Pulsed Neutron Source Research Articles

Formation Evaluation Workflow Assesses Mass-Transport Complex Reservoirs

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 203016, “Formation Evaluation in Mass-Transport Complex Reservoirs,” by Ulises Bustos, Schlumberger; Carlos Duran, Petróleos Sudamericanos; and Alvaro Chapellin, Schlumberger, et al., prepared for the 2020 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, held virtually from 9-12 November. The paper has not been peer reviewed. Mass-transport deposits (MTDs) are sedimentary, stratigraphic successions remobilized after initial deposition but before substantial lithification and transported downslope by gravitational processes as non-Newtonian rheological units. In the complete paper, the authors present an openhole advanced formation-evaluation approach that enables assessment of tight-matrix and natural-fracture systems at a level not previously accomplished in these types of geological formations. Introduction The considered wildcat project by Petroleos Sudamericanos is in the Lower Magdalena Valley hydrocarbon province in Colombia. From a stratigraphic point of view, the targets belong to tertiary deposits from the lower Neogene. Gravity-driven processes are complex and include creep, slide, slump, debris flow, and multiphase granular flows. The remobilized sedimentary deposits resulting from these processes are called MTDs or mass-transport complexes (MTCs) and are the main target job. Overlaying a crystalline basement, four MTC cycles were identified (although the present work only covers three MTC cycles) deposited in shallow marine environments. Each cycle consists of quartzite; phyllite; and schistose metamorphic rocks, largely gneiss with strong milonitization effects and foliated tremolitic marble in the top of the sequence. A summary of these types of rock is provided in the complete paper. The non-Archie nature of these rocks represents a challenge for formation evaluation. For reducing these uncertainties, a volumetric model with spectros copy dry-weight elements and nuclears was created that enabled solution of the total porosity, which was then benchmarked against the lithology-independent total nuclear magnetic resonance (NMR) porosity. The saturation computation was achieved with the fast neutron cross section method (FNXS) for the gas component and with total carbon for the liquid hydrocarbon fraction. The natural fracture system was analyzed with borehole image logs and with radial sonic-based dispersion analysis. The integration of matrix and natural-fracture assessment provided a robust formation evaluation that enabled identification of the main interest zones across the MTC cycles. Multifunction Spectroscopy for Matrix Analysis The multifunction spectroscopy tool is 1.72 in. in diameter and 18.3 ft long, consisting of a pulsed neutron generator and four detectors. The first detector is the compact neutron monitor, sensitive to fast neutrons and located adjacent to the high-output pulsed neutron source, measuring neutron output with high accuracy and precision. The second (near) and third (far) gamma-ray detectors are used for inelastic and capture spectroscopy measurements. The fourth and farthest-spaced detector (deep) uses an yttrium aluminum perovskite scintillator, which is involved in gas detection and assessment. The nuclear spectroscopy measurement is performed in energy and time domains; both aspects are described in detail in the complete paper.

Numerical simulation and analysis of the pulsed neutron source method measuring the prompt neutron decay constant of a Godiva-like subcritical facility

The theory and method of the pulsed neutron source (PNS) method measuring the prompt neutron decay constant α0 of a subcritical system was introduced. Using the Monte Carlo code JMCT, the neutron transport process in a Godiva-like subcritical facility was simulated. The α0 value of the facility was obtained with PNS method, and was compared with the α-k power iteration result. To investigate the factors affecting the calculated α0 value of the PNS method, the system response, the fitting residual distributions, and the neutron energy spectra of different time intervals were analyzed. It is observed that the statistical fluctuation is the key factor leading to the inaccuracy of the α0 calculation value of the facility. Furthermore, to obtain an effective α0 value with the PNS method, the reasonable width of fitting time window was discussed by analyzing the relationship of the calculated α0 values and the fitting time width in this paper.

Exploring laser-driven neutron sources for neutron capture cascades and the production of neutron-rich isotopes

