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.
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.
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 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.
A multiple ion-counting total evaporation technique has been developed for precise analysis of sub-picogram (pg) quantities of
238
Pu by thermal ionization mass spectrometry (TIMS). A resin bead ...loading procedure was tailored to minimize uranium (U) contamination during loading. This loading technique, coupled with a mass spectrometry protocol that minimizes U ionization and removal of bulk U with ion exchange chromatography, allows for single pg-sized aliquots of plutonium (Pu) to be measured without interference from
238
U. This technique has the potential to provide complete isotopic characterization of trace amounts of Pu by TIMS, without the need for alpha spectrometry.
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.
This interlaboratory study measured thorium concentrations and isotope compositions in uranium ore concentrates from different geographical locations to examine whether thorium impurities may be ...useful forensic signatures for uranium ore concentrates found out of regulatory control. Measured
230
Th/
232
Th in fifteen uranium ore concentrates record over three orders of magnitude of compositional variation. Results demonstrate that
230
Th/
232
Th used in combination with U/Th ratios resulted in a unique signature for individual uranium ore concentrates from different processing locations. Data presented here suggest potential for
230
Th/
232
Th and U/Th to be used as comparative signatures to investigate the provenance of seized uranium ore concentrates.
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.
During 2017–2018 Los Alamos National Laboratory, Lawrence Livermore National Laboratory and the China Institute of Atomic Energy collaborated in an interlaboratory
231
Pa/
235
U radiochronometry ...exercise. The laboratories used different analytical methods to obtain a consensus model purification date for CRM U010 of December 28, 1958 ± 198 days and for CRM U850 of May 20, 1958 ± 363 days. These results agree with previously reported model dates using the
230
Th/
234
U radiochronometer as well as the production histories of these materials. The concordance of interlaboratory data confirms the ability of laboratories to make reproducible radiochronometry measurements using distinct analytical approaches.
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