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The optical properties of Makrofol samples are investigated under various fluences of alpha exposure (2 MeV at 5 × 10 2 , 10 3 , 5 × 10 3 , 10 4 , 5 × 10 4 , 10 5 , 5 × 10 5 and 10 6 alphas.cm2 alongside the unirradiated ones (pristine). Several analyses, including UV–visible, diffused reflectance spectroscopy (DRS), photoluminescence (PL), Fourier transform infrared/attenuated total reflectance (FTIR-ATR), X-ray photoelectron spectroscopy (XPS) and sessile drop technique, are carried out to reveal the subsequent variations in the optical features of the irradiated polymer foils. The optical transmittance of the irradiated samples notably increases against the pristine ones, while it undergoes a+ plateau over various fluences. Additionally, the scattering events are more prominent in pristine samples over UV (240–400 nm) and IR (900–1040 nm) compared to the irradiated ones. While there are negligible physical alterations on the polymer surface, the photoluminescence emission gradually decreases with increasing alpha fluences in the irradiated samples mainly due to the reduction in the population of the aromatic rings. The latter is also verified by means of the surface chemical analyses such as XPS, FTIR-ATR and sessile drop/contact angle measurements. XPS reveals that the alpha particles give rise to the successive scissions of C–C and C O bonds and the consequent recombination events in the form of C–O bonds, evidenced by the changes in their abundance percentages. Concurrently, the surface hydrophilicity initially elevates up to a certain fluence and then reduces at higher fluences, indicating a couple of competitive mechanisms are involved in the context of the interactions of the alpha particles with the Makrofol polycarbonate (PC). • The optical properties of Makrofol samples are investigated under alpha exposure. • The variations in the optical features of the irradiated polymer foils are studied. • UV–Visible reveals a drastic increase of spectral transmission in favor of irradiated PC. • XPS spectra demonstrate a reduction of carbonyl abundance in terms alpha fluences. • The contact angle levels down against alpha fluence. [ABSTRACT FROM AUTHOR]

• Using 211At to study α radiation's impact on Th(Ⅳ) and U(Ⅵ) extraction by TiAP. • The effects of α and γ radiation on Th(Ⅳ) and U(Ⅵ) extraction by TiAP are similar. • The modified extraction behavior mainly stems from the radiolysis product HDiAP. Tri- iso -amyl phosphate (TiAP) is considered as a promising alternative to tri-butyl phosphate (TBP) for the reprocessing of spent nuclear fuels. However, how radiation alters the extraction properties of the extractant and what is the mechanism causing this phenomenon has not been determined, especially under alpha radiation. This study investigates the extraction of Th(IV) and U(VI) by 36 % TiAP - n-dodecane (n-DD) after exposure to alpha radiation from 211At, and compared with gamma radiation at an equivalent dose. The results indicate that the effect of alpha radiation on TiAP has a similar trend to gamma radiation, and the concentration of HNO 3 plays a crucial role in the extraction of Th(IV) and U(VI) by irradiated TiAP. Even at low doses (10 kGy), radiolysis of the extractants remains observable. In addition, the stripping of extracted Th(Ⅳ) from the irradiated organic phase is more difficult than U(VI), which is consistent with previous investigations on gamma radiation. Theoretical calculations suggest that the [DiAP]− ligand formed by HDiAP as a radiolysis product of TiAP is closely related to the strong extraction ability of Th(Ⅳ) in the extraction system after radiation at low acidity, since the [DiAP]− ligand exhibits a higher coordination ability than TiAP and HDiAP, especially with Th(IV). The outcomes of this work not only provide a procedure for exploring the alpha radiation of extractions based on a short half-life nuclide, but also demonstrate the connection between the radiolysis products and the change of extraction performance, which are helpful for us to gain a better understanding of the potential of TiAP to be used in the separation and purification of Th(Ⅳ) and U(Ⅵ) in reprocessing plants. [ABSTRACT FROM AUTHOR]

