I think instead of death penalty they should work for factories without pay and that's their penalty.
instead of dying without doing anything why don't they just work for something that could help others lives
I agree. Totally. The best way to punish them is to make them work for the benefit of the society.
For example, they could have been involved in the recovery and clean-up of the Fukushima or Chernobyl Accidents instead of innocent people who lost their lives to save the mankind.
"The next task was cleaning up the radioactivity at the site so that the remaining three reactors could be restarted, and the damaged reactor shielded more permanently. About 200,000 people ('liquidators') from all over the Soviet Union were involved in the recovery and clean-up during 1986 and 1987. They received high doses of radiation, averaging around 100 millisieverts. Some 20,000 of them received about 250 mSv and a few received 500 mSv. Later, the number of liquidators swelled to over 600,000 but most of these received only low radiation doses. The highest doses were received by about 1000 emergency workers and on-site personnel during the first day of the accident."
As regards death penalty, I believe it's a waste of money. There are better ways to use those guys...