Decommissioning of a facility in a historical reactor at SRS: achieving both historical significance preservation and effective in-situ decommissioning - 15275
The Savannah River Site (SRS) is an 802 square-kilometer United States Department of Energy (US DOE) nuclear facility located along the Savannah River near Aiken, South Carolina, where Management and Operations are performed by Savannah River Nuclear Solutions, LLC (SRNS). In 2004, US DOE recognized SRS as a structure within the Cold War Historic District of national, state and local significance because it is composed of the first generation of facilities constructed and operated from 1950 through 1989 to produce plutonium and tritium for our nation's defense. US DOE agreed to manage the SRS 105-C Reactor Facility as a potentially historic property due to its significance in supporting the U.S. Cold War Mission and for potential for future interpretation. The Disassembly Basin (DB) in C Reactor was evaluated for action under CERCLA. Data indicated there were over 830 curies of radioactivity associated with the basin sediments and approximately 9.1 million (M) liters (L) of contaminated water, not including a large quantity of activated reactor equipment, scrap metal, and debris on the basin floor. The release of DB water could potentially migrate to the aquifer and contaminate groundwater. The need for an action was identified to reduce risks to personnel in the facility and to eliminate the possible release of contaminants into the environment. In-situ decommissioning was selected as the remedy. The remedial action proceeded in stages: -Above-grade modifications to the interior of DB building -Relocation of irradiated scrap and reactor components to the deepest segments of the DB - Construction of a metal building to house evaporators - Forced evaporation of the DB's radiologically contaminated water - Grouting with special hybrid grouts - Removal of the evaporators and temporary building. Since the building itself was not demolished and will remain unchanged in appearance with the exception of filling the DB with grout, this ISD removal action/methodology did not adversely impact the historical significance of the 105-C Reactor Building, in accordance with the National Historic Preservation Act, nor did it adversely affect the ability to determine the full extent and details of preservation at some later date. Both special hybrid grout materials met all requirements. Overall average 7-day compressive strength for the dry area mix was 1.54 MPa (223 psi) and for the underwater mix 2.94 MPa (427 psi).Overall 28-day compressive strength for the dry area mix was 2.88 MPa (417 psi) and for the underwater mix 4.99 MPa (724 psi). A limited amount of testing was also performed at 91 days, where the overall compressive strength for the dry area mix was found to be 9.40 MPa (1363 psi) and for the underwater mix 13.98 MPa (2028 psi). All compressive strength values far exceeded the 0.34 MPa (50 psi) minimum requirements. The special, flowable-fill grouts designed and used for P- and R-Reactor ISD and used again for this 105-C ISD removal action resulted in considerable labor, cost, and schedule savings versus conventional materials. As an added bonus/benefit, the CO{sub 2} footprint of the SRS C-Reactor DB ISD was minimized by using a small amount of cement and byproduct material to produce the structural fill materials. (authors)