Efficiency as a function of MEQ-CWT for large area germanium detectors using LLNL phantom.

The lung counting system at Kalpakkam, India, used for the estimation of transuranics deposited in the lungs of occupational workers, consists of an array of three large area germanium detectors fixed in a single assembly. The efficiency calibration for low energy photons was carried out using ²4¹Am and ²³²Th lung sets of Lawrence Livermore National Laboratory phantom. The muscle equivalent chest wall thickness (MEQ-CWT) was derived for the three energies 59.5, 75.95 (average energy of ²³²Th) and 238.9 keV for the series of overlay plates made of different adipose mass ratios. Efficiency as a function of MEQ-CWT was calculated for individual detectors for the three energies. Variation of MEQ-CWT from 16 to 40 mm resulted in an efficiency variation of around 40 % for all the three energies. The array efficiency for different MEQ-CWT ranged from 1.4×10⁻³ to 3.2×10⁻³, 1.5×10⁻³ to 3.3×10⁻³ and 1.1×10⁻³ to 2.3×10⁻³ for 59.5, 75.95 and 238.9 keV, respectively. In the energy response, efficiency was observed to be maximum for 75.95 keV compared with 59.5 and 238.9 keV.

Environmental transportation of tritium and estimation of site-specific model parameters for Kaiga site, India.

Tritium content in air moisture, soil water, rain water and plant water samples collected around the Kaiga site, India was estimated and the scavenging ratio, wet deposition velocity and ratio of specific activities of tritium between soil water and air moisture were calculated and the results are interpreted. Scavenging ratio was found to vary from 0.06 to 1.04 with a mean of 0.46. The wet deposition velocity of tritium observed in the present study was in the range of 3.3E-03 to 1.1E-02 m s(-1) with a mean of 6.6E-03 m s(-1). The ratio of specific activity of tritium in soil moisture to that in air moisture ranged from 0.17 to 0.95 with a mean of 0.49. The specific activity of tritium in plant water in this study varied from 73 to 310 Bq l(-1). The present study is very useful for understanding the process and modelling of transfer of tritium through air/soil/plant system at the Kaiga site.

Transfer coefficient of 137Cs from feed to cow milk in tropical region Kaiga, India.

In the transport model for the prediction of the concentration of (137)Cs in milk, the transfer coefficient from feed to milk, F(m), is an important parameter. Site-specific transfer coefficient from feed to cow's milk, for (137)Cs in the Kaiga environment, a nuclear power station site in India, determined over a period of 10 y is presented in this paper. The value is determined from (137)Cs concentration in milk and grass samples of the Kaiga region and the result ranged from 6.43E-03 to 1.09E-02 d l(-1) with a geometric mean value of 8.0E-03 d l(-1). The result is compared with that for (40)K, determined concurrently at the same region and ranged from 3.06E-03 to 3.48E-03 d l(-1) with a geometric mean value of 3.26E-03 d l(-1). This parameter is quite useful in decision-making for implementing countermeasures during a large area contamination with (137)Cs in tropical areas like Kaiga.

Studies on the rain scavenging process of tritium in a tropical site in India.

This study presents the results of one of the first systematic experiments on tritium ((3)H) concentrations in ground level air against that in rainwater near a pressurized heavy water reactor in a tropical region. The samples were collected over the rainy season of three years (2007, 2008 and 2010). For this study, 31 data sets were collected and interpreted based on the theoretical information available in the literature. The specific activity ratio of (3)H between rainwater and air moisture at ground level was calculated for each data set. The average specific activity ratio was found to be 1.96 ± 2.72. A correlation (r = 0.82, p < 0.001) was observed between the total rain hours in a day and the rainwater (3)H activity. Higher rain duration with slower rain rate yielded higher (3)H concentrations as more time was available for the scavenging/wash out process to take effect together with lower dilution. The present data also suggested the need to further investigate the influence of raindrop distribution and other local meteorological parameters on the (3)H wash out process. An attempt was also made to predict the (3)H concentration in air moisture samples using a Gaussian plume dispersion model and the values were compared with the measured (3)H activity. The measured values were generally lower than the predictions.

Soil to leaf transfer factor for the radionuclides ²²6Ra, 4°K, ¹³7Cs and 9°Sr at Kaiga region, India.

