Evaluation Of Radiation Damage Research Articles

Specific radiation damage is a lesser concern at room temperature.

Carrying out macromolecular crystallography (MX) experiments at cryogenic temperatures significantly slows the rate of global radiation damage, thus facilitating the solution of high-resolution crystal structures of macromolecules. However, cryo-MX experiments suffer from the early onset of so-called specific radiation damage that affects certain amino-acid residues and, in particular, the active sites of many proteins. Here, a series of MX experiments are described which suggest that specific and global radiation damage are much less decoupled at room temperature than they are at cryogenic temperatures. The results reported here demonstrate the interest in reviving the practice of collecting MX diffraction data at room temperature and allow structural biologists to favourably envisage the development of time-resolved MX experiments at synchrotron sources.

Characterization of a non-contact imaging scintillator-based dosimetry system for total skin electron therapy

Surface dosimetry is required for ensuring effective administration of total skin electron therapy (TSET); however, its use is often reduced due to the time consuming and complex nature of acquisition. A new surface dose imaging technique was characterized in this study and found to provide accurate, rapid and remote measurement of surface doses without the need for post-exposure processing.Disc-shaped plastic scintillators (1 mm thick × 15 mm ) were chosen as optimal-sized samples and designed to attach to a flat-faced phantom for irradiation using electron beams. Scintillator dosimeter response to radiation damage, dose rate, and temperature were studied. The effect of varying scintillator diameter and thickness on light output was evaluated. Furthermore, the scintillator emission spectra and impact of dosimeter thickness on surface dose were also quantified. Since the scintillators were custom-machined, dosimeter-to-dosimeter variation was tested. Scintillator surface dose measurements were compared to those obtained by optically stimulated luminescence dosimeters (OSLD).Light output from scintillator dosimeters evaluated in this study was insensitive to radiation damage, temperature, and dose rate. Maximum wavelength of emission was found to be 422 nm. Dose reported by scintillators was linearly related to that from OSLDs. Build-up from placement of scintillators and OSLDs had a similar effect on surface dose (4.9% increase). Variation among scintillator dosimeters was found to be 0.3 ± 0.2%. Scintillator light output increased linearly with dosimeter thickness (~1.9 × /mm). All dosimeter diameters tested were able to accurately measure surface dose.Scintillator dosimeters can potentially improve surface dosimetry-associated workflow for TSET in the radiation oncology clinic. Since scintillator data output can be automatically recorded to a patient medical record, the chances of human error in reading out and recording surface dose are minimized.

Calculation of dpa rate in graphite box of Tehran Research Reactor (TRR)

Radiation damage is an important factor that must be considered while designing nuclear facilities and nuclear materials. In this study, radiation damage is investigated in graphite, which is used as a neutron reflector in the Tehran Research Reactor (TRR) core. Radiation damage is shown by displacement per atom (dpa) unit. A cross section of the material was created by using the SPECOMP code. The concentration of impurities present in the non-irradiated graphite was measured by using the ICP-AES method. In the present study the MCNPX code had identified the most sensitive location for radiation damage inside the reactor core. Subsequently, the radiation damage (spectral-averaged dpa values) in the aforementioned location was calculated by using the SPECTER, SRIM Monte Carlo codes, and Norgett, Robinson and Torrens (NRT) model. The results of “Ion Distribution and Quick Calculation of Damage” (QD) method groups had a minor difference with the results of the SPECTER code and NRT model. The maximum radiation damage rate calculated for the graphite present in the TRR core was 1.567 × 10−8 dpa/s. Finally, hydrogen retention was calculated as a function of the irradiation time.

An upgrade of the materials irradiation facility with in-situ electrical resistivity measurement at the Demokritos TANDEM accelerator

As an important part of fusion materials research, evaluation of radiation damage in fusion materials has been emphasized more than a half century. In order to improve our understanding of radiation damage in fusion materials, an upgrade has been performed of the materials irradiation facility IR2, which is located at the NCSR “Demokritos” 5.5 MV TANDEM accelerator. The upgraded facility allows irradiation at higher ion beam currents while ensuring that the target temperature remains below 10 K. It provides in-situ electrical resistivity measurements on several samples for real-time monitoring of radiation damage as well as in-situ post-irradiation annealing up to 300 K. The upgraded IR2 facility has been successfully employed in radiation damage and recovery studies of metallic materials with applications in fusion research.