There is still no consensus regarding the ultimate cause of the famous 3–4-year population cycles of lemmings. According to the plant stress hypothesis, herbivore population peaks are caused by stress factors that force plants to reallocate stored defensive proteins to transportable and easily digestible N-compounds. One possible plant stress factor is ionization caused by exhalation of the radioactive noble gas radon, which is enhanced after spring tides, i.e., tides at new or full Moon. I hypothesized that increased ionization caused by radon accumulation in the subnivean space after peak spring tides, which occur close to perihelion (31 December–05 January, when the Earth–Sun distance is shortest), and at 3.8-year intervals, results in increased protein digestibility of mosses, which are important food for lemmings. Population outbreaks of Norway lemming Lemmus lemmus occurred two years after peak spring tides during 1871–1910, when also perigee (the time when the Earth–Moon distance is shortest) coincided with spring tides and perihelion. Thereafter this relationship weakened, and lemming peaks became less pronounced and more related to plant seed indices. As we have now entered a new 30-year period with coincidence of spring tide, perihelion and perigee, I predict more regular and pronounced lemming outbreaks in the next decades, unless radon accumulation is prevented by frequent lack of a stable snow cover due to global warming. • Population cycles of lemmings follow the 3.8-year cycle in peak spring tides close to perihelion, i.e., peak spring tides. • Radon exhalation is enhanced at peak spring tides. • Ionization caused by radon accumulation beneath the snowpack is a possible plant stress factor that favor lemmings. • Populations of Norway lemming peaked after peak spring tides, in particular when peak spring tides coincided with perigee. [ABSTRACT FROM AUTHOR]

The main obstacle to applying aluminum oxide doped with carbon and magnesium (Al 2 O 3 :C,Mg)-based fluorescent nuclear track detectors (FNTDs) in radionuclide therapy with alpha emitters is that it has not been known how to achieve an accurate and in situ dose assessment for in vitro cellular experiments. In this study, we developed an automatic 3D track reanalysis algorithm (ATRA) to analyze the alpha energy spectra in FNTDs. The algorithm provides an excellent track identification rate and an excellent track linking rate (0.961) without significant variations in various track densities. The algorithm also achieves a reliable track detection rate exceeding 0.927 for track densities at the level of in situ measurement, and it successfully measures the alpha energy spectra for obtaining the absorbed dose. We also confirmed that the track overlap clearly interferes with accurate track reconstruction for track densities beyond 1.5 × 106 tracks cm−2. We provided a correction equation that can be used to obtain the actual alpha tracks for high track densities; the equation may also correct estimations of absorbed doses due to alpha particles. • Automatic 3D track reanalysis algorithm (ATRA) was developed. • The track detection rates of ATRA exceeded 0.927 at in situ measurement level. • The effect of track overlap on ATRA was quantified with various track densities. • Correction equation was provided for correcting absorbed dose due to alpha particle. [ABSTRACT FROM AUTHOR]

In this study, the design, simulation and construction of three micro pattern gas-detectors, THGEM, with different geometric dimensions are presented. Moreover, their ability of operation in SQS mode to determine the incident rays position without using any conventional imaging system is investigated. In the presence of UV absorbing gas mixtures, the proportional mode of the gas detector operation is followed by SQS mode as soon as the visible light column appears at the ray entrance location. In the method employed, each THGEM hole as an image pixel independent of other holes can operate in SQS mode with emerging a light column. As a consequence, it can be used for alpha beam imaging since the brightness of each hole at a certain voltage is proportional to the number of primary electrons entering the hole. [ABSTRACT FROM AUTHOR]

• Chemical durability of nuclear glass was studied by considering combined effects of vapor hydration and radiation. • No significant impact of ionizing effect was observed on the leaching behavior of hydrated glass. • The presence of pre-hydrated layer, especially the secondary phases, showed major impacts on glass chemical durability. During the long-term disposal of high-level nuclear waste glass in the geological disposal facility, the nuclear glass could be exposed to an unsaturated vapor environment prior to the direct contact with groundwater. Additionally, glass will experience damages due to self-irradiation. In this study, experiments were performed to investigate the chemical durability of glass after being hydrated and irradiated. This study proposes an attempt to investigate the impact of ionizing effect by applying alpha or gamma radiations to the pre-hydrated glass. The impact on chemical durability is evaluated by leaching the hydrated and irradiated glass samples. With the studied doses, 8 Giga Gy of alpha radiation or 100 kGy of gamma radiation, no significant modification of chemical durability is observed upon irradiation. On the other hand, leaching of pre-hydrated glass shows the increase of the initial release of Si, which is considered to be related to the dissolution of secondary phases. Furthermore, the total dissolution of hydrated layer is observed, which would result in the release of radionuclides at the same rate as Si does and thus needs further investigation. [ABSTRACT FROM AUTHOR]

