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