Why are the transuranics so important?

Transcription

1 Application of ICP-MS and AMS for determination of Pu- and U-isotope ratios for source identification Lindis Skipperud, Norwegian University of Life Sciences Why are the transuranics so important? Long lived (T 1/2 up to 8x10 7 y) Man-made sources weapon production (Pu-239), nuclear fuel cycle satellite battery (Pu-238), fire alarms (Am-241), Alfa-emitters; high radiological toxicity bone seekers. Multi valence gives complicated environmental chemistry and biochemistry 1

2 Isotope ratios and sources Actinides have source related isotope composition. Isotope ratios can act as fingerprint in the environment Uranium: Natural, Enriched, Depleted, Reprocessed U-234, U-235, U236, U-238 Plutonium: Weapon production, nuclear weapon tests, reactor type and burn up Pu-238, Pu-239, Pu-240, Pu-241, Pu-242 ISOTOPE LABORATORY DEP PARTMENT PLANT AND ENVIRONMENTAL SCIENCES Key Question Can the plutonium isotopic signatures be used effectively in complex environmental systems to define the relative contributions from potential sources? 2

3 Isotope Laboratory, UMB Perkin Elmer Elan 6000, ICP-MS Canberra 7401 Mixer/router 1501, α-spectrometry AMS THE 14UD TANDEM ACCELERATOR Dept. Nuclear Physics Australian National University 3

4 Measuring isotope ratios in water and sediment -Objectives Different sources often exhibit characteristic uranium or plutonium isotope ratios and these ratios can be used to identify the origin of contamination, calculate inventories, or follow the migration of contaminated sediments and waters Weapons-grade plutonium is characterized by a low content of the 240 Pu isotope 240 Pu/ 239 Pu isotope ratio < global weapons fallout and spent nuclear fuel from civil reactors have higher 240 Pu/ 239 Pu isotope ratios. 240 Pu/ 239 Pu 0.5 Different sources different Pu isotope ratios Pu powered reactors Global fallout Weapons grade Pu Naval reactors ( 235 U enriched) Civil reactor waste Pu/ 240,239 Pu 4

5 Kara Sea, Novaya Zemlya fjords Sources isotope ratios tio) -238/Pu (activity rat Pu Abrosimov Stepovogo Ob Yenisey Open Kara Kara Gate GF Pu-240/Pu-239 (atom ratio) Pu in Mayak PA area Background Mayak PA was established 1948 to produce Pu for Soviets atom weapon program Routine and accidental releases of radioactive waste have caused severe contamination to the surrounding areas. 5

6 Pu isotope ratios in Techa River io) +240 (activity rat 238/ Oughton, DH., Fifield, LK., Day, JP., Cresswell, RC., Salbu, B., Skipperud, L., Strand, P., Drozhco, E., and Mokrov, Y., (2000) Env. Sci. Tech. Techa River Asanov ( ) EURT (1957) Karachay (1951-) Res. 10 (1952-) Res. 11 (1964-) /239 (atom ratio) Isotope ratios in the Mayak Reservoir 10 sediments Pu-240/Pu-239 0,6 0,5 0,4 0,3 0,2 0, , , , , , , , , , , ,00 Pu-238/Pu-239, 240 Core1, 0-10cm Core1, 10-20cm Core 1, 20-25cm Core2, 0-10cm Core2, 10-20cm Core3, 0-10cm Core3, 10-20cm Core3, 20-30cm Core4, 0-2cm Core4, 2-4cm Core4, 4-6cm Core4, 6-8cm Core4, 8-10 Core4, 10-15cm Core4, 15-20cm Core4, 20-25cm Core5, 0-2cm Core5, 2-4cm Core5, 4-6cm Core5, 6-8cm Core5, 8-10cm Core5, 10-15cm Core6, 0-5cm Skipperud, L., Oughton, DH., Salbu, B., Strand, P., Drozcho, E., and Mokrov, Y., (2004) Plutonium contamination in soils and sediments at Mayak PA, Russia Health Physics 6

7 New and old sources Weapon source Civil source Calculated Isotope ratio Isotope ratio amount 240 Pu/ 239 Pu 238 Pu/ 239, Pu 25 % (10 TBq) 75 % (30 TBq) Up to 0.60 Up to 1.6 Ob and Yenisey Estuaries Some of the sampling sites in Ob and Yenisey estuaries (below), with sources of weapons related contamination (left) 7

8 Pu isotope ratios in surface sediments in Ob River compared to the Yenisey 240 Pu/ 239 Pu atom ratios , n=7 (Skipperud et al., 2004) 240 Pu/ 239 Pu atom ratios = 0.16, n=2 (Skipperud et al., 2004) Estuary 240 Pu/ 239 Pu atom ratios , n=8 (Skipperud et al., 2004) River 240 Pu/ 239 Pu: n=8 (Skipperud et al., 2004) ISOTOPE LABORATORY DEP PARTMENT PLANT AND ENVIRONMENTAL SCIENCES Size fractionation and source identification in Yenisey estuary water 8

9 Trace of weapon grade Pu found in colloidal phase all the way into Kara Sea Pycnocline 24,3 psu Near bottom ,9 psu 73 Pycnocline 28 psu Particulate (>0,45 um) Colloidal (8kDa-0,45um) LMM (<8kDa) Surface 0 psu Surface 23,8 psu Pycnocline 28 psu Surface 0,1 psu Near bottom 0 psu Lind, OC., Oughton, DH., Salbu, B., Skipperud, L., et. al., (2006) Earth and Planetary Science Letters ISOTOPE LABORATORY DEP PARTMENT PLANT AND ENVIRONMENTAL SCIENCES Trace of weapon grade Pu found in colloidal phase all the way into Kara Sea Lind, OC., Oughton, DH., Salbu, B., Skipperud, L., et. al., (2006) Earth and Planetary Science Letters 9

10 This study has shown The movement of Pu contamination from the KMCIC installations has been detected almost 3000 km downstream from the plant both in sediments and water. It has now reached the coast of Kara Sea. Pu-isotopes ratios in various Mayak samples has identified the presence of different sources and confirmed recent reports of civil reprocessing at Mayak 240 Pu/ 239 Pu and 238 Pu/ 239, 240 Pu isotope ratios in discharges from Mayak have increased with time. between 30 and 70 % of Pu further down River Techa ( km) can originate from other sources than the early weapon production Using isotope ratios is an useful technique in identification of Pu sources And ICP-MS has proven to be a good tool together with traditional α-spectrometry when it comes to analysing uranium and plutonium and its isotope ratios in contaminated areas and hot particles. Accelerator mass spectrometry has proved to be a powerful method for measuring low- level U- and Pu activity concentrations and U- and Pu isotope ratios. 10

11 Thank you! 11