Most modern construction homes, with properly seal basement walls, drainage ect. do not need sump pumps. So it could be removed and sealed, but do you want to?
Depending on where you are when the water table rises, anywhere near where the river flows today they are having this issue, you can still get seepage from it if there is any defects in the floor or basement walls. If the contractor building the house did not have the landscaping gutters ect. correct do you completely trust their coating of the basement walls? The house I grew up in had a sump and it was there do to there almost always being a high water table. In fact we had the house treated for termites once and they drilled holes in the basement floor to pump the chemical they used under the foundation and every hole they drilled there was a 6" fountain of water that came out.
My recommendation would be consider sump hole suction to reduce your radon. It caps the sump hole while leaving the water sump operational and adds a pump that evacuates excessive amounts of radon from under your home and vents it into the outside air where it gets diluted to a safe level. This way you would be protected (to a degree) from future cracks in the basement floor or walls allowing radon to enter. You would want to discuss your options with a contractor that has experiance in remediating radon issues to be certain that any particular sollution would work for your home.
