Will radioactive water be spread?

Tsunamis (and waves in general) don't actually move the water they're traveling through over any significant distance. It's the wave's energy that's moving, not the water itself.

Like the "Maxican Wave" spectators form in a stadium during games. Here the wave moves, but people don't.

this is only true until the sea meets land.

Exactly. The water level is raised, and then water "falls" along the path of least resistance, in the case of shore - it will certainly flow onto land.

If the water did spread, it would also dilute the radioactivity. So not really a concern.

Operating equipment like a particle accelerator is surely not cheap. If they decide that it would be better to share time on newer equipment rather than face the rising maintenance costs of older, less capable equipment, scrapping it is likely the best option.