I do tend to believe that even if all the nuclear fuel spills into the ocean, the effect is negligible compared with all the other pollution ... like, elevated levels of mercury in tunas globally due to pollution from coal power plants, bleaching of coral reefs due to elevated CO2-levels in the oceans, sea levels rising, etc. I tend to believe the problem is not nuclear power as such, but that our lifestyle requires only more and more power, and all sources of power is problematic to some degree.

Regarding nuclear power, what seems most important is to shut down the eldest and least secure plants. There are still Chernobyl-style reactors running - not only that the design of newer reactors are much, much more secure than the Chernobyl-style design, but also that the old reactors are ... simply, old. Nuclear reactors do have limited lifetime. Shutting down a nuclear plant without building a replacement plant first may be non-trivial - hence, the fierce popular resistance against nuclear power is one of the reasons why nuclear power is unsafe.