Previous SAR-OSL dating studies using quartz extracted from Romanian and Serbian loess samples report SAR-OSL dose–response curves on fine grained (4–11 μm) quartz that grow to much higher doses compared to those of coarse-grained (63–90, 90–125, 125–180 μm) quartz. Furthermore, quartz SAR-OSL laboratory dose response curves do not reflect the growth of the OSL signal in nature. A main difference in coarse- and fine-grained quartz dating lies in the alpha irradiation history, but the effect of mixed alpha-beta fields has so far received little attention. In the present study we investigate whether the alpha dose experienced by fine grains over geological cycles of irradiation and bleaching may have an effect on the saturation characteristics of the laboratory dose response. By applying time resolved optically stimulated luminescence we confirm that the OSL signals induced in quartz by alpha and beta radiation follow the same recombination path. We also show that a mixed alpha-beta dose response reproduces the beta dose response only up to about 800 Gy. Assuming an a-value of 0.04 we have shown that laboratory alpha and beta dose response curves overlap up to effective alpha doses of ∼50 Gy. Based on these results, we conclude that exposure of fine grains to alpha radiation during burial and transport cycles prior to deposition, as well exposure to the mixed radiation field experienced during burial are not responsible for the age discrepancies previously reported on fine and coarse grained quartz extracted from Romanian and Serbian loess. [ABSTRACT FROM AUTHOR]

The technical innovation of boron-doped diamond on top of a silicon layer as alpha nuclide measurement device offers promising advances, since the energy-resolved measurement takes place in-situ in water without matrix separation. Several experiments were performed to detect disturbance factors by investigating the yield of 241 Am in the presence of main or minor drinking water elements. The results show that an activity was detected by the sensor in any case. Generally, the yields were higher with NaNO 3 as electrolyte than with Na 2 SO 4 , due to speciation and higher hydrogen formation. A reduced yield was observed for nitrate as electrolyte and maximum concentrations of Ca, Mg, PO 4 , and F in drinking water. The generally high standard deviation of the measurement, which is mainly due to hydrogen evolution, mass attenuation, and surface site occupation, does not allow for an exact determination of a present α-contamination. However, a significant aqueous alpha activity can be detected. [ABSTRACT FROM AUTHOR]

This work presents the TL and OSL response of beryllium oxide detectors exposed to alpha, beta and X radiation beams. The samples were characterized, and they presented good reproducibility, good linearity interval, low energy dependence, and an acceptable fading. The luminescent response was better for the OSL technique. [ABSTRACT FROM AUTHOR]

Abstract: Radioimmunotherapy (RIT) is a therapeutic modality which delivers alpha, beta or Auger emitters directly to targeted cancer cells. It has the advantage of regressing tumors while reducing non-targeted toxicities with the help of the targeting antibody. RIT applications relate to hematologic malignancies and now extend to solid tumors. Therapeutic efficacy of solid tumor RIT was limited by the inadequate penetration of radioimmunoconjugate (RIC). This paper reviews the properties of tumor vasculature abnormalities, the mechanisms of RIC penetration into solid tumors and strategies to enhance RIC delivery to facilitate RIT in reaching its full potential as a systemic cancer therapy. [Copyright &y& Elsevier]

Abstract: Radon (222Rn) gas produces decay progeny that emits high energy alpha (α)-particles. Epidemiological studies have shown that exposure to 222Rn is linked with elevated risk of developing lung cancer, however clear mechanisms leading to such effects have not been delineated. Cytokines play a critical role in inflammation and their dysregulated production often contributes to disease pathogenesis. In this study, Bio-plex multiplex technology was employed to investigate modulations of 27 pro-inflammatory cytokines following exposure of human monocytic cells to 1.5Gy of α-particle radiation. Concurrently, DNA damage was assessed by examining the formation of phosphorylated H2A histone family X (γ-H2AX) sites. Of the 27 cytokines assessed, 4 cytokines were shown to be statistically downregulated by ∼2 fold relative to the untreated controls and included the interleukin (IL) family of proteins (IL-2, IL-15 and IL-17) and macrophage inflammatory protein 1 beta (MIP-1b). Interferon-inducible protein-12 (IP-12), vascular endothelial growth factor and regulated on activation normal T cell expressed and secreted (RANTES) were shown to be high expressors and upregulated. Cells irradiated with α-particles ranging from 0.27 to 2.14Gy showed statistically significant, dose-dependant increases in γ-H2AX formation. These data suggest that α-particle radiation causes dysregulation in the production of a number of pro-inflammatory cytokines and results in significant DNA damage. [Copyright &y& Elsevier]

