NKS Radioactive particles in a Nordic context Hot II

Transcription

1 NKS Radioactive particles in a Nordic context Hot II Brit Salbu & Ole Christian Lind Isotope laboratory, Norwegian University of Life Sciences

2 Background Radioactive particles in a Nordic context - Hot II A significant fraction of radionuclides will be present as discrete particles of various characteristics in any nuclear event in which refractory elements are released Radioactive particles are defined as localised aggregates of radioactive atoms that give rise to an inhomogeneous distribution of radionuclides significantly different from that of the matrix background (IAEA, CRP ) Aquatic environment: >0.45 μm and less than 1 mm - fragment(iaea CRP, 2001) Aerosol particles in air: 1 nm μm (Manahan, 1994)

3 Background Radioactive particles in a Nordic context - Hot II Radioactive particles represent point sources of short- and long-term radioecological significance, and the The failure to recognise their presence may lead to significant errors in the short- and long-term radiological evaluation of the impact of radioactive contamination at a particular site A series of existing and potential sources (e.g. Kola Nuclear Power Plant or nuclear terrorist attacks) can contribute with radioactive to the Nordic countries The Nordic radioecological community would benefit from acquiring more knowledge on the phenomenon of radioactive particle contamination competence on both classical and novel analytical techniques available for characterisation of radioactive particles

4 IMPACT OF RADIOACTIVE PARTICLES SHORT TERM Radioactive particles can be subject to atmospheric transport Problems within micro-dosimetry Skin dose Inhalation- transmembrane uptake Ingestion via food retention times in the gastrointestinal tract Underestimated total inventory of radioactive contamination: Inhomogeneous distributions problems with representative sampling Incomplete dissolution measuring too low concentrations Problems with effective countermeasures Often designed for ionic species

5 ENVIRONMENTAL IMPACT ASSESSMENT MODELS INFO NEEDED Link: Particle characteristics - weathering rates - ecosystem transfer - biological uptake Assessments based on Becquerels only will suffer from large uncertainties sufficient

6 Objectives Radioactive particles in a Nordic context - Hot II 1. Arranging a seminar at UMB with invited international speakers With focus on: existing and potential sources of radioactive particle contamination identification, isolation and characterisation of radioactive particles 2. A review report and a database on sources and characteristics of radioactive particles of relevance to the Nordic countries Based on: literature survey outcome of the seminar experience within the working group

7 Hot II -Participants Norwegian University of Life Sciences (UMB), Norway Ole Christian Lind (coordinator) & Brit Salbu Risø National Laboratory, Denmark Per Roos Institute for Energy Technology, IFE, Norway Rajdeep Singh Sidhu Swedish Defence Research Agency, FOI, Sweden Ulrika Nygren Lund University, Sweden Ylva Ranebo & Elis Holm Radiation and Nuclear Safety Authority, STUK, Finland Roy Pöllänen

8 Joint seminar: NKS seminar on radionuclide speciation and radioactive particle studies in a Nordic context Participants: 35 scientists from China, Denmark, Finland, Lithuania, Monaco, Norway, Spain, Sweden Lectures: 18 Invited lecturers: 7..\..\..\WORD\Prosjekter\NKS HOT II\Seminar april 2007\Programme - NKS Seminar at UMB april 2007.doc Discussions included: Suggestion for new methods for particle characterisation: LA-ICP-MS, defined leaching experiments, employment of unconventional techniques Focus on effects: free radical induction, biomarkers (ROS, SOD)

9 Joint seminar: Oscarsborg Festning NKS seminar on radionuclide speciation and radioactive particle studies in a Nordic context Very successful meeting, especially with respect to: Very good scientific lectures Socially relaxed and friendly atmosphere: good climate for ongoing and future collaboration Cost-effective arrangement (joint seminar) Many scientific questions unanswered Meetings are needed to bring further collaboration Nordic seminars useful

10 SOURCES OF RADIOACTIVE PARTICLES Nuclear weapon tests (more than 2000 atm., at ground, under water, under ground tests) Peaceful nuclear explosions (PNE) Aircraft accidents with conventional explosions of nuclear weapon Use of depleted uranium (DU) weapons Nuclear reactor explosions and fires Satellite and submarine accidents with nuclear reactors Effluents from nuclear installations Leaching from dumped nuclear material U-mining and tailing Particles from all sources investigated (NKS, IAEA)

11 SOURCES OF RADIOACTIVE PARTICLES NUCLEAR EXPLOSIONS AND SAFETY TESTS Atmospheric nuclear weapon test sites (AMAP, 1998) Particle from Semipalatinsk test site Peaceful underground nuclear explosions in Russia (AMAP, 1998)

