THE WASTE ISOLATION PILOT PLANT: A SUCCESS STORY HAPPENING NOW

摘要

The Waste Isolation Pilot Plant (WIPP) repository (Fig. 1) in New Mexico is the world’s only operatingdeep geological repository for safe disposal of long-lived radioactive wastes/materials (LLRM). It hasbeen: 1) certified by the United States (U.S.) Environmental Protection Agency (EPA), and 2) permittedby the New Mexico Environment Department (NMED) for safe disposal of up to 175,584 cubic meters(m3) of defense-generated, transuranic radioactive waste (TRUW)a. The waste includes approximately 12tons of plutonium with a half-life in excess of 24,000 years, remote-handled (RH)a TRUW containerswith surface dose rates of up to 10 sieverts per hour (Sv/h), and 50,000 m3 of regulated hazardousconstituents. The WIPP repository is situated at a depth of approximately 650 m a 250-million-year-old,600-m-thick, virtually impermeable bedded salt formation, the Salado Formation (Fig. 1). Contacthandled(CH)a TRUW contained in standard 208-liter drums or standard waste boxes (SWBs) will bestacked three high in the disposal rooms and surrounded by bagged magnesium oxide (MgO) backfill.RH TRUW canisters measuring 0.66 m in diameter with a maximum length of 3.07 m and a maximumweight of 3.63 tons will be emplaced in pre-drilled horizontal holes in the walls of the disposal rooms.The salt surrounding the disposal rooms will gradually encapsulate the emplaced waste within a fewhundred years, thereby creating a virtually impermeable monolith. In addition to being virtuallyimpermeable and self-healing, another significant advantage of undisturbed bedded salt like that found atthe WIPP site and region is the geological structure. This structure justifies the development andapplication of relatively simple conceptual and numerical models for post-closure safety and performanceassessments (SAs/PAs) that are readily understood and credible. Prior to the certification of WIPP, theability of the WIPP repository to contain and isolate LLRM, i.e., the WIPP Safety Case, was subjected toan intense, multi-year review by the public, oversight groups, and regulators. It was crediblydemonstrated that the WIPP repository will safely contain the emplaced TRUW for at least 10,000 years,even if breached by multiple human intrusions. Specifically, the natural barriers at the WIPP site provideat least a ten-fold, and more likely at least a 30-fold, safety factor relative to the very stringentrequirements defined in the radioactive waste disposal regulations.The siting, design, construction, and certification process that preceded the March 1999 opening of WIPPwas not easy, quick, or cheap. However, it resulted in many valuable lessons learned. Furthermore,conditions embodied in the governing laws,(1,2) certification,(3) and permit(4) for WIPP require the U.S.Department of Energy (DOE) Carlsbad Field Office (CBFO), formerly the Carlsbad Area Office (CAO),to maintain scientific and operational programs for at least another 35 years. By establishing activestrategic partnerships and collaborations with the CBFO, other organizations stand to benefit from theintellectual and financial investments residing at CBFO.