Hydrogen is considered an important energy carrier and fuel within the context of sustainable energy technologies. However, finding the ways to produce hydrogen in a more nature-friendly manner is vital while increasing the use of hydrogen in energy applications. In the current study, environmental impacts of five different hydrogen production options via nuclear energy are comparatively assessed through a life cycle assessment (LCA) technique in five impact categories; abiotic depletion potential (ADP), acidification potential (AP), global warming potential (GWP), ozone depletion potential (ODP), and human toxicity potential (HTP). Required thermal and electrical energy for production processes are supplied from nuclear power plants (NPPs). Energy and material inputs for production processes are defined. For the extensive LCA calculations, a powerful software is employed. According to the LCA study results, the GWPs of employed hydrogen production methods, namely high temperature electrolysis (HTE), conventional electrolysis (CE), 3-,4-, and 5-step Cu-Cl cycles, are 0.4768, 0.7071, 1.320, 1.201, and 1.346 kg CO2 eq per kg of hydrogen respectively. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.