Primordial radionuclides in sand sediments that are often used as constructing materials are one of the sources of radiation hazard in dwellings. Activity concentrations of the primordial radionuclides of 40K, 226Ra and 232Th have been measured in sand sediments collected from streams and streamlets lying within and around the uranium mineralization deposit blocks of Kylleng-Pyndensohiong, Mawthabah Areas of West Khasi Hills District, Meghalaya, India. The technique of gamma-ray spectroscopy using a NaI(Tl) detector with a PC-based multi channel analyser was applied for determination of the activity concentrations. The activity of the sand sediments obtained in this study ranges from 95.3 to 1,088.8 Bq kg−1 for 40K; 38.3 to 784.1 Bq kg−1 for 226Ra and 78.0 to 316.1 Bq kg−1 for 232Th. Sand sediments from two sampling locations lying within the mineralization zone show highest concentrations of these radionuclides. The radiological hazards of the sand sediments were calculated using various models given in the literature. The radium equivalent activity was found to be higher than the accepted standard criterion value of 370 Bq kg−1 and the values of external and internal hazard indices were also found to be higher than unity in these two sampling locations. Besides these two sampling locations, a sampling location lying at a nearby distance from the mineralization zone also exhibits hazard indices values greater than unity.

An estimation of the indoor background radiation dose distribution was carried out in dwellings of eleven villages located within and around the uranium mineralization area of Kylleng-Pyndensohiong, Mawthabah in West Khasi Hills District of Meghalaya, India. The ambient indoor gamma radiation level was monitored using Thermo Luminescence Dosimeters (TLDs) while the indoor radon and thoron concentration was measured using twin-cup dosimeters employing Solid State Nuclear Track Detectors (SSNTDs). Results obtained from the study reveals that the local inhabitants of villages located close to the mining site receive higher doses than those inhabitants of villages located at a much farther distance from the mining site. The average total annual effective dose was found to be varying from 1.2 mSv y−1 in the village of Langpa to 3.4 mSv y−1 in the village of Nongbah Jynrin. The data obtained will serve as a reference in documenting changes to environmental radioactivity if mining is to be carried out in the future.

A study of background radiation and the distribution of radionuclides in the environment of the proposed uranium mining sites of Kylleng-Pyndensohiong (Mawthabah) areas, West Khasi Hills District, Meghalaya, India, has been carried out with the objective of establishing a baseline radiation level of the region. Topsoil samples collected from the region are analysed for radioactivity measurements of primordial radionuclides by gamma-spectrometry technique. Direct dose measurement using a survey meter was also carried out simultaneously. Measurement carried out in the region shows that the activity concentration of 238U and 232Th in soil samples is found to be highest in Kylleng with respective median values of 335.3 Bq kg−1 and 283.9 Bq kg−1 followed by Syngkai with activity concentration of 285.3 Bq kg−1 and 257.4 Bq kg−1 for 238U and 232Th, respectively. The distribution of 40K concentration in the study area is found to be in the range of 173.1–359.0 Bq kg−1 which is below the global and Indian average values of 420 Bq kg−1 and 394 Bq kg−1, respectively. The contribution of the primordial radionuclides to the total dose of the study area is found to be very high with a range of 136.8–334.5 nGy h−1 in comparison to the global as well as Indian average values.

The behaviour of ubiquitous radon (Rn222), thoron (Rn220) and their progeny in the indoor atmosphere generally reflect a complex interplay between a number of processes, the most important of which are radioactive α-decay, ventilation, attachment to aerosols and deposition on the surfaces. The present work involved a long-term (1997–2000) passive monitoring of Rn222 and Rn220 in the indoor environment of the North-Eastern region of India. This region being a zone of high seismicity, the indoor radon and thoron measurement of the region will provide a better insight and a valuable database for any study related to radon and thoron anomalies.

The present work looks into the modification in spectroscopic and thermal behaviour of polyimide (PI), induced by 23kGy dose of 2MeV electron. The pristine and the irradiated polymers were characterised by Fourier transform IR spectroscopy (FT-IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Though emergence of any new structures after irradiation was not observed, yet a decrease in thermal stability of the polymer accompanied by decrease in the melting temperature was observed after irradiation.

