Simplify the following text for a Grade 13 native English-speaking person.
Original: There is concern about the levels of nuclear waste the former Soviet Union dumped in the sea which included six nuclear submarine reactors and ten nuclear reactors , and the effect this will have on the marine environment .
Simplified: There is concern about radioactive contamination from nuclear waste the former Soviet Union dumped in the sea and the effect this will have on the marine environment . According to an official `` White Paper '' report compiled and released by the Russian government in March 1993 , the Soviet Union dumped six nuclear submarine reactors and ten nuclear reactors into the Kara Sea between 1965-1988 .