The production of neutron-rich isotopes and the occurrence of neutron capture cascades via laser-driven (pulsed) neutron sources are investigated theoretically. The considered scenario involves the interaction of a laser-driven neutron beam with a target made of a single type of seed nuclide. We present a comprehensive study over $95$ seed nuclides in the range $3\le Z \le 100$ from $^7_3$Li to $^{255}_{100}$Fm. For each element, the heaviest sufficiently-long-lived (half life $> 1$ h) isotope whose data is available in the recent ENDF-B-VIII.0 neutron sublibrary is considered. We identify interesting seed nuclides with good performance in the production of neutron-rich isotopes where neutron capture cascades may occur. The effects of the neutron number per pulse, the neutron-target interaction size and the number of neutron pulses are also analyzed. Our results show the possibility of observing up to $4$ successive neutron capture events leading to neutron-rich isotopes with $4$ more neutrons than the original seed nuclide. This hints at new experimental possibilities to produce neutron-rich isotopes and simulate neutron capture nucleosynthesis in the laboratory. With several selected interesting seed nuclides in the region of the branching point of the $s$-process ($^{126}_{51}$Sb, $^{176}_{71}$Lu and $^{187}_{75}$Re) or the waiting point of the $r$-process (Lu, Re, Os, Tm, Ir and Au), we expect that laser-driven experiments can shed light on our understanding of nucleosynthesis.

Particularities of spatial kinetics of hybrid thorium reactor installation containing the long neutron source based on magnetic trap

In this work, we study the features of the spatial kinetics of installation as a hybrid thorium reactor with an elongated plasma neutron source based on a magnetic trap. The active zone of the installation under study consists of an assembly of hexagonal fuel blocks of a unified design and a long solenoid with a high-temperature plasma column passing through the axial region of the core. Combining engineering expertise in creating nuclear reactors with a physics-technical potential for obtaining high-temperature plasma in a long magnetic trap we ensure the solution of the multidisciplinary problem posed. These studies are of undoubted practical interest, since they are necessary to substantiate the safety of operation of such hybrid systems. The research results will allow optimizing the active zone of the hybrid system with leveling the resulting offset radial and axial energy release distributions. Results of our study will be the basis for the development of new and improvement of existing methods of criticality control in related systems such as “pulsed neutron source – subcritical fuel assembly”

EXPERIMENTAL STUDY ON NEUTRON CORRELATION ANALYSIS FOR A SUBCRITICAL SYSTEM DRIVEN BY A PULSED SPALLATION NEUTRON SOURCE IN KUCA

The Feynman-α and the Rossi-α methods have been frequently employed to determine the subcriticality of subcritical reactor systems driven by Poisson source such as Am-Be neutron source. In actual accelerator-driven systems (ADS), a spallation device will be applied as an intense neutron source. This device will be probably operated in a pulse mode and it is impossible to apply a conventional analysis method to determine the subcriticality in any ADS. In previous theoretical studies, some advanced formulae of neutron correlation analysis for spallation neutron source have been presented. However, the experimental study has been hardly reported to date. The major objectives of this study are to examine experimentally an applicability of these complicated formulae to a subcritical reactor system driven by an actual pulsed spallation neutron source and to determine the prompt-neutron decay constant α of the system. To achieve these goals, we constructed an ADS core at the Kyoto University Critical Assembly (KUCA). The core was composed of highly-enriched uranium fuel assemblies surrounded by many polyethylene reflector assemblies. We carried out a series of the Feynman-α and the Rossi-α analyses for the system driven by pulsed spallation source. As a result, the prompt-neutron decay constants were experimentally obtained by using a fitting formula. The prompt-neutron decay constants determined by Feynman-α and Rossi-α analyses agrees with each other within a statistical error range of least-squares fitting.

Pulsed neutron imaging for differentiation of ice and liquid water towards fuel cell vehicle applications.

This study is the first report on liquid water and ice imaging conducted at a pulsed spallation neutron source facility. Neutron imaging can be utilised to visualise the water distribution inside polymer electrolyte fuel cells (PEFCs). Particularly, energy-resolved neutron imaging is a methodology capable of distinguishing between liquid water and ice, and is effective for investigating ice formation in PEFCs operating in a subfreezing environment. The distinction principle is based on the fact that the cross sections of liquid water and ice differ from each other at low neutron energies. In order to quantitatively observe transient freezing and thawing phenomena in a multiphase mixture (gas/liquid/solid) within real PEFCs with high spatial resolution, a pulsed neutron beam with both high intensity and wide energy range is most appropriate. In the validation study of the present work, we used water sealed in narrow capillary tubes to simulate the flow channels of a PEFC, and a pulsed neutron beam was applied to distinguish ice, liquid water and super-cooled water, and to clarify freezing and thawing phenomena of the water within the capillary tubes. Moreover, we have enabled the observation of liquid water/ice distributions in a large field of view (300 mm × 300 mm) by manufacturing a sub-zero environment chamber that can be cooled down to -30 °C, as a step towards in situ visualisation of full-size fuel cells.

