We present a combined TEVA-DGA chromatography chemistry to purify single-element fractions of Pu, Am, and Np from bulk (mg-level) U materials. Plutonium and Np are first sorbed onto TEVA resin using ...a 4 + redox adjustment with a hydroxylamine hydrochloride and sodium nitrite treatment, with U + Am eluting directly onto DGA resin. Americium is then purified from U on DGA using 0.1 M HNO
3
as a U eluent. A subsequent TEVA column is used to separate Pu from Np using hydrogen peroxide to oxidize Np into the 5 + oxidation state for elution through TEVA. Our presented TEVA-DGA method is able to produce high-purity, single-element fractions of Pu (90% recovery), Am (98% recovery), and Np (62% recovery) from mg-levels of U, and does so in three days of column chemistry.
We present a chromatography chemistry for purifying protactinium from uranium metal alloys containing weight-percent concentrations of niobium. Niobium is precipitated in 9 M HCl
without
the ...co-precipitation of Pa as demonstrated by gamma-ray spectrometry. Protactinium is further purified using Bio-Rad™ anion resin AG® 1-X8 and 9 M HCl + 0.0128 M HF. A Pa/Nb separation factor of 85,000 and a 90% Pa recovery is demonstrated, which is amenable to
231
Pa concentration determination by isotope dilution and
231
Pa/
235
U model age calculation for nuclear forensics.
The accurate interpretation of uranium metal
230
Th/
234
U and
231
Pa/
235
U radiochronometry model ages requires an understanding of how uranium parent nuclides and decay progeny (
230
Th and
231
...Pa) behave during uranium metal casting. In order to directly measure the spatial distribution of
230
Th and
231
Pa in uranium metal before and after vacuum induction melting (VIM), Los Alamos National Laboratory identified uranium metal feedstock, characterized the metal feedstock, conducted a controlled casting experiment of an approximately 120 kg uranium metal rod, and characterized the cast metal. This study presents radiochronometry results and quantified
230
Th and
231
Pa VIM separation factors from bulk uranium.
The isolation and purification of protactinium from uranium materials is essential for
231
Pa–
235
U radiochronometry, but separating Pa from uranium-niobium alloys, a common material in the nuclear ...fuel cycle, is challenging due to the chemical similarity of Pa and Nb. Here we present three resin chromatography separation techniques for isolating Pa from U and Nb which were independently developed by three different laboratories through ad hoc adaptations of standard operating procedures. Our results underscore the need for and value of purification methods suitable for a diversity of uranium-based materials to ensure the operational readiness of nuclear forensics laboratories.
The radiochronometric model age is an important signature in nuclear forensic analysis. Recent studies have illustrated the need for controlled experiments on the behavior of decay products during ...uranium metal casting to provide a foundation for interpretation of discordant model ages. A variety of uranium metal and alloy samples cast under known conditions were analysed by three laboratories. This work is the first multi-laboratory study of its kind to explore how these progeny isotopes are chemically fractionated from uranium metal during casting. The intercomparison allowed for capability demonstration and method development on samples and provided data to increase our understanding of the behavior of decay progeny in these complex systems.
In this study, data from thirteen laboratories from around the world are presented for a successful certification of uranium isotope ratios in uranium ore concentrate (UOC) certified reference ...materials from the National Research Council Canada. Different mass spectrometric measurement principles (including SF‐ICP‐MS, quadruple ICP‐MS, TIMS, MC‐ICP‐MS, SIMS and AMS) and measurement procedures were employed. In general, data from all sources exhibit good consistency with TIMS and MC‐ICP‐MS showing superior performance. The three candidate UOC CRMs (UCLO‐1, UCHI‐1 and UPER‐1) have natural uranium isotope ratios with certified values of 0.5304(7) × 10−4, 0.5475(2) × 10−4 and 0.5361(4) × 10−4 for n(234U)/n(238U) and 0.007 2563(13), 0.007 2563(10) and 0.007 2542(11) for n(235U)/n(238U), respectively, with expanded uncertainty (k = 2) applicable to the last digit of the value given in the parentheses. Information values for n(236U)/n(238U) in these three CRMs, measured by AMS, are also provided: 10 × 10−12, 200 × 10−12 and 22 × 10−12. The uncertainties of the proposed certified values of uranium isotope ratios in UOC CRMs are superior to available reference materials, and the values of n(234U)/n(238U) and n(236U)/n(238U) show significant variation among the three CRMs.
Key Points
Collaboration involving 13 international laboratories employing different mass spectrometric measurement principles (SF‐ICP‐MS, Q‐ICP‐MS, TIMS, MC‐ICP‐MS, SIMS, AMS) and measurement procedures.
Successful certification of uranium isotope ratios in uranium ore concentrate CRMs UCHI‐1, UCLO‐1 and UPER‐1 from the National Research Council Canada.
Suitable for validation of methods used for uranium isotope ratio measurements.
Improved methods employed at Los Alamos National Laboratory for
231
Pa/
235
U radiochronometry are outlined. We present elution curves obtained during
233
Pa tracer preparation from
237
Np. ...Additionally, we report model ages for uranium certified reference materials (CRMs) exhibiting a range of
235
U enrichments including the first
231
Pa/
235
U model ages for CRMs U200 and U900. Our results enable these CRMs to be used, with increased confidence, as quality control materials during nuclear forensics investigations.
A nuclear forensics investigation involving a uranium ore concentrate relies on accurate and precise analysis of impurities. Analytical data defensibility requires the use of reference materials as ...part of quality control. This study presents a compilation of trace element concentration results of the CUP-2 Uranium Ore Concentrate Standard measured by 11 different laboratories. The laboratories employed various dissolution methods, analytical preparation methods, and instrumental platforms. The data presented here contain concentrations of 66 impurities with up to 138 individual data points for each impurity. Consensus values have been assigned to each impurity following a statistical analysis of the data set.
Application of the
231
Pa/
235
U radiochronometer for nuclear forensic investigations is challenged by a lack of certified reference materials with
231
Pa/
235
U model purification dates. The Japan ...Atomic Energy Agency, Los Alamos National Laboratory, and Lawrence Livermore National Laboratory completed an interlaboratory study measuring
231
Pa/
235
U model ages of New Brunswick Laboratory CRM U100. Results from independent laboratories were combined to calculate a consensus
231
Pa/
235
U model purification date for CRM U100 of March 26, 1959 ± 237 days. This
231
Pa/
235
U consensus date for CRM U100 may be used by the nuclear forensic community for quality control of
231
Pa/
235
U radiochronometry measurements of unknown materials.