PROGRESS IN RETRIEVAL AND CLOSURE OF FIRST HIGH-LEVEL WASTE TANKAT HANFORD: SINGLE-SHELL TANK C-106

摘要

One of the most challenging environmental remediation activities facing the United States is thernretrieval and permanent disposal of approximately 90 million gallons of radioactive waste storedrnin underground tanks at Department of Energy (DOE) facilities. The Hanford Site stores roughlyrn60 percent of this waste. Successful retrieval, treatment, and disposal of this waste represents arnsignificant step towards eliminating potential threats to human health and the environment, andrnreducing the nations stockpile of radioactive waste.rnThe Hanford Federal Facility Agreement and Consent Order (HFFACO) establishes, amongrnother things, regulatory requirements for single-shell tank (SST) waste retrieval and SST farmrnclosure. The HFFACO requires retrieval of as much waste as technically possible, with wasternresiduals not exceeding 360 cubic feet in 530,000 gallons or larger tanks; 30 cubic feet in 55,000rngallons or smaller tanks; or the limit of waste retrieval technology, whichever is less.rnIn fiscal year (FY) 2002, the DOE Office of River Protection (ORP) commissioned thernAccelerated Tank Closure Demonstration (ATCD) Project at the Hanford Site to establish andrndemonstrate the technical, regulatory, and administrative aspects of tank waste retrieval andrninterim closure. Tank C-106 was the first SST retrieved and will be the first SST closed underrnthe auspices of the ATCD Project.rnTank C-106 was built during the early 1940’s with a nominal capacity of 530,000 gallons. It isrnthe third tank in a cascade series of three tanks and contained 10 million curies of radioactivityrnprior to initiation of waste retrieval operations. As a result of high-heat safety issues during thern1990’s and concerns regarding the addition of raw water to control waste temperatures in a SSTrnthat exceeded its design life by several decades, a decision was made to retrieve the waste fromrnTank C-106.rnInitial retrieval of waste from Tank C-106 was conducted during the late 1990’s to successfullyrnresolve the high-heat safety concerns. Final retrieval of waste from Tank C-106 was completedrnin December 2003 using oxalic acid dissolution and modified sluicing methods. Efforts arernunderway to initiate closure of Tank C-106 in accordance with approved closure plans and in arnmanner consistent with the future Record of Decision for the Tank Closure EnvironmentalrnImpact Statement.rnThis paper describes the background, methods, accomplishments, and issues associated withrnretrieving waste from Tank C-106 to the limits of technical feasibility. In addition, future plansrnfor interim and final closure of Tank C-106 are discussed.