[en] Radiation detectors used to search for the existence of exceptionally rare phenomena, such as double-beta decay and dark matter interactions, as well as tiny traces of environmental radioactivity, require the elimination of background signals. Modern detection systems created from ultra pure materials and operated deep underground may be sensitive enough to 'see' these rare phenomena, but background activity in Pb gamma-ray shielding could still be a critical stumbling block owing to alpha and beta emissions of Pb, Bi, and Po in the mass 210 chain. To minimize the probability of overwhelming activity from Pb, the alpha activity of 210Pb is quantified. However, a reliable quantification procedure that does not require large volumes of chemicals has not yet been established. Two procedures created for this purpose have been tested for the quantification of alpha activity in lead. Both procedures were designed to start with less than 10g Pb samples to reduce reagents needed and combined precipitation with column separation to isolate 210Pb, followed by alpha spectrometry. One procedure shows promise for obtaining high recoveries and good separation.

[en] Understanding the dissolution characteristics of uranium oxides is of fundamental scientific interest. Bench scale experiments were conducted to determine the optimal dissolution parameters of uranium(IV) oxide (UO₂) powder in solutions of ammonium carbonate ((NH₄)₂CO₃) and hydrogen peroxide (H₂O₂). Experimental parameters included variable peroxide and carbonate concentrations, and temperature. Results indicate the dissolution rate of UO₂ in 1 M (NH₄)₂CO₃ increases linearly with peroxide concentration ranging from 0.05 - 2 M (1:1 to 40:1 mol ratio H₂O₂:U), with no apparent maximum rate reached under the limited conditions used in our study. Temperature ranging studies show the dissolution rate of UO₂ in 1 M (NH₄)₂CO₃ and 0.1 M H₂O₂ (2:1 mol ratio H₂O₂:U) increases linearly from 15 C to 60 C, again with no apparent maximum rate reached. Dissolution of UO₂ in solutions with constant (H₂O₂) and ((NH₄)₂CO₃) ranging from 0.5 to 2 M showed no difference in rate; however dissolution was significantly reduced in 0.05 M (NH₄)₂CO₃ solution. The results of this study demonstrate the influence of (H₂O₂), ((NH₄)₂CO₃), and temperature on the dissolution of UO₂ in peroxide-containing (NH₄)₂CO₃ solutions. Future studies are planned to elucidate the solution and solid state complexes in these systems.

[en] A boron carbide capsule has been designed and used for spectral-tailoring experiments at the TRIGA reactor at Washington State University. Irradiations were conducted in pulsed mode and in continuous operation for up to 4 hours. A cadmium cover was used to reduce thermal heating. The neutron spectrum calculated with MCNP was found to be in good agreement with reactor dosimetry measurements using the STAY'SL computer code. The neutron spectrum resembles that of a fast reactor. Design of a capsule using boron carbide enriched in ¹⁰B shows that it is possible to produce a neutron spectrum similar to ²³⁵U fission.

[en] A boron carbide shield was designed, custom fabricated, and used to create a fast fission energy neutron spectrum. The fissionable isotopes 233, 235, 238U, 237Np, and 239Pu were separately placed inside of this shield and irradiated under pulsed conditions at the Washington State University 1 MW TRIGA reactor. A unique set of fission product gamma spectra were collected at short times (4 minutes to 1 week) post-fission. Gamma spectra were collected on single-crystal high purity germanium detectors and on Pacific Northwest National Laboratory's (PNNL's) Direct Simultaneous Measurement (DSM) system composed of HPGe detectors connected in coincidence. This work defines the experimental methods used to produce and collect the gamma data, and demonstrates the validity of the measurements. It is important to fully document this information so the data can be used with high confidence for the advancement of nuclear science and non-proliferation applications. The gamma spectra collected in these and other experiments will be made publicly available at https://spcollab.pnl.gov/sites/gammadata or via the link at http://rdnsgroup.pnl.gov. A revised version of this publication will be posted with the data to make the experimental details available to those using the data.

[en] A unique set of fission product gamma spectra was collected at short times (4 minutes to 1 week) on various fissionable materials. Gamma spectra were collected from the neutron-induced fission of uranium, neptunium, and plutonium isotopes at thermal, epithermal, fission spectrum, and 14-MeV neutron energies. This report describes the experimental methods used to produce and collect the gamma data, defines the experimental parameters for each method, and demonstrates the consistency of the measurements.

[en] A novel reaction pathway for production of "2"4"0Am is reported. Models of reaction cross-sections in EMPIRE II suggest that deuteron-induced activation of a "2"4"0Pu target produces maximum yields of "2"4"0Am from 11.5 MeV incident deuterons. This activation had not been previously reported in the literature. A "2"4"0Pu target was activated under the modeled optimum conditions to produce "2"4"0Am. The modeled cross-section for the "2"4"0Pu(d, 2n)"2"4"0Am reaction is on the order of 20–30 mbarn, but the experimentally estimated value is 5.6 ± 0.2 mbarn. We discuss reasons for the discrepancy as well as production of other Am isotopes that contaminate the final product