Radioactive cesium chloride can sometimes glow blue in the dark. https://en.wikipedia.org/wiki/Goi%C3%A2nia_accident#Opening_the_capsule

Plutonium RTG sources don't glow, but they have attracted fatal attention by being hot: https://en.wikipedia.org/wiki/Lia_radiological_accident#The_accident

If alien biology is present, I think bioaccumulation of radioactive substances, as suggested in another post, is an interesting direction to take.

People frequently survive radiological accidents. If you want to make it realistic, read up on the above accidents and others, decide source type and strength, exposure time and technology level of medical treatment, and wrap your drama around that.

Have you read "The Martian" by Andy Weir? >!He wanted to include a radiological accident with an RTG, but couldn't find a way to make it realistic without killing the protagonist.!< He does his best at making the science realistic, and I think his stories, and especially the world-building, are all the better for it.