There's lots of info on the Net about "seed collecting, "seed saving," and "seed storage."
Come to think of it, there have been a few discussions here at THG on those topics as well.
Even though you're harvesting the seed after letting the plant go to flower and the flowers go to seed, the accepted terms seem to be the ones I listed above; the term "seed harvesting" isn't generally used (even though it's probably the most descriptive).
My rapini seed pods will probably burst open next week or the week after, along with my komatsuna pods. Broccoli romanesco, too. I had no grand seed-saving plan; I just got behind in harvesting the plants a while ago. When they flowered, the bees visited them. I can't bring myself to deprive bees of flowers they like, so...now I have TONS of seed pods...I'll just have to dig the plants up to plant new veggies this month, but I've still seen bees feeding on stray flowers...
I know; it's a personal problem...
Happy gardening and seed saving!
Sunset Zone 17, USDA Zone 9