Transfer factors are the most important parameters required for mathematical modeling used for environmental impact assessment of radioactive contamination in the environment. In this paper soil to leaf transfer factor for the radionuclides 4°K, ²²6Ra, ¹³7Cs and 9°Sr is estimated for Kaiga region in Karnataka state, India. Among the plants in which study is carried out, ²²6Ra, 4°K, ¹³7Cs and 9°Sr activity in leaves of herbaceous plants is higher than that of tree leaves. Soil to leaf transfer factor for ²²6Ra, 4°K, ¹³7Cs and 9°Sr was found to be in the range of 0.03-0.65, 0.32-8.04, 0.05-3.03 and 0.42-2.67 respectively.

Evaluation of 25 y of environmental monitoring data around Madras Atomic Power Station (MAPS), Kalpakkam, India.

The Environmental Survey Laboratory at Kalpakkam, India carries out elaborate monitoring programme involving atmospheric, terrestrial and aquatic samples for radioactivity to evaluate the impact of operating two pressurised heavy water reactors. This paper presents the evaluation of 25 y (1983-2008) data. Statistical analysis of the environmental data for different radionuclides showed that the data best fits log-normal distribution. The data analysed showed that fission products such as (137)Cs, (90)Sr and (131)I were due to global fallout only. A ratio of 0.2 was obtained for (90)Sr to (137)Cs in air filter samples, only during Chernobyl accident period. The transfer factor of (137)Cs and (90)Sr for rice was computed to be 0.23 and 0.03 and vegetables 0.25 and 0.10, respectively. Activation products (3)H and (41)Ar are the only radionuclides that are related to MAPS operation. A strong correlation (r = 0.9) was observed between (3)H activity in air and (3)H discharged to the atmosphere. A similar correlation (r = 0.8) was observed in (3)H concentration in seawater and (3)H discharged in the liquid waste. The annual internal dose due to (3)H and annual external dose due to (41)Ar evaluated in the last 25 y show that the members of the public received less than 2 % of the dose limit (1 mSv y(-1)) set by ICRP 72.

Estimation of site-specific deposition velocities and mass interception factor using 7Be and the prediction of deposition pattern of radionuclides at Kaiga site, India.

Site-specific wet, dry deposition velocities and mass interception factors at Kaiga site, where three PHWR type power plants are operational, using 7Be as a tracer are presented. Mean wet and dry deposition velocities for Kaiga site were found to be 7.4 x 10(-2) m s(-1) and 3.0 x 10(-4) m s(-1), respectively. Mass interception factors for vegetation were found to be 0.7-5.6 m(2) kg(-1) dry weight with a mean of 2.4 m(2) kg(-1) dry weight. The site-specific data were used for the prediction of radionuclide distribution pattern in soil and vegetation in the case of a hypothetical air contamination.

Evaluation and assessment of 25 years of environmental radioactivity monitoring data at Tarapur (India) nuclear site.

The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between (137)Cs in discharge canal seawater and station discharged activity and correlation of (137)Cs, (60)Co, and (131)I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of (137)Cs and (131)I in seawater versus biota are discussed. A good correlation between (137)Cs in seawater and (137)Cs in liquid waste discharged was observed (R(2) = 0.8, p < 0.001). Similarly, correlation was good for Nerita and discharged concentration of (137)Cs, (131)I and (60)Co (R(2) = 0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean (137)Cs decreased from the pre-operational levels: 7.0-3.6 Bq kg(-1) in soil, 0.91-0.016 Bq L(-1) in milk and 0.28-0.036 Bq kg(-1) in vegetation. Similarly, the mean (90)Sr in these matrixes decreased from 3.9 to 0.26 Bq kg(-1); 0.37-0.011 Bq L(-1) and 0.34-0.022 Bq kg(-1) respectively. Cesium-137 of about 700 microBq m(-3) was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.

Assessment of daily intake of trace elements by Kakrapar adult population through ingestion pathway.

