Kaschuck Yu.A., Krasilnikov A.V., Prosvirin Kaschuck Yu.A., Krasilnikov A.V., Prosvirin D.V., Tsutskikh A.Yu.D.V., Tsutskikh A.Yu.

SRC RF TRINITI, Troitsk, RussiaSRC RF TRINITI, Troitsk, Russia

Status of theStatus of thedivertor neutron flux monitor divertor neutron flux monitor

design and integrationdesign and integration

10.04.2006 ITPA-10 Moscow, Russia10.04.2006 ITPA-10 Moscow, Russia

Requirements :Requirements :Total neutron strength 10Total neutron strength 101414 - 5 - 510102020 n/s n/s Accuracy Accuracy 10%10%Temporal resolutionTemporal resolution 1 1 msms

Neutron Flux Monitoring System as Neutron Flux Monitoring System as a tool for ITER fusion power measurementa tool for ITER fusion power measurement

Proposed NFM System Proposed NFM System consists of:consists of:External NFM External NFM – – set of set of 235235U fission chambersU fission chambersInternal NFM Internal NFM –– 235235UU micro fission chambersmicro fission chambers

Divertor NFM Divertor NFM –– 235235U and U and 238238U FCU FC

Key FC propertiesKey FC properties: : - high radiation resistance - high radiation resistance - - wide dynamic rangewide dynamic range of measurements of measurements - - low sensitivity to gamma radiationlow sensitivity to gamma radiation- high temperature operation - high temperature operation - - technology availabilitytechnology availability - - long-time experience of application in fission reactorlong-time experience of application in fission reactor

NFM Systems IntegrationNFM Systems Integration

Integration Integration ::

Micro fission chambersMicro fission chambers – – behind blanket modules behind blanket modules inside tokamakinside tokamak

External NFMExternal NFM - set of - set of FC in moderator at the FC in moderator at the radial port plug (limiter)radial port plug (limiter)

Divertor NFMDivertor NFM – set of – set of FC inside divertor FC inside divertor cassettecassette

Issue of the integrationIssue of the integration::

meet ITER requirementsmeet ITER requirements

provide absolute calibrationprovide absolute calibration

Analysis of present NFM system operation and Analysis of present NFM system operation and integration shows the necessity integration shows the necessity of high sensitive neutron of high sensitive neutron flux monitor at the divertor level to provide diagnostic flux monitor at the divertor level to provide diagnostic requirements and possibility of absolute calibrationrequirements and possibility of absolute calibration Arrangement of Arrangement of high sensitive high sensitive 235235U (~1.5g) and high U (~1.5g) and high purity purity 238238U (~1.5g) fission chambers will meet required U (~1.5g) fission chambers will meet required accuracy and temporal resolution for neutron flux dynamic accuracy and temporal resolution for neutron flux dynamic range over 7 orders of magnituderange over 7 orders of magnitude In both case the proposed fission chamber is a In both case the proposed fission chamber is a combination of low and high efficient chamber with combination of low and high efficient chamber with sensitivity difference 1:10sensitivity difference 1:1033

Divertor Neutron Flux MonitorDivertor Neutron Flux MonitorConception:Conception:

Divertor Neutron Flux MonitorDivertor Neutron Flux Monitor

Design features:Design features: 238238UU FC has a BFC has a B44C (~1g/cmC (~1g/cm22 of of 1010B) thermal neutron B) thermal neutron

shield to reduce transmutation changes of efficiencyshield to reduce transmutation changes of efficiency 235235UU FC will be surrounded by water moderator FC will be surrounded by water moderator (thickness 5-7 cm) to increase sensitivity. Water can be (thickness 5-7 cm) to increase sensitivity. Water can be used from cassette cooling systemused from cassette cooling system Additional blank chamberAdditional blank chamber will be used for will be used for background contribution measurements (EM noise, background contribution measurements (EM noise, gammas, etc)gammas, etc) Divertor NFM system includes three similar modules Divertor NFM system includes three similar modules located toroidal around the VV to increase sensitivity and located toroidal around the VV to increase sensitivity and guarantee a cross calibrationguarantee a cross calibration

Specification of DNFM Fission ChambersSpecification of DNFM Fission Chambers Fission chamber

1 2 3 4

Radiator type 235U (90%) 238U (99.998%)

Electrode area, cm2 1300 38 1300 38

Mass of radiator, g 1.66 1.910-3 1.66 1.9 10-3

Sensitivity, cps/(n/cm2s)

1.331.6 10-

3 1.2 10-3 10-6

Dimensions* ( l ), mm

250 500 250 500

Temperature, C 350 350

* - including water moderator

Divertor NFM IntegrationDivertor NFM Integration

Divertor NFM IntegrationDivertor NFM Integration

DNFM response analyzed using MCNP 4C code:DNFM response analyzed using MCNP 4C code: the simplest model includes full torus vacuum vessel and the simplest model includes full torus vacuum vessel and shielding blanket modules (SS+Hshielding blanket modules (SS+H22O) with elliptic cross-O) with elliptic cross-

sectionsection monoenergetic (14 MeV) toroidal symmetric neutron monoenergetic (14 MeV) toroidal symmetric neutron source with poloidal distribution and peaking factor 1source with poloidal distribution and peaking factor 133

MCNP Analysis of DNFM OperationMCNP Analysis of DNFM Operation

Neutron flux (1Neutron flux (114MeV)14MeV) at the divertor level has been at the divertor level has been calculatedcalculated Detection efficiency variations were analyzed for vertical and Detection efficiency variations were analyzed for vertical and horizontal plasma core shift horizontal plasma core shift Fast neutron fluxes for calibration point source moving toroidally Fast neutron fluxes for calibration point source moving toroidally along the VV axis were calculatedalong the VV axis were calculated Detection efficiency variation versus neutron source peaking Detection efficiency variation versus neutron source peaking factor is under analysis now (factor is under analysis now (in progressin progress))

MCNP analysis results:MCNP analysis results:neutron group fluxes at the divertor levelneutron group fluxes at the divertor level

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0 3.0 5.0 7.0 9.0 11.0 13.0 15.0

En, MeV

Fn,

cm-2

s-1

MCNP analysis resultsMCNP analysis results::DNFM efficiency variations for vertical and horizontal DNFM efficiency variations for vertical and horizontal

plasma core shiftplasma core shift

-10%

-5%

0%

5%

10%

-50 -40 -30 -20 -10 0 10 20 30 40 50

Shift, cm

Eff

icie

nc

y v

ari

ati

on

, %

Vertical

Horizontal

DNFM integration in the new divertor DNFM integration in the new divertor cassettecassette

DNFM integration in the new DNFM integration in the new divertor cassettedivertor cassette

ConclusionsConclusions

We are planning to continue DNFM activity:We are planning to continue DNFM activity: Improve the MCNP model including a divertor cassette Improve the MCNP model including a divertor cassette

with T dome support with T dome support Development of DNFM fission chamber prototypes for Development of DNFM fission chamber prototypes for

ITER relevant tests (high temperature operation, wide ITER relevant tests (high temperature operation, wide neutron flux range measurement etc.)neutron flux range measurement etc.)

Integration in the novel divertor cassetteIntegration in the novel divertor cassette Advance calibration scenario including DNFMAdvance calibration scenario including DNFM DNFM official status needs to update (at the moment - DNFM official status needs to update (at the moment - RFRF voluntaryvoluntary task as not credit diagnostic) task as not credit diagnostic)