Enhancement of sub-thermal neutron flux through cold polyethylene

Fritz, Dominik; Danon, Y.; Liu, Emily

doi:10.3233/jnr-210010

Cited by 8 publications

(3 citation statements)

References 3 publications

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“…The polyethylene target is a 7" by 7" slab that is 1" thick with a 1/8" aluminum thermal conductor in the center. For more information on the cold moderator system refer to Reference [10].…”

Section: Low-temperature Moderator Systemmentioning

confidence: 99%

Validation of S(α, β) thermal neutron scattering libraries using pulsed-neutron die-away experiments

et al. 2023

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Validation of the accuracy of S(α, β) thermal scattering law (TSL) evaluations for moderator materials is an important task for the development of high-performance nuclear engineering systems. Many recent thermal neutron scattering evaluations have had limited experimental validation. Like other nuclear data, validation of TSL libraries has historically been by integral criticality benchmarks. While sufficient for general study, these benchmarks often have limited sensitivity to the tested TSLs, and compounding uncertainties from other nuclear data can make validation ambiguous. In some cases, no criticality benchmarks exist that are sensitive to the TSLs of interest. With the development of high-performance next-generation thermal nuclear reactors, alternative validation of applicable TSLs is of high importance. By performing thermal neutron measurements via pulsed-neutron die-away (PNDA) experiments, along with parallel simulations, the integral performance of various TSL evaluations can be compared to measured experimental data. An experimental testbed using a D-T neutron generator, moderator sample, and thermal neutron detector was assembled at Rensselaer Polytechnic Institute. A Thermo Scientific D211 Deuterium-Tritium Neutron generator is used to generate 10 μs neutron pulses. Various targets of different sizes and geometries are used to moderate the neutrons. Multiple detector types and configurations were tested to optimize the experiment. The room-temperature polyethylene TSL evaluation is well vetted and is similar across different evaluations. This makes it an ideal evaluation to compare with the experimental results.

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Section: Low-temperature Moderator Systemmentioning

confidence: 99%

Validation of S(α, β) thermal neutron scattering libraries using pulsed-neutron die-away experiments

et al. 2023

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“…In order to produce the neutron flux required for the total cross section measurements in the thermal energy region, two different targets were utilized: the Enhanced Thermal Target (ETT) [5] and the Enhanced Thermal Target with a cold moderator coupled to it (ETTC) [6]. In order to produce neutrons, an approximately 55 MeV electron beam is directed towards a water-cooled Ta target inside of the ETT.…”

Section: Neutron Production Targetsmentioning

confidence: 99%

Thermal Cross Section Measurements At The RPI LINAC

et al. 2023

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Recently, a cold moderator was designed and developed for use at the Rensselaer Polytechnic Institute Linear Accelerator (RPI LINAC). This cold moderator proved to easily and safely couple to an existing neutron producing target, while enhancing neutron flux below 0.02 eV by up to a factor of 8 by cooling polyethylene down to 29 K. This cold moderator capability allowed for significantly improved counting statistics below 0.02 eV not previously possible due to a poor signal to background ratio. Additionally, testing was performed to characterize the energy resolution of the new cold moderator system and found the system easily capable of resolving resonances in Ta-181 at 4 and 10 eV, while also clearly resolving the Bragg edges found in Be metal below 0.01 eV. Following the design and development of a cold polyethylene moderator, a series of thermal total cross section measurements were performed for polyethylene, polystyrene, Plexiglas and yttrium hydride in the thermal region. These measurements serve to help validate thermal scattering law (TSL) evaluations in the 0.0005 – 1 eV energy range. For polyethylene and polystyrene, two sets of experiments were performed – one with the Enhanced Thermal Target (ETT) and another with the ETT plus the new cold moderator capability (ETTC). The yttrium hydride and Plexiglas measurements were only performed with the ETTC. The measurements for polyethylene help to validate the data processing methodology when using the ETTC, while extending the measured range of polyethylene down to 0.0005 eV. Two different Plexiglas, Plexiglas G and Plexiglas G-UVT, and two different concentrations of yttrium hydride, H/Y = 1.85 and 1.68, were measured. Overall, all materials had generally good agreement with their ENDF/B-VIII.0 TSL evaluations, though some discrepancies were noticed. In the case of the yttrium hydride, the high energy oscillations in the hydrogen cross section and the low energy Bragg edges in the yttrium cross section were clearly seen. These measurements represent the first total cross section measurements that encompass the entire thermal region from 0.0005 – 1 eV for polystyrene and yttrium hydride.

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“…RPI's work on constructing the new cold moderator system [3,4,5] and measurement details [6,7,8,9] has been documented extensively elsewhere and is mentioned only briefly in Section 2. Section 3 outlines ORNL's evaluation work.…”

Section: Introductionmentioning

confidence: 99%

Status Report of Joint RPI/ORNL NCSP Task for Thermal Neutron Total Cross Section Measurements

Chapman,

Ramic,

Brown

et al. 2023

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A new cold neutron moderator system was developed and constructed at the Rensselaer Polytechnic Institute (RPI) Gaerttner Linear Accelerator. This system was then used to measure the neutron total cross section in the thermal energy range for polyethylene, polystyrene, Lucite, and yttrium hydride. In tandem with these measurements, a fitting procedure was developed at Oak Ridge National Laboratory to vary computationally simulated phonon density of states until a fit with differential and integral data was achieved. This model, combined with the new RPI total cross section data, was used to generate thermal scattering law files for the materials measured at RPI.

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Enhancement of sub-thermal neutron flux through cold polyethylene

Cited by 8 publications

References 3 publications

Validation of S(α, β) thermal neutron scattering libraries using pulsed-neutron die-away experiments

Validation of S(α, β) thermal neutron scattering libraries using pulsed-neutron die-away experiments

Thermal Cross Section Measurements At The RPI LINAC

Status Report of Joint RPI/ORNL NCSP Task for Thermal Neutron Total Cross Section Measurements

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