Radiation Sensitivity of <i>in Vitro</i> Evaluation System of Pharmacokinetics in Boron Neutron Capture Therapy (BNCT) Using Three-Dimensional Artificial Human Tumor Tissue Model

One of the important matters that must be determined in advance when performing BNCT treatment is the optimization of neutron irradiation time and dose. In this article, following the previous article (2.52 × 1012 n/cm2) (Case 1), double irradiation (5.04 × 1012 n/cm2) was further performed (Case 2) by verifying the radiation sensitivity performance of the artificial tumor tissue NHDF3D/BxPC3 and the possibility of evaluating the optimum neutron dose required for treatment was examined. As a result, although the radiation damage rate in the normal tissue NHDF3D and the tumor tissue BxPC3 increased in proportion to the irradiation dose due to heavy irradiation in Case 1 or more, the increase in the damage rate in the normal tissue exceeded the tumor tissue. Furthermore, the tumor/normal tissue damage ratio T/N ratio showed the maximum value in Case 1, and the dose ratio in Case 2 with a higher dose showed a tendency to decrease. From the above experimental facts, it was shown that irradiation dose optimization is possible to some extent by an evaluation method using an artificial tumor tissue.

Atomic displacement cross-sections for neutron irradiation of materials from Be to Bi calculated using the arc-dpa model

Displacement cross-sections for an advanced assessment of radiation damage rates were obtained for a number of materials using the arc-dpa model at neutron incident energies from 10 −5 eV to 10 GeV. Evaluated data files, CEM03 and ECIS codes, and an approximate approach were applied for the calculation of recoil energy distributions in neutron induced reactions. Three sets of displacement cross-sections based on the use of low-energy data from JEFF-3.3, ENDF/B-VIII.0, and JENDL-4.0u were prepared. Files contain also cross-sections calculated using the standard NRT model. Special efforts were made to estimate the uncertainty of obtained displacement cross-sections.

Nonlinear ultrasonic response of voids and Cu precipitates in body-centered cubic Fe

Interpreting nonlinear ultrasonic signals detected in a nondestructive evaluation of radiation damage requires the knowledge of the correlation between defects and nonlinearity. In this work, molecular dynamics simulations are performed to study the effect of distributed vacancies, voids, Cu atoms, and Cu precipitates on the nonlinear ultrasonic response in body-centered cubic (bcc) Fe. The nonlinearity parameter calculated from the second harmonic amplitude in the perfect lattice is 2.73. Vacancies are found to increase the nonlinearity. However, clusters of vacancies in the form of spherical voids show an opposite effect. This finding can be used to conveniently distinguish vacancies from voids in the material. Unlike vacancies, individual Cu atoms decrease the nonlinearity. Clustering of Cu atoms into Cu precipitates further decreases the nonlinearity. Interestingly, precipitates with a diameter of 2 nm and larger exhibit a similar effect despite their different structure and coherency with the Fe matrix.

Radiation damage evaluation of the CCD detector induced by high energy protons

In order to help the designers to improve the CCD detector design, reliability and applicability for applications in particle detection or space applications, the radiation damage evaluation of the CCD detector induced by high energy protons are presented. The radiation experiments were carried out at the cyclotron accelerator with energies of 100, 60, and 30 MeV. The degradations of the CCD parameters such as the overall system gain, linear saturation output, dark current, dark signal non-uniformity (DSNU), random noise, dynamic range (DR), and quantum efficiency (QE) induced by proton radiation are analyzed. The degradations versus the proton fluences are presented. The degradations induced by different proton energies are compared. The degradation mechanisms of the CCD parameters induced by proton radiation damage are demonstrated in detail.

Improved atomic displacement cross-sections for proton irradiation of aluminium, iron, copper, and tungsten at energies up to 10 GeV

Abstract Displacement cross-sections for an advanced assessment of radiation damage rates were obtained for a number of structural materials irradiated with protons at energies from threshold up to 10 GeV. The proposed calculation method utilises an athermal recombination-corrected dpa model with corrections obtained from simulations using the binary collision approximation model. Justification of the method was performed using available measured and systematics data.

Evaluation of effective threshold displacement energies and other data required for the calculation of advanced atomic displacement cross-sections

Minimum displacement threshold energy, averaged displacement threshold energy, effective displacement energy, and parameters of arc-dpa equations were estimated for 70 materials from Li to U using available experimental data.Obtained data can be used for approximate calculation of the radiation damage rate for materials irradiated with neutrons in the different facilities.

Evaluation of radiation damage in belt-line region of VVER-1000 nuclear reactor pressure vessel

Regarding irradiation damage, the most sensitive region in the reactor pressure vessel (RPV) is the area adjacent to the reactor core; the so called belt-line region. Belt-lines and their related heat affected zones (HAZs) in the belt-line region are constantly under neutron and gamma irradiation and have a higher potential to various flaws. The microscopic defects produced in materials due to irradiation are referred to as radiation damage; the units of displacements per atom (DPA) are used routinely to characterize the extent of such damage. In this research, for a typical VVER-1000 (V446) RPV, the areas of the highest neutron radiation flux (belt-line) is first identified by using a Monte Carlo neutron transport code. This is used to calculate and validate the neutron flux and fluence at the belt-line. Employing the PTRAC output from MCNP and the SRIM Monte Carlo code, radiation damage in the RPV is simulated and assessed in terms of DPA. The integrated damage for a full effective year is evaluated to be order of 5E-04 displacements per cm thickness of RPV belt-line metal.

