I am certain that the shielding on these was totally adequate.
I read that the former soviet union had a bunch of these as well, and that many disappeared
and I am sure that ours were set to detonate immediately upon being armed, would be shocked if they were not
I would not be surprised if the shielding on them was so inadequate, that after lugging one on your back for a couple of days, you were going to die of radiation exposure anyway.