Nuclear bosses at the Sellafield plant in Cumbria say a reprocessing facility, at the centre of a leak probe should be working again by Spring 2006.
The Thorp complex could reopen in the Spring of 2006
Acid containing 20 tonnes of uranium and 160kg of plutonium spilled from a ruptured pipe at the Thorp complex into a sealed cell earlier this year.
A subsequent inquiry by the Nuclear Installations Inspectorate (NII) found "significant deficiencies" at the site.
Operator British Nuclear Group said the complex should be working again by May.
Work at Thorp was halted when the leak, which could have occurred as long ago as August 2004, was discovered in April.
Two senior members of staff were disciplined after its discovery.
Officials said a clean-up operation is making good progress and about half the recommendations of the NII have been implemented.
A British Nuclear Group spokesman said: "The provisional internal planning assumption was that all areas of the plant would be operational by March 2006.
"We now have a firm plan for Thorp re-start which takes account of the extensive work required to re-start the plant and will allow a prudent amount of time for NII assessment and endorsement of the repair option.
"Due to the complexity of the plant, it will progressively start up over a period of weeks.
"Following completion of the repair work and processing of the recovered liquor through the chemical separation process, shearing of fuel is programmed to commence in May 2006.
"The re-start plan will remain under constant review to take account of any additional regulatory requirements."