Concentration of trace elements such as Fe, Cu, Ni, and Zn were measured in cereals, pulses, vegetables, fish, meat, milk, egg, and water samples collected around Kakrapar, Gujarat, India. A wide variation of the trace element concentration was observed among all the dietary matrices. The concentration of Fe is comparatively more in all the dietary matrices. The concentrations of these elements are translated into intake rates through ingestion pathways. Daily intake (milligrams/day) of Fe, Cu, Ni, and Zn by adult population of Kakrapar, Gujarat were 16.5 +/- 6.2, 3.3 +/- 1.2, 1.8 +/- 1.0, and 3.6 +/- 1.3, respectively. Dietary sources of Fe, Cu, and Ni by Kakrapar adult population are comparable with RDA. In case of Zn, the daily dietary intake is comparatively lower than that of RDA.

Assessment of radiological significance of naturally occurring radionuclides in soil and rock matrices around Kakrapar environment.

The activity and gamma-absorbed dose rate due to the naturally occurring radionuclides in the terrestrial environment such as (238)U, (232)Th and (40)K were determined in soil and rock samples collected around Kakrapar Atomic Power Plant site, using gamma-ray spectrometry. The mean concentration levels measured in Kakrapar soil from naturally occurring radioisotopes such as (238)U, (232)Th and (40)K are lower than the corresponding global average values obtained in worldwide soil. The external hazard index (H(ex)) and absorbed gamma dose rate in air outdoors is observed to be 0.04-0.18 and 3.1-14.1 nGy h(-1), respectively.

An attempt for modeling the atmospheric transport of 3H around Kakrapar Atomic Power Station.

Prediction of downwind tritium air concentrations in the environment around Kakrapar Atomic Power Station (KAPS) was studied on the basis of Gaussian plume dispersion model. The tritium air concentration by field measurement [measured tritium air concentrations in the areas adjacent to KAPS] were compared with the theoretically calculated values (predicted) to validate the model. This approach will be useful in evaluating environmental radiological impacts due to pressurised heavy water reactors.

Use of faecal excretion function for quick estimation of initial and existing lung burden for occupational exposure control due to 239Pu for S-class of intake.

Two functions namely initial lung deposition and lung retention per unit faecal excretion rate are constructed primarily based on the excretion pattern of four subjects exposed to (239)Pu. In the absence of initial clear knowledge about the class of compound inhaled, faecal to urine excretion ratio was used to infer the type of inhaled class. Trends in the urine and faecal data had suggested that the intake was due to mixed class of plutonium compound for each case. With the assumption of 1:1 mixture of plutonium M&S class inhaled compound, faecal excretion rates for only S-class intake were worked out. Uptake inferred based on their urinary data had suggested it to be of similar level within 40% of uncertainty for 5 microm particle size distribution. Data, all the four cases, were pooled for analysis citing the similar level of intake, particle size distribution, nature and pattern of work. The function obtained was tested for S-class lung retention and faecal excretion rate value. These functions are handy tool for estimating initial lung burden and lung retention value for low level of S-class plutonium intake based on subject faecal analysis data.

Biosorption of heavy metals and radionuclide from aqueous solutions by pre-treated arca shell biomass.

In this study biosorption potential of pre-treated arca shell biomass for lead, copper, nickel, cobalt and cesium was explored from the artificially prepared solution containing known amount of metals. The effects of pH, initial concentration, biosorbent dosage and contact time were studied in batch experiments. Effects of common ions like sodium, potassium, calcium and magnesium on the sorption capacity of pre-treated arca biomasses were also studied. To analyse the homogeneity of the biomaterial, experiments were performed for eight lots arca shell biomass for all the studies elements and it was observed that relative standard deviation in uptake capacity was within 10% for all elements. At equilibrium, the maximum total uptake by shell biomaterial was 18.33+/-0.44, 17.64+/-0.31, 9.86+/-0.17, 3.93+/-0.11 and 7.82+/-0.36 mg/g for lead, copper, nickel, cesium and cobalt, respectively, under the optimised condition of pH, initial concentration, biosorbent dose and contact time. Effect of all the common ions jointly up to concentration of 50 ppm was negligible for all the elements but at higher levels the cations affects the uptake capacity. Sorption isotherms were studied to explain the removal mechanism of both elements by fitting isotherms data into Lagergren, Freundlich and Langmuir equations. Halls separation factor estimated under optimised condition also favours the sorption potential of these elements using arca shell biomass. Arca shell biomass can be effectively and efficiently employed for removal of studied elements after optimisation of parameters.

Biosorption of lead and copper from aqueous solutions by pre-treated crab and arca shell biomass.