Evaluated displacement and gas production cross-sections for materials irradiated with intermediate energy nucleons

Atomic displacement and gas production cross-sections were obtained for a number of materials to calculate radiation damage and gas production rate in nuclear- and fusion reactors, and neutron spallation sources. An advanced atomistic modelling approach was applied for calculations of the number of stable displacements in materials.

Calculation of neutron and gamma fluences on VVER reactor pressure vessel

Embrittlement is one of the most important effects affecting reactor pressure vessel (RPV) aging. RPV is irradiated with neutrons and gammas, especially fast neutrons, which mainly lead to embrittlement of RPV during operation lifetime of nuclear reactors. Therefore, the radiation-induced embrittlement of the RPV should be carefully evaluated. In this paper, a preliminary calculation was performed using the MCNP5 code to identify the areas in the RPV of the VVER-1000/V320 reactor where the neutron and gamma fluxes are maximum. Also, the neutron and gamma fluence distributions on the RPV were investigated and evaluated along with their energy spectra. These calculations are the starting point for the evaluation of radiation damage to RPV of VVER reactors.

The Effect of Solvation on the Radiation Damage Rate Constants for Adenine.

It is well known that water plays an important part in almost all biological systems and that inclusion of solvation effects might therefore be of utmost importance in studies of radiation damage to DNA. In the present investigation, we have studied the effect of different solvation models in calculations of Gibbs free energies and reaction rates for the reaction between the OH radical and the DNA nucleobase adenine by conducting density functional theory calculations at the ωB97X-D/6-311++G(2df,2pd) level with the Eckart tunnelling correction. The solvent, water, was included through either the implicit polarizable continuum model (PCM) or through explicit modelling of micro-solvation by a single water molecule at the site of reaction as well as by the combination of both. Scrutiny of the thermodynamics and kinetics of the individual sub-reactions suggests that the qualitative differences introduced by the solvation models do not significantly alter the conclusions made based solely on simple gas-phase calculations. Abstraction of the amine hydrogen atoms H61 and H62 and addition onto C8 remain the most likely reaction pathways.

Ionizing/displacement synergistic effects induced by gamma and neutron irradiation in gate-controlled lateral PNP bipolar transistors

A kind of gate-controlled lateral PNP bipolar transistor has been specially designed to do experimental validations and studies on the ionizing/displacement synergistic effects in the lateral PNP bipolar transistor. The individual and mixed irradiation experiments of gamma rays and neutrons are accomplished on the transistors. The common emitter current gain, gate sweep characteristics and sub-threshold sweep characteristics are measured after each exposure. The results indicate that under the sequential irradiation of gamma rays and neutrons, the response of the gate-controlled lateral PNP bipolar transistor does exhibit ionizing/displacement synergistic effects and base current degradation is more severe than the simple artificial sum of those under the individual gamma and neutron irradiation. Enough attention should be paid to this phenomenon in radiation damage evaluation.

Objective evaluation of radiation damage in a nucleoprotein complex.

Objective evaluation of radiation damage in a nucleoprotein complex.

Dose and temperature distribution in spent fuel containing material

Spent fuel containing material (SFCM) can arise during severe nuclear reactor accident by melting of a reactor core and surrounding material (corium) or during accident in spent fuel storage. It consists of nuclear fuel, fission products, activation products and materials from fuel cladding, concrete, etc. The paper deals with dose and temperature characteristics inside the SFCM after transition of the molten mixture to solid state. Calculations were made on simplified spherical models, without connection to some specific nuclear accident. The dose rate was estimated for alpha, beta and gamma radiation in times over the course of 30 years from the end of the fission chain reaction. Concentration of helium generated in the material by alpha decay was calculated. For the dose rate values estimation, computation code ORIGEN 2.2 with dosimetric library ENDF/B-IV were used. Temperature distribution inside the solid SFCM was calculated by FLUENT code. As source of heating, energy of radioactive decays was taken. Estimated dose and temperature characteristics can be used, e.g. for evaluation of radiation damage and temperature behaviour of SFCM or for radiation test design of corium simulating materials.

Tagged MRI based cardiac motion modeling and toxicity evaluation in breast cancer radiotherapy.

