neutronic activation analysis for iter fusion reactor activation analysis for iter fusion reactor...

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Neutronic Activation Analysis for ITER Fusion Reactor

Barbara Caiffi

100° Congresso Nazionale SIF

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Outlook

Nuclear Fusion

International Thermonuclear Experimental Reactor (ITER)

Neutronics Computational Tools

Activation Analysis for ITER Reactor

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1 g ( 21H,3

1H) 7*108 KJ

1 g 235U 8*107 KJ1 g petrol 40 KJ1 g coal 0.04 KJ

Nuclear Fusion

How much energy from...

D + T → 4He (3,5 MeV) + n (14,1 MeV)

Q=17.6 MeV

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Fuel Availability on the Earth DEUTERIUM: natural abundance 0.0154 % of H → reserve in the oceans 2 1016 Kg

TRITIUM: β radioactive with 12 years half life, not available in large quantities

What is available?

LITHIUM:

from 1 kg of Lithium can be produced 0.43 kg of tritium Lithium reserve in Earth crust [1] → 1.3 10 9 Kg , TRITIUM: 5.6 10 8 Kg

Lithium reserve in the ocean [1] → 2.3 1014 Kg TRITIUM: 1014 Kg

1kg of D-T fuel produces 7* 108 MJ ≈ 200 GWh

Year World Energy Consumption: 145 Gwh[2]

[1]U.S. Geological Survey, 2012, commodity summaries 2011: U.S. Geological Survey[2]IEA, Annual Report 2013

Fusion could fulfil energy supply for 1.5 billion years

n+ 6Li → t + α + 4.8 MeVn+ 7Li → n + t + α -2.8 MeV

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Iced DT pellet as a fuel Heating trough laser compression Works in pulse mode only

Inertial Confinement

How to Achieve Fusion

Magnetic Confinement

At temperature required for fusion to occur, plasma is completely ionized

Charge particles can be confined using magnetic field

Application of this concept are the Tokamak (like ITER)

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TokamakRESULTING FIELD LINES

The plasma is a secondary winding of a transformer. The resultant toroidal plasma current provides for Ohmic

heating and generates the poloidal magnetic field Bθ

Poloidal coils generated an additional toroidal magnetic field B

φ

for greater stability

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Economy of a TokamakIgnition : fusion charge products compensate for energy loss ( α in the case of DT plasma).

n τE>3T

f c , abQab<σ v>ab(T )4(1+δab)

−Abr√T=F (T )

Break-even : Fusion energy released must exceed the energy supplied.

E FUηIN E IN

=Q p=1

~2 1020 m-3s

~2 1019 m-3s

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n : ions density τ

E : confinement time

nτE

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Where we are now?

Maior radius 6.2 mMinor radius 2 mVolume 830 m3

Plasma current 15 MAToroidal field 5.3 TDensity 10 20 m-3

Peak Temperature 2*108 KFusion Power 500 MWPlasma Burn 300-500 s

ITER parameters

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500 MW of fusion power from 50 MW input power

MAIN GOAL: Q>10

ITER SITE: Cadarache (France)

TER TIMELINE:2008: Site levelling2010: Start Tokamak complex excavation2013: Start Tokamak complex construction2014: Arrival of first manufactured components2015: Begin tokamak assembly 2019: Complete tokamak assembly2020: First Plasma2027: First D-T Operation

ITER Project

CADARACHE

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ITER Machine

28 m

30 m

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28 m

30 m

ITER Machine

VACUUM VESSEL

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28 m

30 m

ITER Machine

BLANKET

VACUUM VESSEL

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28 m

30 m

ITER Machine

BLANKET

VACUUM VESSEL

DIVERTOR

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28 m

30 m

ITER Machine

BLANKET

VACUUM VESSEL

DIVERTOR

POLOIDAL FIELD COILS

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30 m

ITER Machine

BLANKET

VACUUM VESSEL

DIVERTOR


TOROIDAL FIELD COILS

28 m

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28 m

30 m

ITER Machine

BLANKET

VACUUM VESSEL

DIVERTOR


TOROIDAL FIELD COILS

CENTRALSOLENOID

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ITER Machine

28 m

30 m

VACUUM VESSEL

44 openings (“ports”):● 18 upper ports● 17 equatorials ports● 9 lower ports

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Neutronics in Fusion Technology

induce radioactivity in the structural materials as well as in the coolant

damage materials through atom displacement, affecting mechanical and electric

properties.

produce hydrogen and helium, which make welding difficult if > 1 appm

heat superconducting coils reducing their effectiveness

Neutrons:

These effects must be studied!

