[en] In this work we present novel techniques for high precision index of refraction measurements for transparent crystals, and demonstrate a change from neutron irradiation. Radiation damage affects the structure of material, which can be read out nondestructively in transparent crystals. There is some difference in gamma-ray and neutron interactions which may be useful in characterization. Ionization from gamma rays produces color centers in the material, producing distinct spectral absorption, and some small shift in the index of refraction. Neutrons produce atomic recoils and, while the recoils do some ionization, they have a much greater efficiency for lattice displacement than do gamma rays, and these displacements can have a greater effect on the index of refraction. Using CaF_2 crystals exposed to neutron radiation, together with a new high precision technique of detecting changes of index of refraction, we establish proof that this type of measurement can be used to monitor neutron exposure. This can provide a basic study of material changes with radiation and, with calibration of material in known neutron fields, this may even find application to neutron dosimetry

[en] Highlights: • A reactor burnup benchmark of TINDER, coupling MCNP6 to CINDER2008, was performed. • TINDER is a poor candidate for fuel depletion calculations using its current libraries. • Data library modification is necessary if fuel depletion is desired from TINDER. - Abstract: Accurate burnup calculations are key to proper nuclear reactor design, fuel cycle modeling, and disposal estimations. The TINDER code, originally designed for activation analyses, has been modified to handle full burnup calculations, including the widely used predictor–corrector feature. In order to properly characterize the performance of TINDER for this application, a benchmark calculation was performed. Although the results followed the trends of past benchmarked codes for a UO₂ PWR fuel sample from the Takahama-3 reactor, there were obvious deficiencies in the final result, likely in the nuclear data library that was used. Isotopic comparisons versus experiment and past code benchmarks are given, as well as hypothesized areas of deficiency and future work

[en] The Wright Nuclear Structure Laboratory has recently acquired a gas-filled recoil separator previously used at Berkeley National Laboratory for heavy-element synthesis. The separator will be used to separate reaction recoils from primary beam particles and fission products following target bombardment. Commissioning of the separator has recently been completed, and the structure of ²⁰³Rn investigated

[en] Highlights: • Air radiolysis can be used as a secondary marker for stand-off detection of nuclear materials. • Ozone has a lower background than other radiolytic products in air but with a high radiolytic yield. • Special nuclear materials are strong alpha emitters, with a denser ionization in air than gammas. • The current work examines ozone production from a ²¹⁰Po alpha-particle source. • Measurements examine O3 yields for flowing air and low build-up times, to saturation at long times. Radioactive materials ionize air surrounding them and produce molecules such as ozone and nitrogen oxides. Concentrations of these species above background can serve as a marker for radioactive materials and provide a means for stand-off detection of nuclear materials. Ozone is one of the primary radiolytic products in air and has a lower background level than oxides of nitrogen, so it is a molecule of interest for this study. Actinides of interest include ²³⁹Pu and ²³⁵U, which are strong alpha emitters which have a high linear energy transfer in air. Ozone yield, saturation, and decay time are dependent on creation and destruction processes which change with charge density, ozone density, radiation dose rate, and type of radiation, motivating measurements of ozone yield and saturation level from alpha radiation with dose rates more typical of actinide sources. As a stand in for Pu and U, studies were performed on ozone yield in air from the alpha particle emitter ²¹⁰Po. The sample was enclosed in a 0.96 ± 0.01 L Teflon cylinder and both air flow and build-up measurements were performed, with air flow of ~1 L/min and build up times to 3966 min corresponding with 2640 Gy. Build up measurements showed an ozone concentration increase at short times (t ≤ 10 min) with a yield of G(O₃) = 7.7 ± 0.3 molecules/100 eV. Air flow measurements showed a radiation chemical yield for ozone of G(O₃) = 7.6 ± 0.2 molecules/100 eV. These yields are larger than in previous, very old alpha particle studies but consistent with low rate gamma and electron beam studies. To use ozone as a secondary marker of special nuclear materials the saturation level in still air is important. The extracted ozone saturation level in the cylinder is 1.35 ppm with a half life of 74 ± 3 min.

