A new primary standardization of 229Th

Baerg, 1981, Multiple channel 4-Pi-Beta-gamma-anti-coincidence counting, Nucl. Instrum. Meth. Phys. Res., 190, 345, 10.1016/0029-554X(81)90298-6 Baerg, 1976, Live-timed anti-coincidence counting with extending dead-time circuitry, Metrologia, 12, 77, 10.1088/0026-1394/12/2/006 Berger, M.J., 2000. Counting yields for beta and alpha particle sources. NISTIR 6464. BIPM et al., 1995. Guide to the expression of uncertainty in measurement. International Organization for Standardization, Switzerland. Cassette, 1992, Experimental evaluation of Tdcr models for the 3 Pm liquid scintillation-Counter, Nucl. Instrum. Meth. Phys. Res. A, 312, 95, 10.1016/0168-9002(92)90135-Q Dickens, 1981, Energies and intensities of gamma-rays from decay of Th-229 and daughters in equilibrium, Radiochem. Radioanal. Lett., 47, 331 ENSDF, 2006. Evaluated Nuclear Structure Date File. 〈http://www.nndc.bnl.gov/ensdf/〉, Brookhaven National Laboratory (Upton, NY). Fitzgerald, 2008, Liquid-scintillation-based anticoincidence counting of Co-60 and Pb-210, Appl. Radiat. Isot., 66, 937, 10.1016/j.apradiso.2008.02.037 Gunther, E., 2003. CN2003, Private Communication. Helmer, 1986, Emission probabilities of gamma-rays associated with the decay of Th-229 and its daughters, Appl. Radiat. Isot., 37, 139, 10.1016/0883-2889(86)90062-6 ICRU, 1994, Particle Counting in Radioactivity Measurements, ICRU Report 52, 56-57, International Commission on Radiation Units and Measurements (Bathesda, MD). Inn, 2008, A blueprint for radioanalytical metrology CRMs, intercomparisons, and PE, Appl. Radiat. Isot., 66, 835, 10.1016/j.apradiso.2008.02.022 Laureano-Perez, 2007, A liquid-scintillation-based primary standardization of Pb-210, Appl. Radiat. Isot., 65, 1368, 10.1016/j.apradiso.2007.06.012 LNHB, 2007. LS Sources Data, published online at the website of the Labortoire National Henri Becquerel. Lucas, 1998, Calibration of the massic activity of a solution of Tc-99, Appl. Radiat. Isot., 49, 1061, 10.1016/S0969-8043(97)10020-3 NIST, 2000. Standard Reference Material 4927F, Hydrogen-3 Radioactivity Standard, Certificate, available upon request and at 〈http://ts.nist.gov/measurementservices/referencematerials/〉. NIST, 2007. Electron Stopping Power and Range Tables (ESTAR), available online at 〈http://physics.nist.gov/PhysRefData/Star/Text/ESTAR.html〉. ORNL, 2007. Specifications for High Purity Th-229, Nuclear Medicine Program, Oak Ridge National Laboratory. Rattan, 1981, A method for the simultaneous estimation of Th-228 and Th-229, J. Radioanal. Chem., 67, 95, 10.1007/BF02516233 Taylor, 1994 Wolfram Research, I., 2001. Mathematica. Version 4.1. Zimmerman, 2004, Construction and implementation of the NIST triple-to-double coincidence ratio (TDCR) spectrometer, Appl. Radiat. Isot., 60, 433, 10.1016/j.apradiso.2003.11.055 Zimmerman, 2004, Application of the triple-to-double coincidence ratio method at national institute of standards and technology for absolute standardization of radionuclides by liquid scintillation counting, Radioanal. Methods Interdiscip. Res.—Fundam. Cutting-Edge Appl., 868, 76, 10.1021/bk-2004-0868.ch006 Q(John Keightley): My question is regarding the impurity ratio of Th-228 to Th-229 which you stated was determined as (1.7±0.2)×10−2. You said that the peaks were well resolved, and since this value is simply a ratio, could you comment on the magnitude of the uncertainty, which is approximately 10%. A(Ryan Fitzgerald): The 10% uncertainty is a consequence of the spread of results from NIST's alpha-spectrometry and gamma spectrometry measurements. Q(Arvic Harms): Is the Th-228 supported, or simply decaying? A(Ryan Fitzgerald): It is simply decaying.