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Due to their high specificity and efficacy, RNA interference (RNAi)-based strategies have been used for fundamental functional genomics studies in a number of insects. However, its potential for translational applications in pest management is also of great interest. The lack of suitable RNAi triggering approaches, however, so far has largely precluded the implementation of RNAi-based approaches to target aphids. In this work, we first demonstrate that Flock House virus (FHV), an insect virus, can infect multiple aphid species, including the green peach aphid, Myzus persicae (M. persicae), the corn leaf aphid, Rhopalosiphum maidis (R. maidis), and the bird cherry-oat aphid, Rhopalosiphum padi (R. padi), by both microinjection and oral feeding. Using green fluorescent protein (GFP) as an indicator, we showed that the defective interfering RNA (DI-634) of FHV RNA2, which is generated autonomously during wild-type (WT) virus replication, can carry foreign sequences, and further for their functional expression. More importantly, the engineered DI-634 was incorporated into virus particles in co-infections with WT FHV. Using FHV virions containing genetically modified DI-634, the accumulation levels of the M. persicae mRNAs for Cathepsin L (CatL) and Sugar Transporter 4 (ST4), were decreased by ~ 35% and ~ 30–50%, respectively when virions were injected intrathoracically into aphids. Finally, and of more practical relevance, oral acquisition of these engineered FHV virions caused lethality of M. persicae. In summary, as a proof-of-concept, our work demonstrates that FHV can be a valuable RNAi tool for fundamental research, and suggests opportunities for using engineered insect viruses as biological agents for aphid pest control.

Using data from 82 classroom observations conducted in a large urban school district, we explore how kindergartners spend their time in general and across schools serving children from lower and higher income households. Consistent with prior research, we find that kindergartners spend the majority of instructional time on reading and mathematics, with little time devoted to other subjects. On average, 2.5 hours are spent on noninstructional activities such as transitions. Kindergartners in lower income schools spend more time on reading and mathematics and experience more noninstructional time. They also spend substantially less time being physically active and have fewer opportunities to choose their own activities than their peers in higher income schools.

The technique of spectral radiography has been shown to accurately discriminate a material’s elemental composition by using known X-ray physics. In previous work, we presented a system for determining the total compositional mass of UO2 powder. This is achieved with a state-of-the-art pixelated spectrometer and a high-fidelity physical model. Similar to other radiographs, the system suffers from partial-volume attenuation where the sample projection onto a pixel is only a fraction of the pixel area, leaving the rest unattenuated. This study updates the physical model to account for fractional area which challenges the existing algorithm. We present how this update is made and explore approaches to stabilize the algorithm through parameter scaling, constrained optimization, and hyperparameter selection. We applied the updated algorithm to calculate the total uranium and oxygen mass of UO2 powder simulations. The average relative error on total uranium mass was reduced from 1.4% to 0.068% and on total oxygen mass from 122.2% to 4.2%.

Plastic scintillators based on thermoplastics, such as polystyrene and poly(vinyl toluene) (PVT), are capable of neutron and γ radiation detection via pulse shape discrimination (PSD) when overdope...

This article reports findings from a one-year evaluation of a kindergarten math enrichment program. A randomized design was used to assess the impact of High 5s on children’s math skills, attitudes...

This datasheet on Barley virus G covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Vectors & Intermediate Hosts, Diagnosis, Biology & Ecology, Environmental Requirements, Seedborne Aspects, Impacts, Prevention/Control, Further Information.

Poor program implementation constitutes one explanation for null results in trials of educational interventions. For this reason, researchers often collect data about implementation fidelity when conducting such trials. In this article, we document whether and how researchers report and measure program fidelity in recent cluster-randomized trials. We then create two measures—one describing the level of fidelity reported by authors and another describing whether the study reports null results—and examine the correspondence between the two. We also explore whether fidelity is influenced by study size, type of fidelity measured and reported, and features of the intervention. We find that as expected, fidelity level relates to student outcomes; we also find that the presence of new curriculum materials positively predicts fidelity level.

The Non-Proliferation Treaty and other non-proliferation agreements are in place worldwide to ensure that nuclear material and facilities are used only for peaceful purposes. Antineutrino detectors, sensitive to reactor power and fuel changes, can complement the tools already at the disposal of international agencies to safeguard nuclear facilities and to verify the States’ compliance with the agreements. Recent advancement in these detectors has made it possible to leverage them to reduce the likelihood of an undetected diversion of irradiated nuclear material. Here we show the sensitivity of antineutrino monitors to fuel divergence from two reactor types: a traditional light-water reactor and an advanced sodium-cooled reactor design, a likely candidate for future deployment. The analysis demonstrates that a variety of potential diversion scenarios can be detected by such a system. We outline recent developments in monitoring capabilities and discuss their potential security implications to the international community., Nuclear reactors can be used for energy generation or for dangerous weapons and therefore their monitoring is crucial. Here the authors discuss detecting antineutrino from a nuclear reactor and use it for nuclear safeguards in a diversion scenario.

WOS: 000478608100031, PubMed ID: 31148155, Transfusion-dependent thalassaemia (TDT) requires red blood cell concentrates (RBCC) to prevent complications of anaemia, but carries risk of infection. Pathogen reduction of RBCC offers potential to reduce infectious risk. We evaluated the efficacy and safety of pathogen-reduced (PR) Amustaline-Glutathione (A-GSH) RBCC for TDT. Patients were randomized to a blinded 2-period crossover treatment sequence for six transfusions over 8-10 months with Control and A-GSH-RBCC. The efficacy outcome utilized non-inferiority analysis with 90% power to detect a 15% difference in transfused haemoglobin (Hb), and the safety outcome was the incidence of antibodies to A-GSH-PR-RBCC. By intent to treat (80 patients), 12 center dot 5 +/- 1 center dot 9 RBCC were transfused in each period. Storage durations of A-GSH and C-RBCC were similar (8 center dot 9 days). Mean A-GSH-RBCC transfused Hb (g/kg/day) was not inferior to Control (0 center dot 113 +/- 0 center dot 04 vs. 0 center dot 111 +/- 0 center dot 04, P = 0 center dot 373, paired t-test). The upper bound of the one-sided 95% confidence interval for the treatment difference from the mixed effects model was 0 center dot 005 g/kg/day, within a non-inferiority margin of 0 center dot 017 g/kg/day. A-GSH-RBCC mean pre-transfusion Hb levels declined by 6 center dot 0 g/l. No antibodies to A-GSH-RBCC were detected, and there were no differences in adverse events. A-GSH-RBCCs offer potential to reduce infectious risk in TDT with a tolerable safety profile., Ege University Hospital Blood Centre, Izmir, Turkey

Mixed-spectrum reactors (MXR) have been investigated for a wide variety of applications. Typical MXR core designs are based on fast configurations with moderating material inserted within localized regions of the core. Limited analysis has been conducted on assessing important performance and safety aspects. Three main safety-related metrics are devised in this article to validate the feasibility of MXR designs. A long-lived MXR variant was taken as a case study for this analysis. Reactivity feedback mechanisms were evaluated, along with power peaking effects and fast flux damage. Neutron transport simulations found that distortions are manageable in all three areas, with notable improvements in fluence limits and Doppler broadening coefficients. Power peaking effects can be significantly dampened by slight addition of gadolinium in the fuel and by carefully selecting the reflector material.

An approach for determining the optimal laser parameters (i.e., pulse energy, focused spot size, wavelength, and pulse duration) for correlating single-event transients induced via two-photon absorption (TPA) and heavy ions is presented. The approach focuses on identification and extraction of waveform characteristics, or “features,” and minimizing the error between features produced by TPA and ions. Modifying optical parameters can directly impact the waveform features of the TPA-induced transients. Consequently, optimal laser parameters that minimize the error between features extracted for laser- and ion-induced waveforms can be determined. In this paper, the laser pulse energy and spot size were varied, while maintaining a fixed pulse duration and wavelength, and the resulting transients were compared to ion-induced transients. When the optimized optical parameters are used, excellent agreement was achieved between laser- and ion-induced transient waveforms in a silicon-germanium heterojunction bipolar transistor (SiGe HBT). In addition, a one-to-one correlation between heavy-ion linear energy transfer (LET) and laser pulse energy was obtained for a particular spot size ( $\omega _{0} = 1.89\,\,\mu \text{m}$ (HW $1/e^{2}$ )). These results show that a correlation between LET and pulse energy is achievable when the remaining optical parameters are selected appropriately. Although the results presented are for SiGe HBTs, the generality of the approach should allow it to be extended to other semiconductor platforms.

Multimetallic layered composites (MMLCs) have shown an excellent potential for application under extreme environments, e.g., accident-tolerant fuel cladding, because of their low oxidation tendency and high corrosion resistance. Interfacial phases or complexions in nanocrystalline materials accelerate the annihilation of defects and enhance the radiation resistance of materials, making MMLCs with engineered interlayer phases compelling to deploy in extreme conditions. However, implementation of MMLCs in full capacity remained a challenge due to a lack of fundamental understanding of the underlying mechanisms governing the characteristics of the interface between the metallic layers. The precise role of interlayer phases in MMLCs and their interaction with defects, specifically under extreme conditions, is still unexplored. Pursuing atomistic simulations for various Inconel-Ni MMLCs model materials, we revealed accelerated defect mobility in interlayers with larger crystalline misorientation and the inverse relationship between the interface sink strength to the misorientation angle. Furthermore, we found a linear relation between interlayer misorientation angle with the density of radiation-induced defects and radiation enhanced diffusion. Finally, our results indicate that radiation-induced material degradation is accelerated by the higher defect formation tendency of MMLCs with a high-angle interlayer interface.

If dark matter has mass lower than around 1 GeV, it will not impart enough energy to cause detectable nuclear recoils in many direct-detection experiments. However, if dark matter is upscattered to high energy by collisions with cosmic rays, it may be detectable in both direct-detection experiments and neutrino experiments. We report the results of a dedicated search for boosted dark matter upscattered by cosmic rays using the PROSPECT reactor antineutrino experiment. We show that such a flux of upscattered dark matter would display characteristic diurnal sidereal modulation, and use this to set new experimental constraints on sub-GeV dark matter exhibiting large interaction cross-sections., 11 pages, 8 figures

Plastic scintillators offer a cost-effective and scalable option for detection of special nuclear materials. Traditional plastic scintillators are based on thermoplastics such as poly(vinyl toluene) (PVT) and polystyrene. When over-doped with select fluorescent molecules, PVT and polystyrene scintillators are capable of distinguishing between neutrons and gamma ray via pulse shape discrimination (PSD). While this formulation has been extensively studied and commercialized, the resulting scintillators are restricted to applications involving rigid thermoplastics. In order to achieve flexible and elastomeric properties, a new class of elastomer scintillators based on polysiloxanes has been explored. This work details elastomeric polysiloxane scintillators based on a commercial resin and a commercial primary dopant, 2,5-diphenyloxazole (PPO) and a synthesized dopant, 9,9-dimethyl-2-phenyl fluorene (PhF). PPO-polysiloxane scintillators showed PSD capabilities surpassing commercial thermoplastic analogues at low concentrations of PPO (FoM 1.33 ± 0.03 at 450 keVee for 5wt% PPO). PhF-polysiloxane scintillators were also capable of PSD, comparable to the commercial sample, but notably had a high light yield, of 144% EJ-299-33. This work serves as a proof of concept that polysiloxane scintillators can be capable of good PSD and high light yield at low dopant loadings.

In proton-based radiotherapy, proton radiography could allow for direct measurement of the water-equivalent path length (WEPL) in tissue, which can then be used to determine relative stopping power (RSP). Additionally, proton radiographs allow for imaging in the beam's-eye-view. In this work, a proton radiography technique using a flat-panel imager and a pencil-beam scanning (PBS) system is demonstrated in phantom. Proton PBS plans were delivered on a Varian ProBeam system to a flat-panel imager. Each proton plan consisted of energy layers separated by 4.8 MeV, and a field size of 25 cm × 25 cm. All measured data is binned into a layer-by-layer delivery in post processing. To build a calibration curve correlating detector response to WEPL, the plans were delivered to slabs of solid water of increasing thickness. Pixel-by-pixel detector response in the time/energy domain is then fit as a function of WEPL. Tissue equivalent phantoms are imaged for evaluation of WEPL accuracy. A spatial resolution phantom and a head phantom are also imaged. For all experiments, the detector was run with an effective pixel size of 0.4 mm × 0.4 mm. The proposed method reconstructed RSP with mean errors of 2.65%, -0.14%, and 0.61% for lung, soft tissue, and bone, respectively. In a 40 mm thick spatial resolution phantom, a 2 mm deep pinhole with 1 mm diameter can be seen. The accuracy and spatial resolution of the method show that it could be implemented for patient position verification. Further development could lead to patient-specific verification of RSP to be used for treatment guidance.

Reactor neutrino experiments have seen major improvements in precision in recent years. With the experimental uncertainties becoming lower than those from theory, carefully considering all sources of ν ¯ e is important when making theoretical predictions. One source of ν ¯ e that is often neglected arises from the irradiation of the nonfuel materials in reactors. The ν ¯ e rates and energies from these sources vary widely based on the reactor type, configuration, and sampling stage during the reactor cycle and have to be carefully considered for each experiment independently. In this article, we present a formalism for selecting the possible ν ¯ e sources arising from the neutron captures on reactor and target materials. We apply this formalism to the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, the ν ¯ e source for the the Precision Reactor Oscillation and Spectrum Measurement (PROSPECT) experiment. Overall, we observe that the nonfuel ν ¯ e contributions from HFIR to PROSPECT amount to 1% above the inverse beta decay threshold with a maximum contribution of 9% in the 1.8-2.0 MeV range. Nonfuel contributions can be particularly high for research reactors like HFIR because of the choice of structural and reflector material in addition to the intentional irradiation of target material for isotope production. We show that typical commercial pressurized water reactors fueled with low-enriched uranium will have significantly smaller nonfuel ν ¯ e contribution.

When post-irradiation materials from the nuclear fuel cycle are released to the environment, certain isotopes of actinides and fission products carry signatures of irradiation history that can potentially aid a nuclear forensic investigation into the material's provenance. In this study, combinations of Pu, Cs, and Ba isotope ratios that produce position (in the reactor core) independent monitors of irradiation history in spent light water reactor fuel are identified and explored. These position independent monitors (PIMs) are modeled for various irradiation scenarios using automated depletion codes as well as ordinary differential equation solutions to approximate nuclear physics models. Experimental validation was performed using irradiated low enriched uranium oxide fuel from a light water reactor, which was sampled at 8 axial positions from a single rod. Plutonium, barium and cesium were chemically separated and isotope ratio measurements of the separated solutions were made by quadrupole and multi-collector inductively coupled mass spectrometry (Cs and Pu, respectively) and thermal ionization mass spectrometry (Ba). The effect of axial variations in neutron fluence and energy spectrum are evident in the measured isotope ratios. Two versions of a combined Pu and Cs based PIM are developed. A linear PIM model, which can be used to solve for irradiation time is found to work well for natural U fuel with

Background Nucleic acid-targeted pathogen inactivation technology using amustaline (S-303) and glutathione (GSH) was developed to reduce the risk of transfusion-transmitted infectious disease and transfusion-associated graft-versus-host disease with red blood cell (RBC) transfusion. Study design and methods A randomized, double-blind, controlled study was performed to assess the in vitro characteristics of amustaline-treated RBCs (test) compared with conventional (control) RBCs and to evaluate safety and efficacy of transfusion during and after cardiac surgery. The primary device efficacy endpoint was the postproduction hemoglobin (Hb) content of RBCs. Exploratory clinical outcomes included renal and hepatic failure, the 6-minute walk test (a surrogate for cardiopulmonary function), adverse events (AEs), and the immune response to amustaline-treated RBCs. Results A total of 774 RBC unis were produced. Mean treatment difference in Hb content was -2.27 g/unit (95% confidence interval, -2.61 to -1.92 g/unit), within the prespecified equivalence margins (±5 g/unit) to declare noninferiority. Amustaline-treated RBCs met European guidelines for Hb content, hematocrit, and hemolysis. Fifty-one (25 test and 26 control) patients received study RBCs. There were no significant differences in RBC usage or other clinical outcomes. Observed AEs were within the spectrum expected for patients of similar age undergoing cardiovascular surgery requiring RBCs transfusion. No patients exhibited an immune response specific to amustaline-treated RBCs. Conclusion Amustaline-treated RBCs demonstrated equivalence to control RBCs for Hb content, have appropriate characteristics for transfusion, and were well tolerated when transfused in support of acute anemia. Renal impairment was characterized as a potential efficacy endpoint for pivotal studies of RBC transfusion in cardiac surgery.

With nuclear technology and analysis advancements, site access restrictions, and ban on nuclear testing, computationally-generated nuclear forensic signatures are becoming more important in gaining knowledge to a reclusive country’s weapon material production capabilities. In particular, graphite-moderated reactors provide an appropriate case study for isotopics relevant in Pu production in a clandestine nuclear program due to the ease of design and low thermal output. We study the production characteristics of the X-10 reactor with a goal to develop statistically-relevant nuclear forensic signatures from early Pu production. In X-10 reactor, a flat flux gradient and low burnup produce exceptionally pure Pu as evident by the 240 Pu/ 239 Pu ratio. However, these design aspects also make determining reactor zone attribution, done with the 242 Pu/ 240 Pu ratio, uncertain. Alternatively, the same ratios produce statistically differentiable results between Manhattan Project and post-Manhattan Project reactor configurations, allowing for attribution conclusions.

In imaging arrays, the sensors are typically packed as tightly as possible to maximize spatial resolution, which leads to detector-to-detector scatter, or cross talk, adding to image noise and hindering contrast. In this paper, we compare custom-made quartz-based Cherenkov detectors with an inherent energy threshold to low-energy photons to standard sodium iodide detectors, which are typically used for x-ray detection due to their efficiency and spectroscopic capabilities. In particular, we evaluate pulse pileup and cross talk effects in high-flux applications. The quartz detectors, while having reduced intrinsic efficiency, outperform the sodium iodide with regards to pileup and cross talk. Simulation further shows that even at a 4 mm edge-to-edge separation, cross talk contributes less than 2% of the total signal in Cherenkov detectors.

Background and Objectives Pathogen reduction technology using amustaline (S-303) was developed to reduce the risk of transfusion-transmitted infection and adverse effects of residual leucocytes. In this study, the viability of red blood cells (RBCs) prepared with a second-generation process and stored for 35 days was evaluated in two different blood centres. Materials and Methods In a single-blind, randomized, controlled, two-period crossover study (n = 42 healthy subjects), amustaline-treated (Test) or Control RBCs were prepared in random sequence and stored for 35 days. On day 35, an aliquot of 51Cr/99mTc radiolabeled RBCs was transfused. In a subgroup of 26 evaluable subjects, 24-h RBC post-transfusion recovery, mean life span, median life span (T50) and life span area under the curve (AUC) were analysed. Results The mean 24-h post-transfusion recovery of Test and Control RBCs was comparable (83·2 ± 5·2 and 84·9 ± 5·9%, respectively; P = 0·06) and consistent with the US Food and Drug Administration (FDA) criteria for acceptable RBC viability. There were differences in the T50 between Test and Control RBCs (33·5 and 39·7 days, respectively; P 0·05). Following infusion of Test RBCs, there were no clinically relevant abnormal laboratory values or adverse events. Conclusion RBCs prepared using amustaline pathogen reduction meet the FDA criteria for post-transfusion recovery and are metabolically and physiologically appropriate for transfusion following 35 days of storage.

BACKGROUND Plasma thawed and stored at 1 to 6°C for up to 5 days (thawed plasma [TP]) provides rapid availability in emergencies and reduces plasma waste, but it carries risks of coagulation factor loss or activation, bacterial outgrowth, and viral contamination. We characterized changes in amotosalen/ultraviolet A (UVA) light pathogen-reduced, fresh-frozen plasma (FFP) and plasma frozen within 24 hours (PF24) with post-thaw storage. STUDY DESIGN AND METHODS Amotosalen/UVA light-treated FFP and PF24 were thawed after approximately 3 to more than 12 months of frozen storage and held at 1 to 6°C for 5 days. Global assessments of coagulation and hemostatic, antithrombotic, and activation markers indicative of function were assessed. RESULTS Day 5, thawed amotosalen/UVA light-treated FFP and PF24 contained levels of Factors II, V, VIII, IX, X, von Willebrand factor ristocetin cofactor (vWF:RCo), fibrinogen, antithrombin III (ATIII), protein C, and protein S similar to the levels measured in Day 5 TP, as described in the Circular of Information. Thrombin generation was robust on Day 5 (amotosalen/UVA: FFP = 1866 ± 402 nM/minute; PF24 = 1800 ± 277 nM/minute). Most factor activities on Day 5, including von Willebrand factor-cleaving protease (ADAMTS-13), were more than 90% of Day 0 values, except for known labile Factors V and VIII and protein S. All units contained greater than 0.4 IU/mL protein S and α2 plasmin inhibitor on Day 5. Global functional indices, including thrombin-antithrombin complexes, nonactivated thromboplastin time, and thrombin-generation peak height, did not indicate activation of the coagulation cascade, although isolated units showed raised levels of Factor VIIa and Complement 3a. CONCLUSION Amotosalen/UVA light-treated FFP and PF24 demonstrated retention of procoagulant and antithrombotic activity after 5 days post-thaw storage at 1 to 6°C.

Nuclear forensics has a broad task to characterize recovered nuclear or radiological material and interpret the results of investigation. One approach to isotopic characterization of nuclear materi...

Cargo containers constitute the most critical component of global trade: 108 million containers represent the movement of about 95% of the world's manufactured goods. The steady increase in cargo container shipments has had a profound effect on world security: the threat associated with smuggling of shielded special nuclear material is elevated every year. Containers reaching the borders of the U.S. are currently not radiographically inspected due to time and dose considerations stemming from the use of bremsstrahlung beams for imaging. Bremsstrahlung spectra are low-energy peaked, resulting in low penetration values, especially through dense cargoes. The use of monoenergetic radiography beams could alleviate many of these problems due to higher energy and low background continuum. Using Monte Carlo simulations of a realistic imaging scenario with support from previous experimental measurements, we demonstrate how the use of monoenergetic photon beams in radiography can simultaneously reduce the radiation dose imparted to the cargo and any potential stowaways while increasing image quality. Dual-energy methods are leveraged to calculate material atomic number. Image quality is evaluated by measuring the noise standard deviation, contrast-to-noise ratio, and the pixel error as the dose is decreased.

