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One of the proposed materials for structural application in compact high-temperature reactors (CHTRs) is Nb-1Zr-0.1C alloy. Using the Variable Energy Cyclotron at the Variable Energy Cyclotron Centre, Kolkata, Nb-1Zr-0.1C alloy was irradiated with a 160-MeV oxygen (O6+) ion up to three different doses. Emulation of neutron irradiation by ion irradiation could be achieved as the weighted recoil spectra of the oxygen ion are found to be similar to the neutron recoil spectra of CHTRs within recoil energy ranging from 100 eV to 100 keV. The irradiated materials along with one as-received sample were characterized using different X-ray diffraction line profile analyses (XRDLPAs) to systematically evaluate microstructural parameters. A decrease in the domain size with an increase in microstrain and dislocation density is observed at first dose and then found to saturate with further irradiation. An increase in the Wilkens arrangement parameter indicates the formation of less correlated dislocations (clusters) after irradiation. Transmission electron microscopy analysis of as-received and highest-dose samples shows the formation of densely populated defect clusters after irradiation. Nanohardness increased after irradiation due to pinning of the dislocation movement by point defects and defect clusters/loops, as well as carbides in the matrix. The results extracted from the XRDLPAs are compared with our earlier studies of light ion–irradiated (H+) Nb-1Zr-0.1C alloy and oxygen-irradiated pure Nb to understand the effect of the type of ion and the alloying elements, respectively, on the evolution of the microstructure. It may be concluded that changes in dose and dose rate affect the movement of point defects toward sinks. Hence, possible correlated dislocation formation is observed in light ion–irradiated Nb alloy, but correlation is found to decrease with dose for heavy ion–irradiated Nb alloy. On the other hand, the presence of finely dispersed carbides restricts the formation of dislocation loops by making complexes with the defects in heavy ion (O6+)–irradiated Nb-1Zr-0.1C alloy, which is in contrast to pure Nb irradiated using the heavy ion (O6+) in a similar environment. [ABSTRACT FROM AUTHOR]

The daily soil radon activity has been measured continuously over a year with BARASOL BMC2 probe at a measuring site of Jadavpur University Campus in Kolkata, India. The dependency of soil radon activity with different atmospheric parameters such as soil temperature, soil pressure, humidity, air temperature, and rainfall has been also analyzed. The whole study period is divided in four seasons as proposed by the Indian Meteorological Department (IMD). Minimum soil radon level has been observed during the winter season (December–February). On the other hand, higher soil radon level has been observed both for summer and monsoon. Except soil pressure, all other variables have shown positive correlation with soil radon activity. Among five variables, soil temperature has been the most significant variable in terms of correlation with soil radon level whereas maximum humidity has been the least significant correlated variable. It has been observed that considerable reduction of soil radon level occurred after four heavy rainfall events during the study period. The combined effect of these multi-parameters on soil radon gas has been evaluated using machine learning methods like principal component regression (PCR), support vector regression (SVR), random forest regression (RF), and gradient boosting machine (GBM). In terms of performances, RF and GBM have performed much better than SVR and PCR. More robust and consistent results have been obtained for GBM during both training and testing periods. [ABSTRACT FROM AUTHOR]

Ionospheric effects like scintillations and anomalous variations in total electron content (TEC) monitored with Global Positioning System (GPS) satellites of L1 frequency over Kolkata, West Bengal, India, in April–May 2015 were studied together with radon activity in soil recorded by solid-state nuclear track detector (SSNTD) during summer of 2015 in the same city, with a view to identify possible precursory signals for earthquakes that occurred in the Nepal Himalayas during April–May 2015. Weak-to-intense fluctuations even up to saturation levels in some links of GPS satellites and anomalies in TEC were observed in the pre-earthquake days, although 2015 was a medium-to-low solar activity year. Prominent near-simultaneous anomalies of all three precursors were observed prior to the two massive earthquakes of magnitude > 7 that devastated vast areas of Nepal in 2015. The occurrence of anomalies and spurious pulses has been studied in the present work, and the effectiveness of analysing together two different types of earthquake precursors for short-term prediction of high-magnitude earthquakes has been discussed. Moreover, this is the first work on the Nepal Himalayan region in which ionospheric scintillation and TEC have been studied concurrently with soil radon in Kolkata for earthquake precursor research. [ABSTRACT FROM AUTHOR]

Human blood, beside its multi-functional activities, may carry different ionizing radiation emitters to the whole body, spatially alpha emitters, acquired through unknowing ingestion of different food staffs and inhalation of contaminated air. This may the cause different health hazards. Estimation of alpha radioactivity in blood is necessary to get a basic idea about the level of alpha radio activity in human blood and assess whether there is any correlation of this with the possible ailment patterns of human. This study may also provide useful data to health science for further analysis in search of any correlation between the levels of blood alpha radioactivity in humans with age, sex and/or occurrence of diseases. Alpha radioactivity has been measured in blood samples collected from 285 participants, including people diagnosed with cancer, at Apollo Gleneagles Hospitals, Kolkata, West Bengal, India. The measurements have been done with the help of solid state nuclear track detector (SSNTD). Alpha(α) activity in the blood samples has been found to be lowest in participants who had mild diseases like common cold and flu and highest in those suffering from cancer. Average blood α-activity for all participants is found to be 66.3 ± 2 Bq/kg with minimum and maximum α-activity being 8.7 Bq/kg and 221.4 Bq/kg respectively. Average α-activity is highest in participants suffering from carcinoma and lowest in apparently healthy participants. Positive correlation is found between the participants' blood α-activity and their ages. No correlation has been found between blood α-activity and the haematological parameters considered in this study. [ABSTRACT FROM AUTHOR]

Air radon survey was carried out at different underground locations at Kolkata using radon monitor. Average radon concentration for basements was found to be 22.70 ± 1.12 Bq/m with maximum 59.00 ± 7.18 Bq/m and minimum 8.50 ± 3.14 Bq/m. Average level for sub-ways was 23.05 ± 2.59 Bq/m fluctuating between maximum 39.00 ± 1.24 Bq/m and minimum 13.50 ± 1.78 Bq/m. In comparison, open air background at basement entrance was 19.44 ± 1.06 Bq/m and subway entrance was 18.58 ± 1.14 Bq/m. Annual effective dose was calculated to assess probable health risk. Radon concentration level and annual effective dose were found well below safe levels recommended by International Agencies WHO and UNSCEAR. [ABSTRACT FROM AUTHOR]

Radon anomaly acts as a precursor to seismic events. Hence the fluctuation pattern of time series of radon bears a lot of significance. Multifractal detrended fluctuation analysis (MFDFA) has been applied successfully in past to various geo-electrical signals. The time series of earthquake related radon signal of duration three years (November 2005-November 2008) obtained from our experiment performed at Kolkata, India was analyzed in the framework of MFDFA. The study revealed that the fluctuation of radon concentration is multifractal in nature. [ABSTRACT FROM AUTHOR]