OCCUPATIONAL SERVICES INC. - 2006

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Identification and Quantification of Unknown Radiorlw.:lidl's in a Piece of X-Ray Equipment Santa Ana Zoo Pag!.: S of 10 July 25, 2006 EXHIBIT A ~ Occupational Services, Inc. 6397 Nallcl' Ridge Drive' Sail Diego, CA 9212/ Phone: 858-55t5-tJ736 . Fax: 8j8-558-6766 . H'H'H'.occserv.rnm Connie Sv..'cet, Collt:ction Manager Santa Ana Zoo I RO I E. Chestnut ^ vc. Santa Ann, CA 92701 April 12, 2006 I{e: A~l'"eement for the Identificatiun and Quantification of Unknown Radionculides in a Piece of X-Ra:\' Equipment. Dear Connie: I hl-lvC not been able to identify this plCce of e4uipment however, I did locate some information related to thorium valves or thorium vacuum tubes which may be part oflhc electronic circuits in the tank you described and ~howed in a photograph. "Large lransmitting tubes have tungsten filaments containing a small trace of thorium. A thin layer of thorium atoms forms on the outside of the wire when heated, serving as an efficient source of electrons. The thorium slowly evaporates from the wire surface, while new thorium atoms diffuse. to the surface to replace them. Such thoriated tungsten cathodes routinely deliver lifetimes in the tens of thousands of hours." If Thorium is present in t1,e tnnk v..'e may be able to 111casurt: it with st:nsill\'c survt:y meters and perhaps obtain n gamma spectrum identifying the radionuclidt:. r will have to do this at your facility. There is a chance that Thorium may bt: pn:sent, but in quantities too small to measure from the outside of the tank.lfthe tank 1S filled with oil this increases the likelihood that we "".ill not bc able to detect a small amount of thorium ifit is present.lf\ve cannot detect the thorium, then the oil may have to be draint:d from the tank and a survey done on the inside of the tank. This will ha\'e to be dUTlt: a~ a separate project, unless YOll can dmin and collect the oil before I arrive. You may have to do this in any event to properly dispose of both the oil and the piece of equipment. The cost for the survey and a report is fifteen hundred dollar~ ($1,500.00). Payment is due upon receipt of our report. Ifthis agreement nnd the attached terms and conditions are satisfactory lo you please sign below and return a copy to OSr. For: Occupational Services, Inc. For: Santa Ana Zoo ~f.-d. 4-12-0fl Nicola Rinaldi, Health Physicist Date Connie Sweet Date President Collection Manager SEE IMPORTANT TERMS AND CONDITIONS Il'i ATTACHMENT A Payment Terms: Payment dnc upon receipt of report