Abstract: Exposure to radon and its progenies represents one of the greatest risks of ionizing radiation from natural sources. Nowadays, these risks are assessed by the extrapolation of biological effects observed from epidemiological data. In the present study, we made a dose response curve, to evaluate the in vitro response of A549 human lung cells to α-radiation resulting from the decay of a 210Po source, evaluated by the cytokinesis blocked micronuclei assay. The clonogenic assay was used to measure the survival cell fraction. As expected, the results revealed an increase of cellular damage with increased doses made evident from the increased number of micronuclei (MN) per binucleated cell (BN). Besides this study involving the biological effects induced by direct irradiation, and due to the fact that radiation-induced genomic instability is thought to be an early event in radiation carcinogenesis, we analyzed the genomic instability in early and delayed untargeted effects, by using the medium transfer technique. The obtained results show that unirradiated cells exposed to irradiated medium reveal a higher cellular damage in earlier effects when compared to the delayed effects. The obtained results may provide clues for the biodosimetric determination of radon dose to airway cells at cumulative exposures. [Copyright &y& Elsevier]

Abstract: Natural sources contribute a large fraction of the radiation exposure of the general public. Under the linear no-threshold hypothesis risk decreases in proportion to decreasing dose without a threshold. We use recent estimates of doses to the red bone marrow to calculate the number and proportion of cases of leukemia in England induced by natural radiation. We calculate that about 5% of cases of leukemia, excluding chronic lymphocytic leukemia, up to the age of 80 years are induced by this background radiation. In young people up to the age of 25 years the attributable fraction is about 15%, substantially lower than a previous estimate. [Copyright &y& Elsevier]

Abstract: We have experimentally studied the effects of α-particle radiation on isotopically enriched lithium hydride (6LiH) and its corrosion product lithium hydroxide (6LiOH) to determine, in particular, the type and amount of gases evolved during irradiation. SRIM Monte Carlo simulations suggest that irradiating these materials with 2.2-MeV α-particles will ionize atoms and form hydrogen vacancies in the target material, and that these α-particles will penetrate 13.5 and 9μm into LiH and LiOH, respectively. Using an accelerator to irradiate LiH and LiOH with 2.2-MeV α-particles released only H2 and CO2; no other product gases were observed. At 25°C, doses that simulated 66.5years of actinide exposure (with accelerated fluxes) produced 2.3×105 mol/(cm3 J) H2 in LiH and 2.3×106 mol/(cm3 J) H2 in LiOH, in the form of a ∼9-μm-thick surface layer on LiH. More H2 evolved from LiOH than from LiH. We argue that the production of H2 gas was the result of radiolysis, rather than radiation-induced chemical reaction. [Copyright &y& Elsevier]

Abstract: Aim: The monoclonal antibody cetuximab, targeting the epidermal growth factor receptor (EGFR), is a promising molecular targeting agent to be used in combination with radiation for anticancer therapy. In this study, effects of cetuximab in combination with alpha-emitting radioimmunotherapy (RIT) in a panel of cultured human squamous cell carcinomas (SCCs) were assessed. Methods: SCC cell lines were characterized and treated with cetuximab in combination with anti-CD44v6 RIT using the astatinated chimeric monoclonal antibody U36 (211At-cMAb U36). Effects on 211At-cMAb U36 uptake, internalization and cell proliferation were then assessed in SCC cells. Results: Cetuximab in combination with 211At-cMAb U36 mediated increased growth inhibition compared to RIT or cetuximab alone in two cell lines. However, cetuximab also mediated radioprotective effects compared to RIT alone in two cell lines. The radioprotective effects occurred in the cell lines in which cetuximab clearly inhibited cell growth during radiation exposure. Cetuximab treatment also influenced 211At-cMAb-U36 uptake and internalization, suggesting interactions between CD44v6 and EGFR. Conclusions: Results from this study demonstrate the vast importance of further clarifying the mechanisms of cetuximab and radiation response, and the relationship between EGFR and suitable RIT targets. This is important not only in order to avoid potential radioprotective effects, but also in order to find and utilize potential synergistic effects from these combinations. [ABSTRACT FROM AUTHOR]

