Nuclear Energy has been appointed as the main candidate to supply in the near future the energy needed to extract hydrogen from water or from steam-methane reforming process. This association will generate a new and complex industrial plant. As in any other industrial system, to assure safe operation of this plant, many risk analyses will need to be performed. In recent years, the traditional Hazard and Operability Study (HAZOP) has frequently been used as a first risk analysis approach of similar engineering cases. Considering the non-comparable characteristics of this new hybrid system (Hydrogen generation/Nuclear Power Plant), a new safety analysis approach was developed to perform this task. First, the concept of the traditional failure mode and effects analysis (FMEA) for the risk priority number (RPN) has been adapted and applied to HAZOP study. Thus, a HAZOP_rpn concept was created. The HAZOP_rpn is able to evaluate the risk level over the system caused by an abnormality on the physical phenomena. The approach created from the fusion of the HAZOP and traditional RPN has been named hybrid HAZOP. Following this, the fuzzy inference was established over hybrid HAZOP system defining another approach to safety assessment and risk estimation, named Fuzzy Hybrid Hazop (FHH). In this paper, these new approaches and concepts are applied to steam-methane reforming hydrogen production plant linked to a high-temperature gas-cooled nuclear reactor (HTGR). In the traditional Probabilistic Safety Assessment (PSA) study, an operational historic and failure data information are absolutely necessaries, however, using the FHH the critical initiating events and their consequences can be determined from the experts� opinions. The set of results demonstrated the great adherence of the fuzzy hybrid HAZOP approach to this kind of problems. It also endorses the advantages of using a fuzzy inference system to model the uncertainty parameters levels in risk analysis.

HAZOP, fuzzy, PSA, nuclear-powered hydrogen plant.