Inelastic Neutron Scattering Spectrometer INDIGO (Indirect Geometry) at the DARIA Compact Neutron Source

The characteristics of an indirect-geometry spectrometer and possibilities of its creation on a compact pulsed neutron source under conditions of its low luminosity are estimated. The configuration of a secondary spectrometer with a position-sensitive detector and a curved crystal analyzer is proposed, which ensures the capture of scattered neutrons at the largest solid angle. The main parameters of the instrument are calculated analytically. Based on the technical requirements for the parameters of the instrument, the numerical simulation is constructed and calculations of the instrument resolution as a function of the energy transfer are performed applying the Monte Carlo method. The analytical resolution function and the resolution function obtained from the simulation show good agreement when considering the contribution from the pulse width. An estimate of the neutron flux on the sample is obtained. The in-principle possibility of implementation of the neutron spectroscopy method under conditions of a compact source is shown.

Determination of effective temperatures of hydrogenated and deuterated alcohols using the VESUVIO spectrometer

We studied the effective temperatures of hydrogen and deuterium in normal 1-propanol, 2-propanol and n-butanol and fully deuterated 2-propanol and n-butanol at the VESUVIO spectrometer (ISIS Pulsed Neutron and Muon Source, Rutherford Appleton Laboratory, UK). We found that the effective temperature of H (D) is about 3.9 (2.9) times higher than room temperature, where the experiments were performed. The results from the present analysis were compared to the results from the standard data treatment available in the MANTID software for DINS data, and to results from Molecular Dynamics simulations. We find that the final results obtained following these independent routes agree within few points per cent. We also provide a detailed discussion on how to handle experimental backgrounds, the need to analyze groups of detectors to increase the signal-to-background ratio, and we suggest a range of scattering angles for which the analysis is more robust.

High count rate pulse shape discrimination algorithms for neutron scattering facilities

The performance of EJ-270, a 6Li loaded pulse shape discriminating plastic scintillator was tested for use in applications with high thermal and epithermal neutron fluxes such as neutron scattering facilities. The short decay time of EJ-270 make it of interest for high count rate applications. To realize this, 4 PSD algorithms were tested. The algorithms were selected based on the potential for high rate applications and simplicity. These algorithms were the charge integration method with and without the addition of a digital low pass filter, a measurement of the time to 10% of peak amplitude and a method we call the “tail sum” which utilizes a digital low pass filter and sums a small number of samples in the tail of each pulse. These algorithms were benchmarked using the figure of merit, the γ-sensitivity and potential rate capability. The charge integration method gave the highest figure of merit of 1.37 using a long window of 272.5 ns but had a γ-sensitivity of 2×10−6 which was poorer than the tail sum algorithm. The tail sum algorithm was able to achieve a figure of merit of 1.36 with a window of 250 ns and a γ-sensitivity on the order of 10−7. Reducing the integration windows to match the fastest algorithm of time to 10% resulted in the tail sum outperforming the other algorithms with a figure of merit of 1.26 and a γ-sensitivity of 6×10−7. The short charge integration method and tail-sum were compared on the EMMA beamline at the ISIS pulsed neutron and muon source. The tails sum demonstrated better separation between the γ-rays and thermal neutron at an incident peak neutron rate of 9.6×105 neutrons per second.

Advanced Small-Angle Scattering Instrument Available in the Tokyo Area. Time-Of-Flight, Small-Angle Neutron Scattering Developed on the iMATERIA Diffractometer at the High Intensity Pulsed Neutron Source J-PARC

A method of time-of-flight, small-angle neutron scattering (TOF-SANS) has been developed based on the iMATERIA powder diffractometer at BL20, of the Materials and Life Sciences Facility (MLF) at the high-intensity proton accelerator (J-PARC). A large-area detector for SANS, which is composed of triple-layered 3He tube detectors, has a hole at its center in order to release a direct beam behind and to detect ultra-small-angle scattering. As a result, the pulsed-neutron TOF method enables us to perform multiscale observations covering 0.003 < q (Å−1) < 40 (qmax/qmix = 1.3 × 104) and to determine the static structure factor S(q) and/or form factor P(q) under real-time and in-situ conditions. Our challenge, using unique sample accessories of a super-conducting magnet and polarized neutron, is dynamic nuclear polarization (DNP) for contrast variation, especially for industrial use. To reinforce conventional SANS measurements with powder materials, grazing-incidence small-angle neutron scattering (GISANS) or reflectivity is also available on the iMATERIA instrument.

On the Issue of Stability and Safety of the Superbooster, a Pulsed Neutron Source

A high-intensity pulsed neutron source can be constructed according to the principle of a superbooster, i.e., a neutron multiplying system of the neutron-generating target of the proton accelerator with proton energy of about 1 GeV in the subcritical reactivity modulation system. Usually, superboosters are considered to be safe and reliable nuclear facilities. However, as indicated in this paper, a powerful superbooster may prove to be less stable in operation than a pulsed reactor. Therefore, the problems of its safety call for close study.

