On July 4, 1994, during daily inspection of Resources Conservation and Recovery Act regulated tanks, Rocky Flats Building 771 operations personnel discovered small leaks at the valve flanges of three tanks. The tanks currently contain only small amounts of plutonium contaminated liquid in drain lines or in the bottom of the tank. The contamination was contained in the containment wrap surrounding the tank's drain valve flanges on two of the tanks, while the wrap on the third tank had removable alpha contamination up to 1,000,000 disintegrations per minute (dpm). There was no contamination on the floor beneath the contaminated wrap. The operator who discovered the contamination was wearing three pairs of surgeon's gloves and a full face respirator as required by the radiological work permit for the surveillance. One of the gloves was contaminated with 50,000 dpm of removable alpha but no other contamination was detected on the operator. (ORPS Report RFO--EGGR-771OPS-1994-0041)
Managers immediately posted the area as requiring anti-contamination clothing and facility personnel wrapped the contaminated containment wrap. Managers also instructed facility personnel to decontaminate and tighten the leaking flanges within twenty-four hours, as required for Resources Conservation and Recovery Act regulated tanks. There was no release of radioactivity nor damage to any equipment.
While reviewing this event, ONS personnel learned that all flanged piping containing liquids at Rocky Flats has flanges covered with shrink wrap made of shrinkable polyethylene material. Some piping containing acid also has pH-sensitive paper within the transparent containment wrap. Site personnel believe that this treatment helps to detect incipient flange leakage and thus minimize the spread of contamination. Rocky Flats has practiced this flange treatment since 1973 and site personnel believe that it has resulted in significant reduction in the spread of contamination and cleanup costs. DOE personnel can obtain additional information on the application of shrink wrap, material specification, or procurement by contacting Steve Pfaff, DOE facility representative at Rocky Flats, at (303) 966-6713.
The use of shrink wrap as a barrier to prevent spread of contamination is consistent with DOE policy described in DOE/EH-0256T, Radiological Control Manual, which states "DOE shall ensure that radiation exposures to its workers and the public and releases of radioactivity to the environment are maintained below regulatory limits and deliberate efforts are taken to further reduce exposures and releases in accordance with a process that seeks to make any such exposures or releases as low as reasonably achievable." The manual provides further guidance on radiological design considerations in article 128.