Li Reaction Research Articles

Correction to: Theoretical analysis of the double-differential cross-sections of neutron, proton, deuteron, $$^3$$He, and $$\alpha$$ for the $$\text {p}+^6$$Li reaction

Correction to: Theoretical analysis of the double-differential cross-sections of neutron, proton, deuteron, $$^3$$He, and $$\alpha$$ for the $$\text {p}+^6$$Li reaction

Assessing the biological effects of boron neutron capture therapy through cellular DNA damage repair model.

Boron neutron capture therapy (BNCT) is a targeted radiotherapy that relies on the 10B (n, α) 7Li reaction, which produces secondary particles with high linear energy transfer (LET), leading to a high relative biological effectiveness (RBE) in tumors. The biological effectiveness of BNCT is influenced by factors such as boron distribution and concentration, necessitating improved methods for assessing its radiobiological effects and clarifying the sensitivity of the differences in different factors to the biological effects. This paper introduces a method to evaluate the biological effects of BNCT using the cellular repair model. This method aims to overcome some of the limitations of current evaluation approaches. The primary goal is to provide guidance for clinical treatments and the development of boron drugs, as well as to investigate the impact of the synergistic effects of mixed radiation fields in BNCT on treatment outcomes. The approach involves three key steps: first, extending the radial energy deposition distribution of BNCT secondary particles using Geant4-DNA. This allows for the calculation of initial DNA double-strand breaks (DSBs) distributions for a given absorbed dose. Next, the obtained initial DSB distributions are used for DNA damage repair simulations to generate cell survival curves, then thereby quantifying RBE and compound biological effectiveness (CBE). The study also explores the synergistic effects of the mixed radiation fields in BNCT on assessing biological effects were also explored in depth. The results showed that the RBE of boronophenylalanine (BPA) and sodium borocaptate (BSH) drugs at cell survival fraction 0.01 was 2.50 and 2.15, respectively. The CBE of the boron dose component was 3.60 and 0.73, respectively, and the RBE of the proton component was 3.21, demonstrating that BPA has a significantly higher biological impact than BSH due to superior cellular permeability. The proton dose significance in BNCT treatment is also underscored, necessitating consideration in both experimental and clinical contexts. The study demonstrates that synergistic effects between disparate radiation fields lead to increased misrepairs and enhanced biological impact. Additionally, the biological effect diminishes with rising boron concentration, emphasizing the need to account for intercellular DNA damage heterogeneity. This methodology offers valuable insights for the development of new boron compounds and precise assessment of bio-weighted doses in clinical settings and can be adapted to other therapeutic modalities.

Preliminary study of a compact epithermal neutron absolute flux intensity measurement system for real-time in-vivo dose monitoring in boron neutron capture therapy

Boron neutron capture therapy (BNCT) is a radiotherapy technology that selectively kills tumor cells via the 10B(n, α)7Li reactions. Epithermal neutrons (0.5 eV–10 keV) are emitted and converted into thermal neutrons, which have a larger neutron capture reaction cross-section, by slowing down in the human body before reaching the tumor. Recently, the development of an epithermal neutron absolute flux intensity measurement technique has become crucial for real-time in-vivo dose monitoring in BNCT. In this study, a concept for a measurement system consisting of multiple compact scintillator with optical fibers detectors covered with neutron absorbers of various thicknesses is proposed. The designed system achieves a consistent response to epithermal neutrons with a theoretical coefficient of variation not higher than 5% for both LiCAF and EJ-254 scintillators. The theoretical feasibility of the proposed measurement system was investigated by an irradiation experiment carried out at the heavy water neutron irradiation facility at the Kyoto University Reactor. The experimental results indicated that further improvement and refinement are necessary to meet the high accuracy and precision required for real-time dose monitoring in clinical applications.

