The Waste Isolation Pilot Plant (WIPP) site in New Mexico, USA, hosts the world’s only operating deep geological repository for safe disposal of long-lived radioactive wastes/materials (LLRMs) that can serve as a unique state-of-the-art source, resource, and role model for other similar programs. When filled to capacity, the WIPP repository will contain and isolate 175,584 m3 of LLRMs, including 12 to 17 tons of plutonium-239 (239Pu) and containers with surface dose rates of up to 10 sieverts per hour (Sv/h). Clearly, the safe long-term performance of a repository containing 239Pu, which has a half-life in excess of 24,000 years, is of paramount importance to current and future generations and environments. Typically, considerable reliance is placed on engineered barriers systems (EBSs) to contain and isolate LLRMs with very long half-lives, such as 239Pu. In contrast, the WIPP disposal concept relies on the host geological-media (rock salt) to contain and isolate the disposed LLRMs. Therefore, the WIPP repository demonstrates that:
• Deep geological disposal of LLRMs is safe and can be accomplished without costly EBSs; and
• A carefully sited and designed repository in rock salt provides the optimal natural solution to safe deep geological disposal of LLRMs.