The “mass trespass” is the culmination of a weekend of protests against the £2bn plant where Laing O’Rourke/Buouygues will be the main contractor and a Kier/Bam joint venture is gearing up to start a £100m groundworks contract.
The Stop New Nuclear campaign said it is looking for “people who are prepared to be arrested”.
The campaigners said: “Our aim is to make the trespass as safe and dignified as possible.
“All our activities are bound by the principles of non-violent direct action. We are holding a camp immediately before the trespass so that everyone involved has a voice in planning the action itself.
“On the day of the trespass, we will attempt to reintroduce some of the biodiversity that has been stripped through EDF’s premature preliminary works.
“Once inside we will scatter wildflowers and other species native to this site.
“EDF is Eagerly Destroying Fields even though it doesn’t yet have permission to build the reactors – nor does it have approval for the reactor design, or even a final investment decision.”