arXiv subjects

R. V. Duncan

Publications and source records attributed to R. V. Duncan.

10 recordsLinked to original sources

arXiv2026

Determination of Tritium Content in D2 Gas and Heavy Water

A simple experimental method for the determination of tritium concentration in natural hydrogen and deuterium gas down to the femtomole level is described. Palladium and platinum catalysts were used to react hydrogen and oxygen, creating water that could be analyzed in a Revvity Quantulus GCT 6220. This analysis produced sub-femtomole detection limits of tritium present in hydrogen gas or heavy water. A contamination level of $\sim 1\text{ femtomole/SL}$ was found in the $\text{D}_2$ gas sample that was analyzed. A contamination level of $\sim 0.025\text{ femtomole/SL}$, which is below the noise level of the Quantulus, was found in the standard hydrogen gas sample that was analyzed. The choice of palladium or platinum catalyst did not significantly affect the resulting tritium measurement. By showing that common $\text{D}_2$ samples can be contaminated with trace amounts of tritium orders of magnitude above natural abundance, this test demonstrates that a baseline tritium measurement for deuterium samples is highly important for determining the validity of results in nuclear fusion yield experiments.

nucl-ex↗

arXiv2026

Alpha Particle Induced Collision Cascade Fusion

We report experimental and computational investigations of a collision-cascade mechanism to induce deuterium-deuterium (D-D) fusion. Evidence of neutron production was observed from a pressurized deuterium target exposed to energetic alpha particles emitted by a $^{210}\text{Po}$ source. A 5-mCi $^{210}\text{Po}$ alpha source was placed within a chamber containing pressurized deuterium gas, and neutron emission was monitored for 18 h using two Mirion SN-S $^{3}\text{He}$ neutron detectors. Alpha particles incident on pressurized deuterium gas produced an average excess of $\sim$74 neutrons after background subtraction, corresponding to a fusion neutron rate of $\sim$2.24 n/s. With LiD in the pressurized deuterium, the average excess increased to 268 neutrons, corresponding to 8.1 n/s. Since D-D fusion branches into two equally likely pathways, these correspond to a fusion rate near 4.5 and 16.2 fusions per second, respectively. MCNP simulations incorporating experimental geometry, source activity, and detector configuration predicted neutron yields within 5.4% of the measured values and reproduced the detector response within experimental uncertainty. The tight agreement between measured and simulated neutron counts suggests that energetic alpha-particle interactions within the deuterium may contribute to measurable D-D fusion reactions through the D(d,n)$^{3}\text{He}$ channel.

nucl-ex↗

arXiv2026

Production of Low-Density Aerogel Nuclear Fuels for Use in Fission Fragment Rockets and Novel Reactor Design

Graphene hydrogels were created and loaded with uranyl nitrate or thorium nitrate and freeze-dried to produce graphene aerogel nuclear fuels. These aerogels had densities between 0.018-0.035 g/cm3 and consisted of ~7.3 +- 0.5% uranium/thorium by mass. The ultra-low density of the aerogels allows for high energy ions to escape the fuel particles without depositing all their energy as heat, as is typical in nuclear fuels. Their measured alpha activity was ~16 pCi/mg, which could be enhanced up to ~49 pCi/mg by decreasing the thickness of aerogel samples to allow all alpha particles to escape. Additionally, high energy neutrons were used to induce fission to provide a source of fission fragments from the aerogel fuels. This novel form of nuclear fuel has potential applications in space propulsion such as fission fragment rocket engines, as well as in terrestrial applications for modular reactors, direct conversion methods, and in medical radiotherapeutics.

cond-mat.mtrl-sci↗

arXiv2025

Boron Nitride Coatings for the Enhanced Detection of Neutrons in CR-39

The neutron detection efficiency of Columbia Resin 39 (CR-39) nuclear track detectors was assessed for AmBe, 252Cf, and D-T (14 MeV) neutron source spectra. A boron nitride (BN) coating for CR-39 was developed to enhance the neutron detection efficiency by converting neutrons into energetic alpha particles through the well-known 10B(n,a)7Li reaction. Separate partially coated CR-39 pieces were exposed to each neutron source and subsequently analyzed under optical microscope and through large-area Scanning Electron Microscopy (SEM) imaging over the irradiated area. The detection efficiency (tracks per neutron) was evaluated for each source spectra under optical and scanning electron microscopes and with or without BN coating. This resulted in a comprehensive guide to neutron detection with various sources using CR-39.

physics.ins-det↗

arXiv2025

Enhanced Tritium Production in Irradiated TiD2 from Collisional Fusion in the Solid-State

Ongoing research in new nuclear mechanisms hold the potential for beneficial developments in nuclear power cycle designs. Recent reports investigated the possibility of lattice dynamics to influence nuclear processes in metals. Results from Steinetz et al., at the NASA Glenn Research Center indicated that it may be feasible to initiate deuterium deuterium fusion reactions that are enhanced using electron screening to reduce the deuterium deuterium fusion barrier. This article presents tritium production results from both simulations and experiments targeting specific nuclear processes in an effort to identify the source of higher energy neutrons observed in those results. We explore two pathways of tritium generation in TiD2 through this fusion cycle. Tritium production from TiD2 in the University of Missouri Research Reactor, where the neutron spectrum was approximately 90 percent thermal, was within 25 percent of the predicted amount from simulations, and well explained by known nuclear reactions without invoking screening enhanced recoil-induced fusion. Tritium production from TiD2 in the cyclotron vault at MURR, where the neutron spectrum was completely energetic with almost no thermal neutrons, was a factor of 2.9 to 5.1 times higher than predicted from simulations using known nuclear reactions. This indicates the likelihood of an additional mechanism, such as collision-induced fusion in the solid state, increasing the credibility in the results from Steinetz et al.

nucl-ex↗

arXiv2024

Helium Detection in Technical Materials

Materials used to study nuclear fusion can retain atmospheric helium unless pretreated before an experiment. Understanding helium outgassing is important for accurate diagnostics in experiments surrounding nuclear fusion. The presence of helium is often cited as the primary evidence that a nuclear reaction has occurred, so it is imperative that known sources of helium are mitigated prior to proceeding with novel nuclear experiments. It is also necessary to ensure hermiticity when transferring gas aliquots from an experiment to a mass spectrometer. In this article, we present studies of detecting helium leak rates in systems used in novel nuclear experiments. We also present studies of helium retention in materials subjected to various heating profiles and atmospheric concentrations. Without pretreatment, stainless-steel 316 retains between 15 $\unicode{x2013}$ 240 pmol of $^{ 4}$He or an areal outgassing amount of 0.07 $\unicode{x2013}$ 1.20 pmol/$cm^{ 2}$. It also may reabsorb $^{ 4}$He from the atmosphere in time. These studies also demonstrate that it is necessary to pretreat most materials prior to performing experiments where the presence of $^{ 4}$He is being used as an indicator for novel nuclear reactions.

physics.ins-det↗

arXiv2024

Prospects For A New Light Nuclei, Fission Fusion Energy Cycle

Future advanced nuclear rocket propulsion, and the availability of new nuclear power cycle designs, will benefit substantially from the large current investment in alternative nuclear energy that is underway today. We propose a new nuclear cycle which includes the primary fission of lithium-6, followed by secondary fusion of deuterium and tritium, and a secondary fission of lithium-7 by tritium. This cycle does not produce nuclear waste from its nuclear fuel, since all byproducts of these cascade reactions are stable, provided that the triton production during the primary reaction is fully consumed in the secondary reactions. This cycle may, however, activate surrounding technical materials from its neutron flux. This light-element nuclear fuel is readily obtained through the ongoing expansion of the lithium mining industry and electric vehicle (EV) battery recycling industries.

physics.soc-ph↗

arXiv2024

Simulating Radiation Shielding Effectiveness Against Three Neutron Sources

Laboratories and Universities regularly apply for approval from the United States Nuclear Regulatory Commission (NRC) to use neutron generators for experimental research. To comply with the regulations set by the NRC, adequate shielding is necessary to ensure that the radiation dose rates experienced by an operator, and outside the walls of any containment buildings, are below the prescribed levels. Typically, the neutron source needs to be shielded such that the radiation dose rate experienced by any user is less than 0.25 mRem/hr (500mrem/2000-hour work-year). To address this requirement, we investigate the effectiveness of boronated concrete, boronated water, and light water shielding materials and their applicability to three neutron sources. We present our findings on the radiation shielding design and calculations for three neutron sources situated inside shielding layers. Our modeling utilized the Monte Carlo n-Particle transport codes (MCNP6.2) to simulate neutron attenuation of the shielding. The simulation results reveal that a light water shielding can sufficiently reduce the dose rate for an individual located as close as two meters from the source. Therefore, this shield design can effectively decrease the radiation dose below the maximum recommended limit.

physics.ins-det↗

arXiv2023

Photoneutron Yield for an Electron Beam on Tantalum and Erbium Deuteride

An electron beam may be used to generate bremsstrahlung photons that go on to create photoneutrons within metals. This serves as a low-energy neutron source for irradiation experiments [1-3]. In this article, we present simulation results for optimizing photoneutron yield for a 10-MeV electron beam on tantalum foil and erbium deuteride (ErD$_3$). The thickness of the metal layers was varied. A tantalum foil thickness of 1.5 mm resulted in the most photons reaching the second metal layer. When a second metal layer of ErD$_3$ was included, the photoneutron yield increased with the thickness of the secondary layer. When the electron beam was directly incident upon a layer of ErD$_3$, the photoneutron yield did not differ significantly from the yield when a layer of tantalum was included. The directional photoneutron yield reached a maximum level when the thickness of the ErD$_3$ layer was around 12 cm. About 1 neutron was generated per $10^4$ source electrons. When using a 2-mA beam current, it is possible to generate up to $10^{ 12}$ neutrons per second, making this combination a relatively-inexpensive neutron generator.

physics.acc-ph↗

arXiv2023

The Fission Fragment Rocket Engine for Mars Fast Transit

In this paper we discuss the advantages and challenges of utilizing Fission Fragment Rocket Engines (FFREs) to dramatically reduce transit time in space travel, for example, traveling to Mars. We discuss methods to decrease the size and weight of FFREs. These include utilizing metallic deuterides as moderators, driving the engines with electron beam bremsstrahlung, and operating the FFREs as subcritical assemblies, not as nuclear reactors. We discuss these and other new innovations based upon improved materials and technology that may be integrated into a revolutionary nuclear rocket technology.

physics.soc-ph↗