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  • Author or Editor: P. Kalsi x
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Abstract  

Alpha to spontaneous fission branching ratios of heavy actinides such as238Pu and240Pu in solution have been determined by solid state nuclear track detectors (SSNTDs). The detectors used in the present studies are LR-115, CR-39 (DOP), Lexan polycarbonate and Tuffak polycarbonate. Before using Tuffak polycarbonate, a detailed and systematic study on the registration and chemical etching characteristics of fission fragment tracks in this detector was also carried out. The experimentally measured values of alpha to spontaneous fission ratios by this method are found to agree well with the expected values.

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Abstract  

The fission track registration efficiency of diethylene glycol bis allyl carbonate (dioctyl phthalate doped) [CR-39 (DOP)] solid state nuclear track detector (SSNTD) in solution medium (K wet) has been experimentally determined and is found to be (9.7 ± 0.5) × 10−4 cm. This is in good agreement with the values of other SSNTDs. The gamma irradiation effects in the dose range of 50.0–220.0 kGy on the bulk etch rate, V b and the activation energy for bulk etching, E of this solid state nuclear track detector (SSNTD) have also been studied. It is observed that the bulk etch rates increase and the activation energies for bulk etching decrease with the increase in gamma dose. These results have been explained on the basis of scission of the detector due to gamma irradiation.

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Abstract  

Various plutonium compounds are handled in nuclear facilities of BARC. Hence, there is a possibility of occupational workers getting exposed to Pu. In vitro bioassay monitoring in which Pu is separated by chemical procedures from excreta samples and estimated by alpha-spectrometry, is the method of choice for the evaluation of internal dose to the occupational workers handling Pu. However, this method requires a suitable Pu tracer for reducing the uncertainties due to chemical yield in the separation, electro-deposition and counting efficiency. 242Pu is commonly used as a tracer but due to its non-availability, efforts were made earlier to indigenously synthesis 236Pu by proton irradiation of 237Np in BARC-TIFR pelletron facility. The present study, reports the feasibility of using 236Pu as a radiochemical yield monitor (tracer) in bioassay samples.

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Abstract  

Effects induced by γ -irradiation in the dose range of 0-10 Mrad on Tuffak polycarbonate track detector films have been studied by thermogravimetry (TG). The samples were irradiated with 60Co γ -rays for doses of 3, 5 and 10 Mrad. The TG studies indicate that unirradiated and the γ -irradiated samples degrade in two steps. The kinetics of the two steps of degradation was also evaluated from the TG curves. Irradiation enhances the degradation rate and the effect increases further with increasing radiation dose. The activation energy values calculated for all the steps decrease on irradiation. A linear relationship observed between the decrease in activation energy and the dose received by the sample suggests the possibility of the use of Tuffak polycarbonate detector as γ dosimeter.

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Abstract  

The effects of gamma-irradiation at a dose range of 5-56 Mrad on the fission track registration efficiency of the Tuffak polycarbonate track detector from dry (K dry) as well as the solution media (K wet) are investigated. Fission tracks were recorded in the gamma-irradiated detectors along with the unirradiated ones by an electrodeposited source of 252Cf and also separately from a 252Cf solution. The fission track registration efficiencies for the irradiated detectors were determined in comparison with those of the unirradiated detectors. The results show that while the K dry values for the irradiated detectors decrease by about 2-10%, the corresponding K wet values decrease by about 3-20% as compared to unirradiated detectors . Further, the bulk etch rates were found to increase with the increase in gamma dose. The changes induced in the gamma-irradiated detectors as a function of dose have been studied also by thermogravimetry (TG).

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Abstract  

A transmission-corrected -ray counting method has been employed for the assay of uranium in crude Na2U2O7 cakes produced at the Uranium Conversion Facilities. A 3×3 NaI(TI) detector was used in conjunction with a 400-channel analyzer. The observed count rate of the 1 MeV -ray emitted by the238U in the sample was corrected for sample self-attenuation, measured with a65Zn (-energy 1115 keV) transmission source. A calibration factor determined by measuring a standard of known amount of radioactive material in the same form and geometry as the unknown sample was used to convert the transmission corrected count rate to the amount of uranium in the weighted sample. Another -spectrometric method is described for the assay of the U-content in the MgF2 slag produced during the magnesiothermic reduction of UF4 to U-metal ingots at the natural U-conversion plant.

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Abstract  

The alpha-decay constant to fission cross section ratio for epi-cadmium neutron induced fission of 237Np, 241Am have been measured using solid state nuclear track detectors (SSNTDs). The measured values were (0.63±0.14).109 s-1.cm-2, (2.31±0.46).1012 s-1.cm-2 for 237Np and 241Am, respectively. The alpha to spontaneous fission branching ratio for 243Am was also measured to be (2.66±0.50).1010 using SSNTDs. These ratios are useful as signatures for the trace level identification of these actinides.

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