The present work looks into the property changes of polytetrafluoro ethylene as a reaction to 23kGy dose of 2MeV electron irradiation. A systematic investigation of modification in physico-chemical properties of the polymer by electron irradiation has been carried out by different characterisation techniques viz. fourier transform IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction analysis. The electron irradiation induced chain scission in the polymer, which resulted in the appearance of some new absorbance bands in the IR region, the formation of relatively stable free radical, decrease in melting point, reduction in thermal stability and decrease in crystallinity of the polymer.

The stopping power of an impinging electron beam depends on the atomic number and the atomic weight of the target material. Both the scattering and the slowing down of electrons increase with increasing target atom mass. Moreover high-energy electrons in the vicinity of heavy metal nuclei emits bremsstrahlung. In the present work, the energy loss of electrons when it traverses the layered metallic targets, has been calculated as the total energy loss which is the sum of the energy loss by ionisation and that due to bremsstrahlung emission. The effect of electron energy loss is observed in the modification in track properties of polyallyldiglycol carbonate (PADC). The etching behaviour of PADC was improved which might be due to the effect of bremsstrahlung emission. A comparative study has been carried out to study the effect of metallic targets of different atomic numbers on the energy loss phenomena.

In the present work, the effect of four different doses of 62MeV protons, on the fission fragment track etching characteristics of two polymers, viz. polycarbonate (Makrofol-N (MFN)) and polyimide (PI) are studied by nuclear track technique. The bulk etch-rate of PI increased by around 30% at the highest proton dose, whereas the activation energy of etching remained almost constant for the same. A considerable increase in the bulk etch-rate of MFN was observed (75%) at the highest proton dose. The activation energy of etching of the fission fragment tracks in MFN was also found to be an inverse function of dose.

Optical and thermal responses of two cellulose detectors, Cellulose triacetate (Triafol-TN) and Cellulose acetate butyrate (Triafol-BN), to four different doses of 62 MeV protons were studied using spectroscopic, thermal and track-etching techniques. The spectroscopic analysis revealed that though the optical band-gap in the polymers was affected by proton irradiation, the polymers showed high resistance against any major structural modification by radiation. The thermal stability of the polymers was found to be affected by proton irradiation. The activation energy of etching was found to be almost constant for both the polymers even after irradiation. It is hoped that the findings in this work would be of significant relevance to material science and applications of polymers.

A systematic investigation of proton-irradiated polycarbonate (makrofol-N (MFN)) and polyimide (PI) has been carried out using some spectroscopic and thermal techniques. Four different doses (10, 30, 60, and 80kGy) of 62MeV protons were used in the present study to check the dose-dependent behaviour of the irradiated polymers. No decrease in intensity of the absorbance bands (obtained from FT–IR spectra) of the irradiated MFN denoted the degradation of these polymers. Thermal analysis further corroborated the fact that chain-scission is the dominant phenomena in irradiated MFN samples resulting in the reduction of its thermal stability by about 19%, while on the other hand, there was a 20% increase in the thermal stability of PI due to proton irradiation, which can presumably be due to the cross-linking of some of the degraded molecules by irradiation.

The aim of our study is to describe the dose dependent proton induced modifications in Polytetrafluoro ethylene (PTFE) by using Fourier Transform Infra-red spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and X-ray diffraction analysis (XRD). The shifting of the main peak along with a decrease in its intensity, the decrease in thermal stability and melting point and the formation of stable free radicals were observed in the polymer by proton irradiation.

It is a well-known fact that proton irradiation leads to an increase in track registration sensitivity of some polymers. In the present work, the effect of the proton beam irradiation through metal foils (gold and aluminium) on polyallyldiglycol carbonate (PADC) has been studied by track technique. An increase in sensitivity of PADC adjacent to the gold foils has been found which is attributed to the effect of ionisation by the secondary particles emitted from the metal targets due to proton bombardment.

Swift heavy ions interact predominantly through inelastic scattering while traversing through any polymeric medium producing excited/ionised atoms. Beyond a certain threshold, they affect the lattice structure leading to remarkable flexibility in engineering many physical and mechanical properties of the polymer. Polyallyldiglycol carbonate (PADC) is a class of polymeric detectors which finds its applications in various fields. In the present work, PADC samples were irradiated by four different fluences (≈1012–1013cm−2) of 62MeV protons from heavy ion accelerator (ISL) at HMI, Berlin. The modifications in the proton irradiated polymers as a function of fluence have been studied through different characterisation techniques such as Fourier Transform IR, UV-Vis, Electron Spin resonance, Thermogravimetric analysis, Differential Scanning Calorimetry and Track studies. The optical band-gap was found to be constant while a decrease in transmittance of PADC was observed with the increase in proton fluence. The thermal stability of PADC was found to be an inverse function of fluence. Further, these proton irradiated PADCs were exposed to fission fragments from 252Cf source and the bulk etch-rate was improved with the increase in proton fluence and was found to be increased by 90% for the PADC irradiated at the highest fluence as compared to the pristine. Thus, proton irradiation has led to degradation of the polymer by chain scission converting it into an easily etchable material.

