The Identification and Control of Microorganisms at Three Mile Island Unit 2

Microbial contamination of the reactor and related systems at Three Mile Island Unit 2 caused concern because of the ability of microorganisms to facilitate corrosion and to degrade the underwater visibility. Microorganisms first had a direct impact on defueling and decontamination operations in mid-1985 when the visibility in the fuel pools became limited due to a large population of euglena. In early 1986, the defueling operators experienced a total loss of visibility in the reactor caused by higher order microorganisms in the water. While the development of control techniques was complicated by the radionuclides and the chemical constituents in the water, adequate biological control was accomplished using hydrogen peroxide as a biocide. No evidence of microbially induced corrosion was observed on any components removed from the reactor, the defueling tools, or the fuel storage canisters.