Purpose: Diffusing alpha-emitters radiation therapy (DART) is a new form of brachytherapy enabling the treatment of solid tumors with alpha radiation. The present study examines the antitumoral effects resulting from the release of alpha emitting radioisotopes into solid lung carcinoma (LL2, A427, and NCI-H520). Methods and Materials: An in vitro setup tested the dose-dependent killing of tumor cells exposed to alpha particles. In in vivo studies, radioactive wires (0.3 mm diameter, 5 mm long) with 224Ra activities in the range of 21-38 kBq were inserted into LL/2 tumors in C57BL/6 mice and into human-derived A427 or NCI-H520 tumors in athymic mice. The efficacy of the short-lived daughters of 224Ra to produce tumor growth retardation and prolong life was assessed, and the spread of radioisotopes inside tumors was measured using autoradiography. Results: The insertion of a single DART wire into the center of 6- to 7-mm tumors had a pronounced retardation effect on tumor growth, leading to a significant inhibition of 49% (LL2) and 93% (A427) in tumor development and prolongations of 48% (LL2) in life expectancy. In the human model, more than 80% of the treated tumors disappeared or shrunk. Autoradiographic analysis of the treated sectioned tissue revealed the intratumoral distribution of the radioisotopes, and histological analysis showed corresponding areas of necrosis. In vitro experiments demonstrated a dose-dependent killing of tumors cells exposed to alpha particles. Conclusions: Short-lived diffusing alpha-emitters produced tumor growth retardation and increased survival in mice bearing lung tumor implants. These results justify further investigations with improved dose distributions. [Copyright &y& Elsevier]

Abstract: Liquid phase epitaxy method was used to prepare YAG:Ce and YAG films (thickness 2–) from the fluxes based either on PbO or BaO. bands of ions were observed peaking at 340 and 457nm. A hybrid photomultiplier was used to measure scintillation response of the LPE films using 239Pu alpha particle source. Some of YAG:Ce films show photoelectron yield close to that of YAG:Ce single crystal. Iron contamination degrades significantly the film scintillation performance. [Copyright &y& Elsevier]

Abstract: Radioimmunotherapy has proven clinically effective in patients with non-Hodgkin''s lymphoma. Radioimmunotherapy trials have so far been performed with β-emitting isotopes. In contrast to β-emitters, the shorter range and high linear energy transfer (LET) of α particles allow for more efficient and selective killing of individually targeted tumor cells. However, there are several obstacles to the use of α-particle immunotherapy, including problems with chelation chemistry and nontarget tissue toxicity. The α-emitting radioimmunoconjugate 227Th-DOTA-p-benzyl-rituximab is a new potential anti-lymphoma agent that might overcome some of these difficulties. The present study explores the immunoreactivity, in vivo stability and biodistribution, as well as the effect on in vitro cell growth, of this novel radioimmunoconjugate. To evaluate in vivo stability, uptake in balb/c mice of the α-particle-emitting nuclide 227Th alone, the chelated form, 227Th-p-nitrobenzyl-DOTA and the radioimmunoconjugate 227Th-DOTA-p-benzyl-rituximab was compared in a range of organs at increasing time points after injection. The immunoreactive fraction of 227Th-DOTA-p-benzyl-rituximab was 56–65%. During the 28 days after injection of radioimmunoconjugate only, very modest amounts of the 227Th had detached from DOTA-p-benzyl-rituximab, indicating a relevant stability in vivo. The half-life of 227Th-DOTA-p-benzyl-rituximab in blood was 7.4 days. Incubation of lymphoma cells with 227Th-DOTA-p-benzyl-rituximab resulted in a significant antigen-dependent inhibition of cell growth. The data presented here warrant further studies of 227Th-DOTA-p-benzyl-rituximab. [Copyright &y& Elsevier]

