One reason that irradiated food is not readily available in most grocery stores is that

Avariety of foods have been approved for irradiation in the united states, for several different purposes. for meats, separate approval is required both from the fda and the usda.however, irradiated foods are not widely available yet. some stores have sold irradiated fruits and vegetables since the early 1990s. irradiated poultry is available in some grocery stores—mostly small, independent markets— and on menus of a few restaurants. on the other hand, most spices sold wholesale in this country are irradiated, which eliminates the need for chemical fumigation to control pests. american astronauts have eaten irradiated foods in space since the early 1970s. patients with weakened immune systems are sometimes fed irradiated foods to reduce the chance of a life-threatening infection. in addition, irradiation is widely used to sterilize a variety of medical and household products, such as joint implants, band-aids, baby pacifiers, cosmetic ingredients, wine and bottle corks, and food packaging materials.

I'm not sure but i will try to find out