Natural Uranium Radioactivity Solution Standard: SRM 4321d

A new natural uranium solution standard has been produced and will be disseminated by the National Institute of Standards and Technology (NIST) as Standard Reference Material 4321d. The standard is certified for the massic activities of 234U, 235U, and 238U in solution, and it is based on isotopic mass data for the metallic Certified Reference Material (CRM) 112-A (originally issued as SRM 960) that was obtained from THE U.S. Department of Energy, New Brunswick Laboratory. The metallic CRM was chemically cleaned, dissolved, and gravimetrically diluted to prepare a master solution, which was quantitatively dispensed into 5 mL aliquots that were contained within flame-sealed glass ampoules for each SRM unit. Homogeneity among SRM units, verifying solution homogeneity, was substantiated by photonic-emission integral counting with a NaI(Tl) well counter. Confirmatory measurements were performed by liquid scintillation counting for the total massic activity, and by isotope dilution α spectrometry for the 234U and 238U massic activities.

Preparation of 188 W from Unenriched Targets in Middle Flux Nuclear Reactors

Ways of increasing massic activity of 188W resulting from irradiation of tungsten targets in the middle flux nuclear reactor IRT-T have been analyzed. Calculation and experimental results of evaluating the influence of blocking effect on accumulation of target radionuclides are presented. The possibility to increase effective activation cross section by creating definite target shape has been experimentally proven.