Annual Report 2009/2010 - JUWEL - Forschungszentrum Jülich

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5.14. Reconstruction of the Activity of Point Sources for the Accurate Characterization of Nuclear Waste Drums by Segmented Gamma Scanning T. Krings, E. Mauerhofer Corresponding author: tho.krings@fz-juelich.de Abstract This work improves the reliability and accuracy in the reconstruction of the total isotope activity content in heterogeneous nuclear waste drums containing point sources. The method is based on 2 -fits to the angular dependent count rate distribution measured during a drum rotation in segmented gamma scanning. A new description of the analytical calculation of the angular count rate distribution is introduced based on a more precise model of the collimated detector. The new description is validated and compared to the old description using MCNP5 simulations of angular dependent count rate distributions of Co-60 and Cs-137 point sources. It is shown that the new model describes the angular dependent count rate distribution significantly more accurate compared to the old model. Hence, the reconstruction of the activity is more accurate and the errors are considerably reduced which leads to more reliable results. Furthermore, the results are compared to the conventional reconstruction method assuming a homogeneous matrix and activity distribution. Introduction Radioactive waste must be characterized in order to verify its conformance with the national regulations for intermediate and final storage. Segmented gamma scanning (SGS) is the most widely applied non destructive analytical technique for the characterization of radioactive waste drums. The isotope specific activity content is generally calculated assuming a homogeneous matrix and activity distribution for each measured drum segment [1]. However, real radioactive waste drums exhibit non-uniform isotope and density distributions heavily affecting the reliability and accuracy of activities reconstruction in SGS [2,3]. The presence of internal shielding structures in the waste drum contributes generally to a strong underestimation of the activity in particularly for radioactive sources emitting low energy gamma-rays independently of their spatial distribution. In a previous work an improved method to quantify the activity of spatially concentrated gamma-emitting isotopes (point sources or hot spots) in heterogeneous waste drums with internal shielding structures has been developed [4]. The activity of the isotope was determined by numerical simulations and 2 -fits of the angular dependent count rate distribution recorded during the drum rotation in SGS using an analytical expression derived from a geometric model. From the quantification of Cs-137 and Co-60 activities in real heterogeneous waste drums it was demonstrated that the improved method enhances largely the accuracy of the reconstructed activity in comparison to the conventional method which assumes a homogeneous density and activity distribution. However, the isotope activity was estimated with a high uncertainty mainly due to the response of the collimated 129
gamma-ray detector approximated by a pseudo Dirac function in the applied geometric model. In this work the analytical expression of the improved method is revised for a more precise calculation of the angular dependent count rate distribution and thus of the activity by modifying the collimated detector response. Further, the new and the old collimator functions are compared by analyzing the angular dependent count rate distributions of Co-60 and Cs- 137 point sources simulated with MCNP5 (Monte Carlo N-Particle Code) in different matrices. The obtained results are compared to the conventional method. different matrices. The obtained results are compared to the conventional method. Geometric Setup Fig. 94: Geometric model of the experimental setup used for segmented gamma scanning. The upper part shows the top view and the lower part shows the side view of the detector with a drum segment containing an activity point source. Fig. 94 shows the geometric model of the segmented gamma scanner used for the characterization of nuclear waste at our institute. The emitted photons are detected with an n-type coaxial HPGe detector (30% relative efficiency). The active detector crystal has a diameter of 4.96 cm and a length of 5.31 cm. The detector is shielded by means of a lead cylinder with a cylindrical collimation window. The collimator has a length of 20.6 cm and a diameter of 22 cm. The collimation window has a radius of 2 cm. The distance from the center of the nuclear waste drum to the detector surface is 74.6 cm. Each segment is scanned in 12 steps which leads to a rotation of the drum of 30° in each step. Each geometric quantity in Fig. 94 can thus be calculated according [5]. We also refer to this work 130
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Mitglied Mitglied der der Helmholtz
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Forschungszentrum Jülich GmbH Inst
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TABLE OF CONTENTS 1 Preface .......
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6.2.2 Doctoral Thesis .............