Recent research showed radiation for breast cancer can increase heart risks (1, 2). In Ref. (2), it has been noted that for every Gy of radiation a women’s heart risk rises 7.4%. However, the correlation between radiation dose and heart tissue damage is still an open problem. A more accurate model of heart damage will significantly improve the heart safety for patients underwent radiotherapy. Modern radiation treatment planning systems (TPS) use computed tomography (CT) images for dose calculation and evaluation. For evaluation of heart toxicity from radiotherapy, the dose-volume histogram (DVH), which is generated by overlying radiation dose distribution on heart delineations in CT images, is widely used. However, there are three major factors that deteriorate the accuracy of TPS-calculated heart dose distribution. First conventional CT is a fundamentally static imaging modality without the capability to capture and depict the cardiac motion. Instead, heart is usually blurred in CT images due to the motion artifacts. Second, without special contrast dye, CT provides limited contrast between blood in heart chambers and the surrounding myocardium. The heart region in TPS is actually a mixture of myocardium and blood, although only the radiation dose to the myocardium is accountable for heart risks. Finally, there is significant intra- and inter-fractional heart motion. As heart beats involuntarily during and between radiation treatments, myocardium deforms and moves non-rigidly against the fixed radiation beam so that the static dose distribution calculated in CT based TPS does not reflect the accurate radiation dose distribution in heart. There is also concern on the choice of the heart function for the evaluation of radiation damage. Based on radiation beam geometry, only part of the heart will receive clinically significant level of radiation during breast cancer treatment. It is possible that the global heart function remains stable temporarily while cells in the irradiated part of the myocardium lose part or all of their functions. In this case, regional heart function, which can be derived from regional heart wall motion and strain analysis, is a better indication of heart damage corresponding to radiation dose. Although cardiac MRI is widely used in radiology for the diagnosis of heart disease, its application in radiation treatment planning is limited. For multiple reasons, it is not practical to use MRI directly for radiation treatment planning of breast cancer patients. However, via multimodality deformable image registration (DIR) between MRI and CT, MRI images may play a more critical role in the evaluation of the heart damage from whole breast radiation. Tagged MRI (tMRI) (3) is a relatively new imaging protocol that has been implemented in the detection and diagnosis of regional heart functional loss. tMRI methods record regional heart wall motion information as they create identifiable landmark bands (tags) in the myocardium to establish dense point to point correspondence between images. ECG-gated tMRI image sets can be acquired at different phases of the cardiac cycle using the corresponding pulse sequence. The 4D (3D plus time) cardiac motion model can be retrieved by image registration between tMRIs at different phases. In the following sessions, we use tMRI as an example to explain how additional heart function information in MRI is retrieved. It is our objective to demonstrate the additional information retrieved from MRI can help the evaluation and protection of heart risks for breast cancer patients, and we want to discuss the possibility of using MRI to establish a more accurate correlation between regional heart functional loss and radiation dose.

Evaluation of radiation damage induced by a proton beam at the KOMAC facility

The 100-MeV proton linacs of the Korea Multi-purpose Accelerator Complex (KOMAC) started machine operation in 2013, and a 20-MeV or a 100-MeV proton beam has been provided to users who want to utilize a proton beam for their research and development at the KOMAC. Under proton beam irradiation, the target material will experience radiation damage induced by the proton beam, and this radiation damage can be evaluated as a function of the displacement per atom (DPA). Therefore, we used the SRIM (stopping and range of ions in matter) to investigate the damage rate induced by a 20-MeV or a 100-MeV proton beam. In this paper, we will introduce the results obtained by using SRIM calculation, for the radiation damage as a function of the proton energy, beam current, target material and target dimension.

Uncertainty analysis of infinite homogeneous lead and sodium cooled fast reactors at beginning of life

The objective of the present work is to estimate breeding ratio, radiation damage rate and minor actinide transmutation rate of infinite homogeneous lead and sodium cooled fast reactors. Uncertainty analysis is performed taking into account uncertainty in nuclear data and composition of the reactors. We use the recently released ENDF/B-VII.1 nuclear data library and restrict the work to the beginning of reactor life.We work under multigroup approximation. The Bondarenko method is used to acquire effective cross sections for the homogeneous reactor. Modeling error and numerical error are estimated.The adjoint sensitivity analysis is performed to calculate generalized adjoint fluxes for the responses. The generalized adjoint fluxes are used to calculate first order sensitivities of the responses to model parameters. The acquired sensitivities are used to propagate uncertainties in the input data to find out uncertainties in the responses.We show that the uncertainty in model parameters is the dominant source of uncertainty, followed by modeling error, input data precision and numerical error. The uncertainty due to composition of the reactor is low. We identify main sources of uncertainty and note that the low-fidelity evaluation of 16O is problematic due to lack of correlation between total and elastic reactions.