Radioactive tracer Application in Oceanographic Study in North - - PowerPoint PPT Presentation

Radioactive tracer Application in Oceanographic Study in North Atlantic- Baltic Sea

Jixin Qiao DTU-Nutech

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DTU Nutech, Technical University of Denmark

Nuclear properties of important U isotopes

Nuclide Half-life, y Abundance, % Decay mode Method of production

232U

68.9 trace α

232Th(α, 4n) 233U

1.59×105 trace α

233Pa β- decay 234U

2.46×105 0.0059-0.0050 α nature

235U

7.04×108 0.7202-0.7198 α nature

236U

2.34×107 trace α

235U(n,γ) 238U(n,3n) 240Pu α decay 238U

4.47×109 99.2752-99.2739 α nature

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DTU Nutech, Technical University of Denmark

236U sources in the environment

Source term Production/ Pathway Amount

Natural Uranium Ore Neutron capture 1.5 kg Rock (0-1000 m) Neutron capture 22 kg Earth Crust Surface Thermal neutron 10 kg Ocean Rock weathering 0.5 kg SUM 34 kg Anthropogenic Global fallout Direct atmospheric release and growth of 240Pu 900 kg Nuclear reactor Neutron activation 106 kg Nuclear accidents & reprocessing plants Release/discharge Small fraction

• f reactor 236U

SUM 106 kg

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Steier et al. Nucl. Instr. Meth. In Phys. Res. B 2008, 266, 2246-2250. Christl et al. Geochim. Cosmochim. Acta 2012, 77, 98-107.

DTU Nutech, Technical University of Denmark

Importance of 236U

• Geologic study: uranium prospecting, dating, erosion study
• Nuclear safeguards: identify uranium source, trace uranium

contamination from nuclear fuel or waste, reprocessing activities, hot cell facilities, production of medical radioisotopes

• Hydrology and oceanography study: water mass movement,

geochemical processes

• Astronomy: a marker of supernova debris

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Typical levels of 236U in the environment

Location

236U/238U ratio

Rock 1×10-14 - 5×10-14 Uranium ore 10-12 - 10-10 Atlantic Ocean 10-9 -10-10 North Sea 5 ×10-9 - 22 × 10-9 Japan Sea 10-9 Soil in Ichikawa, Japan 2 ×10-8 - 1 × 10-7 Soil 200 km from Chernobyl power plant 2 × 10-7 - 4 × 10-7 Soil from the close vicinity of Chernobyl power plant 10-6 - 10-3 Depleted uranium (DU) contaminated areas in Kosovo 10-7 - 10-3 Uranium processing factories, USA 10-6 - 10-4 Irish Sea sediment (affected by Sellafield reprocessing plant) 10-6 - 10-5 Commercial reagents and artificial standard materials 10-6

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Steier et al. Nucl. Instr. Meth. In Phys. Res. B 2008, 266, 2246-2250. Skaguchi et al. Sci. Total Environ. 2009, 407, 4238-4242. Christl et al. Nucl. Instr. Meth. In Phys. Res. B 2013, 294, 530-536 and 2008, 266, 2246-2250.

DTU Nutech, Technical University of Denmark 6 25-04-2014

10 L filtrated seawater

Add 10 ml conc. HNO3, 10 mL 0.1g/mL Fe, N2 bubbling 10 min. Add 10% NH3·H2O to pH 9, Siphon supernatant and centrifuge remaining slurry

Supernatant Precipitate

Add 20 mL conc.HNO3, digest under 200˚C for 2h. Evaporate to near dryness

Precipitate

Dissolve with 15 mL 3 M HNO3

Sample solution

• ca. 30 mL

1.Load the sample 2.Wash with 40 mL 3 M HNO3 3.Wash with 20 ml 6 M HCl 4.Elute U with 10 mL 0.025 M HCl U T E V A

Add 3 mg Fe, 10% NH3·H2O to pH9, centrifuge

U eluate Discard AMS measurement for 236U/238U Precipitate

Wash with 2×10 mL H2O, Dry, ash, mix with Ag powder

Take 0.5 mL sample, add 5 ng In, diluted to 5 mL with 0.5 M HNO3

ICP-MS measurement for 238U

Analytical procedure overview

Qiao et al. Analytical Chemistry 2015, 87, 7411-7417.

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Tracer application of 236U along Danish coast

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Roskilde Fjord North Sea Baltic Sea Kattegat Jutland Zealand

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a) b) c) d) a) b) c) d)

a) 2013 surface, b) 2013 bottom, c) 2014 surface, d)2014 bottom

DTU Nutech, Technical University of Denmark

Tracer application of 236U in Baltic Sea

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Sampling year 2015

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129I in the Baltic Sea and Kattegat (April

2007)

Yi, Hou et al. ES&T 2011 Surface water Deep water

DTU Nutech, Technical University of Denmark

Speciation of 127I and 129I in surface water in the Baltic Sea

127I-/ 127IO3

• 129I-/ 129IO3

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Depth profiles of 129I in the Baltic Sea

10 5 6 7 8 9 11 3 4 1 2 12 14 13 15

Salinity

129I (108 atoms/L)

30 20 10 200 100 200 100 30 20 10

5 6 7

2007 2006

a

b

c d

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Tracer application along Greenland coast

Sampling year 2012 Sampling year 2013

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Thank you!

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