Search

Several intense energy irradiation testing facilities are functional to study the effects of radiation damage in fusion materials. Tungsten is a potential candidate material to build the plasma-facing armour components of fusion reactors. Therefore, it is vital to estimate the radiation-induced primary damage in the material, particularly due to the large amount of transmutation nuclides produced in the high-energy neutron sources. The basic evaluated nuclear data libraries provide the essential neutron reaction data to estimate the transmutations and their effects during irradiation. However, much of the important high-energy neutron reaction data are often not explicitly provided to directly study their impact on radiation damage. Such inexplicit nuclear reaction data, especially for the transmutation nuclides, can have a significant effect on the estimation of primary radiation damage. A new specific methodology has been developed to unravel information from these inexplicit nuclear reaction data from the basic ENDF-6 libraries and use them with explicit data for estimating the primary radiation damage. The energy distributions of transmuted nuclides (the recoil nuclei in general) and light charged particles produced as a result of several types of neutron–nucleus interactions in tungsten, are quantified using the cross-sections from ENDF / B-VIII.0 and TENDL-2019 basic evaluated nuclear data libraries and their inter-comparisons are carried out. The neutron-induced atomic displacements and heating in tungsten are estimated for irradiations under the fusion and IFMIF-DLi neutron spectra. It shows that the transmutation reactions under these neutron spectra can sometimes contribute more than 50% of the total primary damage, most of which can be from inexplicit nuclear reaction data. Significant differences between the two sources of basic evaluated nuclear data libraries, especially in the production of transmutation nuclides and consequently, in their contributions to damage are observed. The present study helps to illustrate the importance of inexplicit nuclear reaction data and the usefulness of the ENDF-6 libraries for estimating primary radiation damage due to transmutations in plasma-facing materials. [ABSTRACT FROM AUTHOR]

Hadron therapy (HT) is a technique that uses accelerated ions, notably protons, and carbon ions, to destroy tumors. It has demonstrated high success rates in the treatment of certain cancers resistant to irradiation. In HT, the majority of the dose is delivered to the tumor volume by electromagnetic interactions with atomic electrons. However, it is important to note that the primary particles used in HT can induce nuclear reactions, generating undesirable secondary radiation, certainly neutrons. As a result, a significant portion of the patients' body may be exposed to the secondary background radiation field. Thus, these unwanted secondary neutrons should be evaluated. The purpose of this research in first is to characterize the secondary neutron production (SNP) during the administration of Hadrons with energies 140 MeV proton, and 264 MeV/u carbon ions ( C) in a soft tissue phantom. Second, comparing the neutron spectrum for different angles for protons and carbon ions for carbon targets to experimental data. Our results show that the neutron spectra (thick target neutron yields TTNYs) at energies less than 20 MeV, using the INCL4.6/GEM models and JQMD/GEM across a wide range would be suitable for the Monte Carlo transport simulation. [ABSTRACT FROM AUTHOR]

In the present work, the neutron yield of a Pu-Be neutron source has been calculated by using two methods, calculation with the SOURCES4C code developed at LANL and via an equation, respectively. The present work aims to determine and compare the two methods in obtaining the yields and spectra of an (a,n) type neutron source. The source used for this work is being held at IFIN-HH, and was well experimentally characterized in previous work. The results of the present work compare well with the experimental data. [ABSTRACT FROM AUTHOR]

Featured Application: Numerical modelling of yields and distributions of nuclear fusion products in magnetically confined plasma. Velocity distributions of fuel nuclei enter the formulae for distributions of products of fusion reactions in plasma. The formulae contain multiple integration, which is a computationally heavy task. Therefore, simplifications of the integrand are advantageous. One of possible simplifications is the use of closed-form analytical distributions of fast deuterons and tritons, accounting for slowing down and pitch-angle scattering and neglecting the speed diffusion. The plausibility of such a model has been studied from the viewpoint of its influence on the calculated spectra of fusion neutrons. Calculations have shown that the speed diffusion effect on suprathermal ion distribution tails does not significantly alter the qualitative behaviour of energy and angle distributions of fusion products in a beam-heated plasma. [ABSTRACT FROM AUTHOR]

