8 October 2003 – BNFL said Tuesday it had begun the trial of a chemical removal process that may significantly reduce the discharges of the radionuclide Tc-99 from it Sellafield nuclear reprocessing plant.
Laboratory trials have indicated that the addition of the chemical tetraphenylphosphoniumbromide (TPP) to Sellafield discharges could enable Tc-99 to be removed from the discharge stream.
Although the trial will result in some discharges of Tc-99, the objective of the trial is to determine how effective TPP is in reducing Tc-99 from discharges. TPP may not prove to be effective on a plant scale, but a trial is the only way to determine this.
The trial has been made possible following confirmation by Nirex that the resultant solid waste product will be suitable for eventual disposal and agreement to the trial from the Environment Agency and the Health and Safety Executive (Nuclear Installations Inspectorate) as the appropriate regulatory bodies.
Tc-99 discharges arise when medium active concentrate (MAC) from Magnox reprocessing is treated in the Enhanced Actinide Removal Plant (EARP). This plant removes the most significant radioactive substances but is unable to remove Tc-99 from the discharge stream.
The trial will entail the processing through EARP of 240m3 of MAC in separate batches of 27m3. TPP will be added to each batch and the resultant Tc-99 retaining solid will be contained in cement and stored in stainless steel drums at Sellafield.
Effectiveness of the trial will not be fully known until early in 2004, following a review of the results by BNFL, the Health and Safety Executive (Nuclear Installations Inspectorate), the Environment Agency and Nirex.
BNFL Sellafield’s Head of Environment, Health & Safety, John Clarke said,
“This trial is the culmination of a lengthy period of intense research and development into Tc-99 discharge abatement. The current discharge limit for Tc-99 discharge is 90TBq per year and this limit could be reduced to 10 TBq per year from about 2006. The TPP trial may enable lower discharges of Tc-99 from Sellafield prior to 2006 but it must be recognised that this is by no means certain. The Ministerial Meeting of the OSPAR commission held in June this year concluded that Tc-99 discharge reduction prior to 2006 is entirely subject to technical feasibility. Only once all the data from the trial has been collated and examined will we know if the TPP process works.”