2D single crystal Bragg-dip mapping by time-of-flight energy-resolved neutron imaging on IMAT@ISIS

The cold neutron imaging and diffraction instrument IMAT, at the second target station of the pulsed neutron and muon source ISIS, is used to investigate bulk mosaicity within as-cast single crystal CMSX-4 and CMSX-10 Ni-base superalloys. Within this study, neutron transmission spectrum is recorded by each pixel within the microchannel plate image detector. The movement of the lowest transmission wavelength within a specified Bragg-dip for each pixel is tracked. The resultant Bragg-dip shifting has enabled crystallographic orientation mapping of bulk single crystal specimens with good spatial resolution. The total acquisition time required to collect sufficient statistics for each test is ~ 3 h. In this work, the influence of a change in bulk solidification conditions on the variation in single crystal mosaicity was investigated. Misorientation of the (001) crystallographic plane has been visualised and a new spiral twisting solidification phenomena observed. This proof of concept work establishes time-of-flight energy-resolved neutron imaging as a fundamental characterisation tool for understanding and visualising mosaicity within metallic single crystals and provides the foundation for post-mortem deduction of the shape of the solid/liquid isotherm.

Radionuclides in target station coolant in the China Spallation Neutron Source

The China Spallation Neutron Source (CSNS) is the first pulsed neutron source in China for multidisciplinary research. After operation with 80 kW proton beam for 4 months, 3 circuits of target station coolant, light water 1/2/3 were sampled, and radionuclides in coolants were measured. The results showed that, activity concentration of H-3 in coolant can be up to the magnitude of 1.00E+06 Bq/L, and the H-3 amount in light water 1 was the highest and the amount in light water 3 was the lowest, agreeing with the radiation field exposed by coolants. For Be-7, due to the complicated filtering and trapping process, amount of Be-7 in coolant differed from a minimum of 7.15E+01 Bq/L to a maximum of 4.58E+03 Bq/L. Comparison of the results with former measurements and simulated results were conducted. Permitted volumes for coolant discharge were presented. And the work time in the equipment room of cooling system after the beam is shut off is safe. Results in this research could provide reference data and measurement methods for similar accelerator devices.

Tuning Neutron Resonance Spin-Echo Spectrometers with Pulsed Beams

The neutron spin-echo spectroscopy technique involving pulsed beams can be used to effectively access a wide range of space-time correlations of condensed matter. In this study, the features of this technique, in particular, the modulation of the intensity with zero effort (MIEZE) by using pulsed beams, which is based on the quantum-state manipulation of the neutron spin and energy, are comprehensively examined. A formulation of the MIEZE combined with the time of flight method (TOF MIEZE) is established by considering the characteristics of the pulsed neutron beams. Moreover, a parameter, namely, the detuning parameter, is introduced as a measure of the magnitude of detuning from the optimized instrumental state, known as the spin-echo condition. The phase and frequency shifts of the neutron intensity signals resulting from the TOF MIEZE under various configurations are investigated systematically. It is found that the detuning parameter equals the derivative of phase with respect to the TOF, whose zero-point corresponds to the spin-echo condition. The theoretical predictions on phase and frequency shifts by the established formulation are well validated by the experiments using an intense pulsed neutron source. The detuning parameter helps clarify the principle of the TOF MIEZE technique and can provide practical guidance regarding the implementation and optimization of spectrometers.

Development and testing of algorithms for performing computation of detector readings from a pulsed neutron source

To provide the possibility of computation of detector readings from a pulsed neutron source (time dependent readings) the development of algorithms and their realization to upgrade precision Monte Carlo code MCU are considered in this work. New version of the MCU code was tested, which included comparison with experimental results. The experiments were made by Lawrence Livermore National Laboratory in the late sixties. Neutron transport from a pulsed source through layers of various materials was studied in these experiments. The comparison of the MCU calculation results obtained for these experiments with the corresponding MCNP-6 calculations results is also given in this work.