DT Fusion Reaction

QDT

=17.6 MeVP

FUSION=500 MW

Φn=1014 n/cm2s

on the First WallNEUTRON14.1 MeV

80% of total energy

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Shutdown Dose RateThe safety on a fusion plant requires a deep knowledge of the radiation map due to: “prompt” neutron and γ γ produced by activated material, in particular after the shutdown,

when maintenance is planned.

Three step procedure:

Monte Carlo calculation of the spectral neutron flux in the materials

Deterministic calculation of the radioactivity induced by neutrons as a function of irradiation or decay time

Monte Carlo γ transport and calculation of the dose rate in the region of interest

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Rigorous 2 Steps (R2S) Method

INPUT CODE OUTPUT

●MCNP Input File (3D geometry, materials, cross section libraries, neutron source)

MCNP5 - N Neutron flux and spectra map

1) Monte Carlo neutron transport2) Deterministic activation calculation3) Monte Carlo γ transport

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Neutron flux n/cm2s

INPUT CODE OUTPUT



VOXEL

Neutron spectrum


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INPUT CODE OUTPUT




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Rigorous 2 Steps (R2S) Method1) Monte Carlo neutron transport2) Deterministic activation calculation3) Monte Carlo γ transport

INPUT CODE OUTPUT



●Material●Irradiation Scenario●Decay Time

FISPACTActivity map

γ source

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Rigorous 2 Steps (R2S) Method1) Monte Carlo neutron transport2) Deterministic activation calculation3) Monte Carlo γ transport

INPUT CODE OUTPUT



●Material●Irradiation Scenario●Decay Time

FISPACTActivity map

γ source

● MCNP Input File(3D geometry, materials, cross section libraries, γ source)● γ-to-dose factors

MCNP5 - P Shutdown dose rate map

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Direct 1 Step (D1S) Method

Substitute Capture with activation-induced radiative decay. Neutron and decay γ transport treated in a single run. Special, ad hoc generated, “capture ”cross section data.

(n,γ prompt

) (n,γ activation decay

)

Cons: Ad hoc libraries should be produced for the activation dose relevant

nuclides, so an a priori decision has to be made. Each set of libraries is suitable just for 1 cooling interval.

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Shutdown Dose Rate BenchmarksShutdown Dose Rate Benchmark at FNG[3]

Shutdown Dose Rate Benchmark at JET[4]

[3] P. Batistoni, M. Angelone, L. Petrizzi, M. Pillon, Benchmark Experiment for the Validation of Shut-Down Activation and Dose Rate in a Fusion Device, J. Nucl. Sci. Techn., Suppl. 2, p. 974-977 (2002) [4]PETRIZZI, L., et al, “Benchmarking of Monte Carlo based shutdown dose rate calculations for applications to JET”, ICRS-10, Madeira, 2004

Mock-up of ITER First Wall (Water & Steel IG)

Max diff < 25%

Agreement between a factor 2 -3

In JET benchmark agreement is worse because of the lack of information about the technical drawing ( geometry, impurity content)

Good experimantal vs calculated data agreement

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ITER project goals:100 μSv/h 106 s after the shutdown in the Port Interspace Region [ ϕ~107 n/

(cm2s)] where maintenance is planned

4m

3m 2m

PORT PLUG

PORT INTERSPACE

BIOSHIELD

PIPE FORESTTBM FRAME

TBM 2

TBM 1

Shutdown Dose Rate in the ITER European TBM Port

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European Test Blanket Module (TBM) Port

Modules for tritium production tests, containing: Breeder (lithium) Neutron multiplier to improve efficiency

n+ 6Li → t + α + 4.8 MeV

n+ 7Li → n + t + α -2.8 MeV

HCPB Breeder Unit

HCLLBreeder Unit

Inlet LiPb Pipe

Outlet LiPb Pipe

Helium cooled plates Helium cooled

plates Lithiated pebbles + beryllium pebbles

Helium Cooled Pebble Bed (HCPB): Breeder: lithiated ceramic pebbles (Li

4SiO

4 or Li

2TiO

3 )

