Aspects of the present disclosure include systems that include reaction vessels and reaction vessel caps. In certain aspects, the reaction vessels include a reaction chamber and a groove disposed around a top opening of a reaction chamber. The system also includes a RV cap that includes a cap body, a RV plug, and a lower wall that includes an outer radial groove disposed above an outward projecting ridge of the lower wall. When the cap is inserted into the RV, the RV plug of the RV cap is sealingly inserted into the reaction chamber of the RV, a ridge of the RV mates with the outer radial groove of the RV cap, and an outward projecting ridge of the RV cap mates with the radial groove of the RV. Also provided are methods and sample analysis systems, which may employ the RV/RV cap systems of the present disclosure.