LUE-200 Accelerator—A Photo-neutron Generator For The Pulsed Neutron Source “IREN”

This article reports about the construction and status of the accelerator facility at the Laboratory of Neutron Physics (FLNP) in the Joint Institute for Nuclear Research (JINR, Dubna), the driver of an intense pulsed resonance neutron source. The general scheme of the electron linear accelerator and features of its basic systems are presented. LUE-200 consists of two accelerating sections on a traveling wave with an operating frequency of 2856 MHz with RF power compression systems of the SLED type. The pulse current of the beam at the output of the accelerator reaches 2 A with a pulse duration of 80–100 ns. At the average energy of beam particles from 60–65 MeV and a cycle repetition rate of 50 Hz, the average beam power reaches ≈ 600 W. The integral neutron flux from the non-multiplying target reaches ∼ 1012 s−1.

Power spectral analysis for a subcritical reactor system driven by a pulsed spallation neutron source in Kyoto University Critical Assembly

ABSTRACT For a subcritical reactor system driven by a periodically pulsed spallation neutron source in Kyoto University Critical Assembly, a series of power spectral analysis on frequency domain is carried out to determine the prompt-neutron decay constant and quantitatively to confirm a non-Poisson characteristics of the neutron source. Not only the cross-power but also the auto-power spectral density has a considerable correlated noise component even at a deeply subcritical state, where no correlated component could be observed under a pulsed DT(14MeV) neutron source. The non-Poisson character of the spallation source must enhance the correlation amplitude of these power spectral densities. Moreover, the Degweker’s factor (m 2-m 1 2)/m 1 2 of 0.082 ± 0.021, which is a quantitative indication of the non-Poisson character, is determined from the present analysis and is consistent with that obtained by a previous Rossi-α analysis for the same subcritical system driven by the spallation source. The non-zero value of the factor convinces us again that the present source has a different statistical distribution from the Poisson. The prompt-neutron decay constant obtained from the present analysis well agreed with that done from the above previous Rossi-α analysis.

Progress in Simulating/Realisation SESANS in Time-of-Flight Mode at Pusled and Stationary Neutron Sources

We created software to simulate the Larmor precession in a setup for SESANS with adiabatic/radio frequency flippers in magnets designed to measure the time-of-flight on pulsed or stationary neutron sources. The values and spatial configurations of the magnetic fields of the existing prototype magnets we used as input data. For an empty setup, we calculate the polarization of a “divergent ribbon beam” 2 cm high, depending on the neutron wavelength λ. In the “scattering experiment”, we show how to convert λ to the “spin-echo length” δ. For λ = 10 A, flippers at a distance of 140 cm and a radio frequency 1 MHz we find δ ≈ 10 μm. Extension to δ = 20 μm is realistic.

Development of an in Situ 3He NSF Using SEOP Technique with an Evaluation System for the Pulsed Neutron Source

A 3He spin filter is a useful device for polarizing a neutron beam. We are developing the 3He spin filters for users of the material and life science facility of the Japan Proton Accelerator Research Complex (J‑PARC). An in situ SEOP system with a 3He polarization evaluation system using nuclear magnetic resonance (NMR) method of adiabatic fast passage and electron paramagnetic resonance (EPR) was developed. We conducted an experiment on the neutron beam line BL10 (NOBORU) of J-PARC to confirm the consistency of 3He polarization, estimated using the neutron transmission, NMR and EPR. The polarization of 3He, evaluated using the different methods, was consistent and the evaluation system operated normally for about 6 h.

Pulsed Fast Reactor IBR-2 after Modernization

Condensed matter study using nuclear physics methods is one of the main research areas at the Joint Institute for Nuclear Research (JINR), which is stated in the JINR Charter. Since the mid-sixties of the last century, such studies have been successfully carried out at the pulsed reactors/boosters of the JINR. The IBR-2, a powerful high-flux pulsed reactor of periodic operation, was commissioned in 1984 at an average power of 2 MW. In 2007, the reactor reached the service life limit on fuel burn up and fluence on the reactor vessel and was shut down for modernization and replacement of the main equipment. The goal of the modernization was to improve the safety, reliability and experimental possibilities of the reactor for the next 25 yrs of operation. By 2010, the installation of new equipment was completed and followed by a successful physical and power startup. Since 2011, the modernized IBR-2 reactor resumed its operation as a user facility. The IBR-2 reactor with its unique technical approach produces one of the most intense neutron fluxes at the moderator surface among the world’s neutron sources: 1016 n/cm2/s, with a peak power of 1850 MW in pulse. Current status of the reactor, neutron scattering instruments, other experimental facilities and experimental infrastructure will be presented. The designated service lifetime of the IBR-2 will end towards 2030. To keep the experience in the field of condensed matter investigations and to provide a neutron source that complements the steady state PIK reactor, JINR has started activities dedicated to the conceptual design of a new advanced pulsed neutron source at the world level. The parameters of a new source and technical approaches will also be given in the article.