[en] India has an active programme for using thorium as third stage self- sustaining nuclear fuel. A significant amount of thorium is also used in the gas mantle industry. The presently estimated monazite deposits amounting to five million tonnes are distributed in the beach sands of south western and eastern coasts and some areas in Andhra Pradesh. The sands are processed for recovery of rare earth minerals and thorium. The mineral processing and thorium separation involves hazards to workers from exposure to radiation, radioactive and silica bearing dusts as well as from conventional chemicals used in the processing. Releases of wastes from the plants may necessitate environmental surveillance. The present paper reviews the hazards envisaged, steps taken to mitigate such hazards and achievements in this regard in the thorium industry in India. (author)

[en] A review of International Atomic Energy Agency (IAEA) publication on regulation for the safe transport of radioactive material has been completed and issued as Safety Standards series No. ST-1 in 1996. Various changes on some major issues involving transport of radioactive material (RAM), such as, type A package activity limits, exemption for total activity as well as concentration of radionuclides, special provision for transporting uranium hexafluoride, criticality safety index for fissile material, type C package for carrying RAM by air etc. have been incorporated in this current revision. In this paper the justification and technical basis for these regulatory changes are discussed. In view of this, appropriate changes in national regulations for transport of RAM have to be incorporated. (author)

[en] This system uses a main counter for the sample activity measurement and a large area guard counter for background reduction. Both these counters operate in the G.M. region. When operated in anticoincidence mode and in 6'' lead shield the background of the counting system is less than 1 cpm. The counting medium is argon gas and isopropyl alcohol vapour is used as quenching agent. A parallel gas flow arrangement is presently developed which facilitates continuous operation of the system. The characteristics of the system having this arrangement are studied and described. (author)

[en] Measurements of concentration of positive and negative ions and condensation nuclei (CN), have been carried out indoors with the help of a atmospheric ion analyser and a portable small particle detector respectively at variety of locations such as near a high way, in a comparatively clean area, in an x-ray room and at a reactor environment. The average levels of ions vary between few hundreds and a few thousands ions per cm³ and of CN from about 2x10⁴ to 7x10⁴ per cm³ depending upon the ongoing activities at the location. The data are presented and the influence of outdoor pollution is discussed in the context of the behaviour of air ions and CN. (author)

[en] Measurements of radon levels in the area of Dottingen/Eifel in Germany is reported

[en] A compact electronic pocket dosemeter, 110 mm x 24 mm x 18 mm in size, based on a low cost commercially available Si diode developed is described

[en] The background radiation levels at 30 locations in and around the Jahangirnagar University Campus (JUC) were measured using a LiF(TLD-100) thermoluminescent dosimeter (TLD). In addition, dose rates at three pre-selected locations were measured on a monthly as well as quarterly basis for one year period (July 1993 - June 1994). The dose rate ranges from 1016 to 2167 μSv.y^-1 (101.6 to 216.7 mrem.y^-1) with a mean value of 1595 μSv.y^-1 (159.5 mrem.y^-1). These values are comparable with those of pre- and post-operational values for the reactor site. The estimated average annual effective dose equivalent to the inhabitants at the study areas was found to be 1276 μSv (127.6 mrem). Variation of background radiation level with meteorological parameters, namely, temperature, rainfall, relative humidity and pressure was also studied. The influence on the dose rate of the meteorological parameters was observed. (author)

[en] Quick determination of the profile of ground contamination following a potential fallout of radionuclides over a wide area around a nuclear power plant in a post accident situation is of great importance for emergency management. An aerial gamma spectrometry system (AGSS) developed for this purpose consists of high efficiency NaI(Tl) scintillation detectors, an 8085 microprocessor based 256 channel scanning pulse height analyzer, a global positioning system (GPS) and a radio modem. In an aerial survey, the AGSS mounted in an aircraft scans the radionuclides contamination on ground as it simultaneously collects spectral and positional information in contiguous time intervals. For the programmed functioning of the AGSS, an integrated software package has been developed using micro soft visual basic operating under MS Windows. The software package correlates the spectral and positional data acquired by the AGSS in test flights over contaminated ground and maps the activity profile on-line onto a digitized site-map of the area. The package also facilitates simultaneous transmission of the information to a emergency control centre by means of the radio modem and its parallel processing. Several features of the software like zooming of a selected area for close scrutiny, on-line assessment of the radiological status of any desired area just with a mouse click etc., are incorporated in the package to make it comprehensive, user friendly and as a powerful aid in quick decision making process. The package also includes interactive communication with the AGSS for setting up various system parameters, initiation of the monitoring, on line interruption in monitoring to perform the processing of current spectrum for checking channel drift etc. The system software has been tested by deploying the system in a helicopter and flying over areas with simulated ground contamination in three successive aerial exercises. (author)

[en] CR-39 and LR-115 type II track detectors to be used for radon exhalation measurements have been calibrated. The configurations fitted with detectors in Can technique in the open cup mode are cylindrical plastic cup (PC) and conical plastic cup (CPC). The experiment was performed in radon exposure chamber having monodisperse aerosols of 0.2 μm size, to find the relationship between track density and the radon concentration. The calibration factors for PC and CPC type dosimeters with LR-115 type II detector were found to be 0.056 and 0.083 tracks cm^-2d^-1 (Bqm^-3)^-1 respectively, while with CR-39 detector the values were 0.149 and 0.150 tracks cm^-2d^-1 (Bq m^-3)^-1. Employing the Can technique, measurements of exhalation rates from solid samples used as construction materials, are undertaken. Radon exhalation rate is found to be minimum in cement samples while in fly ash it is not enhanced as compared to coal samples. (author)

[en] This paper deals with the committed effective dose equivalent from polonium-210 to the public of Tiruchirappalli district in south India on consumption of cereals, vegetables and animal food. It is demonstrated that the activity of ²¹⁰Po is non-uniformly distributed between cereals, vegetables and animal food. Among cereals, the green gram recorded a higher activity of ²¹⁰Po (0.62 Bq.kg^-1) than the others tested. The study also recorded a relatively enhanced activity in raw rice (0.90 Bq.kg^-1) than in boiled rice (0.03 Bq.kg^-1). Among vegetables, the tubers accumulated more ²¹⁰Po than the shoot growing vegetables. The muscle of prawn (Macrobrachium rosenbergii) recorded the highest level of ²¹⁰Po activity (13.9 Bq.kg^-1) among the animal food. With reference to dosimetry, the animal food was identified to contribute higher radiation dose (0.38-29.5 μSv.y^-1) than the cereals (0.05 - 1.9 μSv.y^-1) and vegetables (0.05 - 1.9 μSv.y^-1). Among animal food, the fish contributed a substantial level of α radiation dose to man. Though activity in raw rice was higher than the activity in boiled rice, the dose delivered from raw rice was substantially low since the average consumption of this rice represents only 7 kg.y^-1 when compared to the consumption of boiled rice (108 kg.y^-1). From the dose estimates made, it was evident that the total dose received by the general public (2.7 μSv.y^-1) from ²¹⁰Po was well below the dose limit of 1mSv.y^-1. (author)