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Swinhoe, Martyn Thomas

Publications and source records attributed to Swinhoe, Martyn Thomas.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Use of a deuterium-deuterium neutron generator for the Add-A-Source waste matrix correction technique

Neutron generators offer an alternative to radioactive sources in the application of active techniques for nondestructive assay of nuclear materials. The Add-A-Source technique has enabled improvements in the ability to accurately measure waste bearing nuclear materials by measuring and correcting for the non-nuclear matrix effect. The technique has historically been performed with a Cf-252 spontaneous fission source. Here, in this work, we have demonstrated the use of a Deuterium-deuterium neutron generator in place of the Cf-252 source. A DD generator enables operational advantages and allows the simplification of the instrument design, while offering equivalent corrective performance as a Cf-252 source.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

A new generation of uranium coincidence fast neutron collars for assay of LWR fresh fuel assemblies

The active uranium neutron coincidence collar provides a means of non-destructively assaying the fissile linear density of Light Water Reactor fresh fuel assemblies containing low enriched uranium. These neutron collars can operate in two modes: a thermal and a fast mode. In fast mode, a neutron collar has an added cadmium (Cd) liner in the sample cavity of the detector to reduce the impact of the burnable poison (thermal neutron absorber) on the detector signal (doubles). The main advantage for operating in fast mode is a detected signal that is less dependent of the burnable neutron poison content and thus less dependent on facility operator declarations. The drawback is that operating in fast mode requires a longer measurement time (~hour vs tens of minutes for thermal mode) to achieve the statistically needed precision in the measurements. The trend in the modern reactor fuel assemblies is moving to higher burnup by using higher initial enrichment and, consequently, a higher number of burnable poison rods to compensate the initial neutron reactivity. The increase of the burnable poison loading has motivated the development of a new generation of high efficiency fast neutron collars to allow practical measurements in-field by nuclear inspectors. This paper describes the development and performance evaluation of a new generation of neutron collars, for both boiling water reactor (BWR) and pressurized water reactor (PWR) fuels, jointly developed between the US Department of Energy, through Los Alamos National Laboratory, and the Euratom Safeguards Directorate of the European Commission. In this work, we present here calibrations with reference fuel assemblies at Los Alamos National Laboratory as well as the results of in-field measurement campaigns in fuel fabrication plants with modern commercial fuel assemblies. The experimental results show that a typical PWR verification can be made in a total time of 30 min with an uncertainty in the measured mass of 2% at one standard deviation (1σ). A BWR verification can be made in 47 min with an uncertainty in the measured mass of 1.9% at 1σ, or a total time of 20 min with 1σ uncertainty in the measured mass of 2.5%.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Action Sheet 55 Measurement Campaign Summary

Neutron collars have long been used by international inspectorates to determine the 235 U loading of fresh light water reactor (LWR) fuel in nuclear fuel fabrication facilities. Burnable poisons are strong thermal neutron absorbers that are frequently used to increase the lifetime of LWR fuel in a reactor. These poisons have made the traditionally thermal neutron collar measurements challenging because they force inspectors to rely on operator declarations of the burnable poison content of the fuel in order to correct for the decreased count rate caused by the added thermal neutron absorption of the poison. Work has been conducted internationally to try to eradicate the reliance on operator declarations. The Euratom Fast Collar for BWR Fuel (EFCB) is one promising technique to manage this issue.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

EURATOM Fast Collar for BWR (EFCB) Field Calibration Exercise

A neutron collar for the measurement of fresh BWR fuel assemblies (EFCB) has been designed and built by Los Alamos National Laboratory (LANL) and the Euratom Safeguards Directorate (Euratom). The design was similar to a previous collar designed for the measurement of fresh PWR assemblies. A key feature of both of these collars is that they operate in fast mode (preventing the return of thermal neutrons into the assembly by means of a cadmium liner) to reduce the effect of burnable poisons on the measurement. The current report describes the results of the field calibration exercise that was carried out at the ENUSA Fuel Fabrication Plant in Juzbado, Spain from May 28 to May 31, 2019.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2019

Scintillation detectors

Devices/apparatuses are disclosed that include a photoemitting component, a photosensitive component deposited on the photoemitting component, a charge collection component, and a hollow enclosure for housing the photoemitting component, the photosensitive component, the charge collection component, or combinations thereof. Methods for making and using the apparatuses are also disclosed.

Ianakiev, Kiril D.↗
DOE OSTI2019

Time behavior of the emission of 1274 keV gamma-rays from UF 6

22 Na ingrowth originating from fluorine-alpha interactions has been proposed as a chronometer for UF 6 cylinders. Furthermore, these proposals have ignored the prompt 1274 keV gamma-ray contribution from 19 F(α, p). We have shown that this contribution is significant and cannot be ignored when using this as a chronometer for UF 6 .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Annual IPCA2 Performance Report for JFY18

This report summarizes the results of monthly control measurements of IPCA2 performed over the period of October 2018 through March 2019 and represents an annual performance overview for JFY18. Note that the start of the measurements in October 2018 was defined by the start of the contract agreement. Monthly measurements of Plutonium neutron detection efficiency, AmLi stability, Curium stability and HPGe gamma spectra of Plutonium standards were performed and analyzed. All the results are shown with respect to original control bounds established from 2013- 2017 data in. Updated control bounds established based on this JFY18 data for use during JFY19 measurements are summarized in Appendix A. Based on Pu efficiency measurements, the performance of the IPCA2 during this reporting period was stable within 0.6% at 1 σ level. Measurements were compared to room temperature and humidity and no dependence was found for any detector performance. The end of this report contains summary of all IPCA2 measurements performed since October 2018 and includes discussion of troubleshooting and repair activities performed over the reporting period.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Evaluation of Various Collimators for UF6 Gas Pipe Measurement

