S. P. Prabhu

Application of alpha track registration technique for plutonium estimation in bioassay samples

Bioassay monitoring is carried out for occupational workers handling plutonium (Pu) in nuclear facilities. In India, presently Pu estimation in bioassay samples is done by alpha spectrometry. The minimum detectable activity (MDA) of alpha spectrometry is 0.5mBq for a counting period of 1 day. To reduce the load of sample counting on alpha spectrometry, an alternative method based on alpha track registration in solid state nuclear track detectors (SSNTDs) is developed in the present paper. For this purpose, few urine samples of normal subjects spiked with known amounts of Pu in the range of 0.5-5.5mBq were exposed to CR-39 SSNTDs. The total number of alpha tracks seen in the CR-39 films of the sample and the standard were used to calculate the amount of Pu in the sample. The results of alpha track registration technique were also compared with that obtained by the well-established alpha spectrometry and were found to agree well within +/-30%. The minimum amount of Pu that can be analyzed by this method is 0.18mBq for an exposure period of 45 days.

Alpha source preparation of actinides by micro-precipitation

Alpha spectrometry is used for qualitative and quantitative analysis of actinides in biological and environmental samples. This technique requires a thin, homogenous and carrier-free deposit. Numerous methods for source preparation are electrolytic deposition, spontaneous deposition, micro-precipitation, direct evaporation, vacuum sublimation, etc. The most widely used method for preparation of actinides for alpha spectrometry is electro-deposition of actinides onto a stainless steel planchette. This procedure is time consuming, requires elaborate equipment and is expensive. Micro-precipitation method on the other hand is comparatively faster and more reliable. Thus, the present study was taken-up to optimize various parameters for rapid alpha source preparation of actinides by micro-precipitation method.

Nasal swab reference levels for plutonium based on aerosol characteristics and breathing patterns of individuals

In plutonium (Pu) handling facilities, there is a potential for internal exposure of radiation workers along with external exposure. Nasal swabs (NS) taken rapidly, on site, help in not only providing an early estimate of internal dose due to inhalation of Pu but also in decision making for medical intervention. However, the Committed Effective Dose (CED) computed based on the observed NS activity and that estimated from bioassay measurements of individuals may vary significantly. One of the reasons would be the use of default particle size (5 µm) for computing the CED based on the activity on NS. Other parameters like breathing pattern and levels of exercise would also influence the NS reference activity level and hence their impact needs to be assessed. This study indicated that observed NS reference levels had a direct dependence on all these parameters and use of default parameters for evaluation of internal dose based on NS activity would result in large uncertainties in the dose assessment.

Rapid Column Extraction Method for Uranium in Urine

The conventional method used for estimation of uranium (U) in bioassay samples takes nearly 4–5 days for complete sample analysis. In cases of incidental exposures, there is a need to reduce overall analysis time for the estimation of U in bioassay samples. Therefore, efforts were made in the present study to develop a comparatively rapid method for analysis of U in urine. For this purpose, a known amount of U(natural) standard was added to synthetic urine samples (1 L) and separated from by solid phase extraction chromatography using TRU resin (Eichrom Technologies, Inc.). The radiochemical yield recovery observed for U was 92.6% by this method. As a part of quality assurance, the method standardized in the present study was applied for estimation of U in urine samples collected from members of the public (MOP) and the results were compared to those previously obtained using ion exchange chromatography and fission track analysis (FTA).