Stuck, 0 bytes

In Stuck, an empty program prints Hello, World!.

Radiation will have no effect on this program because it has no bits.

I got the idea for this from "Hello, World!"

Google Sheets, 67 bytes

=let(x,"Hello, World!",y,"Hello, World!",if(x=y,x,"Hello, World!"))

The formula can take a hit in any of the three Hello Worlds except the space therein. The only way to bitflip that string so that it throws an error would be to change one of the characters to " (00100010₂). That cannot happen with letters because they have a 1 in the second left position, and the string doesn't contain a b (01100010₂). The space (00100000₂) can be bitflipped to a quote though.

The formula can also take many kinds of hits in the latter instance of x, and certain kinds of hits elsewhere. For example, the latter = (00111101₂) can be bitflipped to < (00111100₂) while keeping the formula functional. I'm ignoring those "safe" hits for the time being, as well as the space bitflip.

Hits in these substrings will thus be assumed to be fatal: