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Absolute neutron yield measurement using divertor NFM

Absolute neutron yield measurement using divertor NFM. Kaschuck Yu.A., Krasilnikov A.V., Prosvirin D.V., Tsutskikh A.Yu. SRC RF TRINITI, Troitsk, Russia. 11.04.2006 ITPA-10 Troitsk, Moscow reg., Russia.

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Absolute neutron yield measurement using divertor NFM

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  1. Absolute neutron yield measurement using divertor NFM Kaschuck Yu.A., Krasilnikov A.V., Prosvirin D.V., Tsutskikh A.Yu. SRC RF TRINITI, Troitsk, Russia 11.04.2006 ITPA-10 Troitsk, Moscow reg., Russia

  2. ITER neutron diagnostic system for total neutron yield measurements

  3. Neutron sources for ITER neutron diagnostic calibration Initial calibration • Radionuclide neutron sources: Cf, Am-Be – well-know neutron spectrum, constant neutron yield, isotropic emission • Neutron generators: compact switchable fusion neutron source (d-t, d-d) Running cross-calibration • Plasma core as “certified” neutron sources - ITER discharges with well-know plasma parameters: total neutron yield, plasma position, ion temperature and fuel density profile, etc.

  4. Neutron sources for ITER neutron diagnostic calibration Commercial available 252Cf neutron sources produced by “Research Institute of Atomic Reactor”, Dimitrovgrad, RF 252Cf neutron sources <En> = 2.14 MeV • Yn up to 21010n/s • mCf ~ 8.5 mg • dYn ~ 1-2% • size:  7  25 mm

  5. Neutron sources for ITER neutron diagnostic calibration • DT neutron generators: neutron yield up to 1011 n/s; sealed tube lifetime 100-500 hours; mass 30 - 100 kg; size 2001000 mm • anisotropic emission due to neutron backscattering at the NG construction; • target water cooling is necessary for NG with neutron yield higher 1010 n/s • on-line neutron flux monitoring is necessary due to neutron yield variation during operation;

  6. NGM-17, TRINITI Yn ~ 1011n/s TFTR DT neutron generator Yn ~ 108 n/s A. L. Roquemore 9 ITPA Daejeon, Korea, Oct 2005 Neutron generator emission anisotropy

  7. Divertor Neutron Flux Monitor DNFM conception: • Arrangement of high sensitive 235U and high purity 238U fission chambers meet ITER requirements Design features: • 238UFC has a B4C thermal neutron shielding • 235UFC surrounded by water moderator • both FC has low and high sensitive volume (1:103) • blank chamberfor background measurements • 3 similar DNFM modules located toroidal around the ITER VV to provide cross calibration

  8. Divertor Neutron Flux Monitor DNFM calibration analysis with MCNP 4C code: • Model includes full torus vacuum vessel and shielding blanket modules • Simulation of point sources (14 MeV and 252Cf) moving toroidally along the plasma axis • Fast neutron group fluxes (1 14 MeV) at the divertor level were analyzed

  9. Divertor Neutron Flux Monitor DNFM calibration: neutron group fluxes produced by 14MeV neutron source moving along VV axis

  10. Divertor Neutron Flux Monitor DNFM calibration: neutron group fluxes produced by 252Cf source moving along VV axis

  11. Divertor Neutron Flux Monitor DNFM calibration: fast and direct neutron fluxes vs toroidal angle for point DT neutron source moving along VV axis

  12. Divertor Neutron Flux Monitor DNFM calibration: relative count rate in case 1,2 and 3 NFM at the divertor for 14 MeV neutron source along VV axis

  13. Calibration scenario

  14. Calibration scenario Crossing of factory test, NTA calibration and operation range for NFM based on fission chambers.

  15. Calibration scenario Requirements for in-vessel calibration • special handling tools and certified container for operation with radionuclide source • neutron source mechanical support in the machine • additional detectors for neutron flux measuring support • execution time • schedule of calibration

  16. Conclusions • Both types of neutron sources DT generator and 252Cf are necessary for DNFM calibration • Source intensity ~1010 n/s is enough for DNFM calibration: • 252Cf is commercial available • DT generator has less anisotropy emission • Source moving in range  90 is enough for one DNFM detector calibration, but movement around full torus is required for two or three detectors to guarantee further cross-calibration • MCNP calculation support for initial calibration and further running cross-calibration is necessary to take into account calibration source spectrum and anisotropy • NTA has significant importance for neutron filed simulation, initial test and running cross-calibration

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