Viv dae a ANALYTICAL DEVELOPMENT IN PROGRESS The Instruments Brarch of the Health and Safety Laboratory has been developing a scintillation anti-ccincicence counter for low level beta measurements. This is designed around a solution phosphor containing the active material in a volume of 5 to 10 ml. The problem has been worked on by three groups; the Analytical Branch developing the method of obtaining the active material in solution, Professor Kallmann of NYU working on the development of the optimum phosphor, and the Instrunents Branch working on the development of instru- mentation. The chemical operations were largely devoted to the separation of Y°° from the radiostrontium plus strontium carrier obtained in our normal chemical procedures. I+ was desirable to extract the r®° into an organic solvent that would also be a suitable solvent for the fluors; such as terphenyl and the substituted anthracene. Initial experiments showed that certain compledng agents which gave organic soluble compounds with Y also acted as quenchers for the phosphor. This was true of TTA (thenoyl trifluoroacetone). Other reagents such as oxine gave poor extraction coefficients. Tributyl phosphate (TBP) has been used in the extraction of rare earths from very strong nitric acid solution. The resulting organic layers, however, were found to show very great quenching. This is due to the presence of nitric acid mich also extracts into TBP. It was not possible to wash out the HNO,, as the Y activity was also removed in the process. Extracting Y from saturated ammonium nitrate solutions with TBP gave an organic layer which could be prepared as a good liquid phosvhor. The pulse heights obtained are equivalent to phosphors prepared directly from TBP. Both 75% and SO% saturated ammonium nitrate solutions also gave good extraction results, allowing easier manipulation than if completely saturated. This technique should allow the reacy measurement of very low levels of Y°° as carrier-free isotope, since the background of such a scintillation counter could be maintained at @ lowlevel. This procedure may also be used for determination of Ce*** which is one of the known non-fractionating fission products present in aged fallow debris. The second development is the use of a@ comparative logarthmic absorption plot for isotors identification. In this methec;: the logarithm of the relative activity of the unknown with various aluminum absorbers is plotted against the logarithm of the relative activity of a known isotope such as P**. ten) CVa UNSLASSIFIZO 7 The slope of the resultin