Why worry about radiation aboard early Soviet submarines?

What radiation risks are meant in the comparison with Soviet nuclear submarines?

Some early boats had reactor and coolant-system problems that could expose crews, and an escape capsule does not resolve a slow leak during operation.

The concern focuses on some early Soviet submarines and their reactor and coolant systems. Leaks could expose a crew to radiation while the boat remained in operation. An escape capsule would not solve that kind of slow exposure, and not every submarine carried one. The issue is therefore different from abandoning a vessel during an immediately obvious sinking.