BNFL has still not been able to divert radioactive liquid waste streams from its Magnox reprocessing plant at Sellafield. The diversion is planned to to avoid discharging the technetium-99 in the waste stream to the sea.
BNFL committed itself to the diversion concept 18 months ago, and was due to start diverting the Magnox plant's medium active concentrate (MAC) to a high-level liquid waste stream at the end of March 2003. The liquid stream is eventually vitrified in borosilicate glass.
BNFL said that its scheme was hit by a problem "late in the day" as it was conducting the initial diversion trials. All key radionuclides had to be within acceptable levels in order to be handled by an evaporator, but the level of uranium,was higher than expected.
The higher uranium level had been caused by the method used to clean out the evaporator prior to the trial's start up. The evaporator had to be shut down, washed out, and restarted using a different cleaning method before the trials could recommence.
MAC material already stored in the downstream tanks cannot be diverted for vitrification, as it contains a range of other chemicals that are not compatible with the storage regime for high-active liquor waiting for the vitrification process.
The current proposal is to continue to process that material through the Earp plant, and that will result in discharges of Tc-99 up to the 90TBq/yr level until 2006, when the discharges would fall to 10TBq/yr.