How can we restrict some crucible users reaching SVN repository in our team?

[Fatma Nur Sevgi]

Our company uses crucible for code review. Also we uses additionally Jira and SVN with crucible. We noticed that when we review a code with crucible by using svn repository, sometimes everyone see the code which will review, sometimes no one see the code. While we review a code with crucible, certain members should see the code and the others should not see the code which will review. In addition to that, these certain members will determined by administrator. 

Could you help us for this problem ? We are glad of other features of crucible but this svn usage problem is adversity for us.