What is minimum safe bend radius for rg213 cable?
It will vary from manufacturer to manufacturer. One general rule is not bend less than 10 times the diameter of the cable. So a cable that is 0.5 inches in diameter should have a radius of no less than 5 inches.
This for free formed loops. If part of a fixed assembly the bend radius can be less.
Much depends on the type of insulation used. Over time, the center conductor can actually displace the insulation and end up moving toward the shield. This will change the impedance and might eventually lead to a short.