The triplicate sampling and analysis will be performed 3 times over the course of 6 weeks  The shelf life of the WRM is expected to be 24 months; however, after 12 months the WRM values are to be reverified by triplicate analysis.  The ongoing use of the WRM as an LCS will also verify the stability of the solution. D.8 SAMPLING THE WRM The WRM shall be diluted gravimetrically in triplicate. Samples will be aliquoted in volumes of 1.5 mL each (~30 mg uranium per sample). This process will follow the sampling plan given by ORNL/TM-2020/1657, Nuclear Analytical and Chemical Isotopics Laboratories Sample Analytical Plan for Spent Fuel Specimens, Section 2. The weights of each aliquot shall be documented. The uncertainties of the weight measurements shall be factored into the final analyte concentration NOTE: The uncertainties associated with these dilutions must also be factored into the final analyte uncertainty. The diluted WRM samples will be portioned out into two fractions; Equivalent of 20-25 mg uranium, gravimetrically according to ORNL/TM-2020/1657, Nuclear Analytical and Chemical Isotopics Laboratories Sample Analytical Plan for the Sister Rod Spent Nuclear Fuel Specimens, (Section 2)  These subsamples will be submitted for Davies-Gray analysis (to be performed according to CSD-AM-NCL-IN04, Modified Davies-Gray Titration: The Determination of Uranium by Iron(II) Reduction in Phosphoric Acid Followed by Chromium(VI) Titration.  Details for the gravimetric spike of plutonium, curium, and americium analytes are given in Appendix D-B (Table D-B.1)  The separations and analyte characterizations will then be performed via the methodologies described in ORNL/TM-2020/1657, Nuclear Analytical and Chemical Isotopics Laboratories Sample Analytical Plan for the Sister Rod Spent Nuclear Fuel Specimens. NOTE: Owing to differing isotopic composition of the elements used in the WRM, the suggested enriched isotopic spike levels are provided in Appendix D-B, Table D-B.3. D.9 UNCERTAINTY ANALYSISThe total uncertainties associated with each analyte concentration will be calculated, using the principles of the Guide to the Expression of Uncertainty in Measurement (GUM), to a 95% confidence level (k = 2). D.10 ASSIGNED VALUES AND VERIFICATION The assigned values for elemental content in the WRM will be defined by the certificate concentration on the NIST-traceable reference materials and the total weight added. The assigned values will be given in micrograms per gram of uranium, essentially negating any potential issues with evaporation over time.  The measured analytes will be used to verify assigned values in micrograms per gram of uranium.  The WRM analyte verification will be accepted if the measured value and the determined value are within the respective uncertainties of the measurement methods. D.11 REQUIRED RECORDS Document all laboratory work in a project-numbered notebook according to the Records Management subject area in the Standards-Based Management System. D-5 ORIGEN Model with details about the irradia...

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