Rapid analysis technique for strontium, torium, and uranium in urine samples

Rapid analysis for Sr-90, Th-232, and U-238 in human urine samples collected in a radiation emergency can be developed by co-precipitation with calcium phosphate and separation using a Sr-resin (Eichrom Technologies, Inc.) column. The nuclides were measured by inductively coupled plasma mass spectrometry (ICP-MS) or a low background beta-counter. Spike tests yielded a good recovery of above 90%. Fractions of Sr-90 and the other nuclides (Th-232 and U-238) were separated in about 2 hours. It was judged that the developed method would be an effective bioassay method in radiation emergency

Precise measurement 236U/238U isotope ratio measurement in 10-8 range as well as 234U/238U and 235U/238U using thermal ionization mass spectrometry: Application to nuclear accident soil samples

The principal isotopes of uranium e.g. 235U and 238U are of primordial origin and 234U present in radioactive equilibrium with 238U. Anthropogenic uranium also contains small amount of 236U, formed by neutron capture of 235U in nuclear industrial processes. 236U has been noticed in the environment as a result of nuclear activities including nuclear explosions, nuclear plant accidents or dumping of nuclear waste. Therefore, it can be a good fingerprint for investigating nuclear power plant accident soil samples. A multicollector Isotopx Ltd. Phoenix 62X thermal ionization mass spectrometer (TIMS) equipped with wide aperture retardation potential (WARP) energy filter was optimized for the determination of 236U/238U isotope ratios in the isotopic range of 10-8 in a reference material supplied by University of Vienna. We have selected soil samples from Chernobyl (Ukraine) and Fukushima (Japan) affected by nuclear power plant accident, Kosovo (Serbia) due to depleted uranium (DU) bombardment and Hiroshima (Japan) due to atom bomb. We validated our method with reference standard materials e.g. NIST 4350b (River sediment in USA). Soils were digested by microwave system with acid mixture of HNO3, HF and HClO4. A modified method was used for isolation of U using Anion Exchange resin-UTEVA to remove high concentration of Fe from Japanese soil sample for high precision analysis by TIMS. Detection limit of 236U/238U ratio by TIMS yielded 10-9~10-10. Uranium ore sample which has not been affected by nuclear accidents yielded to 10-10. Results of 236U/238U ratio for Chernobyl and Kosovo soil were in range of 10-4~10-5, whereas NIST 4350b, Fukushima and Hiroshima soil sample were under 10-7. The Radioactive dis-equilibrium of 234U/238U, enrichment and depletion of 235U/238U were noticed in some soil samples in addition to significant evidence of 236U/238U.URANIUM BIOGE

