D. N. Sharma

Comparative study of different methods for the activity quantification of 3H and 14C radionuclides in dual labeled samples using liquid scintillation analyzer

Different methods such as full spectrum DPM (FSDPM), dual isotope estimation and inclusion methods were studied for the activity quantification of (3)H and (14)C in dual beta labeled samples using liquid scintillation analyzer. A standardized Packard tritiated water was used as tritium source and (14)C activity was standardized by CIEMAT/NIST method and compared with the results obtained by the above three methods. Minimum detectable activity was 2100dpm/l for (3)H and 1200dpm/l for (14)C with a counting time of 300min. The accuracy of the results obtained was found to be within +/-10% for (3)H: (14)C activity ratios 1:1, 1:2, 2:1, 6:1, 9:1, 13:1 and 18:1.

Standardisation of water-moderated 241Am–Be neutron source using De Pangher neutron long counter: experimental and Monte Carlo modelling

A convenient neutron source is made for calibration of neutron survey instruments and personal dosimeters that are used in various nuclear installations such as fuel reprocessing, waste management, fuel fabrication and oil and well logging facilities, etc. This source consists of a bare (241)Am-Be neutron source placed at the centre of a 15-cm radius stainless steel spherical shell filled with distilled water. This paper describes the standardisation of the source at Bhabha Atomic Research Centre, using De Pangher neutron long counter both experimentally and using the Monte Carlo simulation. The ratio of neutron yield of water moderated to the bare (241)Am-Be neutron source was found to be 0.573. From the simulation, the neutron-fluence-weighted average energy of water-moderated (241)Am-Be source (fluence-weighted average energy of 2.25 MeV, dose-weighted average energy of 3.55 MeV) was found to be nearly the same as that of a (252)Cf source (fluence-weighted average energy of 2.1 MeV, dose-weighted average energy of 2.3 MeV). This source can be used for calibration in addition to (252)Cf, to study the variation in response of neutron monitoring instruments.

Lyoluminescence characteristics of trehalose dihydrate.

Lyoluminescence (LL) of trehalose dihydrate showed a linear gamma ray sensitivity in the dose range 0.1-5 x 10(2) Gy. At increased sample weight dissolved, the LL/mg showed a reduction when the microcontroller based integrated measurement system was used. The LL/mg was found to be independent of the sample weight when the instantaneous peak output observed by the electrometer amplifier on dissolution of the phosphor was taken as a measure of LL yield. The LL spectral measurement of trehalose dihydrate in luminol solution (LL sensitizer) confirms an energy transfer from the radiation induced free radicals to luminol molecule to produce light.

Study on enhanced atmospheric dispersion of 41Ar at the Trombay site

An extensive study has been carried out within the site of Bhabha Atomic Research Centre, Trombay, for examining the atmospheric dispersion of (41)Ar released from research reactors. The release rate, release height, meteorological parameters and geographical information were used to establish correlation between theoretical estimation using Gaussian plume dispersion model (GPDM) and dose/dose rate data obtained from Gammatracers (GTs). Ten monitoring locations were selected in five sectors and at different downwind distances from the release point. Analysis of dose rate data shows that the maximum dose rate (7.19 μSv h(-1)) and the total annual dose (1051 μSv) were observed at a downwind distance of 0.36 km. Average dose rates of all monitoring locations were varying from 0.03±0.02 to 0.12±0.07 μSv h(-1). The average dose rate increases at the monitoring locations placed at N to NE sectors during monsoon, and for monitoring locations placed at SW and SSE sectors during winter. The maximum dose rates, monthly and annual doses recorded by GT, have been compared with predicted values. Most of the locations show statistically significant coherence in the case of monthly dose.

Validation of efficiency tracing and zero detection threshold techniques using liquid scintillation analyser TriCarb.

Efficiency tracing with unquenched 14C and zero detection threshold with unquenched 3H as tracers are practical and simple techniques which have been implemented to quantify the activity of various beta emitters using liquid scintillation analyser. These techniques are used to study the influence of quench level on activity quantification and the activity levels up to which these techniques are applicable. The results indicate that, for an activity level of 166.67 Bq, both the techniques are in good agreement with the reference activity with a relative discrepancy of ≤4.6 %. The relative discrepancy of ~10 % is observed for extreme quench values of ~111. For all the radionuclides with the activity level of 1.67 Bq, the uncertainty in activity quantification raises to ~8 % and for the activity level from 8.33 to 100 Bq, the uncertainty reduces to 1 %.

Radiation safety aspects of the operation of first three synchrotron beam lines of Indus-2

Five synchrotron radiation beam lines are commissioned and now under regular operation at the Synchrotron Radiation Source, Indus-2 at Raja Ramanna Centre For Advanced Technology (RRCAT), Indore, India. Nine beam lines are under trial operation, and six beam lines are in the installation stage. In the early phase of installation of beam lines on Indus-2, three bending magnet beam lines, Extended X-ray Absorption Fine Structure (EXAFS, BL-8), Energy Dispersive X-ray Diffraction (EDXRD, BL-11) and Angle Dispersive X-ray Diffraction (ADXRD, BL-12), were installed and commissioned, after approval from Atomic Energy Regulatory Board (AERB), India. These beam lines are pink (BL-8), white (BL-11) and monochromatic (BL-12), which are housed in specially designed shielded hutches. In order to ensure safety of users and other working personnel from ionizing radiations present in these beam lines, several safety systems are incorporated and safety procedures are followed. The paper describes the radiological safety aspects of the three beam lines during its initial commissioning trials and also the measurements on radiation levels carried out in and around the beam line hutches.

Direct estimation of 90Sr in water samples of spent fuel storage bay using partial counting rate technique

The direct estimation of 90Sr by β counting from a mixture of other β and γ emitter is often difficult due to the efficiency variation among the β-emitters and the unknown nature of the sample. This paper deals with use of a combination of β and γ spectrometry measurements in estimating the activity of 90Sr, pure β emitter from a mixture of other β–γ emitters in water samples. This procedure offers a simple, easy to use, rapid and a reliable method for 90Sr estimation as an alternative to the tedious radiochemical separation procedure in this specific case.