Determination of electron screening potential of 6Li(p, [formula omitted])3He reaction using Multi Layer Perceptron based neural network

Understanding nuclear reactions between light-charged nuclei in the sub-Coulomb energy region is crucial for several astrophysical processes. Accurate determination of the reaction cross-section within the astrophysically important Gamow range is challenging due to electron screening. Various methods, including polynomial fits, R-Matrix, and the indirect Trojan Horse Method (THM), have estimated electron screening energies that exceed the adiabatic limit. This study aims to derive the bare astrophysical S-factor for the reaction 6Li(p,α)3He and to extract electron screening energies using Multi-Layer Perceptron-based Artificial Neural Network (ANN) analysis. Experimental S-factors for 6Li(p,α)3He, obtained from the literature, are reanalyzed with the ANN algorithm to determine the energy-dependent S-factor. The bare astrophysical S-factor is calculated from data above 60 keV, where electron screening is negligible. The electron screening potential is then derived by comparing the shielded S-factor with the bare S-factor. The ANN-based analysis yields an electron screening potential of 220 eV, suggesting that ANN could be a viable tool for estimating electron screening potentials in light nuclei reactions.

Study of one-step and two-step neutron transfer in the reaction 6Li + 9Be* *Supported by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (AP19677087) and by the Russian Science Foundation (24-22-00117)

This paper presents the results of experiments conducted to measure the cross-sections for elastic scattering and nucleon transfer channels in the 6Li+9Be reaction at an incident energy of 68 MeV: 9Be(6Li,6Li)9Be, 9Be(6Li,7Li)8Be, 9Be(6Li,7Li)8Be2+, 9Be(6Li,8Li)7Be, and 9Be(6Li,7Be)8Li. The objective of the study is to elucidate the manifestation of the cluster structure of 9Be. Theoretical analysis of the contributions of the one-step and two-step neutron transfer mechanisms is performed using the distorted wave Born approximation method with the Fresco code. Good agreement between the calculations and the experimental data is obtained for the channels of elastic scattering 9Be(6Li,6Li)9Be, neutron 9Be(6Li,7Li)8Be, and proton transfer 9Be(6Li,7Be)8Li, as well as for the transfer of two neutrons 9Be(6Li,8Li)7Be. The dineutron cluster transfer mechanism makes a dominant contribution to the 9Be(6Li,8Li)7Be reaction channel at forward angles.

Generation of neutron spectra and emission yields from proton-induced reactions on natC and natLi targets using CR-39 detectors

Fast neutron spectrometry and dosimetry at a specified location in a compact radiation environment is difficult due to large size of the conventional neutron spectrometers. In such situations, a small-size bare CR-39 detector can be used as a neutron detector to quantify the fast neutron fraction. In the present study, CR-39 detectors were placed very close to natural lithium and carbon targets during the proton irradiations to acquire the emission neutron spectra. The neutron spectra and the ambient dose equivalents in the forward and lateral directions with respect to the incident proton beam were estimated for both targets at incident proton energies between 8 and 20 MeV. The measured neutron spectra using CR-39 detectors could identify the quasi mono-energetic neutron features from the Li(p,n) and 13C(p,n) reactions effectively. An important observation of the present study is the identification of the fast neutron signature from the 13C(p,n) system from the discrete state de-excitations of excited 14N composite nuclei. The theoretical evaluation of the neutron spectral features and relative neutron energy distributions were performed using the FLUKA: FLUktuierende KAskade, a Monte Carlo simulation package, and the estimates agreed with the experimental results for both systems. The neutron ambient dose equivalents were also estimated from the measured spectra. These neutron fluence and dose estimates at close vicinity to the target can serve as an essential basis for shielding calculations and planning the pertinent radiation protection strategies.

