OK, lets see,
Tennelec: needs gas, gas regulator, someone who would know how to change bottles and how to check gas pressure, flow, etc daily, Also, sophisticated data formatting software (which I forget what it was called) which causes few problems every now and then and harder to resolve by average joe nuke tech or the instrument tech :-)
Protean: does not need gas, simple operation, load the planchets stack, let it count all through the weekend and leave, and better MDA anyways,
seems simple choice to me at least as far as the nuke plants concerned :-)