Abstract:
The present studies have been carried out for the determination of nutritional and toxic
elements and also to estimate the natural radioactivity concentrations in some locally
available baby foods using the nuclear reactor based Neutron Activation Analysis (NAA)
technique. For NAA, 15 samples having about 75 mg of each were prepared in two folds
followed by the standard protocol of NAA for short and long irradiation. Two Certified
Reference Materials (CRMs) namely, IAEA-Soil-7, IAEA-SL-1 and one Standard
Reference Material (SRM) NIST-1633b Coal Fly Ash were prepared in the same way.
The CRMs were used to control the quality of analysis, whereas the SRM was used to
quantify the elements using relative method. In short irradiation scheme, individual
irradiation of 15 samples and 3 CRMs was performed in the pneumatic transfer system
Rabbit Irradiation Channel of the TRIGA reactor for 1 min with the thermal power of
250 kW for the determination of Al, Ca, Mg, Mn, Ti, V, etc. In case of long irradiation,
all the samples, CRMs and the SRM were irradiated simultaneously in the same
irradiation channel for 7 minutes with the thermal power of 2.4 MW for determination of
Na, K, Fe, Cr, Th, U, Zn, etc. All the irradiated samples and CRMs were counted
individually using the HPGe spectrometry system with different decay intervals
depending on the half-lives of the interested elements. For quantification, the relative
standardization approach was applied. The natural activity was measured for
determination of 238U, 232Th, their daughters and 40K in all the 15 samples, using gamma
spectrometry system. For this analysis, about 70g of each sample was packed in a plastic
pot and kept shielded for about 4 weeks before counting to retain secular equilibrium
between the daughters and parents of 238U and 232Th decay series. Counting of each
sample was performed for 20,000 sec on the surface of the HPGe detector. For
quantification, a calibration curve was constructed using Al2O3 based 226Ra standard (800
Bq). For quality control, 4 CRMs namely, IAEA-Soil-6, IAEA-375, IAEA-152 and
IAEA-414 were also packed and counting was taken for them in the same way as of the
sample. An experiment was designed and conducted to determine the correction factors
due to variation of density and chemical compositions of the samples, CRMs and the standard. In some cases lower nutritional values were obtained compared to the quoted
values. The total dose rates and Radium Equivalent Activity were also determined in the
samples. These revealed that the radiation dose rate is approximately ground level and
are within the range of safe limit.
