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<br />Identification and Quantification of{Jnkno\vn RadlO11uclldes in a Pieee of X-Ray Equipment <br />Santa Ana Zoo <br /> <br />Page Xof 10 <br />July 25, lOOt) <br /> <br />EXHlRlT A <br /> <br />~ <br /> <br />Occupafional Services, Inc, <br />6397 NaJUY Ridge Drive - San Diego, CA 92121 <br />Pho!ll-'_' 858-558-6736 . FiLL 858-558-6766 . H'lVWoccserv.com <br /> <br />Connie Sweet, Collection MilIlJgC[ <br />Santa ^na Zoo <br />IXOI E. Chestnut Ave. <br />Santa An3, CA 92701 <br /> <br />Apri I ] 2, 2006 <br /> <br />Re: Agreement for the Identification and Quallliticalion of Unknown Radionculides in a JJiece of X-Ray <br />E'llJipment. <br /> <br />Dear Connie: <br /> <br />I have [Jut been able to identify this piece ofcqllipment hov....ever, I did locate some information related to thorium ,,'alves <br />or thorium vacuum tllhcs which may be part of the electronic circuits in the tank you descrihcd and showed in a <br />photograph. <br /> <br />"Large transmitting tubes have tungsten filaments containing a small trace of thorium. A thin layer of thorium atoms <br />forms on the outside of the wire when heated, serving as an efficient source of electrons. The thorium slowly evaporates <br />from the wire surface, while new thorium atoms diffuse to the surface to replace them, Such thorlated tungsten cathodes <br />routinely deliver lifetimes in the tens of thousands of hours." <br /> <br />If Thorium is present in the tank v.'e may be able to mt:asurc it with sensitive survey meters nnd perhaps obtaltl a gamma <br />spectrum identif)!Jng the raulUnuclide, r will ha\'c to do this at your uicility. There is a chanl.:e that Thorium may be <br />pn:sent, but in quantities too small 10 mCilsure from the outside of the tank. Iftbt: tank is filled with oil this increases the <br />likelihood that we \",ill not be able to detect a small amount of thorium if it is present. ffwc cannot detect the thorium, <br />then the oil may have to be draitwd from the tank and a survey done on the inside of tile tank. This wi]] h<1\'c to he done as <br />a separate project, unless you can drain and collect the oil beJi.)re I arrivl:. You may have to do this in any event to <br />properly dispose of both the oil and the piece of equipment. <br /> <br />The cost for the survey and a repOlt is fIfteen hunJr~J dollars ($1,500.00). Payment is due upon receipt of our report. <br /> <br />[fthis agreement and the attached terms and conditions are satisfactory to you please sign below and rchlm a copy to OSL <br /> <br />For: <br />Occupational Services, lnc. <br /> <br />.for: <br />Santa Ana Zoo <br /> <br />~/.....d <br /> <br />Nicola Rinaldi, Health Physicist Dale Connie Sweet Date <br />President Collection Manager <br />SEE L\IP()I{TANT TERMS AND CONDITiONS IN ATTACHMENT A <br />Payment Terms: Payment due upon receipt of report <br /> <br />4-1:2-0fl <br />