This Letter reports the first measurement of the ^{235}U ν[over ¯]_{e} energy spectrum by PROSPECT, the Precision Reactor Oscillation and Spectrum experiment, operating 7.9 m from the 85 MW_{th} highly enriched uranium (HEU) High Flux Isotope Reactor. With a surface-based, segmented detector, PROSPECT has observed 31678±304(stat) ν[over ¯]_{e}-induced inverse beta decays, the largest sample from HEU fission to date, 99% of which are attributed to ^{235}U. Despite broad agreement, comparison of the Huber ^{235}U model to the measured spectrum produces a χ^{2}/ndf=51.4/31, driven primarily by deviations in two localized energy regions. The measured ^{235}U spectrum shape is consistent with a deviation relative to prediction equal in size to that observed at low-enriched uranium power reactors in the ν[over ¯]_{e} energy region of 5-7 MeV.

The Precision Reactor Oscillation and Spectrum (PROSPECT) Experiment is a reactor neutrino experiment designed to search for sterile neutrinos with a mass on the order of 1 eV/c$^2$ and to measure the spectrum of electron antineutrinos from a highly-enriched $^{235}$U nuclear reactor. The PROSPECT detector consists of an 11 by 14 array of optical segments in $^{6}$Li-loaded liquid scintillator at the High Flux Isotope Reactor in Oak Ridge National Laboratory. Antineutrino events are identified via inverse beta decay and read out by photomultiplier tubes located at the ends of each segment. The detector response is characterized using a radioactive source calibration system. This paper describes the design, operation, and performance of the PROSPECT source calibration system.

Radiography is a powerful imaging technique that has found widespread use in medicine, security, and inspection of industrial processes. The technique is typically performed using either neutrons or photons, but neither of these probes is universally applicable. The authors experimentally realize a significant improvement in the contrast for small elemental variations in an object's composition, by using both neutrons and photons simultaneously in transmission radiography. They present a multiparticle spectroscopic transmission radiography (MPSTR) technique that merges the information obtained from fast-neutron and photon probes produced by deuteron-based nuclear reactions.

Composite fuels are promising candidates for high-burnup fast reactors because of their accommodation of swelling, limited fuel-cladding interactions and flexibility in design. While a proof-of-concept fuel consisting of granules of U-alloys and PuO 2 dispersed within a porous zirconium matrix was successfully manufactured and irradiated, its neutronic and thermal performance remains to be optimized as compared to currently utilized fuels. MCNP6, COMSOL and a sphere packing algorithm were employed to perform the analysis. We found that both the theoretical maximum burnup reached and the temperature profiles are comparable to that of the currently considered alternative fuel. The results are promising and do not indicate any substantial limitation to the deployment of composite fuel. The fuel type merits further research, including full-core simulations. The methodology followed herein also provides a basis for screening different material compositions and guiding materials selection in composite fuels.

This paper describes the pre-conceptual design for a high temperature (>1300 °C), ultra-small (1–10 MWe) modular reactor with a high efficiency (>50%) thermophotovoltaic (TPV) power-block. The integration of the TPV is attractive for increased efficiency over the heat cycles of traditional nuclear power plants (NPP) and increased inherent safety from the elimination of a working fluid. Allowing for heat removal through radiative and passive convective cooling, the design must operate at low power densities. A preliminary sampling of the design space was performed using coupled thermal and neutronic analysis on a simplified model. This study shows the viability of the design and reveals the favorability of using uranium nitride fuel that allow the core to operate safely at approximately 1–2 W/cm3 within the desired temperature limits. Although preliminary, the depletion and economic analyses reveal an operational time on the order of ten thousand days and approximately 43% savings in NPP capital costs.

