As a result of co-operative efforts between BNFL, the Environment Agency, Health and Safety Executive and others, much has already been done to reduce Technetium-99 (Tc-99) discharge levels from Sellafield.
The discharge limit was cut from 200 TBq/year (terabecquerels per year) to 90 TBq/year in 2000. Ministers also asked the Environment Agency to carry out a review of Tc-99 discharges and the Agency's proposed decision was published in September 2001. One of the proposals, to deal with new arisings of Medium Active Concentrate (MAC) (the complex liquid mixture that contains Tc-99 and other, more radiotoxic, radionuclides) using "MAC-Diversion" abatement technology, was implemented in 2003. This will allow the discharge limit to be reduced to 10 TBq/year in 2006.
The Environment Agency also proposed further research on abatement of Tc-99 arising from stored MAC. In October 2003, following approval by regulators, a plant-scale trial began using tetraphenylphosphonium bromide (TPP)—a chemical that precipitates Tc-99 out of MAC. Initial results appear to be encouraging. However, a full evaluation of the trial by the regulators is still under way. If their assessment shows that TPP is acceptable for future use to reduce Tc-99 discharges, it will allow the discharge limits to be cut to below 90 TBq/year before 2006.