Determination of Pu isotopes in soil samples affected by FDNPP accident

Introduction: Plutonium as the other actinides was distributed in the environment as a result of nuclear testing, nuclear fuel production and reprocessing, nuclear accidents (Windscale – 1957, Rocky Flats - 1969, Chernobyl - 1986, etc.) and due to a lesser extent accidental releases. On 11 March 2011, the gigantic tsunami in the northeast Japan region caused the serious damages of the Fukushima Dai-ichi nuclear power plant (FDNPP) resulted in large radionuclides releases to the atmosphere. The great public attention was and still is attracted by Pu which being recognized as a one of the most radiotoxic elements. The previous simulation (Povinec et. al., 2014) allowed to found total amount of Pu isotopes released into the atmosphere at the level 1012 Bq (including 238Pu, 239Pu, 240Pu, 241Pu). Pu aerosols due to wet and dry deposition contaminated environment. It has become necessary to investigate an impact of this actinide on the ecosystems. The first step in that case was to determine the activity level of Pu isotopes in samples material and second to find isotopic composition like: 238Pu/239+240Pu identifies as a fingerprint of nuclear accident. According to Yamamoto et al., 2012 this specific activity ratio for Japanese background (global fallout) was close to 0.03 before FDNPP disaster. Every higher result than those, can be considered as a signal of burned nuclear fuel and due to presence of the other artificial radionuclides (e.g. 137Cs, 134Cs, 90Sr, etc.) can be linked to the Fukushima accident. This study focused on the determination of Pu isotopes in soil samples collected during first few days after FDNPP accident. Material and Methods: The surface (0-10cm) layer soil samples from Fukushima Prefecture were collected during the first few days after FDNPP accident (March 2011). All samples were dried at the temperature 1050 C overnight and passed through 2 mm mesh sieve. Subsequently, samples were placed in the polypropylene cylindrical containers for gamma spectrometric measurements which were carried out at the National Institute of Radiological Sciences (NIRS) using p – type coaxial HPGe detector (ORTEC, GEM 100210) with 100% relative efficiency and resolution of 1.9 keV (FWHM) at 1332.5 keV. The measurement time was relatively short and equaled 1h. After that, samples were homogenized using a ball mill <150μm size and about 10 g of each powdered sample was ashed at 600 0C for organic matter decomposition. Samples were spiked with 242Pu tracer and digested using HF, HNO3 and HCl. Chemically Pu fraction was separated from the aliquot on anion-exchange column filled by DOWEX 1x8 mesh 200-400 (Kierepko et. al., 2009). The alpha spectrometry sources were prepared by NdF3 co-precipitation method (La Rossa et. al., 1992). Pu isotopes activity results were obtained by alpha spectrometry (ALPHA ENSEMBLE – 8 ORTEC) equipped with PIPS detectors with 450 mm2 active area.Results and Discussion: Despite of the main goal of our study that was detection of Pu isotopes in soil material, all samples were subjected to gamma spectrometry measurements for radiocaesium activity determination. We could measure 134Cs as well as elevated level of 137Cs, the obvious signature of the FDDNP accident. The activity concentration of 137Cs ranged between 0.460 ± 0.029 kBq kg-1 and 113.2 ± 7.4 kBq kg-1 for the reference date 11 March 2011 whereas the activity ratio 134Cs/137Cs was close to 1. Isotopic composition of Pu will be presented at the conference. References: 1.Povinec, P.P., et. al., (2014), Fukushima Accident, Radioactivity Impact on the Environment, Elsevier, Amsterdam.2.Yamamoto, M. et. al., (2012), An early survey of the radioactive contamination of soil due to the Fukushima Dai-ichi Nuclear Power Plant accident, with emphasis on plutonium analysis, Geochem. J. 46, 341-353.3.LaRosa, J.J, et. al., (1992), Radiochemical methods used by the IAEA’s Laboratories at Seibersdorf for the determination of 90Sr, 144Ce and Pu radionuclides in the environment samples collected for the International Chernobyl Project, J. Environ. Radioact., 17, 183-209.4.Kierepko, R., et. Al., (2009), Plutonium traces in atmospheric precipitation and in aerosols from Krakow and Bialystok, Radiochim. Acta, 97, 253-255.Convener, Steering Committee IARPIC-2016 Radiation Safety Divisio

