1. IEA IMPLEMENTING AGREEMENT ON NUCLEAR TECHNOLOGY OF FUSION REACTORS International Workshop on Subtask Neutronics Report on ENEA activity in 2004 Paola Batistoni – ENEA Frascati Venice, September 21, 2004

2. OUTLINE  Test Blanket Module (TBM) experiment  Construction of HCPB TBM Mock-up  Benchmarking of T measurement techniques & assessment of uncertainties  Activation experiments  Measurement and analyses of decay heat in Ta irradiated in a first-wall like neutron spectrum (in progress)  Validation of doserate calculations for JET  Numerical benchmark D1S & R2S methods  Comparison with available experimental data  Activation experiment at JET for the validation of activation properties of ITER materials  Activation of EUROFER

3. TBM NEUTRONICS EXPERIMENT 1. Design of mock-up, pre-analysis for measurements of TPR (2003) Helium Cooled Pebble Bed (HCPB) Concept metallic beryllium (1.85 g/cm 3 ) breeder double cassette Li 2 CO 3 powder (7.5% 6 Li) thickness 1.2 cm separated by steel 1-mm-thick walls. Box of stainless steel (AISI-316) external dimension 31.0 cm x 29.0 cm x 31.0 cm, thickness 5 mm

4. Measurements arrangements TPR : 2 independent measurements by Li 2 CO 3 pellets (nat. Li) Tritium activity is in the range A ~ 10 -14 Bq/g/n requiring  5 x 10 15 neutron budget Neutron flux by activation foils in the central beryllium layer Neutron &  -ray spectrum at the end of the central beryllium layer 12 pellets (2mm thick each) in each position to measure the TPR gradient across the ceramic breeder layer

5. 2. Construction of HCPB TBM Mock-up All steel components have been realised in ENEA The cassettes have been filled with Li 2 CO 3 powder

6. we have also realised aluminum mock- ups of beryllium blocks to test the assembly and to check the alignment of vertical channels DESIGN OF TBM NEUTRONICS EXPERIMENT Removable tubes Cassettes aluminum mock-ups of beryllium blocks

7. detector capsules to locate the Li 2 CO 3 pellets in position, as well as the Beryllium capsules to fill the vertical channels

8. The mock up has been shipped to the Institute of Inorganic Materials of Moscow (VNIINM) that will fabricate Be blocks and will assembly the TBM Completion of mock-up construction is expected by the end of 2004

9. 3. Benchmarking of experimental techniques for tritium measurement & assessment of uncertainties (ENEA/TUD/JAERI) DESIGN OF TBM NEUTRONICS EXPERIMENT  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 (completed in 2003) Li 2 CO 3 pellets (starting with pellets enriched in Li-7, all prepared by JAERI) have been 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 (2004, almost completed)

10. First step: HTO samples  All measurements in agreement with theoretical value within total uncertainty.  Uncertainty on theoretical value certified by the provider on the activity of the original HTO (+ diluition procedure).  A < 10 Bq/g larger error bars generally due to background  A >  20 Bq/g uncertanties reduce.  In the TBM mock-up experiment  achieve a specific tritium activity A >  20 Bq/g in the pellet probes,  perform calibration procedure using certified standard solutitions with the lowest possible total uncertainty.

11. Second step: Li 2 CO 3 pellets irradiated at FNS with 14 MeV neutrons  7 Li 2 CO 3 (13 mm diam, 2 mm thick) FNS-Li7 attached to a rotating disk, irradiated for one day on 16,17 or 18 July 2003  6 Li 2 CO 3 (13 mm diameter, 1 mm thick) attached to rotating disk inserted into a cavity inside a beryllium assembly. FNS-Li6-L irradiated for two days on 3 and 4 February 2004, FNS-Li6-H irradiated for four days from 3 to 6 February 2004 The uniformity of irradiation conditions was confirmed by using the activation foils.

12. Preliminary results  total uncertainty between 4.86 % - 6.86 % (2  )  agreement at 10% between TUD and at JAERI within the combined relative uncertainties  measurements performed in ENEA are in agreement with the others at low activity levels, but show and underestimation (15-20%) at higher activity values.  new measurements at TUD/VKTA have shown that disagreement is due the calibration procedure  Further work needed to achieve accurate intercalibration

13. VALIDATION OF DOSERATE CALCULATIONS FOR JET (ENEA/FZK/UKAEA) Numerical benchmark (2003)  direct, 1 step method (D1S) using only MCNP (FISPACT for decay time correction)  rigorous, 2 steps method (R2S) using MCNP/FISPACT/MCNP

14. VALIDATION OF DOSERATE CALCULATIONS FOR JET (ENEA/FZK/UKAEA) Comparison of D1S and R2S with JET measurements during DT1 (2003/2004))  2005 dedicated benchmark experiment during JET DD operation

15. Octant-8, up inboard Irradiation end Irradiation of EUROFER-97 sample e JET during the 2003 TTE Total 14 MeV Neutron Yield = 3.09E+18 n Total 2.5 MeV Neutron Yield = 4.60E+18 n in ~ two weeks Local neutron spectrum unfolded from activation foils ACTIVATION EXPERIMENTS AT JET