Application of portable liquid scintillation counter for on-field measurement of tritium in aqueous samples during radiation emergency.

Screening of aqueous samples for 3H contamination is required to decide suitability of water intended for human consumption during radiation emergency. BARC, Trombay has recently procured Portable Triathler liquid scintillation counter as a screening tool for on-site response to radiation emergency. For this purpose, parameters like, different available scintillators, scintillator to sample ratio and influence of different capacity scintillation vials were optimized for 3H concentration measurement. The study indicated that for 7 mL vials, the optimized scintillator to sample ratio was 4:1 for Optiphase Hisafe II, Ultima Gold Ultra Low Level Tritium, Aqualight AB and Dioxane based scintillators whereas for Ultima Gold AB and Optiphase Hisafe III scintillators it was 3:1. In case of 20 mL vials, the ratio was optimized to 8:1 for all the above mentioned six scintillators. Additionally, the effect of applying counting efficiency using calibration curves generated using distilled water and that obtained using optimized scintillator to sample ratio in various spiked water samples was also studied. Results in 3H concentration (2000-5700 Bq/mL) indicate about ±10% deviation using both the methods for commercially available scintillators. However, in case of Dioxane based scintillator, the deviation was higher (20%). For analysis of 3H concentration ∼200 Bq/mL using commercially available scintillators results in higher deviation of about 21% due to unreliable quench indicating parameter for count rate less than 4000. The study indicated that calibration curves constructed using optimized parameters are universally applicable for determination of 3H concentration in wide variety of water samples.

Standardisation of 133Ba by efficiency extrapolation method and calibration of ionisation chamber.

133Ba has been standardised by direct measurements for the first time in the laboratory using two counting systems: (i) the 4πß (plastic scintillator) -γ coincidence, (ii) the 4πß (proportional counter) -γ coincidence. Furthermore, this standardisation experiment demonstrates the performance and applicability of the recently developed 4πß (plastic scintillator)-γ coincidence system for radionuclides decaying with complex decay schemes as well as for e, X-γ emitters. Additionally, 133Ba solution standards were prepared to calibrate the pressurized 4π γ ionisation chamber and determination of the calibration coefficient. The En score is a statistical indicator of the agreement between two independent estimations. Thus, the performance of the PS system was compared to the result obtained with the PC system using the En score as specified in the ISO13528:2015. The results of measurements are acceptable if En â‰¦ 1.0. An En score of 0.2 was obtained which indicates that, the 133Ba activity concentration obtained by the 4πß (plastic scintillator) -γ coincidence and 4πß (proportional counter) -γ coincidence systems are in agreement. This paper presents the standardisation procedure, the results obtained by the measurements and their comparison.

Regularized Particle Filter based algorithm for the state estimation of orphan gamma source in real time using a backpack gamma spectrometry system.

We demonstrate the capability of Regularized Particle Filter (RPF) based algorithm to localise and quantify an orphan gamma-ray source situated in an unknown area using a single radiation detection system. The radiological measurements are made in the form of gamma spectra at multiple locations using an in-house developed backpack gamma spectrometer based on a 2″ x 2″ NaI(Tl) scintillation detector. We developed an Android application based on RPF which processes the gamma spectra received from the backpack over Bluetooth along with location information acquired from the smart phone's GPS in real time to show the source location in latitude, longitude format and source strength. To examine the performance of the algorithm, the radiological source search operation is carried out with 5.74 GBq 137Cs and 2.66 GBq 60Co in two independent experiments. The sources are located within an error of 10 m in location and 10% in source strength during the multiple experiments. The experiments are conducted in an open field where the attenuating medium for gamma rays would appear homogeneous at all the measurement points. Further improvements in the methodology are required for the localisation and quantification of source in an urban environment with a single detector.

Establishment and Dissemination of Radiological Standards in the Field of Diagnostic Radiology in India.

BACKGROUND: The increased use of ionizing radiation for diagnostic purpose has resulted in an increase in the world population dose. Patient dosimetry in X-ray diagnostic radiology is required to establish diagnostic reference levels (DRLs) and to assess the average dose received by organs and tissues. International bodies have recommended DRLs to be based on dosimetric quantities. AIM: To cater to the increased requirement for dosimetry in diagnostic radiology, international guidelines are provided to establish and disseminate traceable calibration for dosimeters used in X-ray diagnostic radiology. X-ray diagnostic beams established are standardized using a diagnostic range free-air ionization chamber (DFAIC) (20-150 kV). MATERIALS AND METHODS: Characterization of the DFAIC and determination of the correction factors for the air kerma measurements were evaluated experimentally and by theoretical calculations. RESULTS: The paper details the establishment of 18 diagnostic beam qualities using DFAIC along with the associated uncertainties. The overall uncertainty for the air kerma measurements was within ±0.5% at 1 sigma level. Eight diagnostic range air kerma measurements using DFAIC were compared with the medium energy primary standard FAIC (50-300 kV) maintained in the laboratory. CONCLUSION: The air kerma rates agreed within ±1% and are within the overall standard uncertainty of both the chambers at the time of the comparison. Dissemination to the users in the field of diagnostic radiology in the country has been carried out by calibrating their ionization chambers and solid-state detector-based instruments against the DFAIC. The methodology followed to standardize the beams using DFAIC and calibration of dosimeters is presented in this work.

An environmental gamma spectrometry system with CsI(Tl) scintillator and FPGA based MCA for open field deployment.

Inorganic scintillator-based gamma spectrometry is typically carried out under laboratory conditions by using systems that require AC mains supply and dedicated computers for their operation. In this study, an in-house grown CsI(Tl) single crystal scintillator is optically coupled to a bialkali photomultiplier tube (PMT). The output of the PMT is fed to a pulse processing chain consisting of a preamplifier followed by an in-house designed and developed field programmable gate array (FPGA) based multichannel analyzer (MCA). Spectral data from this MCA is sent via serial communication to a microcontroller. A global system for mobile communications (GSM) modem transmits this data in the form of short message service (SMS) packets to a central receiving station, where the spectrum is reconstructed. The requirement of on-site data logging computer to store large spectral data has thereby been eliminated, which, in turn, has eliminated the requirement of AC power supply, reduced the overall power consumption and size of the system, and made it possible to develop a standalone solar-powered unit. For further reduction of overall power consumption, the spectrometer is turned-on only when a Geiger Mueller (GM) counter based gross gamma detection circuit, also included in the system, detects an ambient gamma dose rate beyond a pre-set threshold level. A mathematical methodology has also been implemented for restoration of recorded spectra, shifted due to temperature variations in the environment. All these features have been integrated and a standalone, solar-powered and battery operated field-deployable environmental gamma spectrometry system (EGSS) has been developed and tested for open field deployment. Presence of 41Ar in ambient air was successfully detected by the system.