Novel approaches for 90Sr analyses in contaminated environmental samples

Introduction: Radioactive strontium isotopes are generated with high cumulative fission yield (5 6 %) during thermal neutron fission in a nuclear reactor. The physical half-life of 89Sr (50.52 d) is short but that of 90Sr (28.8 y) is long enough to generate radioecological repercussions1. 90Sr has a long lasting biological half-life (~18 y) in the human body, due to its chemical similarity to calcium the importance of 90Sr analysis is emphasized in case of a nuclear disaster. The world-wide spread of 90Sr, as a background, is derived from the global atmospheric fallout contributed by large-scale atmospheric nuclear weapons tests conducted from 19452,3. In case of local contamination, nuclear accidents are not the only source of 90Sr isotope, misconducted underground nuclear weapon tests, improper handling of by products of nuclear weapon production or normal operation of nuclear facilities (e.g. reprocessing plants) can be taken into account.Material and Methods: The sample analysis can be divided into three parts: sample preparation, strontium separation and detection of 90Sr. Sample preparation consists pretreatment and pre concentration of strontium. For strontium separations many procedures can be applied, such as selective precipitation, liquid liquid separation, extraction chromatography, ion-exchange, ion chromatography. The detection of 90Sr can be carried out using radiometric (gas ionization detector, Cherenkov counter, LSC, etc.) or mass spectrometric (ICP-MS, AMS, RIMS, TIMS, etc.) methods.Results and Discussion: In case of the radiometric detection method, significant spectrum interferences occur due to the continuous nature of the energy distribution of beta radiation. Therefore 90Sr from complex matrices has to be separated from other beta emitter nuclides, such as Th, Pb, Bi, Ra, K isotopes. In nuclear accidental situation, other disturbing nuclides should be considered since all of the fission products generated in nuclear reactors are beta emitters, such as Te, I, Cs, Ag, Ru, Ba isotopes. In case of the mass spectrometric method, the isobaric interferences (90Zr) and the limitation of the abundance sensitivity (peak tail of the natural occurring 88Sr with 82.6 % abundance) can cause problems.Comparing the two methods, the radiometric can perform a lower detection limit with elevated sample size (~10 g or more) and chemical consumption along with quite long measurement time (waiting time for the secular equilibrium between 90Sr and 90Y is two weaks). The mass spectrometric methods have high sample through put and low sample size requirement (1 g or lower). The main limitation is the abundance sensitivity; therefore the detection limit is influenced by the amount of the stable strontium concentration in the environmental samples. References:1Vajda, N. & Kim, C. K. Determination of radiostrontium isotopes: a review of analytical methodology. Appl. Radiat. Isot. 68, 2306-2326, (2010).2Energy, N. O. O. U. S. D. o. United States Nuclear Tests July 1945 through September 1992. (2000) http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf. (Accessed: 14th September 2015)3Mangano, J. J., Gould, J. M., Sternglass, E. J., Sherman, J. D. & McDonnell, W. An unexpected rise in strontium-90 in US deciduous teeth in the 1990s. Sci. Total Environ. 317, 37-51, (2003).Convener, Steering Committee IARPIC-2016 Radiation Safety Divisio

Challenge of 90Sr separation in environmental samples collected from the Fukushima exclusion zone

Fukushima Daiichi nuclear power plant (FDNPP) accident caused radioactive contamination with fission products (I, Te, Be, Cs, Sr isotopes, etc.). The fission products are neutron rich isotopes therefore beta particles will be released from the nucleus to reach stable isotope configuration. Since decay process is accomplished with gamma ray emission, gamma-ray spectroscopy is applied mainly for fission products determination in samples affected by nuclear accident. However, some fission products such as 90Sr, 89Sr are pure beta emitters. Since the energy distribution of the emitted electrons in the beta decay is continuous, element specific separation from the interfering beta emitters is essential for qualitative radioisotopes identification and subsequent measurement.The most important step for reliable 90Sr determination is the highly effective radionuclide separation. Even after five years of the Fukushima accident, there is radioactive contamination in environmental samples caused by radiocaesium isotopes (134Cs and 137Cs) around the Fukushima exclusion zone. The contamination of 90Sr is significantly lower, by four or five magnitudes than radiocaesium isotopes. Under this condition, the decontamination factor of caesium should be higher around six figures in order to eliminate interfering beta particles from radiocaesium isotopes during 90Sr analysis.In recent publication for chemical separation of 90Sr, extraction chromatography is preferred using Sr specific resin (crown ether). Therefore, caesium decontamination factor (DF) was determined in Sr resin using soil samples from the Fukushima exclusion zone with elevated 137Cs contamination (over 3,000 Bq g-1). The caesium separation was not adequate in every case (DF = 104 105), presence of radiocaesium affected the results of 90Sr measurement. Consequently, additional separation steps were required. Caesium purification, with classical selective oxalic acid precipitation method , was achieved with DF range from 50 to 100. However, applying oxalic precipitation combining with Eichrom Sr resin separation, interfering radiocaesium isotopes can be removed with high efficiency (DF>106). The details of this procedure will be discussed during the presentation.International Nuclear Chemistry Congress(INCC 2017