Lithium Neutron Cross Sections During the Manhattan Project and the Quest for the H-Bomb

Neutron cross sections of the stable lithium isotopes 6Li and 7Li were of interest in the 1940s and 1950s in part because of their reactions, which form tritium using moderated neutrons on 6Li and higher-energy neutrons on either isotope. Lithium remains of interest today for use as a blanket and shielding material in fusion reactors, where it can be used to breed tritium for a self-sustaining fuel cycle. During the Manhattan Project, the resonance in the 6Li(n,t) reaction was discovered and later became important for enhancing tritium production for nuclear technologies. The dominant natural isotope 7Li was and remains of interest because of the expense of enriching 6Li. It has been oft reported that the 1954 Castle Bravo nuclear test had a yield twice as large as expected because the nuclear explosive device designers had not properly accounted for the benefits from the 7Li isotope in the fuel; we note that this explanation is false.

New developments of hydrogen impurity online-monitoring in liquid lithium of IFMIF-DONES

On the way to future nuclear fusion power plants, the International Fusion Materials Irradiation Facility (IFMIF) – DEMO Oriented Neutron Source (DONES), is an important key element between ITER and DEMO to study before the influence of DEMO-neutron irradiation on foreseen fusion materials. The core of DONES, currently under construction near Granada, Spain, is based on a circuit containing liquid lithium at elevated temperatures acting as a functional material for the (d,n)-Li reaction in a materials test cell. In addition to this actual function of DONES, there are important aspects of maintenance in which hydrogen isotopes are generated under operating conditions and dissolved in this aggressive and very reactive alkali metal. This implies strong unfavourable effects on the applied structural materials, e.g. hydrogen embrittlement and others.To counteract these unfavourable effects, endangering the safe operation, an Impurity Control System (ICS) is an integral part of the DONES instrumentation. As part of the tasks of the European Neutron Source (ENS) to develop redundant systems for monitoring impurities, a special sub-task was defined for the development of an electrochemical H-sensor for concentrations in liquid lithium, ECHSLL. It is determined by detecting the electrical potentials of the lithium melts compared to a standard Li-based chemical reference system. This allows an inherent material property to be directly correlated (i.e. through appropriate electrochemical instrumentation) with chemical concentration values. This article presents important advancements in the applied ECHSLL technique, such as improving laboratory measurements from stagnant conditions to dynamic and realistic flow conditions of the liquid lithium material, as well as appropriate approaches to overcome the challenges in distinguishing the hydrogen isotopes by ECHSLL system (protium and deuterium among given laboratory conditions).

Strength of bulk aluminum-boron alloys containing helium produced by 10B(n,α)7Li reaction in nuclear reactor

The study of metals and alloys containing helium has garnered significant attention within the nuclear energy community. However, there is limited research on the mechanical behavior of bulk alloys implanted with helium. This study investigates the mechanical properties of several Al-Boron alloys implanted with helium using controlled manipulation of helium doses via boron content under a consistent neutron dose. Results show that HemVn may contribute to strength by approximately 8.4–15 MPa and 16.8–23 MPa for helium doses 3.08 × 1019/cm3 and 6.84 × 1019/cm3, respectively, while lattice damages due to neutron-aluminum reaction contribute to strength by 24∼27 MPa. Subsequent annealing leads to the formation of helium bubbles, resulting in a slightly higher strengthening effect compared to HemVn. Additionally, the work hardening behavior of the alloys can be explained by the Voce model, drawing inspiration from the resemblance between helium bubbles and nanoprecipitates in 7xxx alloys. These findings provide insights to the nuclear energy community.

Valence band XPS spectra of K silicate glasses: Effect of HOMO energies on K, Na and Li leach rates, activation energies and reaction mechanism

X-ray Photoelectron spectra of K-silicate glass valence bands (VBs) are composed of distinct upper and lower bands, separated by a minimum at ∼10 eV binding energy. A third, narrow band at ∼4.5 eV represents the highest energy occupied molecular orbitals (HOMOs). Na and Li glass VBs are similarly composed of upper, lower and HOMOs bands. The HOMOs reside only on NBO atoms (NBO = O atoms of the Si-O-M moiety; M = alkali), are non-bonding orbitals of O 2py character and are located at 4.5, 4.8 and 5.2 eV in K, Na and Li glasses. The order corresponds to alkali leach rates in water. We propose a SN reaction mechanism and Frontier Molecular Orbital concepts for leaching involving the HOMOs of the glasses and the LUMO of an adsorbed water molecule. The activated complex, Si-NBO*-M (NBO* = NBO•••HO-H), is formed through H-bonding of a solvent H2O molecule to NBO.

