Hanford waste tanks - light at the end of the tunnel

The U.S. Department of Energy (DOE) faced several problems in its Hanford Site tank farms in the early nineties. It had 177 waste tanks, ranging in size from 55,000 to 1,100,000 gallons, which contained more than 55 million gallons of liquid and solid high-level radioactive waste (HLW) from a variety of processes. Unfortunately, waste transfer records were incomplete. Chemical reactions going on in the tanks were not totally understood. Every tank had high concentrations of powerful oxidizers in the form of nitrates and nitrites, and some tanks had relatively high concentrations of potential fuels that could react explosively with oxidizers. A few of these tanks periodically released large quantities of hydrogen and nitrous oxide, a mixture that was potentially more explosive than hydrogen and air. Both the nitrate/fuel and hydrogen/nitrous oxide reactions had the potential to rupture a tank exposing workers and the general public to unacceptably large quantities of radioactive material. One tank (241-C-106) was generating so much heat that water had to be added regularly to avoid thermal damage to the tank's concrete exterior shell. The tanks contained more than 250 million Curies of radioactivity. Some of that radioactivity was in the form of fissile plutonium, which represented a potential criticality problem. As awareness of the potential hazards grew, the public and various regulatory agencies brought increasing pressure on DOE to quantify the hazards and mitigate any that were found to be outside accepted risk guidelines. In 1990, then Representative, now Senator Ron Wyden (D-Oregon), introduced an amendment to Public Law 101-510, Section 3137, that required DOE to identify Hanford tanks that might have a serious potential for release of high-level waste