In a conventional light water reactor loaded with a range of uranium and plutonium-based fuel mixtures, the variation in antineutrino production over the cycle reflects both the initial core fissile inventory and its evolution. Under the assumption of constant thermal power, we calculate the rate at which antineutrinos are emitted from variously fueled cores, and the evolution of that rate as measured by a representative ton-scale antineutrino detector. We find that antineutrino flux decreases with burnup for Low Enriched Uranium cores, increases for full mixed-oxide (MOX) cores, and does not appreciably change for cores with a MOX fraction of approximately 75%. Accounting for uncertainties in the fission yields, in the emitted antineutrino spectra, and the detector response function, we show that the difference in core-wide MOX fractions at least as small as 8% can be distinguished using a hypothesis test. The test compares the evolution of the antineutrino rate relative to an initial value over part or all of the cycle. The use of relative rates reduces the sensitivity of the test to an independent thermal power measurement, making the result more robust against possible countermeasures. This rate-only approach also offers the potential advantage of reducing the cost and complexity of the antineutrino detectors used to verify the diversion, compared to methods that depend on the use of the antineutrino spectrum. A possible application is the verification of the disposition of surplus plutonium in nuclear reactors., Comment: 9 pages, 9 figures, 4 tables

Recent measurements of reactor-produced antineutrino fluxes and energy spectra are inconsistent with models based on measured thermal fission beta spectra. In this paper, we examine the dependence of antineutrino production on fission neutron energy. In particular, the variation of fission product yields with neutron energy has been considered as a possible source of the discrepancies between antineutrino observations and models. In simulations of low-enriched and highly-enriched reactor core designs, we find a substantial fraction of fissions (from 5% to more than 40%) are caused by non-thermal neutrons. Using tabulated evaluations of nuclear fission and decay, we estimate the variation in antineutrino emission by the prominent fission parents U-235, Pu-239, and Pu-241 versus neutron energy. The differences in fission neutron energy are found to produce less than 1% variation in detected antineutrino rate per fission of U-235, Pu-239, and Pu-241. Corresponding variations in the antineutrino spectrum are found to be less than 10% below 7 MeV antineutrino energy, smaller than current model uncertainties. We conclude that insufficient modeling of fission neutron energy is unlikely to be the cause of the various reactor anomalies. Our results also suggest that comparisons of antineutrino measurements at low-enriched and highly-enriched reactors can safely neglect the differences in the distributions of their fission neutron energies., Comment: 10 pages, 5 figures, 4 tables. Submitted to PRD

This paper describes the design and performance of a 50 liter, two-segment $^{6}$Li-loaded liquid scintillator detector that was designed and operated as prototype for the PROSPECT (Precision Reactor Oscillation and Spectrum) Experiment. The two-segment detector was constructed according to the design specifications of the experiment. It features low-mass optical separators, an integrated source and optical calibration system, and materials that are compatible with the $^{6}$Li-doped scintillator developed by PROSPECT. We demonstrate a high light collection of 850$\pm$20 PE/MeV, an energy resolution of $\sigma$ = 4.0$\pm$0.2% at 1 MeV, and efficient pulse-shape discrimination of low $dE/dx$ (electronic recoil) and high $dE/dx$ (nuclear recoil) energy depositions. An effective scintillation attenuation length of 85$\pm$3 cm is measured in each segment. The 0.1% by mass concentration of $^{6}$Li in the scintillator results in a measured neutron capture time of $\tau$ = 42.8$\pm$0.2 $\mu s$. The long-term stability of the scintillator is also discussed. The detector response meets the criteria necessary for achieving the PROSPECT physics goals and demonstrates features that may find application in fast neutron detection., Comment: 16 pages, 13 figures; minor edits to design detail and references

This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of $^{235}$U at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, consists of a segmented 4 ton $^6$Li-doped liquid scintillator detector covering a baseline range of 7-9 m from the reactor and operating under less than 1 meter water equivalent overburden. Data collected during 33 live-days of reactor operation at a nominal power of 85 MW yields a detection of 25461 $\pm$ 283 (stat.) inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at 5$\sigma$ statistical significance within two hours of on-surface reactor-on data-taking. A reactor-model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95% confidence level and disfavors the best fit of the Reactor Antineutrino Anomaly at 2.2$\sigma$ confidence level., Comment: 7 pages, 5 figures; v3: Added additional supplemental files