On-line gamma measurements of the enrichment of uranium in UF6 gas in pipes is carried out as part of international safeguards. The 186 keV line from 235 U is measured in NaI detectors. One complication in the analysis is that the 186 keV line also comes from the (time-dependent) amount of uranium-bearing material deposited on the interior walls of the pipe. This contribution has to be subtracted before the enrichment of the gas can be calculated. The relative contributions to the total 186 keV count rate from the gas and from the deposit depends on the amount of deposit, but also on the type of collimation/shielding used between the NaI detector and the gas pipe. Several different collimation/shielding designs have been simulated in order to determine which provides the best performance.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

Characterizing laser-plasma ion accelerators driving an intense neutron beam via nuclear signatures

Compact, bright neutron sources are opening up several emerging applications including detection of nuclear materials for national security applications. At Los Alamos National Laboratory, we have used a short-pulse laser to accelerate deuterons in the relativistic transparency regime. These deuterons impinge on a beryllium converter to generate neutrons. During the initial experiments where these neutrons were used for active interrogation of uranium and plutonium, we observed β-delayed neutron production from decay of 9 Li, formed by the high-energy deuteron bombardment of the beryllium converter. Analysis of the delayed neutrons provides novel evidence of the divergence of the highest energy portion of the deuterons (i.e., above 10 MeV/nucleon) from the laser axis, a documented feature of the breakout afterburner laser-plasma ion acceleration mechanism. Furthermore, these delayed neutrons form the basis of non-intrusive diagnostics for determining the features of deuteron acceleration as well as monitoring neutron production for the next generation of laser-driven neutron sources.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

A comparison of Monte Carlo fission models for safeguards neutron coincidence counters

Monte Carlo simulation is a powerful tool used to model neutron coincidence detectors for international safeguards. The simulation has typically sampled properties such as the fission neutron multiplicity, energy, and direction, from independent probability density functions. However, multiplicity counters detect event-based neutron correlations and thus more accurate fission event modeling is needed. To respond to this need, the Fission Reaction Event Yield Algorithm (FREYA) and the Cascading Gamma-ray Multiplicity with Fission (CGMF) models were added in the newest version of MCNP, MCNP6.2. The models simulate individual fission events conserving momentum, energy, and angular momentum such that correlated particles are emitted. The effects of the new models on simulations of safeguards neutron coincidence counters were studied and compared to standard MCNP simulations. The MCNPX-PoliMi model was also included in the comparison. The properties of fission neutrons from safeguards relevant isotopes were compared to literature references. Then a hypothetical simplified detector was modeled to isolate the effects of specific differences between models. Experimental measurements from previous work were modeled and agreements were compared. Lastly, the probabilities of correlated events occurring in the experimental measurements were calculated with the different models. For example, the probability was calculated of detecting neutrons from both induced fission in uranium and spontaneous fission of Cf-252 in the same fission chain.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Neutron Based Non-Destructive Assay (NDA) Measurement Systems for Safeguard

The objectives of this project are to introduce the assay methods for plutonium measurements using the HLNC; introduce the assay method for bulk uranium measurements using the AWCC; and introduce the assay method for fuel assembly measurements using the UNCL.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Fiscal Year (FY) 2017 Activities for the Spent Fuel Nondestructive Assay Project

The main focus of research in the NA-241 spent fuel nondestructive assay (NDA) project in FY17 has been completing the fabrication and testing of two prototype instruments for upcoming spent fuel measurements at the Clab interim storage facility in Sweden. One is a passive instrument: Differential Die-away Self Interrogation-Passive Neutron Albedo Reactivity (DDSI), and one is an active instrument: Differential Die-Away-Californium Interrogation with Prompt Neutron (DDA). DDSI was fabricated and tested with fresh fuel at Los Alamos National Laboratory in FY15 and FY16, then shipped to Sweden at the beginning of FY17. Research was performed in FY17 to simplify results from the data acquisition system, which is complex because signals from 56 different 3He detectors must be processed using list mode data. The DDA instrument was fabricated at the end of FY16. New high count rate electronics better suited for a spent fuel environment (i.e., KM-200 preamplifiers) were built specifically for this instrument in FY17, and new Tygon tubing to house electrical cables was purchased and installed. Fresh fuel tests using the DDA instrument with numerous configurations of fuel rods containing depleted uranium (DU), low enriched uranium (LEU), and LEU with burnable poisons (Gd) were successfully performed and compared to simulations.1 Additionally, members of the spent fuel NDA project team travelled to Sweden for a “spent fuel characterization and decay heat” workshop involving simulations of spent fuel and analysis of uncertainties in decay heat calculations.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Laser-plasmas in the relativistic-transparency regime: science and applications

Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at “table-top” scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (~10 4 T, according to particle-in-cell simulations of the experiments) at the rear-side of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (~0.1 TV/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 μm laser pulses irradiating planar foils up to 250 nm thick at 2–8 × 10 20 W/cm 2 . These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ~2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. Finally, we discuss the plans and prospects for further improvements and applications.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