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state of NRW. The collaborative pro
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2 Institute’s Profile Due to the
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2.2. Organization chart Reactor Saf
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3 Key Research Topics 3.1. Long Ter
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actinide co-conversion into polyact
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Fig. 7: Non-destructive analytical
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Fig. 9: Thermal treatment of an AVR
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3.8. Product Quality Control of Rad
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3.8.2 Product Quality Control of Lo
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The advantage of working at low vac
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NdPO 4 powder sample, directly rece
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4.5. Non-destructive assay testing
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5 Scientific and Technical Reports
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Results and Discussion The irradiat
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work will focus on the identificati
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Different solvents (iso-propanol an
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e & j) Aggregates of aluminium oxid
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Experimental details The corrosion
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Intensity [CPS] 500 400 300 200 100
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Fig. 24: Left: High resolution TEM
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a) MD model [10] b) Derived Lesukit
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5.4. Minor actinide(III) recovery f
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Extensive extraction studies were p
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of the extraction properties of the
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Cm(III) together with the lanthanid
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using a mixture of CyMe4BTBP and TO
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A more challenging route studied wi
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These preliminary results show that
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The 1-cycle SANEX process is intend
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Continuous counter-current tests us
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Conclusion In this work, it was sho
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shaken by a vortex mixer for 15 min
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100 100 Distribution ratio 10 1 0.1
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Tab. 15: The distribution ratios of
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5.7. Synthesis and thermal treatmen
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Acid-Deficient Uranyl-Nitrate via d
Page 83 and 84: Optical investigation showed a noti
Page 85 and 86: TG /% 100 98 96 94 92 90 88 86 84 8
Page 87 and 88: Radiolysis in the aqueous solutions
Page 89 and 90: is about 4% while the one of the rh
Page 91 and 92: Fig. 59: Compressibility curve for
Page 93 and 94: Conclusion and outlook Monazite-typ
Page 95 and 96: Fig. 63: Description of the unit ce
Page 97 and 98: agents for the synthesis of neodymi
Page 99 and 100: 100 TG 785°C Exo DSC 0,2 0,0 90 -0
Page 101 and 102: After synthesis the product was cen
Page 103 and 104: process of monazite and additional
Page 105 and 106: Tab. 18: Lattice parameters determi
Page 107 and 108: Conclusions For Sm 1-x Ce x PO 4 mo
Page 109 and 110: 5.11. Raman Spectra of Synthetic Ra
Page 111 and 112: The numerical values of all measure
Page 113 and 114: knowledge, these special relationsh
Page 115 and 116: Fig. 80: Raman spectra of LaPO 4 ir
Page 117 and 118: 5.12. MC simulation of thermal neut
Page 119 and 120: content was replaced by hydrogen. C
Page 121 and 122: constant for hydrogen concentration
Page 123 and 124: with a 0 1 -183.88 ± 8.55 and a 2
Page 125 and 126: 5.13. An Improved Method for the no
Page 127 and 128: 2 2 2 d0 R ds d0 dw la( )
Page 129 and 130: The relative uncertainty for the ac
Page 131 and 132: In the drum, 4 ‘hot spots’ for
Page 133: activity of Cs-137 is much more und
Page 137 and 138: shown in Fig. 96. In both cases the
Page 139 and 140: econstruction than the old calculat
Page 141 and 142: Neutron capture cross sections and
Page 143 and 144: Outlook The evaluated data will be
Page 145 and 146: from carbon-based HTR fuel elements
Page 147 and 148: Fig. 102: 3D volume reconstructions
Page 149 and 150: dislocate the 14 C atom from its pr
Page 151 and 152: It can be seen that nearly all trit
Page 153 and 154: Acknowledgement The authors like to
Page 155 and 156: development by investigations of ga
Page 157 and 158: Fig. 109: The left picture shows th
Page 159 and 160: [2] A European Roadmap for Developi
Page 161 and 162: from airborne SWIR Full Spectrum Im
Page 163 and 164: Fig. 113: Visualization of the vege
Page 165 and 166: number of training samples up to 19
Page 167 and 168: Acknowledgements The work presented
Page 169 and 170: three approaches has severe drawbac
Page 171 and 172: neighbours from the list of merge c
Page 173 and 174: it gives a difference in segmentati
Page 175 and 176: [6] I. Niemeyer, F. Bachmann, A. Jo
Page 177 and 178: Monitoring 3 cooperated intensively
Page 179 and 180: facilities and other treaty related
Page 181 and 182: parameters of the SAR system, such
Page 183 and 184: The MGD products used in the study
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Fig. 134 contains the result for th
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[2] H. Maître (ed.), Processing of
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Preparatory Committee to allocate t
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unconditional security assurances f
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safeguards was also requested. Deci
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[16] United Nations Security Counci
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5.24. Development and Application o
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Hardware layer The hardware layer i
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So in most applications the scale u
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The ENDF-B/V and ENDF-B/VI librarie
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5.26. Product control of waste prod
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Polysiloxane which has been investi
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acceptance requirements [3]. In the
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Fig. 145: List of description and d
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6.1. Courses taught at universities
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Umwelt / Energy & Environment 2010;
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6.5. Institute Seminar The IEK-6 or
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6.5.3 Invited talks 2009 30.04.2009
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21.09.2010 Dr. N. Evans: The Chemis
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8 Selected R&D projects 8.1. EU pro
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K. Aymanns: Nominated as deputy re
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Bukaemskiy A.A., Barrier D., Modolo
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11.2. Publications 2009 11.2.1 Jour
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Rezniczek, A.; Richter, B.; Jussofi
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Daniels, H.: Co-conversion of actin
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11.3. Publications 2010 11.3.1 Jour
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Sypula, M.; Wilden, A.; Schreinemac
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(Partitioning) - Stabilitätsunters
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Modolo, G.; Bosbach, D.; Geist, A.;
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12 How to reach us Postal Address F
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By train: Take the train from Aache
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Schriften des Forschungszentrums J
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