[en] Although nuclear transmutation methods for fission have existed for decades, the focus has been on neutron-induced reactions. Recent novel concepts have sought to use both neutrons and photons for purposes such as active interrogation of cargo to detect the smuggling of highly enriched uranium, a concept that would require modeling the transmutation caused by both incident particles. As photonuclear transmutation has yet to be modeled alongside neutron-induced transmutation in a production code, new methods need to be developed. The CINDER2008 nuclear transmutation code from Los Alamos National Laboratory is extended from neutron applications to dual neutral particle applications, allowing both neutron- and photon-induced reactions for this modeling with a focus on fission. Following standard reaction modeling, the induced fission reaction is understood as a two-part reaction, with an entrance channel to the excited compound nucleus, and an exit channel from the excited compound nucleus to the fission fragmentation. Because photofission yield data—the exit channel from the compound nucleus—are sparse, neutron fission yield data are used in this work. With a different compound nucleus and excitation, the translation to the excited compound state is modified, as appropriate. A verification and validation of these methods and data has been performed. This has shown that the translation of neutron-induced fission product yield sets, and their use in photonuclear applications, is appropriate, and that the code has been extended correctly. - Highlights: • The CINDER2008 transmutation code was modified to include photon-induced transmutation tracking. • A photonuclear interaction library was created to allow CINDER2008 to track photonuclear interactions. • Photofission product yield data sets were created using fission physics similarities with neutron-induced fission

[en] Radiation ionizes surrounding air and produces molecular species, and these localized effects may be used as a signature of, and for quantification of, radiation. Low-level ozone production measurements from radioactive sources have been performed in this work to understand radiation chemical yields at low doses. The University of New Mexico AGN-201 M reactor was used as a tunable radiation source. Ozone levels were compared between reactor-on and reactor-off conditions, and differences (0.61 to 0.73 ppb) well below background levels were measured. Simulations were performed to determine the dose rate distribution and average dose rate to the air sample within the reactor, giving 35 mGy of mixed photon and neutron dose. A radiation chemical yield for ozone of 6.5±0.8 molecules/100 eV was found by a variance weighted average of the data. The different contributions of photons and neutrons to radiolytic ozone production are discussed. - Highlights: • Localized ozone production in air may be an indicator of radioactive material. • Radiolytic ozone work is dominated by high radiation fields in the saturation regime. • For low level measurements we used a reactor as a mixed photon/neutron source. • Monte Carlo simulations were performed to understand the dose profile to air. • Different contributions to ozone production are discussed for neutrons and photons

[en] Gas ionization detectors are very widely used for radiation detection and measurement, but for external sources an entrance window is used which can reduce particle energy. For heavy ions this energy loss can be significant enough to affect measurements and very thin windows, such as those composed of silicon nitride (SiN), may be utilized to minimize this effect. For fission spectroscopy, carbon conversion foils are also common in measurements. In the current work, energy losses were measured for ²⁵²Cf spontaneous fission products passing through thin foils of carbon and of silicon nitride. The foils ranged in from 22.5 to 131.0 µg/cm² for C and from 56.4 to 402.2 μg/cm² for SiN. For comparison, simulations were performed with the TRIM program in SRIM-2013 and with MCNP6.2. To understand calculation differences, effective charge from partial ionization was predicted by several methods and compared with results directly using the Bethe stopping power formula.

No abstract available

[en] The Wright Nuclear Structure Laboratory has recently acquired a gas-filled recoil separator previously used at Berkeley National Laboratory for heavy-element synthesis. The separator will be used to separate reaction recoils from primary beam particles and fission products following target bombardment. Commisioning of the separator has recently been completed, and the structure of 203Rn investigated

[en] Ground-state proton radioactivity has been identified from ¹²¹Pr. A transition with a proton energy of E_p=882(10) keV [Q_p=900(10) keV] and half-life t_1/2=10_-3⁺⁶ ms has been observed and is assigned to the decay of a highly prolate deformed 3/2⁺ or 3/2^- Nilsson state. The present result is found to be incompatible with a previously reported observation of ground-state proton radioactivity from ¹²¹Pr, which would have represented the discovery of this phenomenon