|Year : 2018 | Volume
| Issue : 1 | Page : 12-15
Spatial distribution of fallout 137Cs in the marine environment of Kudankulam and its comparison with Indian and Asia-Pacific regional seawater
B Vijayakumar1, G Thomas1, BS Selvi1, PM Ravi2, RM Tripathi2
1 Division of Health Physics, Environmental Survey Laboratory, Kudankulam Nuclear Power Project, Tirunelveli, Tamil Nadu, India
2 Division of Health Physics, Homi Bhabha National Institute; Division of Health Physics, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India
|Date of Submission||31-Jan-2018|
|Date of Decision||04-Mar-2018|
|Date of Acceptance||13-Mar-2018|
|Date of Web Publication||31-May-2018|
Environmental Survey Laboratory, Kudankulam Nuclear Power Project, Kudankulam, Tirunelveli - 627 120, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Benchmarking the fallout 137Cs in the coastal marine environment assumes significance in view of expansion of nuclear power plants (NPPs) in India and the Asia-Pacific region. This paper presents a snapshot of 137Cs activity in marine coastal water samples collected around Kudankulam NPPsite across a 50 km stretch from Kanyakumari to Uvari and attempts to compare with the 137Cs concentration observed across Indian coastal region and Asia-Pacific regional seawater. 137Cs activity of the Kudankulam coast ranges from ≤0.40 to 1.92 mBq/L with a geometric mean (GM) value of 1.0 mBq/L. In general, 137Cs activity in seawater of the entire Indian coastal region varies from 0.30 to 1.25 mBq/L, which may be considered as global fallout.
Keywords: 137Cs, 90Sr, Asia-Pacific, fallout, Kudankulam
|How to cite this article:|
Vijayakumar B, Thomas G, Selvi B S, Ravi P M, Tripathi R M. Spatial distribution of fallout 137Cs in the marine environment of Kudankulam and its comparison with Indian and Asia-Pacific regional seawater. Radiat Prot Environ 2018;41:12-5
|How to cite this URL:|
Vijayakumar B, Thomas G, Selvi B S, Ravi P M, Tripathi R M. Spatial distribution of fallout 137Cs in the marine environment of Kudankulam and its comparison with Indian and Asia-Pacific regional seawater. Radiat Prot Environ [serial online] 2018 [cited 2018 Jun 21];41:12-5. Available from: http://www.rpe.org.in/text.asp?2018/41/1/12/233650
| Introduction|| |
Growing energy demand prompts introduction of nuclear power as an alternative, clean, green, and eco-friendly energy resource which does not contribute to the adverse environmental effects arising from the burning of fossil fuels. The dominant source of anthropogenic radionuclides in the marine environment is global fallout. The global fallout essentially stems from atmospheric weapon tests, past nuclear accidents, discharges of radionuclides from nuclear installations, dumping of nuclear wastes into world's oceans and seas, nuclear submarine accidents, contribution from nuclear weapon test sites, loss of nuclear weapons and radioactive sources and satellite burn-up. To estimate radionuclide inputs from local sources, radionuclide distributions in the world's oceans and seas must be better known so that results of sources of anthropogenic marine radioactivity can be reviewed objectively, comparatively and comprehensively. This requires a detailed study of the present distributions and inventories of the radionuclides of interest in the world's oceans and seas. This paper presents the 137 Cs activity observed in Kudankulam coast from 2004 to 2016 spanning over the preoperational and operational period of environmental radiological surveillance. The reported activity is also compared with the observed levels of 137 Cs activity reported for other Indian coastal waters and Asia-Pacific region. Kudankulam site comprises of twin units of 1000 MWe VVER reactors which belong to the group of pressurized water reactors which constitute the large majority of the nuclear power plants (NPPs) in operation the world over.
| Materials and Methods|| |
About 520 coastal seawater samples have been collected and analyzed for 137 Cs activity over the period 2004–2016. About 42 offshore seawater samples were also collected during the period 2005–2007 up to 10 km offshore in grids of 1, 3, 5, 7, and 10 km from the shoreline from the reactor units. The coastal seawater sampling stations around Kudankulam are shown in [Figure 1]. Seawater samples were collected from both sides of Kudankulam plant covering about 50 km stretch of the Gulf of Mannar. Seawater samples (30 L each) were taken for analysis of 137 Cs and processed as per the standard procedures. After pre-concentration and absorption of 137 Cs on ammonium phosphomolybdate, the assay was carried out using a set of sensitive state of the art measurement systems. For detection and measurement of 137 Cs, a coaxial P-type hyper-pure germanium detector of 110% relative efficiency and 2.0 keV resolution with a well configuration was employed. The minimum detection limit achieved for 137 Cs was 0.4 mBq/L for seawater samples.
