Closed town means Highly RESTRICTED AREA because its related with State secrets, manufacturing for Military/Defence, Nuclear, Space industry. No any Foreign nationals are allowed to visit such restricted areas. Some such restricted areas not able visit even russian citizens, some areas allowed, but not recommended.
Therefore:
1) Raduzhny town is in the list of restricted areas ( its settlement of defence industry and design bureau workers/ specialists)
2) YOU not able/ not allowed travel there