Studying subthreshold resonance using the Trojan horse method

The Trojan horse method was employed to indirectly measure the bare-nucleus reaction cross-section and astrophysical S-factor of the 9Be(p,α)6Li reaction in the low-energy region, utilizing the three-body reaction 2H(9Be,α6Li)n. Comparing the two-body reaction data extracted from the Trojan horse method with that obtained through direct measurements, compatibility is observed in the energy region above approximately 100 keV. Additionally, the THM data successfully reproduces the expected low-energy resonance peak around 270 keV. The THM extraction of the astrophysical factor yields S(0) = 21.0 ± 0.8 MeV b, which surpasses the extrapolation obtained from direct measurements. The 9Be(p,α)6Li reaction channel exhibits a subthreshold resonance with a width of 25 keV, positioned approximately -23 keV below the threshold. However, the strong electron shielding effect near the zero energy position in direct measurements often masks the influence of the subthreshold resonance on the low-energy region. In contrast, the THM method allows us to neglect the electron shielding effect. The THM experimental data were subjected to fitting using the Breit-Wigner function and subsequently compared with directly measured data. Following a comprehensive comparative analysis, it was discerned that the S(0) value obtained through THM exceeded the extrapolated value derived from direct measurements. This disparity was primarily attributed to the influence of the subthreshold resonance.

Study of the 7Be(d,3He)6Li* reaction at 5 MeV/u

The measurement of the 7Be(d,3He)6Li* transfer cross section at 5 MeV/u is carried out. The population of the 2.186 MeV excited state of 6Li in this reaction channel is observed for the first time. The experimental angular distributions have been analyzed in the finite range DWBA and coupled-channel frameworks. The effect of the 7Be(d,3He)6Li reaction on both the 6Li and 7Li abundances are investigated at the relevant big-bang nucleosynthesis energies. The excitation function is calculated by TALYS and normalized to the experimental data. The S factor of the (d,3He) channel from the present work is about 50% lower than existing data at nearby energies. At big-bang energies, the S factor is about three orders of magnitude smaller than that of the (d,p) channel. The (d,3He) reaction rate is found to have a less than 0.1% effect on the 6,7Li abundances.

Neutron-induced thermoluminescence of Dy3+-doped B2O3–Na2O–CaO–P2O5 glasses

Thermoluminescence (TL) materials based on Dy3+-doped B2O3–Na2O–CaO–P2O5 glasses have been developed for neutron detection. After X-ray irradiation, the TL glow peaks were observed at 360 K, and the TL intensities of the 10B- and 11B-enriched samples were similar. After neutron irradiation, a significant difference in the TL intensities was observed between the 10B- and 11B-enriched samples, which indicates that γ-rays and high-energy particles in the 10B (n, α)7Li reaction efficiently induced TL. The TL intensities derived from the 10B (n, α)7Li reaction linearly increased with neutron fluence of 106–1011 neutrons cm−2. Therefore, TL glass materials were successfully developed for neutron detection.

