As strategic infrastructures, nuclear facilities are considered attractive targets for attackers to commit their malicious intention. At the same time, for efficiency, those infrastructures are increasingly implemented, equipped with, and managed by digitally computerized systems. Attackers, therefore, try to realign their attack scenarios through such cyber systems. It is crucial to understand various existing risk assessment methods for cybersecurity in nuclear facilities to prevent such attacks. Risk assessment is designed to study the nature of the originated attack threats and the consequences implied. This paper studies a series of risk assessment methods implemented for security related to cybersecurity of strategic infrastructures, including nuclear facilities. Extended from cybersecurity, the required concepts in nuclear security cover defense-in-depth, synergy of safety and security, and probabilistic safety/risk assessment. Selecting cybersecurity risk assessment methods should integrate these three essential concepts in their evaluation. This paper highlights the suitable and appropriate risk assessment methods that meet security requirements in the nuclear industry as specified in the national and international regulations.