Legacy Waste Retrieval And Treatment Processing Methods At RSRL Harwell Site

Author : Marc RigbyPresented 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

• 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

Solid Waste Storage Tube Facility

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