a lot of information can be found in the ISPE website: It is wise to be a member of the ISPE. There are also member fora that could help you.
some points to address:
A nitrogen cryovessel is some kind of a freezer so therefore if you look in that perspective. you should qualify it like a freezer;
A vapour phase systems works like a heat pump:
energy (heat) leaking into the tank is conducted down to the liquid via hte racks. this energy is absorbed by the liqueis as it vaporises, cooling the tank to an equilibrium. The tank lid is the ony non-vacuum insulated surface, is the main paht for heat leak. Therefore a narrow neck vessel has a lower heat leak than the width neck vessels.
please remember that the cells will freeze in the gas phase of the LN and not in the liquid phase.
I will point out some important thinks you should qualify:
volume of the vessel amount of racks should be oke and the way it is stored above the Liquid phase.
lid should be be able to lock
light in the vessel
temperature gradient in the gas phase
volume alarm (to much LN or to less LN)
open lid alarm (time should be predetermined)
data aquisition of the temperature system
callibration of the temperature probes on different levels in de vessel
documentation needed for electrical schemes, alarmen as build test ect
SOP for storage, maintenance filling procedure ect
hopefully I give you some appropriate answers
it is not that much of a work the difficulty is in to find callibrated probes for these low temperatures.