Device and method for preventing reactor core from melting and preventing radioactive substances from being released to environment

The invention discloses a device and a method for preventing a reactor core from melting and preventing radioactive substances from being released to the environment. The device comprises a pressure container, a steam generator and a safety injection system which are arranged in a containment, wherein a special isolation valve is arranged on a main steam pipeline in the containment, the safety injection system comprises a safety injection pump, a special water injection pipeline is connected between the safety injection pump and the descending section or the bottom of the pressure container, and a special safety injection valve is arranged on the special water injection pipeline. According to the invention, when the main steam pipeline is broken in front of the main steam isolation valve outside the containment in a non-isolated manner or a steam generator safety valve is blocked off, and a steam generator heat transfer pipe is broken, the special isolation valve in the containment isclosed to isolate a coola