12 Air filter samples (UMB) Digital autoradiography (exposure 5 months) of air filter sampled in Vadsø by FFI, between 09:00, 12/11 15:00, 13/

13 RADIOACTIVE PARTICLES FROM NUCLEAR EXPLOSIONS AT SEMIPALATINSK TEL KEM CRATER LAKE Tel kem I and II: U, Pu and 241 Am incorporated in large grains of soil (not vitrified) Ground zero and Balapan: Vitrified particles from high temperature scenarios Tel kem (underground nuclear tests): SEM-XRMA: No U, Pu signals on the surface Confocal μ-srxrf: U and Pu intensity correlated

14 SOURCES OF RADIOACTIVE PARTICLES Nuclear weapon accident at Thule Fire in B-52 Crew bailed out 6 of 7 survived Aircraft with 4 unarmed thermonuclear bombs crashed on the sea ice 2 detonated conventionally U/Pu dispersed on ice and on seabed Re-estimated residual contamination after clean-up: ~10 TBq 239Pu (~3.8 kg) Pu Lα/U Lα ratio B A 0,5 0,45 0,4 0,35 0,3 0,25 0,2 0, μm ESEM x-ray line scan reveal inhomogeneities in Thule Pu/U particle

15 SOURCES OF RADIOACTIVE PARTICLES RELEASES FROM REPROCESSING PLANTS AND PRODUCTION SITES FOR WEAPON GRADE PU Particles observed at several sites, for example: Dounreay, UK beaches closed Sellafield, UK - beaches Mayak PA Techa river Krasnoyarsk-Jenisey river Remobilisation potential U fuel particle, Ravenglass, Irish Sea

16 Case: Uranium mining and tailing in Central Asia thousands of km 2, affects millions of people

17 ESEM with XRMA: U inclusions in NORM particles

18 Radioactive particles are released during all types of severe nuclear events. Nuclear test Semipalatinsk Thule Dounrey Sellafield The source determines the composition, the Kuwait release scenarios dictate Aggregate from the Chernobyl explosion particle properties influencing the environmental impact. Particle composition and structure XRMA act as fingerprint can be used to identify the source Corrosion product Waste in Kara Sea Krasnoyarsk U particle

19 Conclusions - sources Nuclear weapon test fallout particles at all sites, but not reported from Novaya Zemlya Nuclear reactor accidents Windscale Chernobyl The Sosnovyy Bor incident in 1992 Nuclear weapon accident at Thule Technologically Enhanced Naturally Occurring Radioactive Material (TENORM) Reprocessing and Nuclear waste sites Russian nuclear installations: Mayak PA (Chelyabinsk-65) Siberian Chemical Combine (Tomsk-7) Krasnoyarsk Mining and Chemical Industrial Complex (Krasnoyarsk-26) Kola Bay (STUK) Novaya Zemlya and the Kara Sea UK sites: Sellafield, Dounreay So far, no record in the open literature on radioactive particle observations at waste sites at the Kola peninsula such as Andreyeva Bay and Grimicha

20 CONCLUSIONS advanced methods New advanced non-destructive tools have been developed, enabling the determination of: size, shape and morphology by SEM/ESEM with XRMA elemental composition and distribution by SEM with XRMA and μ-srxrf distribution of crystalline phases by μ-xrd porosity channels and cavities - by 3 D μ-tomography variation in the local oxidation states of U and Pu within particles using μ-xanes backed up by μ-xrd Synchrotrons at ESRF, HASYLAB, ANKA have been utilized. Isotope or atom ratios obtained by destructive techniques such as AMS, ICP-MS, SIMS.

21 CONCLUSIONS Following a severe nuclear event with releases of refractory elements, a major fraction of released radionuclides will most probably be associated with particles. Particle characteristics are source-related and releasescenario dependent. Particle characteristics: elemental composition, size distribution, porosity, crystallographic structure and oxidation state of the carrying matrices influence particle weathering, remobilization of associated radionuclides, transfer and bioavailability in ecosystems affected by particle contamination Impact assessments for existing contaminated areas as well as for future events should be improved by implementing results from the present work. Results from HOT II have contributed to the IAEA CRP on radioactive particles.

22 Acknowledgement The authors will thank our colleagues at the University of Antwerp, Belgium, professor Koen Janssens and his group, for fruitful collaboration with respect to particle characterization using synchrotron radiation based X-ray techniques