ITER Diagnostic Port Integration: neutronics issues

1. ITER Diagnostic Port Integration:neutronics issues Alfred Hogenbirk NRG Petten hogenbirk@nrg.eu Info meeting Barcelona 1/3/2011

2. 2 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Overview Introduction Sample cases: CXRS port plug GEPP Conclusion

3. 3 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Introduction Focus of diagnostic port plug neutronics: Port internals: Radiation heating (neutrons and gamma�s) Radiation damage (dpa�s) Helium production Activation Outside port: Radiation levels Heating in TFC and PFC Dose rate after shut-down

4. 4 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Port plug neutronics: basic remarks Diagnostic port plug neutronics complicated terrain: Many responses completely depend on details of the port plug design Often no coarse-to-fine modeling approach possible Detailed models required ? time-consuming analyses, unless intelligent approximations are made Need for 2 categories of responses: Diagnostics inside port plug Radiation levels and dose rates outside port plug Integrated approach required to satisfy both needs

5. 5 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Sample cases CXRS port plug analyses carried out within ITER-NL consortium Equatorial port plug analyses carried out within F4E grant

6. 6 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 CXRS port plug optimization Does the port plug design comply with the ITER requirements? Will the diagnostics actually work? Heating in mirrors Reflectivity of mirrors (degrading by radiation damage) Light transmission of optical fibers

7. 7 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 CXRS model evolution

8. 8 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 CXRS neutron flux distribution

9. 9 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 CXRS neutronics: conclusions Neutronics analyses are crucial ingredient in CXRS port plug design Efficient procedure allows the neutronics analyses to be part of the design loop

10. 10 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 F4E generic equatorial port plug studies Basic questions: ITER requirements fulfilled with default port plug design? If not, what modifications are needed? Approach: Split radiation source in three contributions Minimize each of these sources Focus on largest contributor

11. 11 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Sample of GEPP neutronics results

12. 12 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Contribution from different regions

13. 13 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 GEPP neutronics: dose rate results Dose rates after ITER shutdown were calculated for each of the contributors: Upper port region: 76 �Sv/h Equatorial port region: 147 �Sv/h Divertor port region: 236 �Sv/h Estimated uncertainty: 15% Each of the contributions needs to be reduced to comply with IO requirements (i.e.: < 100 �Sv/h) Note that calculated dose rate is only due to activation of equatorial port interspace walls Approximate calculation of dose rate due to activation of rest of ITER structure yields 400 �Sv/h (estimated uncertainty 40%)

14. 14 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Equatorial port contribution

15. 15 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Gap streaming benchmark

16. 16 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Gap streaming Specifications of gap streaming benchmark: Thickness identical to equatorial port plug (i.e. 160 cm) Gap width identical to actual gap width (i.e. 2.0 cm) Gaps between drawers corresponding to IO specs (i.e. 0.5 cm) Material identical to actual port plug material: 80/20 Stainless Steel/Water Radiation source identical to actual radiation source in equatorial port region Specification of labyrinth:

17. 17 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Gap streaming results:perpendicular cross sections throughneutron flux distribution

18. 18 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Gap streaming: results Neutron flux exiting the simplified port plug model was used to activate the walls of the port plug interspace Assumption: homogeneous irradiation of front wall Calculated parameter: volume-averaged dose rate 106 s after shut-down Results: rel. flux dose rate [�Sv/h] Straight gaps 1.00 146 Varying SS/H2O ratio 0.98 168 Drawers 1.11 166 Labyrinth 0.40 35 Labyrinth (with offset of 10 cm) reduces dose rate by factor of 5 Additional gaps between drawers lead to increased dose rate (+ 14%)

19. 19 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 GEPP neutronics: Conclusions Extensive insight obtained in nature of radiation transport in GEPP design: details of the GEPP design are unimportant for GEPP neutronics, as this is completely governed by the radiation streaming through the gaps ITER requirement on dose rate after shut-down cannot be met if no radical changes are made in various parts of the ITER design Labyrinths in the gaps surrounding the port plugs are a good means of reducing the neutron flux Adequate shielding of the divertor port (e.g. by means of a divertor port plug) is required

20. 20 F4E - NL Industry meeting on Port Plug Integration, Barcelona, 01-03-2011 Conclusions Neutronics analyses can be and should be integral part of port plug integration activities Important aspects of the port plug design are determined by neutronics ITER-NL (NRG) offers relevant experience in port plug neutronics