British Nuclear Fuels says that a new process at its Thorp plant at Sellafield in Cumbria will help clean up the Irish Sea.
Sellafield's total discharges of nitrate into the sea will be halved when the changeover to recycled acid in the plant is complete.
BNFL claims it will help reduce the total amount of nitrates from all sources by one tenth.
The company says that changes are already evident after the first three months of the changeover process.
The company unveiled annual losses of £1.09bn in July, after one-off costs during the year hit more than £800m.
The figure is an improvement on the record £2.32bn of 2002, although losses at an operating level widened to £190m from the £68m last year.
BNFL says it has been laying the ground for the company's future development.