The Savannah River Site, in conjunction with AREVA Federal services, has designed a processto treat dissolved radioactive waste solids with ozone. It is known that in this radioactive wasteprocess, radionuclides radiolytically break down water into gaseous hydrogen and oxygen, whichpresents a well defined flammability hazard. Flammability limits have been established for bothozone and hydrogen separately; however, there is little information on mixtures of hydrogen andozone. Therefore, testing was designed to provide critical flammability information necessary tosupport safety related considerations for the development of ozone treatment and potential scaleupto the commercial level. Since information was lacking on flammability issues at low levelsof hydrogen and ozone, a testing program was developed to focus on filling this portion of theinformation gap. A 2-L vessel was used to conduct flammability tests at atmospheric pressureand temperature using a fuse wire ignition source at 1 percent ozone intervals spanning from noozone to the Lower Flammable Limit (LFL) of ozone in the vessel, determined as 8.4%(v/v)ozone. An ozone generator and ozone detector were used to generate and measure the ozoneconcentration within the vessel in situ, since ozone decomposes rapidly on standing. The lowerflammability limit of hydrogen in an ozone-oxygen mixture was found to decrease from the LFL of hydrogen in air, determined as 4.2 % (v/v) in this vessel. From the results of this testing,Savannah River was able to develop safety procedures and operating parameters to effectivelyminimize the formation of a flammable atmosphere.
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