The nuclear physical properties of austenitic chromium-nickel steel EK-164 (Fe–16Cr–19Ni–2Mo–2Mn–Nb–Ti–B) and its manganese-based modifications EK-164Mn (Fe–16Cr–20Mn–2Mo–Nb–Ti–B) and EK-164MnW (Fe–16Cr–20Mn–2W–Nb–Ti–B) under irradiation (up to 5 effective years) in the neutron spectra of fast power (BN-600) and thermonuclear (DEMO-C) reactors and after irradiation (nuclear cooling up to 1000 years) were determined. The investigations were based on using the ACDAM-2.0 calculation complex with consideration of the elemental (alloying and impurity) compositions of steels and typical neutron spectra of fission (BN-600) and fusion (DEMO-C) reactors. The entire set of nuclear physical characteristics of steels (primary radiation damage; transmutation of elements; radiogenic accumulation of elements, including hydrogen, helium, and boron; γ-dose rate; radioactivity; nuclear energy release; isotope contributions) is obtained and their comparative analysis is performed. The time intervals for fulfilling the criteria of low activation of steels after irradiation (γ-dose rate less than 10 mSv/h, radioactivity less than 1010 Bq/kg, energy release less than 10 W/m3) were determined. [ABSTRACT FROM AUTHOR]

Simulated workplace neutron fields of a 241 Am–Be source moderated by polyethylene spheres have been developed. The characterization in terms of neutron fluence rate and neutron ambient dose equivalent rate, H ∗ (10) , was performed using Bonner sphere spectrometer and the MAXED and FRUIT unfolding codes. The neutron fluence rates and the H ∗ (10) rates obtained from the two codes are in good agreement with the discrepancies of 8% and 6%, respectively. The neutron ambient dose equivalent-averaged energies and the neutron fluence-to-dose equivalent conversion coefficients were also evaluated in comparison between the two codes. The discrepancies are < 10% and 12%, respectively. [ABSTRACT FROM AUTHOR]

The neutron spectra measurement is important for larger fusion devices because it can provide ion temperature diagnostics independent of ion density. In this work, the neutron spectrum in the thermonuclear reaction is analyzed with a different approach, is approximately determined by the Maxwell distribution of the reaction particle, and is independent of the reaction cross section. [ABSTRACT FROM AUTHOR]

A typical reactor representing a flexible source of radionuclide production is the LVR-15. More detailed irradiation conditions available within one core configuration of this reactor will be provided. The most important parameter-neutron flux density in different energy intervals-will be determined experimentally by activation detectors and compared with calculated values. Experimental and calculated values will be used for the estimates of the radionuclide production in case of the selected radioisotopes. [ABSTRACT FROM AUTHOR]

Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies = 20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire energy range being measured, i.e., thermal to 250 MeV. The authors used the neutron fluence spectrum to demonstrate experimentally the contribution of neutrons with different energies to the total dose equivalent and in particular the contribution of high-energy neutrons (=20 MeV). These are valuable reference data that can be directly compared with Monte Carlo and experimental data in the literature. [ABSTRACT FROM AUTHOR]

Neutron fluxes and spectra in the horizontal experimental channels of reactor WWR-M of the Institute for Nuclear Research, National Academy of Sciences of Ukraine (Kyiv) have been calculated using neutron transport Monte Carlo model with fuel enriched in 235U both to 36 and 19.7 %. It is shown that at the very beginning operating with lowenriched fuel, when the reactor core is 28 % filled with "fresh" fuel assemblies, and the remaining cells are filled with beryllium displacers, there is a significant change in the parameters of neutron beams. However, after the reactor will begin to operate at its usual mode, that will be after completing all or most part of the core with fuel assemblies partially burnt out, spectra and fluxes in channels will restore most of their previous values. Some differences are mainly due to changes in composition of the core - the removal of two voluminous vertical water channels located within the core. The work can be helpful to experimenters working with extracted beams at this reactor and so at other reactors that have been converted to low-enriched fuel. [ABSTRACT FROM AUTHOR]

Abstract: In radiation therapy with high-energy photon beams (E >10MeV) neutrons are generated mainly in linacs head thorough (γ,n) interactions of photons with nuclei of high atomic number materials that constitute the linac head and the beam collimation system. These neutrons affect the shielding requirements in radiation therapy rooms and also increase the out-of-field radiation dose of patients undergoing radiation therapy with high-energy photon beams. In the current review, the authors describe the factors influencing the neutron production for different medical linacs based on the performed measurements and Monte Carlo studies in the literature. [ABSTRACT FROM AUTHOR]

Neutron spectrum and ambient dose equivalent has been measured around two 10 MV linear accelerators. Measurements were carried out in Mevatron and Primus model linacs, both made by Siemens. Main differences between those models are the beam collimator and the vault room. Here, Bonner sphere spectrometer with a passive thermal neutron detector has been utilized to measure the neutron spectrum inside the vault. Using an active detector the neutron spectrum was measured at the vault’s door of both accelerators. With a neutron area monitor the dose equivalent was measured by the door at both vault doors. Neutron strength, total fluence rate and ambient dose equivalent were compared, from this was found that shielding conditions are better in the Primus model. [ABSTRACT FROM AUTHOR]