld bead finishing and testing) with robotics. Specialized robots for heavy duty machine handling, precision pick and place and advanced GTAW welding functions with complete integration for their coordinated activities. Complete operation with remote controlled with CCTV camera and vision system. Localized (source) shielding provided for neutron and Gamma radiation.

32 Future Development Development of ODS Alloy clad tubes Development & Fabrication of ODS alloy clad tube welding and Ferritic steel hexcan welding. Automation of subassembly fabrication operations to minimize the radiation exposure and to reduce the manufacturing cost of SAs.

33 Conclusion The valuable experience gained during the manufacture of variety of FBTR subassemblies has lead to design & development of special purpose machines with latest technology for various critical components & subassembly fabrication for PFBR. The technology development efforts that were undertaken by NFC has given, not only rich experience but confidence for launching the PFBR project and the future FBRs under planning by DAE.

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