This [Yareli] build is made for the new Secondary Irradiate arcane released in the Old Peace. Recommended secondaries are [Tenet Cycron], [Kuva Nukor], and [Ocucor]. I would suggest a toxin progenitor to put viral on the weapon, and smite will give you bonus Radiation damage.
Archon shards are completely up to you, I don't have [Flow] or blue shards on my build, but if you really care about energy I'd do a tau blue. Otherwise I chose to put 5 tau reds for cc, but this build is very flexible, and no shard is a requirement.