WANO, IAEA, INPO, NRC have all put together a series of traits, principles and behaviours and these should be considered alongside your company’s goals, vision and behaviours to produce your own culture. People, process and systems is the framework of our culture. The way we do things!
A Self Assessment questionnaire can be developed to measure your maturity.
here is a document from the IAEA telling you how to do this but I think that it is best to use your own. Base it on the grid I have put in the above diagrams