Sorption potential of pretreated crab and arca shell biomass for lead and copper from aqueous media was explored. The effects of pH, initial concentration, biosorbent dosage and contact time were studied in batch experiments. Effects of common ions like sodium, potassium, calcium and magnesium on the sorption capacity of pretreated crab and arca biomasses were also studied. At equilibrium, the maximum uptake by crab shell biomass was 19.83+/-0.29 and 38.62+/-1.27 mg/g for lead and copper, respectively. In case of arca shell biomass the maximum uptake capacity was 18.33+/-0.44 mg/g and 17.64+/-0.31 mg/g for lead and copper, respectively. Combined effect of all the common ions up to 50 microg/ml concentration was negligible for both the metals using both biomasses. Sorption isotherms were studied to explain the removal mechanism of both elements by fitting isotherms data into Lagergren, Freundlich and Langmuir equations.

Gamma dose measurement in dwellings of Agastheeswaram Taluk of Kanyakumari district, lying 30 km radius from Kudankulam nuclear power plant site.

Most of the building materials contain naturally occurring radioactive elements, the most important of which are potassium (40)K and the members of two natural radioactive series, which can be represented by the isotopes of thorium (232)Th and Uranium (238)U. The presence of these radioisotopes in the materials causes external exposure to the people who live in the building. In addition, the disintegration of Uranium (238)U increases the concentration of radon gas (222)Rn and of its daughters in the house. So a systematic indoor gamma dose measurement has been performed in the dwellings of Agastheeswaram Taluk of Kanyakumari district, which is lying within the 30 km radius from the upcoming Kudankulam nuclear power plant site. The geometric mean of annual absorbed dose from gamma radiation in dwellings has been found to be 278 nGyh(-1). The seasonal variation of indoor gamma dose measurements has also been studied. Significant differences have been observed in dwellings built of different materials such as concrete, tiled, etc.

Derivation and validation of a urinary excretion function for plutonium based on occupational exposure.

Formation of a three-component urinary excretion function using the data of occupational exposure cases is described. Measurement results of plutonium inhalation from two subjects over 6000 and 2500 d are used in the derivation of this function. The three-component excretion function obtained is U(t) = 0.0008e(-0.0566(t)) + 0.00009e(-0.0042(t)) + 0.00004e(-0.00008(t)). The function is therefore proposed as a reliable basis to make an uptake assessment for operational control for mixed class of plutonium dominated by M-class chronic exposure.

A non-parametric statistical analysis in the measurement of outdoor gamma exposure to the residents around Trombay.

During this study, non-parametric statistical methods were used to validate the measured gamma dose rate with the calculated one, around Trombay. Portable dose rate digital gamma spectrometry system (target fieldSPEC) was used for in situ measurement of external gamma (gamma) dose rate (measured) with the range of 1 nSv/h-10 Sv/h. The activity concentration of U-238, Th-232, K-40 and Cs-137 in the soil and their respective external dose-conversion factor (nSv/h/Bq/kg) was used to evaluate the gamma dose rate (calculated). Non-parametric statistical tool like Box- and -Whisker Plot, Spearman's (rho) rank Correlation coefficient, the Wilcoxon/Mann-Whitney test and chi(2) distribution test have been applied for validation. The randomness or discrete behaviour of measured and calculated dose rate was obvious from the Box- and -Whisker Plot as mean and median of the two are not equal. The inter quartile range (Q3-Q1), which explains about the dispersion of measured and calculated dose rate were also evaluated and found to be 10 and 16 microSv/y, respectively. The linear association between the order of ranks of the two dose rates was established by using Spearman's (rho) rank correlation that showed a coefficient of R = +0.90 with the intercept +1.9, whereas Pearson's correlation was observed with a coefficient of R = +0.93 with the intercept -25.6. Wilcoxon/Mann-Whitney test shows that, medians of the calculated and the measured dose rate as significantly different under the assumption of null hypothesis and measured dose rate was made to the normal distribution by applying Z-statistics. Value of chi(2) was calculated and found to be 284.95, which was very much greater than the critical value of chi(2)(0.05) = 43.77 at a degree of freedom 30, concluding that there is a highly significant difference between the measured and calculated dose rate at 5% significance level.

