Recognizing exceptional behaviour is an important element in a just culture.
What are you rewarding:
Exceptional behaviour takes place in the context of the overall Safety Management System. A person has reached out, or intervened to "lend the system a hand" where it fell short. But, in the end the working of the overall system, and achieving the shared objective of safety for all was the primary objective of the person. That is truly exceptional behaviour.
There is another variant, and that is where a person behaves exceptionally, mainly to prove his own skill, or rank or to boost his ego in general. These people will find evidence for "the system falling short" all the time, and use this to display their own skill or to assert their superiority over their peers.
Because these two lie so closely together, it is important that in recognizing and rewaring exceptional behaviour you clearly communicate what exceptional actions this person has taken to support the overall system and the mission, and especially how his skills and expertise in working the system has enabled him to do so. For the person, the prevents him falling into the ego-trap, and for the organization this sets the right model.
How you are rewarding:
Very often, explicit, correct and public recognition of what somebody has done is its own reward. The appreciation a person gets for his actions, the respect gained from peers and the increased self-worth will make the experience a very rewarding one. In light of this, reducing the reward to a tangible thing like a prize can even devalue the experience. It is very nice to have contributed to a just cause.
What is very possible is that you reward people who work like this by allowing them to be a trusted reference point for others, by giving them a training, coaching or supervisory position.
Again, in all these situations it is important to protect the person from inadvertently being pushed into the ego-trap: make sure he is proud of what he did, and does not become overly proud of who he is.
In case the good performance is consistently displayed across the team, not just by one particular person, the team management should also be rewarded. Again, the same points apply: make sure you reward the fact that they have organized and managed a team so well in understanding the system and building skills to work with it and anticipate on it. Help them share this information on "how they do this", giving them peer recognition. But also here: beware of the ego-trap!