Segmentation of the Legacy C Area Disassembly Spent Fuel Pool Prepared by: Jon Guy, N&CSE Spent Fuel Project Lead UNCLASSIFIED DOES NOT CONTAIN UNCLASSIFIED CONTROLLED NUCLEAR INFORMATION DC & Reviewing Official: Les Yerger/ L-Area N&CSE. Date: 4/09/2012 . Guidance: IG-SR-03, 2/04
C Reactor Area Background • The C Reactor Facility began operation in early 1955 for the production of nuclear materials. • C Reactor was retired from operation in 1985 with no capability for restart.
C Area Current Mission • Tritium contaminated moderator is stored inside the C Reactor Facility • Irradiated Stainless Steel and Aluminum reactor components are stored in the Reactor Tank and Disassembly Spent Fuel Pool(~3.5 million Gallon) • The C Area 105 Building and specific peripheral buildings are considered to be in a Surveillance and Maintenance Mode awaiting closure by Area Completion Projects
C Area Safety Basis • C Area is considered a Hazard Category 2 facility. • The current Safety Document is a Basis for Interim Operation(BIO) and a TSR • Major hazards: • Legacy reactor contaminated moderator storage (Tritium) • Activated Reactor Components (Stainless Steel and Aluminum) • A small fissile material exist in the dirt layer at bottom of the Disassembly Spent Fuel Pool
C Reactor Area Safety Basis • C-Area • Not continuously manned • Surveillances are completed quarterly • Disassembly Spent Fuel Pool locked with limited access permitted. • Safety Analysis for C Reactor very conservative • No return on Investment • No real need identified for new approach
Why Safety Basis is being revised • Site-wide footprint reduction tied to elimination of the potential ground water release from C Area Disassembly Basin. • Area Completion Projects would be permitted to evaporate the basin water and grout activated scrap “in place” within the Disassembly Basin. • Segmentation of the Disassembly Basin and categorization as a Radiological Facility eases requirements in accordance with the reduced risk. • Return on Investment significant for this project. • Reduce engineering, maintenance and construction cost during evaporation and grouting.
C Reactor Safety Basis Revision Plan • C Reactor Safety Basis • Removed reference to the Disassembly Spent Fuel pool and any associated controls • Acknowledged that a new Auditable Safety Analysis would be the Safety Basis for the segmented Disassembly Basin.
C Reactor BIO Revision Plan • Prepare a Hazard Determination document to support segmentation and downgrade • Activated Reactor components (Example Co 60) • Source Term of water and legacy dirt layer • Additional source terms included in proposed segment. (example: Legacy Spent Fuel Pool Sand Filters • Prepare an Auditable Safety Analysis for the segmented C- Area Disassembly Spent Fuel pool • Auditable Safety Analysis is the safety basis document for facilities categorized as Radiological. • Also act as final Hazard Determination • Approve a Downgrade of the new Segment from Hazard Cat 2 to radiological
Main Issues for Downgrade • Activated Stainless Steel can contain higher than Hazard Cat 3 quantities of some isotopes. • Solid material not releasable from storage location • Grout addition maintains water shielding over activated material
Main Issues for Downgrade • Fissile material in dirt layer at the bottom of basin • New Nuclear Criticality Safety Analysis used to show criticality event not credible • Hydrogen generation due to legacy reactor components interaction with grout • Engineering analysis performed to show not a credible event
Main Issues for Downgrade • Actual physical separation of the new segment from the rest of the C Reactor facility. • The fuel transfer canal between the spent fuel pool and reactor area remained open • Disassembly Final Storage area had open weirs that needed to be sealed. • There was no physical barrier separating the new segment outside the building.
Major Implementation Items for Segmentation • Fuel Transfer canal grouted closed • Final Storage grouted closed • Activated reactor components were located and lowered to maintain water shielding • A new fence will be installed to establish the new segment.
Before and After C Area Final Storage Before After
Before and After Fuel Transfer Canal Before After
Status • The BIO has been revised and Approved • The Auditable Safety Analysis and Segment down grade are approved • All implementation items are complete. • De-watering and grouting of the Disassembly Spent Fuel pool is ongoing.