A method is presented for estimating the possible annual risk that a hydrogen superstructure at a nuclear power plant (NPP) may have in the production of explosive hydrogen. With the observance of safety rules in terms of receiving, storing, transporting and using hydrogen, it is possible to minimize the occurrence of fi re and explosion hazard situations on the hydrogen superstructure. Scheduled repair and overhauls with all diagnostics reduce emergencies and equipment failures in the same way. However, there is a likelihood for the equipment to be found in an abnormal state (breakdown, fi re and explosion) as a result of hydrogen leaks. Depressurization of equipment with leakage of explosive hydrogen in enclosed spaces concurrently with adverse attendant factors may lead to the destruction of the electrolysis plant due to fi re and explosion. With the help of the state graph, the probabilities of a failure of electrolysis equipment because of unplanned breakdowns and possible fi res or explosions indoors due to depressurization of equipment are estimated. To this effect, possible scenarios of breakdowns of the electrolyzer in one and two workshops are considered. In the calculations of the state graph, a system of linear equations was composed for steady-state values only. The calculations have shown that for a configuration involving two electrolysis plants, the possible annual risk would increase. Minimizing the annual risk can be achieved through boosting the capacity of the electrolysis plant still in operation by increasing its productivity in hydrogen and oxygen. The effect will only be achieved if the cost of electricity from nuclear power plants is kept within 0.81 rubles/(kW·h) with a peak electricity tariff at 3.5 rubles/(kW·h).
