Comment (3) from Curt Pendergrass, KY Radiation Health, Department for Public Health

-----Original Message----- From: Pendergrass, Curt (CHFS DPH) Sent: Friday, October 12, 2007 1:18 PM To: 'Janet Schlueter' Subject: FW: CsCl source issue Hello Ms. Schlueter, My Branch Manager, Dewey Crawford, forwarded a copy of your e-mail to me. I am a Toxicologist and not a chemist but the solution to this whole problem with CsCl2 seems pretty straight forward at least to my untrained eye. The disadvantage of CsCl2 is its form (powder) and its extremely high water solubility (186 g CsCl2 in 100 g H2O at 20 °C) See http://specialmetals.chemetall.com/pdf/Cesium_Chloride_highest_purity.pdf . These chemical and physical properties make 137CsCl2 easy to disseminate in the hands of a terrorist. Why not just require sealed source manufacturer's to use a different salt of cesium with decreased water solubility? Say for example, Cesium tetrafluoro aluminate complex 50:50 or 60:40? The CsAlF4 has greatly decreased water solubility compared to the CsCl2 used today (approximately 1.2 g in 100 g H2O at 20 °C). If you do the math that is less than 1% the water solubility of CsCl2. The fact that CsAlF4 is available commercially for industrial use, would lead me to believe that manufacturing of this type of cesium salt, even as radioactive 137CsAlF4, is certainly feasible and potentially economically viable. See http://specialmetals.chemetall.com/pdf/Cesium_Tetrafluoro_Aluminate_Complex_5 0-50_industrial.pdf Another possibility would be to use published methods to convert Cs-137 into Cs- loaded Mo-doped hexagonal tungsten bronze (MoW-HTB) oxides, either in the form of fine grained powders, or as composite granules, which then can be converted to leach resistant ceramics at modest temperatures in the range 600– 1200 °C. These types of Cs-137 ceramics can also be readily prepared through very simple conventional routes involving the blending of cesium nitrate with tungstic acid and other oxide components followed by heating in air. See http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXN-4KVXPXN- 2&_user=10&_coverDate=11%2F30% 2F2006&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_ve rsion=1&_urlVersion=0&_userid=10&md5=55804efbe28d6584d6814ec187b4ba3c A ceramic form of 137CsMoW-HTB thus created would be virtually insoluble in water and therefore extremely difficult to disperse. But as I said, I am no chemist. Hopefully some of the people you have chosen to consult on this matter are. I am sure they can come up with better and simpler options. Regards, Curt Pendergrass Radiation Health Specialist Radioactive Materials Section Radiation Health Branch 275 East Main Street Mailstop HS1CA Frankfort, Kentucky 40621 502-564-3700 x 4140 Fax: 502-564-1492