Certified reference material for radionuclides in fish flesh sample IAEA-414 (mixed fish from the Irish Sea and North Sea).

A certified reference material (CRM) for radionuclides in fish sample IAEA-414 (mixed fish from the Irish Sea and North Seas) is described and the results of the certification process are presented. Nine radionuclides (40K, 137Cs, 232Th, 234U, 235U, 238U, 238Pu, 239+240Pu and 241Am) were certified for this material. Information on massic activities with 95% confidence intervals is given for six other radionuclides (90Sr, 210Pb(210Po), 226Ra, 239Pu, 240Pu 241Pu). Less frequently reported radionuclides (99Tc, 129I, 228Th, 230Th and 237Np) and information on some activity and mass ratios are also included. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in fish sample, for the development and validation of analytical methods and for training purposes. The material is available from IAEA, Vienna, in 100 g units.

The use of ultra filtration in trace metal speciation studies in sea water.

During this work, size fractionation technique "ultra filtration" is used in speciation studies of trace elements in the coastal sea water. Filtration is the most commonly used method to fractionate trace metal species, but often only "dissolved" and "particulate" fraction. The purpose of the present study is to determine colloidal and suspended particulate concentrations of Fe, Zn, Cu, Ni, and Mn in sea water. Suspended particulate matter were separated in three different size groups namely (>2.7 microm, <2.7->0.45 microm and <0.45->0.22 microm) by suction filtration using cellulose acetate and nitrate filter membranes. Thereafter to concentrate the solution with colloidal particle <0.22 microm-1.1 nm (0.5 k Nominal Molecular Weight cut-off Limit {NMWL}), the solution obtained from filtration through <0.22 microm, is sequentially passed through the ultra-filtration membranes having pore diameters of 14 nm (300 k NMWL), 3.1 nm (50 k NMWL), 2.2 nm (30 k NMWL), 1.6 nm (10 k NMWL) and 1.1 nm (0.5 k NMWL) by using Stirred Ultra-filtration Cells, operating in concentration mode. The concentration of Fe, Zn, Cu, Ni, and Mn were measured in suspended and dissolved fraction by ion chromatography, ICP-AES and Atomic Absorption Spectrometer. The salinity of the solution in various dissolved fractions of sequential filtration varies between 30.89-34.22 parts per thousand. The maximum concentrations of colloidal Zn, Cu, Ni and Mn in dissolved fraction were in <2.2->1.6 nm fraction. In case of Fe, colloidal fractions <2.2->1.6 nm and <1.6-<1.1 nm shows higher concentration. The concentration of Zn, Cu, Ni and Mn increase with decrease in size in suspended particulate matter, while the reverse is observed in case of Fe. This size separation data that specifies the partitioning of metals between dissolved and suspended solid phases is necessary for developing physically based models of metal transport in aquatic system.

Studies on the sorption and desorption characteristics of Zn(II) on the surface soils of nuclear power plant sites in India using a radiotracer technique.

Zinc adsorption was studied in the soils of three nuclear power plant sites of India. 65Zn was used as a radiotracer to study the sorption characteristics of Zn(II). The sorption of zinc was determined at 25 and 45 degrees C at pH 7.8+/-0.2 in the solution of 0.01 M Ca(NO3)2 as supporting electrolyte. The sorption data was tested both in Freundlich and Langmuir isotherms and could be described satisfactorily. The effect of organic matter and other physico-chemical properties on the uptake of zinc was also studied in all the soil samples. The results showed that the cation exchange capacity, organic matter, pH and clay content were the main contributors to zinc sorption in these soils. The adsorption maximum was found to be higher in the soil on Kakarpara Atomic Power Plant sites soils having high organic matter and clay content. The zinc supply parameters of the soils are also discussed. In the desorption studies, the sequential extraction of the adsorbed zinc from soils showed that the diethylene triamine penta acetic acid extracted maximum amount of adsorbed zinc than CaCl2 and Mg(NO3)2. The zinc sorption on the soil and amount of zinc retention after extractants desorption shows a positively correlation with vermiculite and smectite mineral content present in the clay fraction of the soil. The amount desorbed by strong base (NaOH) and demineralised water was almost negligible from soils of all the sites, whereas the desorption by strong acid (HNO3) was 75-96% of the adsorbed zinc.