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Summary of Recent Neutronics Integral Experiments on C/E

Summary of Recent Neutronics Integral Experiments on C/E. M. Youssef UCLA. ITER TBM Project Meeting, UCLA, February 23-25, 2004. Background.

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Summary of Recent Neutronics Integral Experiments on C/E

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  1. Summary of Recent Neutronics Integral Experiments on C/E M. Youssef UCLA ITER TBM Project Meeting, UCLA, February 23-25, 2004

  2. Background • Various fusion neutronics integral experiments have been completed or in progress using 14 MeV neutron sources: FNS and Oktavian facilities (Japan), FNG facility (Frascati Italy)SNEG-13 facility (RF), • The purpose is to validate nuclear data libraries and transport codes through comparing the calculated-to-experimental parameters (C/E) for important parameters such as: • In system neutron and gamma spectra, leakage spectra, nuclear heating, • Tritium production rate (TPR) • Activation rates, decay spectra, dose rates, sky shine, etc • Recent activities in this area were reported during the IEA collaboration on fusion neutronics, Kyoto, Japan, December 9, 2003 (started in 1993). This is an example of international collaboration supported by the fusion community. Previous example was the US/JAERI Collaboration 1983-1993) • We review recent C/E values, particularly for of TPR in mockups of test blanket module for ITER (i.e. the Japanese WCPB concept and the EU preparation for testing the HCPB concept at FNG). • Brief discussion on improving techniques for tritium production measurements is discussed.

  3. Concept of the Solid Breeding Blanket designed by JAERI Breeder bed layer (Li2TiO3 or Li2O) Neutron Multiplier bed layer Cooling Water First Wall Reduced Activation Ferritic Steel (F82H)

  4. Target Room II N Target Room I Rotating T-Target Ns :4x1012 n/s Accelerator Fixed T-Target D+ beam - Vac :400 kV - Ib :20 mA Ns :3x1011 n/s Work area 0 5 10m TOF duct Control room Fusion Neutronics Source (FNS) facility The TPR distribution was measured with pellets of Li2TiO3, embedded in the Li2TiO3 layer. Max. Max. In this experiment, Neutron yield; ~2X1011 n/s

  5. Li2CO3-block Detector(NE213) FNS D-T Target F82H/95-%Li2TiO3/Be Assembly • Assembly • 50 x 50 x 30 cm • F82H/Li2TiO3(6Li:95%)/Be assembly • surrounded by Li2CO3 and B4C blocks • D-T neutron conditions • Neutron flux: 1.5 x 1011 n/sec/mA • Irradiated time: 10 ~ 20 h Single Layer Experiment (2001-2002) F82H 3mm 200 6Li-95% Li2TiO3 12mm F82H 16mm Be 300 FNS target 1000 500 f25 200 200 Li2CO3 31 300 (Unit: mm)

  6. TPR for Li2TiO3 and the ratio of the calculated to the experimental result, C/E. • For this particular single layer experiment the calculated TPR with Monte Carlo method is within the experimental error of 10%. • This is not the case however with the most recent experiment with three layers

  7. Detectors (NE213) F82H 1.6mm×10 F82H1.0mm×3 1372mm Be SS316 source reflector Be T target 2 f1200mm 8 2 f630mm 6Li2CO3 (f13)1.23x10226Li/cm3 350mm 40-%6Li2TiO3(f12)1.23x1022 6Li/cm3 Three Layers Experiment and Analysis Three 12-mm thick 40% enriched 6Li2TiO3 layers with a thin F82H layer are set up between 50- and 100-mm thick layers of beryllium The assembly was enclosed in a cylindrical SS-316 reflector to shield the neutrons reflected by the experimental room walls and to simulate the incident neutron spectrum at the DEMO blanket. A blanket assembly Shielding (Li2CO3)

  8. Part of the assembly and the target

  9. C/E values for local TPR The calculation of local TPR is overestimation by 10% to 30% 3rd 2nd 1st breeding layer TPR Average1.21 Average1. 09 Average1.12 Distance from the assembly surface (mm)

  10. Helium Cooled Pebble Bed (HCPB) Concept DESIGN OF TBM NEUTRONICS EXPERIMENT (ENEA/TUD/FZK/JSI) 1. Design of mock-up, pre-analysis for measurements of the tritium production and nuclear heating TBM (HCPB) mock-up in front of FNG target Beryllium Breeder layers

  11. MCNP model of TBM mock-up Air Box of stainless steel (AISI-316) external dimension 31.0 cm (x) x 29.0 cm (y) x 31.0 cm metallic beryllium (1.85 g/cm3) breeder double layers Li2CO3 powder (7.5% 6Li, 2.3 g/cm3) thickness 1.2 cm separated by steel 1-mm-thick walls.   Surrounding shield (Be, steel,PE, optimised in order to produce the proper spectrum inside module) rear ceramic block box AISI-316, dim. 31.0x 12.7x31.0 cm3,Li2CO3 powder (7.5% 6Li, 2.3 g/cm3 • Pre-analysis • Calculation of neutron spectrum & comparison with Test Blanket Module in ITER • Calculation of background / optimisation of surrounding shielding • Calculation of total tritium production • Tritium production ratio and measurament feasibility • Nuclear heating in beryllium

  12. Goal: To measure TPR with an uncertainty not exceeding ± 5% for 3H activity level ~ 10 Bq/g Participants: 9 groups out of 7 countries, however only 7 groups out of 5 countries received the final results Experiments Irradiation of the Li-containing pellets inside the cavity of lithium assemblies (Li2O/FNS, Li/LOTUS) irradiated by D-T neutrons at: FNS and LOTUS Blind samples of water containing tritium The International Comparison of Measuring Techniques, ICMT-2 • The goal was not met • Standard deviation exceeds the deviation of 5% • Agreement depends from the activity level • Errors assigned by participants are not consisted with the observations

  13. Potential Errors Associated with TPR Measuring Techniques • Triton escapes from boundaries of the pellet surface (recoil triton) during neutron irradiation • Tritium releases from the pellet during irradiation • Retention of tritium in the pellet after irradiation • Tritium labile fraction, namely, the fraction of tritium that goes into solution during pellet dissolution • Dissolving and counting procedures All techniques suffer from a small systematic loss of tritium. In each case, the magnitude of these errors is impossible to predict and can be only be assigned

  14. Tritium Escape Factor as a Function of Pellet Material and its Size (Ratio Surface/Volume) Irradiation of lithium-containing pellet by thermal neutrons

  15. Measured Tritium Production Rates for ICMT-2 (FNS Irradiation) Only two organizations (JAERI and MEPhI) have the consistent results for all samples

  16. Minimal Errors Associated with the TPR Measuring Technique for Fusion Neutronics

  17. Benchmarking of experimental techniques for tritium measurement & assessment of uncertainties (ENEA/TUD/JAERI) • Objective • Reduce uncertainties in TPR measurements • Collaboration between ENEA, JAERI and TUD established • HTO samples with different specific activities are prepared by each group: 1/3 samples are measured in the laboratory of origin, the other samples sent to the other laboratories  check the calibration (in progress, close tocompletion) • Li2CO3 pellets (starting with pellets enriched in Li-7, all prepared by JAERI) will be irradiated at each laboratory in a pure 14 MeV neutron field. 1/3 pellets are measured on site, the remaining two sets, 1/3 each, sent to the other laboratories (next step)

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