If hafnium produces this hard radiation only when stimulated to perform a Jerome effect, then those missiles could be carried assembled, as while their own stutterwarp drives are off line the coils don't accumulate charge (this is the base for the whole tugs use to reach distances over 7.7 LY).
The main problem then would be about recovering undetonated missiles, as they should have such charges...
Assembled but "inactive" drives apparently still accumulate charge. This is the risk of tugs take. The new drive must be assembled and brought online. The task is difficult (11+ on d10) with drive engineering as the skill, a typically skilled engineer will fail 80% of the time.
The ask is hazardous, so 3d6 on the failure table.
3-10 = retry (with determination check if 6-10, but this is probably unnecessary)
11-14 = mishap (2d6 on table below)
15+ = serious mishap (3d6 on table below)
Mishaps:
3-6 = superficial damage (drive is still okay and task can be attempted again, repair parts cost 1-10% of drive cost),
7-11 = minor mishap (drive is damaged, but no casualties, 5-50% of drive cost to repair),
12-15 = major mishap (drive seriously damaged, EP=1 explosion applied against engineers, 10-100% cost of repair),
16-18= total mishap (drive destroyed, EP=3 explosion applied against engineers, cost of repair 20%+, but 60% of the time nothing is salvagable).
The "normal" result of attempting to bring a drive online is a minor mishap. Tugships aren't viable because of the difficulty of getting the drive powered up.
Taking an active drive down is worse (15+ on d10), and has worse consequences.
A skill 3 engineer (CQ+2, typical well trained engineer) succeeds 30% of the time, gets a second chance 35% of the time, 12% of the time superficial damage occurs (try again, but long term repair costs), the remaining 23% of the time the drive is damaged beyond local repair and is no longer operable.
Bear this in mind, you break the drive about not quite half the time you try and bring it online.
Tugships are not truly viable for this reason.
The same applies to missiles. About one time in twenty the missile drive will explode, which is...... problematic.