Damaged Fuel Storage and Recovery A Case Study

1. Damaged Fuel Storage and Recovery A Case Study Natraj C. Iyer Savannah River National Laboratory June 2, 2010 Co-Authors: D.L. Fisher, R.L. Thomas, J.E. Thomas, T.J. Spieker International Conference for Management of Spent Fuel from Nuclear Power Reactors May 31,- June 4, 2010, IAEA, Vienna, Austria

2. Outline • Damaged Fuel Storage in Isolation Canisters Called “Oversize (OS) Canisters” • Contents - Early Test Reactor Fuel Pieces and Damaged Fuel • Fuel Direct-Stored or In Other Cans within the OS Canisters • Special Underwater Filter/Deionizer for Damaged Fuel Recovery • Remove Cesium from High Activity Water (up to 5.8E6 Bq/ml in 3800 liters) from Six OS Canisters (No Release Into General Basin Water) • Special Design Apparatus for Underwater Remote Operation • Operation Results • OS Canister for L-Basin Damaged Fuel Storage • Design Features • Damaged Fuel Management at the Savannah River Site: • System to Store Damaged Fuel Underwater, Isolating It from General Basin; • System to Remove Water Activity from Oversize Canisters

3. Spent Fuel Storage Experience • Storage of MTR and non-MTR Spent Fuels • Stainless Steel, Zircaloy and Aluminum Clad Research Reactor Fuel • Aluminum Clad – Depleted Uranium Targets • Fuel Core (Meat): Depleted U, U- Aluminide, U-Sr Hydride, U- Silicide, U-Mo, UO2 • Enrichment: 20 to 93% Variety of SNF in Basin Storage Storage of Variety of Spent Fuels for >40+ Years Primary Basin Storage Facility in U.S. for DOE Spent Fuel

4. Damaged Fuel Storage Configuration in OS Canisters • Fuel Pieces and Damaged Fuel Storage • Tubes, tube sections, and pins • For Example - Fuel irradiated in the site Heavy Water Components Test Reactor and site production reactors: 1957-1963 • Cladding: Zircaloy, Aluminum • Fuel Core: Umetal, UO2 U-Zr, U-Al, U-Mo, U-Fe • Place pieces in cans (Z-cans, B-cans) • Oversize (OS) Canisters • Al or SS Construction • ~4m (14’) Long, 0.33m(~14”) Diameter • J-Tube Vented Z-Can (#Z13) with Fuel Pieces OS Aluminum Canister

5. RBOF Building L-BASIN Building Savannah River Site Deinventory of Receiving Basin for Offsite Fuel • Goal: RBOF De-Inventory by September 2006 – Completed September 2003 • Completed MTR transfer March 2001 • ~3800 Assemblies transferred starting 2-27-97 • Transfer goal was July 2001 • Completed 1st Non-MTR transfer March 2001 • De-inventory shipments included SFO, EBR-II (Oct-00), TRR (Feb-98), Mk-42 (Oct-00), Mk-31 • Completed OS Canister recovery and transfer September 2003

6. Inlet Port Resin Can in Shroud Filter Flow Meter Pump Air Motor Discharge Port Hose to resin column Discharge Inlet SRS Underwater Resin Deionizer Design • Background • Oversize (OS) Cans Contained Fuel Pieces • Oversize (OS) Cans had High Activity Levels (5.8x106 Bq/ml) from Cs-137 • Need to Open OS Cans to Re-Pack Fuel Without Releasing High Activity to Basin • Underwater System Designed and Built to Provide Deionization of OS Cans • Portable, Skid-Mounted System • 28 liters CG8-H resin (strong acid cation resin) • 100 mm Filter - Sintered Stainless Steel Metal Filter • 2 Independent Air Motors with Remote Operation Using Building Air Supply • Attach/Detach Lines with Typical Basin Handling Tools

7. Operation to Flush Oversize (OS) Cans • Inlet at Bottom of Can to Avoid Plugging by Debris in the OS Can • Opened Flanged Connection on the OS Can • Inlet Water from Basin • Outlet Water to Basin • Run for 1 Hour at 12 L/m

8. OS Flushing – Results Performance Example Air Motor Remote Controls • Water Activity Initial (OS Can A3): 120,000 Bq/ml • Water Activity Final (OS Can A3): 1,700 Bq/ml after 1 hour single-pass flushing at 12 lpm through 3800 liter OS Can volume ‘Red-line’ OS Can RO7 Meter to Record Resin Column Activity at “Red Line” Underwater Underwater Deionizer in RBOF

9. OS Flushing – Results • Flushed A3, A1, A2, A6, A7 and A5 Cans 100 R = 1 Gy

10. OS Flushing – Results • 6 OS cans flushed • internal cans containing pieces/failed tubes (vented) • primarily Zr cladding • fuel age: 1958/62 irradiation • 319 Ci Cs-137 captured • 1 cu. Ft CG8-H resin • 1 month total operation • Findings • 3 ruptured Z-cans • 36 lbs. Oxide at bottom of 1 OS can • 12 lbs. fines dispersed thru filter • 6300 R/hr at red line final exposure rate

11. Failed ‘Z’ and ‘B’ Cans Within OS Canisters

12. Damaged Fuel Transferred to L-Basin • Fuel with Through-Clad Breaches May be Acceptable for Continued Direct Basin Storage • Evaluate Cs Release with Sip Test • Evaluate Expected Continued Release Based on Corrosion Model • Evaluate Capacity of Basin Deionization System • Damaged Fuel in Cans Placed in New OS Canisters Oversize (OS) Canisters for L-Basin L-Basin OS Canister Rack

13. OS Canister Improved Design and L-Basin Storage • OS Canister with Improved J-tube • Isolates Enables Gas Release • Fuel Direct-Stored or In Cans within OS Canisters • 13 New OS Canisters Stored in L-Basin for Damaged Fuel • 1 New OS Canister for Resin Column Latest J-tube Design on OS Canister

14. Summary • Damaged Fuel Management at the Savannah River Site: • System to Store Damaged Fuel Underwater: Vented Canister Storage with Isolation of Canister Water from General Basin Water; • System to Remove Water Activity from Oversize Canisters • Savannah River Site Experience in Underwater Storage of Severely Damaged Fuel Successful in Storage/Recovery/Repack Campaign • Fuel Recovery from OS Cans Used Special Design Underwater Deionizer