Those things are locked by a force field. Then, you need to pay attention to a few things:
And that's when you have to take your chances. As difficulty goes higher, the purging cloud comes faster. But at lower difficulties, you can easily fetch those items at your own leisure. They were meant to be retrieved when you are fleeing the purging system. I myself could never reenter them, and they didn't hinder me from my missions either. One of them had 2 of those treasures.
Can you tell me if these cores are needed just to complete the quest asking to gather them, or they do more? Like access to cutscenes, different story plot?
Also I remember I did re-entered kadara's vault after terraforming
My apologies, but I don't remember exactly. The only remnant thing mission I recall is related to Peebee and it's not a task that required those chests. The important chests we have there only have some rare things and the no-sudoku-keys. My first save got corrupted by the new patch and I'm not replaying it right now because I'm not sure what else could have been affected. I'm sparing myself from needless stress.
