Compact modular cassette systems and methods for the synthesis of radiopharmaceutical products are provided, the compact modular cassette system including a modular unit having valve plates, a reaction cassette, a reagent pack, and other seal and connector plates to ensure that reagents can be mixed together inside one or more chambers of the reaction cassette in a timely and efficient manner. When a new chamber for each new reaction or process should be used, a valveless modular system having removable reaction cassettes and the reagent packs may be used. In such a system, the reagent container, the reaction cassette, or both, can be removed from the modular cassette system and discarded after a desired reaction or process has taken place.