Under an IAEA sponsored Regional Co-operative Agreement (RCA) project, IAEA/RCA/07/016 entitled “Establishment of a Benchmark for Assessing the Radiological Impact of Nuclear Power Activities on the Marine Environment in the Asia-Pacific region,”137 Cs data have been generated over the entire coastal region of India covering Gujarat, Maharashtra, Karnataka, Kerala, Tamil Nadu, Andhra Pradesh, Orissa, and West Bengal. The Indian coast was grouped into three regions, viz., Gujarat and Maharashtra, known for high salinity, Karnataka and Kerala, known for high rainfall of peninsular India, and remaining locations under Bay of Bengal. The details of the method, calibration, quality control are discussed elsewhere.
Quality assurance and quality control
The quality of the data was assured by participating the interlaboratory comparison exercises conducted by the IAEA and BARC from time to time for the assay of various natural and anthropogenic radionuclides in diverse environmental matrices to test and re-assure the adequacy of methods, techniques, and instruments that are being used. The results are always within ±10% (95% confidence levels).
| Results and Discussion|| |
[Table 1] gives the levels of 137 Cs observed in coastal and offshore seawater of Kudankulam coast over the period 2004–2016. From the data in [Table 1], it may be inferred that there is no marked change in the concentration of 137 Cs in coastal and offshore seawaters.137 Cs activity in Kudankulam coast was found to be in the range of ≤0.40–1.92. The GM concentration of 137 Cs in seawaters was tending to about 1.0 mBq/L. [Figure 2] gives the trend analysis plot of 137 Cs activity levels observed at Kudankulam coast over the period 2004–2016. [Figure 3] shows the gamma spectrum of seawater samples; it clearly shows the natural radionuclide's present in the seawater and also the fallout 137 Cs.
137 Cs in surface seawaters of the Indian coast has been analyzed in three different regions along with temperature and salinity measurement (Jha et al., 2012). The salinity and temperature of seawater varied in the range of 29.6–37.0 ppt and 26.8°C–28.5°C, respectively, in all the sampling locations. In Gujarat–Maharashtra region, salinity was found higher and temperature was found lower than the other regions. The 137 Cs concentrations in this region ranged from 0.71 ± 0.07 mBq/L in surface seawater at Ratnagiri to 0.91 ± 0.14 mBq/L Porbandar. The median value was 0.82 ± 0.07 mBq/L which is lower than the decay corrected value of 1.6 mBq/L (i.e., 1.24 mBq/L) reported by Povinec et al. In this region, the variation was within a narrow range due to the comparatively closed behavior of the Arabian Sea as reported in the literature. The locations in Karnataka and Kerala region showed a range from 0.30 to 0.71 mBq/L, with a median of 0.61 ± 0.16 mBq/L in the surface water. A lower value was observed in this region, which lies in the west coast up to Trivandrum, as compared to region I. This may be due to coastal water which carries Western Ghats runoff into the Arabian Sea and which has limited circulation into the open sea. In the region of Bay of Bengal,137 Cs shows a variation from 0.37 to 1.25 mBq/L with a median value of 0.94 ± 0.34 mBq/L. The highest value was observed at Nagercoil whereas the lowest value was observed at Machilipatnam (Jha et al., 2012). [Figure 4] shows the frequency distribution of Cs-137 in seawater sample; it is observed that the Cs-137 activity in most of the seawater samples lies between 0.8 and 1.2 mBq/l.
[Table 2] compares the 137 Cs activity of the Kudankulam coast with other coastal Indian and regional marine radioactivity database. In general the concentration of 137 Cs in the Indian coastal water reported in the present study lies in the lower side of the range from 0.26 to 11.47mBq/l reported by Duran et al. 137 Cs range reported for North Indian Ocean, Arabian Sea, and Indian Ocean ranges from 1.6 to 2.1 by Povinec et al. and IAEA TECHDOC 1429 (2005). The present results are in conformity with the reported values in the literature.
|Table 2: Comparison of 137Cs activity concentration in Asia-Pacific regional seawater|
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[Table 3] gives the 137 Cs concentration values observed in coastal seawater samples of other coastal sites in India, namely Tarapur and Kalpakkam, where NPPs are in operation for a very long time. From the data, it may be observed that the values are comparable to other costal seawater samples, and there has been no substantial input from the operating NPPs.
|Table 3: Cs-137 concentrations in coastal seawaters at coastal nuclear power plant sites (2011-2014)|
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| Conclusions|| |
137 Cs activity observed in the Kudankulam coast has been compared with other Indian and Asia-Pacific marine radioactivity database. Apart from fallout, there has been no substantial input from any other source, including discharges from the NPPs operating in the south, west, and east coast of India. This benchmarking study has been found useful in establishing the pre-operational baseline value of 137 Cs in coastal waters around Kudankulam, and regional 137 Cs seawater database will serve as pre-operational data at new virgin proposed coastal nuclear sites across India.
We are thankful to Dr. K. S. Pradeepkumar, Associate Director, HSEG, BARC, for his encouragement and support for this work. We express our sincere thanks to Shri S. V. Jinnah, Site Director, Kudankulam, for full support and for extending excellent infrastructure facilities to ESL at Kudankulam to undertake a study of this nature.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]