What are some Hazardous substances used in nuclear reactor?

Some hazardous substances used in nuclear reactors include uranium, which serves as fuel, and plutonium, a byproduct of nuclear reactions that can be used in advanced reactors. Other hazardous materials include radioactive isotopes like cesium-137 and strontium-90, which can be produced during fission. Additionally, substances like boron and cadmium are used as neutron absorbers, and coolant chemicals can also pose hazards if improperly handled. Proper safety measures are essential to manage these substances and mitigate risks.