Cesium-exchanged Type 4A zeolites can encapsulate high-pressure tritium by physical entrapment in interior pores. We present data on storage capacity related to physical pore volume in the zeolite, and show that storage stability is reasonably good for short periods. Our data also shows that the zeolite releases helium while retaining tritium. Results are analyzed in terms of a diffusion model in the literature. The zeolite showed no structural change after a radiation dose of 108 Gy; it is unclear if radiation affects storage stability.