Work to remove and contain radiation at Dalgety Bay will not be complete until 2019.
The Ministry of Defence (MoD) also confirmed that radioactive material taken from the site will not be stored in Rosyth.
Stephen Ritchie from the MoD’s Defence Infrastructure Organisation (DIO) said construction work to contain the radiation would take place over two summers and was unlikely to get under way next year.
“Although we have agreements to do the ground investigations, we don’t have agreements to do the construction work,” he said.
“That will be subject to negotiations with the land owners.”
Having accepted responsibility for radioactive particles discovered at the shore beside Dalgety Bay Sailing Club, the MoD plans to remove some of the contaminated debris and contain the rest by building a wall and new slipway.
Ground investigation work is expected to start in October, with construction work going ahead in the summers of 2018 and 2019.
Radioactive particles, first discovered at the site in 1990, contain radium-226 which was in paint used to make aircraft dials luminous.
Studies of the coastline suggest incinerated radioactive waste was dumped prior to 1959, when the nearby airbase HMS Merlin was decommissioned.
Updating councillors at south west Fife area committee, Mr Ritchie said radioactive material taken from the site would go to a disposal facility and not Rosyth.
He added: “Material taken off the beach so far has always been stored at Rosyth for future disposal.
“We’ve taken the decision that if we can get rid of it that would be for the long term benefit of everybody.”
Local representatives welcomed the fact the MoD is progressing plans to clean up the shore.
Councillor Lesley Laird said: “It was originally thought the work would be completed by 2018 but that’s not going to be the case.
“I take it as a positive step that they are coming on a very regular basis to community council meetings and south west area committee so communication with the MoD has significantly improved compared to where it was.
“That they are prepared to show up gives us a measure of confidence that this is going to progress.”
Councillor Alice McGarry said the material would probably be taken to a facility in England such as Drigg Low Level Waste Repository.
She added: “There’s been a delay but at least they’ve been up front and told us.”
Roy Green from Dalgety Bay and Hillend Community Council said: “The community council is pleased to see that they are actually starting to make some progress and we hope to see a full programme as promised by the end of the year.”