The next ices up are ice 2 and ice 3, both of which have densities greater than that of water.

So the pressure of frozen ice might not ever rise above 10^9 Pa, mostly staying a little over 10^8 at most. I could be totally wrong.

If I wanted to design an ice bomb that never exploded, I might make sure there were a structural part that failed before the pressure got too high, not really sure.