A silicon photomultiplier based compact gamma spectrometer for environmental gamma radiation monitoring networks.

In this paper, the details of the development and performance characterisation of a compact, low-power gamma spectrometer for environmental gamma radiation monitoring networks are presented. To reduce the power consumption and the size of the spectrometer, a gamma detector comprising a silicon photomultiplier coupled to a Gd3Ga3Al2O12:Ce,B (GGAG:Ce,B) scintillator has been used for gamma spectrometry. Initially, a Monte Carlo simulation study was carried out to verify the suitability of the 5 mm × 5 mm × 5 mm GGAG:Ce,B crystal for spectrometry of gamma sources in the energy range 60-1332 keV. For minimising the power consumption, the signal processing electronics has been custom designed. This electronics was realised using standard off-the-shelf components to reduce the cost. The developed spectrometer is of size 16 cm × 10 cm × 6 cm, weighs 600 g and consumes 600 mW power. The spectrometer is developed such that it could be directly interfaced with GSM/Xbee for wireless communication with the radiation monitoring networks. The lower-level discriminator threshold of the system is 40 keV and the total electronic noise is <20 keV. The experimentally measured sensitivity of the spectrometer for 137Cs (662 keV) is 2.4 cps/µGy/h at 3.5 V overvoltage. The spectrometer offers excellent linearity over the measured energy range of 60-1332 keV and an energy resolution of ~10% for 662 keV gamma-ray at room temperature.

Thermal energy harvester powered piezoresistive pressure sensor system with wireless operation for nuclear reactor application.

To access the crucial parameters of a nuclear reactor during station blackout condition, we have proposed a concept of using thermal energy harvester powered sensors and instrumentation with wireless operation. To demonstrate this concept, low power electronics comprising a micro electro mechanical system piezoresistive pressure sensor, amplifier, and wireless transmitter was developed for measurement of pressure in a reactor process. The required electrical power for the sensor and instrumentation was derived from the thermal energy produced by the reactor process itself. A thermoelectric generator was used as an energy harvester for converting the heat energy from the process to electrical energy. A power management circuitry was used for the management of the power which was fed to the sensor and electronics. The complete instrumentation was tested in a test loop to demonstrate the operation of thermal energy harvester powered sensor with wireless operation for static and dynamic pressure measurements. Static pressure, increase or decrease of pressure with time and pressure oscillations were measured in a wireless mode using the developed instrumentation. Differential mode measurements were also carried out. The concept of thermal energy harvester powered sensor and instrumentation presented in this paper would be suitable for wireless sensor network of self-powered/thermal energy harvester powered sensors and for wearable devices by operators. An overview of the design and development of the instrumentation and the results are presented in this paper.

Development of potentiometric urea biosensor based on urease immobilized in PVA-PAA composite matrix for estimation of blood urea nitrogen (BUN).

A urea biosensor was developed using the urease entrapped in polyvinyl alcohol (PVA) and polyacrylamide (PAA) composite polymer membrane. The membrane was prepared on the cheesecloth support by gamma-irradiation induced free radical polymerization. The performance of the biosensor was monitored using a flow-through cell, where the membrane was kept in conjugation with the ammonia selective electrode and urea was added as substrate in phosphate buffer medium. The ammonia produced as a result of enzymatic reaction was monitored potentiometrically. The potential of the system was amplified using an electronic circuit incorporating operational amplifiers. Automated data acquisition was carried by connecting the output to a 12-bit analog to digital converter card. The sensor working range was 1-1000 mM urea with a response time of 120 s. The enzyme membranes could be reused 8 times with more than 90% accuracy. The biosensor was tested for blood urea nitrogen (BUN) estimation in clinical serum samples. The biosensor showed good correlation with commercial Infinitytrade mark BUN reagent method using a clinical chemistry autoanalyzer. The membranes could be preserved in phosphate buffer containing dithiothreitol, beta-mercaptoethanol and glycerol for a period of two months without significant loss of enzyme activity.