Estimation of nuclear properties in a deuteron–lithium target using JENDL/DEU-2020 for IFMIF and similar irradiation facilities

An accelerator-based neutron source powered by deuteron–Li (d–Li) reactions is among the most promising neutron sources for fusion materials irradiation facilities, such as IFMIF, IFMIF-DONES, and A-FNS. The yield estimation of neutrons and other particles is critical to the design of these facilities. Presently, the McDelicious code is employed for the aforementioned yield estimations, although it is not an open code. Recently, a deuteron-induced reaction library, JENDL/DEU-2020, was released by the Japan Atomic Energy Agency. Thus, employing benchmark tests, such as the Particle and Heavy Ion Transport code System (PHITS) + JENDL/DEU-2020, Monte Carlo N-Particle + JENDL/DEU-2020, and McDelicious, we confirm that PHITS (or Monte Carlo N-Particle (MCNP)) + JENDL/DEU-2020 effectively reproduces the experimental data and McDelicious results. We apply PHITS + JENDL/DEU-2020 to the yield estimations of the neutron, gamma, and charged particles in a Li target and to the yield estimation of the charged particles in the target backplate for A-FNS. The estimated production rates of tritium and 7Be during the continuous operation using a deuteron beam of 40 MeV and 125 mA are 1.4 × 1016 atoms/s (2.3 g/FPY) and 5.9 × 1014 atoms/s (0.21 g/FPY), respectively, and the estimated production rates of He and H in the target backplate for A-FNS are 3.2 × 102 and 1.8 × 103 appm/FPY, respectively.

Theoretical analysis of the double-differential cross-sections of neutron, proton, deuteron, $$^3$$He, and $$\alpha$$ for the $$\text {p}+^6$$Li reaction

Theoretical analysis of the double-differential cross-sections of neutron, proton, deuteron, $$^3$$He, and $$\alpha$$ for the $$\text {p}+^6$$Li reaction

Experimental emulation of 10B(n, α)7Li reaction-induced microstructural evolution of Al-B4C neutron absorber used in the dry storage of spent nuclear fuel

Al-B4C neutron absorber in spent fuel dry storage could suffer significant radiation damage at elevated temperature (∼150–300 °C) mainly via 10B(n, α)7Li reactions. Several recent studies reported significant bubble formation in the absorber, however only from wet storage environment at near ambient temperature (< ∼90 °C). In this study, we irradiated a commercially widely used Al-B4C absorber of interest utilizing 120-keV helium ion-beam accelerator with twelve different conditions; three different doses (0.01, 0.1, and 1 dpa) combined with four different temperatures (room temperature, 150, 270, and 400 °C). This was to investigate the irradiation-induced microstructural evolution of the absorber in dry storage environment in expedited manner instead of time-consuming neutron irradiation test. The effects of irradiation dose and temperature on helium bubble nucleation and growth were investigated by image analysis on BF-TEM images, which showed a typical tendency of increasing bubble size with increasing temperature at the expense of decreasing bubble number density. Helium bubble morphology at grain boundaries was quite similar with the ones reported from the previous studies on the surveillance coupons used in the wet environment, elliptic helium bubbles around B4C particles. Notable difference was the prominent formation of numerous helium bubbles even from the lowest dose (0.01 dpa) at slightly elevated temperature (150 °C), perhaps due to higher irradiation temperature than that of spent fuel pool. This study may experimentally confirm that significant bubble formation and growth in the absorber could be the case from the early stage of the dry storage, even without the participation of hydrogen produced from the absorber corrosion. Particularly in the case of non-clad Al-B4C absorber, possible B4C particle detachment may need to be concerned since the bubble coalescence was concentrated at the interface between Al alloy matrix and B4C particle which would be microcracked under neutron irradiation.

Application of thin boron deposit by electrophoresis as neutron detectors

Abstract Detecting nuclear radiation presents a distinctive challenge, particularly with neutrons, which are neutral particles. The method of direct detection involves the utilization of a converter material, acting as an intermediary. Boron plays a pivotal role in this process, reacting with thermal neutrons to generate alpha particles and lithium, with a notable energy release of 2.314 MeV during the 10B (n,α) 7Li reaction. This facilitates effective identification and measurement of neutrons in radiation detection systems. The paths of the particles α (for E = 1.474 MeV) and Li (for E Li = 0.842 MeV). The active medium of the nuclear detector, typically a gas, undergoes ionization by these highly charged particles, or they form ion pairs that are subsequently collected by electrodes to produce the signal at the detector’s output. Various deposit methods can be used for this purpose, electrophoresis offers a distinct advantage in terms of both simplicity and precision. This study details the utilization of the electrophoresis technique for the deposition of boron on the tube walls of prototype detectors developed within our laboratory.