Abstract: Irradiation of polymer samples using an accelerated beam of He++ ions passed through a 10μm thick window of havar foil, has been performed. Such an irradiation simulates the effects of large α radiation doses, on a vastly reduced time-scale. The experimental set up was designed to allow analysis of volatiles evolved from the irradiated samples by means of a residual gas analyser (RGA). This was located in close proximity to the sample chamber. A radiation study on a poly(urethane) materials using an RGA to analyse volatiles indicated the dominant degradation products to be H2, CO and CO2. A series of polyurethane samples previously conditioned by γ irradiation to between 1 and 5MGy were irradiated in the ion beam. Identification of differences in trends in the rates of volatile evolution between these samples indicated the precise vacuum conditions at the time of irradiation had a major influence. There was also an indication that the surface of the sample had a small effect on rates of volatile evolution. Comparative plots of CO and CO2 evolution for series of 5×1MGy irradiations indicated variations in behaviour between samples with different γ doses. Evolution during the first 1MGy was inhibited for the unirradiated sample, the extent of inhibition diminished with increasing γ dose and was no longer evident in a sample with 1.5MGy γ dose. H2 does not show an equivalent inhibition. Evidence for a low dose crosslinking reaction is put forward as the reason for the inhibition. Chemical reaction mechanisms are postulated and used to explain the differences in behaviour observed between CO/CO2 and H2. [Copyright &y& Elsevier]

Abstract: When confluent cultures of mammalian cells are irradiated with very low fluences of alpha particles whereby only occasional cells receive any radiation exposure, genetic changes are observed in the non-irradiated (“bystander”) cells. Upregulation of the p53 damage–response pathway as well as activation of proteins in the MAPK family occurred in bystander cells; p53 was phosphorylated on the serine 15 residue suggesting that the upregulation of p53 was a consequence of DNA damage. Damage signals were transmitted to bystander cells through gap junctions, as confirmed by the use of genetically manipulated cells including connexin43 knockouts. Expression of connexin43 was markedly enhanced by irradiation. A moderate bystander effect was observed for specific gene mutations and chromosomal aberrations. This effect was markedly enhanced in cells defective in the non-homologous end joining DNA repair pathway. Finally, an upregulation of oxidative metabolism occurred in bystander cells; the increased levels of reactive oxygen species appeared to be derived from flavine-containing oxidase enzymes. We hypothesize that genetic effects observed in non-irradiated bystander cells are a consequence of oxidative base damage; >90% of mutations in bystander cells were point mutations. When bystander cells cannot repair DNA double strand breaks, they become much more sensitive to the induction of chromosomal aberrations and mutations, the latter consisting primarily of deletion mutants. While we propose that the genetic effects occurring in bystander cells are a consequence of oxidative stress, the nature of the signal that initiates this process remains to be determined. [Copyright &y& Elsevier]

A Monte Carlo code is developed for simulating energy spectra of alpha particles from aerosol samples. Geometrical detection efficiency and energy loss of the alpha particles in the source itself and in the material between the source and detector are simulated. Different characteristics of the aerosol particles and medium material are taken into account in the computation. An excellent agreement with earlier results and measurements is found. The code can be applied for example in designing optimal aerosol sampling methods in direct alpha spectrometry. [Copyright &y& Elsevier]

We have previously shown that when confluent cultures of mammalian cells are exposed to very low fluences of alpha particles, fluences whereby as few as 1% of the cell nuclei are traversed by a single particle, genetic effects including specific gene mutations and sister chromatid exchanges (SCE) are induced in neighboring, non-irradiated “bystander” cells. The present investigation was designed to examine the induction of chromosomal aberrations in wild-type CHO cells and its DNA double strand break repair deficient mutant xrs-5 by a broad range of alpha particle fluences yielding mean doses of 0.17–200 cGy. The dose–response curve for the induction of aberrations was curvilinear for both cell lines, with a greater effect occurring at very low fluences owing to aberrations arising in bystander cells. These aberrations were predominately of the chromatid-type. With such fluences, the number of cells with induced aberrations per nucleus irradiated increased up to 4-fold in CHO cells and 15-fold in xrs-5 cells over that expected if aberrations occurred only in irradiated cells. These results are discussed in terms of the hypothesis that the primary DNA damage in bystander CHO cells is oxidative base damage leading to a relatively small bystander effect for gross chromosomal aberrations as compared with mutations or SCE; the larger bystander effect in xrs-5 cells is the result of oxidative damage and non-repaired DNA strand breaks which may result from opposed oxidative lesions. [Copyright &y& Elsevier]