A systematic investigation of 62 r MeV proton irradiated Poly(ethylene terephthalate) (PET) has been carried out using Fourier Transformed Infrared Spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction spectroscopy. The experiments revealed a restoration of the crystalline matrix and simultaneous decrease in thermal stability in the irradiated polymer as a function of dose, indicating that PET underwent both degradation and cross-linking by proton irradiation.

Heavy ion range and energy-loss data provide useful information for designing several nuclear physics experiments where the polymers employed find their use as absorber, in chamber windows and target backings. In the present work, the range and energy-loss rate of 118MeV28Si in LR-115 (cellulose nitrate) and polypropylene (PP) have been calculated by track technique where polyallyldiglycol carbonate was used as a backing detector. The mean range of 28Si in LR-115 has been calculated to be 59.4±2μm and that in PP is calculated to be 74.9±2μm. The experimentally evaluated range values are in agreement with the theoretical range values derived from some computer codes. The Bragg peak has also been obtained at 1.1MeV/nucleon for 28Si in both LR-115 and PP.

The effect of 23kGy dose of 2MeV electron irradiation on polypropylene has been studied by different characterisation techniques, viz. Fourier transform IR spectroscopy, electron spin resonance spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray diffraction analysis. The thermal stability of the polymer was found to be increasing due to electron irradiation. The thermal decomposition temperature as well as the melting temperature in case of irradiated polypropylene was found to increase due to electron bombardment. The isotactic nature of the polymer was found to be unaffected by electron irradiation. An increase in crystallinity of the polymer has also been observed after irradiation.

Heavy ion induced modification in optical absorption studies of the polymers Polypropylene and Polyimide have been carried out to investigate the potential for improvements in their conductivity properties. The polymers were irradiated to four different doses of 140MeV Si-28 and 100MeV Ni-58 ion beams. The optical absorption studies were carried out by UV-Vis spectroscopy. The shift in the absorption edges were correlated to the optical band-gap by Tauc's expression. A decrease in optical band-gap has been observed in the irradiated polymers, but the effect of Ni-58 ions were more pronounced in decreasing the band-gap in the polymers.

Heavy ion range and energy-loss data provide useful information for designing several nuclear physics experiments where the polymers employed find their use as absorber, in chamber windows and target backings. In the present work, the range and energy-loss rate of 118 MeV Si-28 in LR-115 (cellulose nitrate) and polypropylene (PP) have been calculated by track technique where polyallyldiglycol carbonate was used as a backing detector. The mean range of Si-28 in LR-115 has been calculated to be 59.4 +/- 2 mum and that in PP is calculated to be 74.9 +/- 2 mum. The experimentally evaluated range values are in agreement with the theoretical range values derived from some computer codes. The Bragg peak has also been obtained at 1.1 MeV/nucleon for Si-28 in both LR-115 and PP. (C) 2001 Elsevier Science Ltd. All rights reserved.

In the present work, the effect of 2 MeV electron irradiation of Polyallyldiglycol Carbonate (PADC) has been studied for different doses. The optical band-gap derived from the UV-Vis spectra was found to decrease with an increase in electron dose. Fourier Transformed IR analysis showed a decrease in transmittance due to the electron irradiation. Thermogravimetric analysis of the irradiated samples revealed a decrease in the thermal Stability with an increase in electron dose. Differential scanning calorimetry was done to study the dose dependent phase transformations of the samples. X-ray diffraction analysis supported the amorphous nature of the polymer, which was further destroyed due to electron irradiation.

Track formation in polymers is a complex phenomenon in which not only primary but also secondary processes, such as formation of radicals and chemical processes, are involved. In the present work, the influence of 2MeV electrons on the etching properties and the surface topography of polyethylene terephthalate (PET) and polyimide (PI) are studied. The increase in the bulk etch-rate and a decrease in the activation energy of etching were observed for both the polymers. The surface roughness of both polymers was reduced due to electron irradiation.