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. First Wall Reduced Activation Ferritic Steel (F82H) Neutron Multiplier bed layer Breeder bed layer (Li 2 TiO 3 or Li 2 O) Cooling Water Concept of the Solid Breeding Blanket designed by JAERI

4. Fusion Neutronics Source (FNS) facility The TPR distribution was measured with pellets of Li2TiO3, embedded in the Li2TiO3 layer. Control room Work area TOF duct D + beam - Vac :400 kV - Ib :20 mA Accelerator Ns :4x10 12 n/s Rotating T-Target Ns :3x10 11 n/s Fixed T-Target Target Room I N Target Room II 0 510m Max. In this experiment, Neutron yield; ~2X10 11 n/s

5. FNS D-T Target F82H/95-%Li 2 TiO 3 /Be Assembly Li 2 CO 3 -block Detector(NE213) Assembly -50 x 50 x 30 cm -F82H/Li 2 TiO 3 ( 6 Li:95%)/Be assembly surrounded by Li 2 CO 3 and B 4 C blocks D-T neutron conditions -Neutron flux: 1.5 x 10 11 n/sec/mA -Irradiated time: 10 ~ 20 h 200 300  25 Li 2 CO 3 FNS target 1000 F82H 16mm F82H 3mm 6 Li-95% Li 2 TiO 3 12mm Be 31 500 300 200 (Unit: mm) Single Layer Experiment (2001-2002)

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. Three Layers Experiment and Analysis A blanket assembly Shielding (Li 2 CO 3 ) Be F82H 1.6mm×10 F82H 1.0mm×3 2 82 6 Li 2 CO 3 (  13)1.23x10 22 6 Li/cm 3 40-% 6 Li 2 TiO 3 (  12)1.23x10 22 6 Li/cm 3 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. Three 12-mm thick 40% enriched 6 Li 2 TiO 3 layers with a thin F82H layer are set up between 50- and 100-mm thick layers of beryllium Detectors (NE213) T target 1372mm SS316 source reflector Be  1200mm 350mm  630mm

8. Part of the assembly and the target

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

10. 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 Helium Cooled Pebble Bed (HCPB) Concept Beryllium Breeder layers TBM (HCPB) mock-up in front of FNG target

11. MCNP model of TBM mock-up 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 Surrounding shield (Be, steel,PE, optimised in order to produce the proper spectrum inside module) Air metallic beryllium (1.85 g/cm 3 ) breeder double layers Li 2 CO 3 powder (7.5% 6 Li, 2.3 g/cm 3 ) thickness 1.2 cm separated by steel 1-mm-thick walls. rear ceramic block box AISI-316, dim. 31.0x 12.7x31.0 cm 3,Li 2 CO 3 powder (7.5% 6 Li, 2.3 g/cm 3 Box of stainless steel (AISI-316) external dimension 31.0 cm (x) x 29.0 cm (y) x 31.0 cm in beryllium

12. The International Comparison of Measuring Techniques, ICMT-2 Goal: To measure TPR with an uncertainty not exceeding ± 5% for 3 H 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 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 Source of uncertainty Magnitude, % Neutron yield2 Counting efficiency1.5 Lithium atoms0.5 Incomplete recovery of 3 H3 Counting statistics1 Half life0.2 Irradiation, cooling, measuring0.1 Weight0.5 Total~ 4

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) Li 2 CO 3 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 )