Transcript Slide 1
Legacy Waste Retrieval And Treatment Processing Methods At RSRL Harwell Site Author : Marc Rigby Presented by : Malcolm Adam 28th May 2009 History Of The Harwell Site • Harwell was the birthplace of the UK`s Civil Nuclear Programme • Activities encompassed all aspects of the nuclear cycle over 50 years of R&D • Since the early 1990`s the site has been decommissioning redundant nuclear facilities and processing legacy waste into a passively safe state • Overall aim is to return the site to brown field status by 2040 Site Facilities • Five research fission reactors including two material test reactors • One fusion reactor • Accelerators and radioactive handling facilities and laboratories Legacy Waste • Experimental rigs – mechanically size reduced • Bench sweepings and swarf • Manipulator parts • Fuel cladding • Grossly contaminated materials from active cells or from research reactors Solid Waste Storage Tube Facility • Facility constructed between 1952 and 1974 • Long-term storage of RH-ILW waste from on-site facilities • Facility filled to capacity by 1990 • Studies carried out in late 1980`s showed that waste cans within the storage tubes had degraded and required treatment • Construction of a series of Head End Cells and Vault Store for processing recovered waste • Programme started in 1990`s to refurbish the facility and recover the waste cans for processing into NDA-RWMD approved containers Legacy Waste Retrieval Processes At RSRL Harwell Site • Remote Handling Machine (RM1) recovers waste cans from storage tubes into transfer drums • RM1 equipped with active handling cell and remote grab – modular design • Drums exported in shielded lead flask to Head End Cells for processing into 500 litre stainless steel drums • Packaging process involves assay, sorting and loading of waste into drums • Full drums placed into interim storage pending encapsulation • 10,000 waste cans are to be recovered, processed and encapsulated into a passively safe form by 2020 Retrieval Machine 1 & Head End Cell Current Status Of Facility • 30% of RH-ILW has been recovered using remote handling retrieval machines • 20% of waste recovered has been debris • All waste is expected to have been recovered by 2014 • Overall aim is to decommission and demolish the facility • Waste retrieval facility will be decommissioned leaving only the vault store Waste Immobilisation • 500 litre drums recovered from interim storage for addition of grout mix • Staged processing involving – – – – Outer and inner lid removal Grout addition 24 hour curing Grout capping and further curing – Lidding and return to interim storage • Cement encapsulation widely used within UK at all decommissioning sites Immobilisation Of Radium Contaminated Waste • Radon gas emanations occur as part of the radium decay process and must be controlled • Studies carried out investigate different encapsulation techniques using grout • Acceptable results for small particulate but unacceptable for larger items due to voidage • New polymer-based encapsulation method developed which proved greatly superior to cementation for radium containing wastes • Produces a robust block which greatly improves attenuation to radon emanations due to minimal voidage Sectioned Grout & Polymer Encapsulated Cans Trials Comparison Future Waste Arisings & Treatment Methods • Cementation remains the proposed encapsulation method for Harwell solid waste • Occassionally not acceptable for certain wastes requiring additional treatments (WRAT) • An example is GLEEP fuel which has been highlighted as WRAT due to corrosion concerns within the 500 litre drums • Polymer proposed for immobilising GLEEP fuel rods within their current 23 litre storage cans prior to grouting in 500 litre drums • Results indicate this method to be acceptable for meeting NDA RWMD requirements