A model investigating the role of geometry on the alpha dose rate of spent nuclear fuel has been developed. This novel approach utilises a new piecewise function to describe the probability of alpha escape as a function of particulate radius, decay range within the material, and position from the surface. The alpha dose rates were produced for particulates of radii 1 μ m to 10 mm, showing considerable changes in the 1 μ m–50 μ m range. Results indicate that for decreasing particulate sizes, approaching radii equal to or less than the range of the α -particle within the fuel, there is a significant increase in the rate of energy emitted per unit mass of fuel material. The influence of geometry is more significant for smaller radii, showing clear differences in dose rate curves below 50 μ m. These considerations are essential for any future accurate prediction of the dissolution rates and hydrogen gas release, driven by the radiolytic yields of particulate spent nuclear fuel. • An approach to simulate α-dosimetry from spherical particulates is presented. • Probability of α-particle escape for curved surfaces has been derived. • The role of geometry has a considerable influence for particulate radii <50 μm. • Results comparable with previous MCNPX model to within 0.7% of total dose rate. [ABSTRACT FROM AUTHOR]

The preparation of Zinc oxide/polystyrene (ZnO/PS) composite scintillator was carried out with different percentages of ZnO varying from 5 to 50% (w/w) on the quartz substrate. The enhanced absorbance is observed at ~ 385 nm for low % (w/w) of ZnO, which is red-shifted to 390 nm for higher ZnO % (w/w) composite samples. The pristine polystyrene sample showed excitation at ~271 nm, equivalent to the measured bandgap of polystyrene. A photoluminescence emission of 385 nm in ZnO/PS composite is observed, which is equivalent to the measured ZnO bandgap ~3.22 eV. Alpha excited radioluminescence, obtained using 5.2 MeV alpha particles from 239Pu, showed emission at ~387 nm together with polystyrene emission at ~ 430 nm. The scintillation characteristics for the composite samples are investigated using the pulse height spectrum after coupling the composite films with a photomultiplier tube (PMT) and multichannel analyzer (MCA). The significant increase in pulse height is observed for 5% (w/w) or more ZnO in PS. This is clearly discernible in contrast to polystyrene without ZnO. The integrated counts increase linearly up to 20% (w/w) ZnO and showed reduction for 50% (w/w) ZnO/PS sample. The reduction in the counts is attributed to the reduced transmittance for higher % (w/w) ZnO in PS matrix. The maximum detection efficiency and minimum detectable activity (MDA) are ~23% and ~0.4 Bq, respectively, for 50% (w/w) ZnO/PS. Further, a linear response is observed with activity for all scintillating samples. These findings suggest that ZnO/PS composite materials may be a good candidate for efficient monitoring of alpha radioactivity with high sensitivity and very low MDA. • ZnO/PS composite based scintillator with different wt % of ZnO. • The maximum detection efficiency and minimum detectable activity (MDA) are ~23% and ~ 0.4 Bq, respectively, for 50%ZnO-PS. • A linear response is observed with activity for all scintillating samples. [ABSTRACT FROM AUTHOR]

A model to determine the dose rate of a planar alpha-emitting surface has been developed. The approach presented is a computationally efficient mathematical model using stopping range data from the Stopping Ranges of Ions in Matter (SRIM) software. The alpha dose rates as a function of distance from irradiated UO 2 spent fuel surfaces were produced for benchmarking with previous modelling attempts. This method is able to replicate a Monte Carlo (MCNPX) study of an irradiated UO 2 fuel surface within 0.6% of the resulting total dose rate and displays a similar dose profile. • Bragg peak shift due to attenuation through fuel can be approximated as linear. • Bragg curve maintains functional form with peak shift. • Single function can be manipulated to describe all particle paths. • Clarification over error made in literature regarding the probability of alpha escape. • Results comparable to Monte Carlo attempts while improving computational efficiency. [ABSTRACT FROM AUTHOR]