That's completely incorrect. Gun assemblies are the **primary** users of polonium triggers. By design, by material choice, and due to the laws of physics, polonium triggers always have a half-life of fewer than 90 days.
Furthermore, tritium is not a trigger as you allude above; it is a booster.
Gun Assemblies **requires** neutron triggers, by the way. It's that trigger that sparks the chain reaction.
In contrast, implosion assemblies use compression to spark a chain reaction.
You're pretty new around here, by the way. If you have a nuclear question, or just feel the need to spout various nuclear mythology that's in the public domain, ping me.
I'll set you straight time and again (and that's what you want, right, the truth??).