Simulation of Radiation Damage and He Accumulation Induced by 10B(n, α)7Li Reactions in Al-B4C Neutron Absorbers Used in Spent Fuel Pools

Faster than expected surface corrosion and a considerable decrease in the 10B areal density of a non-clad Al-B4C neutron absorber were recently reported from surveillance coupons used in a spent fuel pool for about 8 years, which is only approximately one-fifth of the guaranteed service life of the absorber. Such premature degradation was largely attributed to irradiation-assisted corrosion since numerous gas bubbles filled with He and H were discovered in the Al alloy matrix near B4C particles, and naturally 10B(n, α)7Li reactions were designated as the underlying mechanism for the porosification that may have expedited the absorber corrosion. In this study, the levels of radiation damage and He concentration in the micrographs published in recent experimental studies were estimated to design ion beam irradiation experiments having appropriate parameters to emulate the status of neutron-irradiated non-clad Al-B4C absorbers. TRITON, CSAS6, and SDTrimSP were coupled with modifications for the calculation of dpa and He concentration in irradiated neutron absorbers. The simulations yielded 3.74–6.71 dpa and 0.71–1.64 at% of He after 99 months of use and 3.82–8.39 dpa and 0.73–2.08 at% of He after 40 years of use. The simulations also demonstrated that the radiation damage and He concentration have a weak correlation with the particle diameter. In terms of radiation damage, these results are in good agreement with the reported experimental data, indicating that they can be referred to in the experimental design. The calculated He concentrations, however, may warrant modification to include leakage of implanted He atoms through irradiation-induced microcracks in the B4C particles. Because of the high diffusivity of He, full leakage of He from B4C particles to their boundaries with the Al alloy matrix was assumed for further estimations, which revealed that He concentration could be significantly elevated in the Al matrix near B4C particles.

A neural network potential energy surface of the Li3 system and quantum dynamics studies for the 7Li + 6Li2 → 6Li7Li + 6Li reaction.

A high-precision global potential energy surface (PES) of the Li3 system is constructed based on high-level ab initio calculations, and the root-mean-square error is 5.54 cm-1. The short-range of the PES is fitted by the fundamental invariant neural network (FI-NN) method, while the long-range uses a function with an accurate asymptotic potential energy form, and the two regions are connected by a switching function. Based on the new PES, the statistical quantum-mechanical (SQM) and the time-dependent wave packet (TDWP) methods are used to study the dynamics of 7Li + 6Li2 (v = 0, j = 0) → 6Li7Li + 6Li reactions in the low collision energy region (10-11 to 10-3 cm-1) and the high collision energy region (8 to 800 cm-1), respectively. In the high collision energy region, the calculation results of the SQM method and the TDWP method are inconsistent, indicating that the reaction dynamics does not follow the statistical behavior in the high collision energy region. In addition, we found that the Coriolis coupling effect plays an important role in this reaction. The symmetric forward-backward scattering in the total DCS indicates that the reaction follows the complex-forming reaction mechanism.

A compact scintillator-based detector with collimator and shielding for dose monitoring in boron neutron capture therapy

Boron neutron capture therapy exploits 10B(n,α)7Li reactions for targeted tumor destruction. In this work, we aimed at developing a dose monitoring system based on the detection of 478keV gamma rays emitted by the reactions, which is very challenging due to the severe background present. We investigated a compact gamma-ray detector with a pinhole collimator and shielding housing. Experimental nuclear reactor measurements involved varying boron concentrations and artificial shifts of the sources. The system successfully resolved the 478keV photopeak and detected 1cm lateral displacements, confirming its suitability for precise boron dose monitoring.