Neutron Multiplier: beryllium pebbles

Helium Cooled Lithium Lead (HCLL):Breeder & Neutron Multiplier: PbLi eutectic (liquid at operating temperatures)

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XZ SECTION

XY SECTION

B-Lite:

Official Model for ITER neutronic analysis Represents 40°sector of the reactor Contains only main components TBM Port represented as an homogenized water-

steel block Contains 21216 cells, 27920 surfaces, 26 materials Run 57 histories per second per core (109 histories

take 24h using 250 cores)6 m

8 m

CAD drawing of the TBM Port

ITER ModelMCNP Model

PORT PLUG

PORT INTERSPACE

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ITER Model

900 1000 1100 1200 1300 1400 1500

PORT PLUG

PORTINTERSPACE

MESH1MESH2

y[cm]

TFC

TFC

BLANKET

VACUUM VESSEL

TBM1

PORT PLUG

PORTINTERSPACE

x[cm]

VERTICAL CUT

900 1000 1100 1200 1300 1400 1500

z[cm]

350

250

150

50

-50

-150

-250

MESH1MESH2TFC

TFC

HORIZONTAL CUT

300

200

100

0

-100

-200

-300

TBM2

BIOSHIELD

CRYOSTAT BIOSHIELD

CRYOSTAT

x[cm]

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PORT PLUG

NEUTRON FLUX[n/cm2s]

x[cm]875 975 1075 1175

z[cm]

1E14

1E12

1E10

1E8

1E6

215

165

115

65

15

-35

-85

1014n/cm2s 106n/cm2s 108n/cm2s 107n/cm2s108n/cm2s

PORT INTERSPACE

Calculation performed on rectangular mesh imposed over the geometry (voxel dimensions 10*10*10 cm3)

Jobs run on 600 cores with MPI capability (ENEA cluster CRESCO) , time 24 h

109 histories required variance

reduction techniques (Weight Windows)

250

150

50

-50

-150

z[cm]

x[cm]

1.0E8

5.6E7

3.2E7

1.8E7

1.0E7

NEUTRON FLUX[n/cm2s]

1200 1300 1400 1500 1600

Neutron Flux Map

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LIMIT

Shutdown Dose Rate [μSv/h] 12 days after the shutdown Shutdown Dose Rate [μSv/h]

Shutdown Dose Rate exceeds the limit imposed by the ITER project (100 μSv/h 12 days after the shutdown) close to cryostat and Pipe Forest structure.

Gaps and other experimental ports are the main responsible of the dose Optimization of the gaps and of the experimental port cross talk is currently under investigation

Shutdown Dose Rate in the Maintenance Area Model

Impurity content of Steel 316 IG :- Co60 0.05% wgt – 70% dose -Ta182 0.01% wgt -22% dose

ACTIVATION GAMMA SOURCE[γ/cm3s]

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LIMIT

Shutdown Dose Rate [μSv/h] 12 days after the shutdown Shutdown Dose Rate [μSv/h]






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Shutdown Dose Rate [μSv/h]

LIMIT

12 days after the shutdown Shutdown Dose Rate [μSv/h]






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Port PlugPort

Interspace

LOWERPORT

EQ.PORT

UPPERPORT



Monte Carlo Model

x[cm]875 975 1075 1175

z[cm]1E14

1E12

1E10

1E8

1E6

215

165

115

65

15

-35

-85

1014n/cm2s 106n/cm2s 108n/cm2s

Neutron Flux in Port Plug

n/(cm2s)

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Conclusions● The worldwide efforts in fusion technology aim at developing, in the long-term, power reactors which can contribute substantially to the supply of electricity.

●The construction and operation of the experimental fusion device ITER (”International Thermonuclear Experimental Reactor”) is an essential next step towards this long-term goal.

● The availability of qualified computational tools and nuclear data for the neutron transport simulation and the calculation of activation and material damage is a pre-requisite to enable reliable design calculations for these facilities.

● An automated R2S shutdown dose rate calculation tool was made and used to evaluate the actual design European TBM Port.

● From preliminary results, the shutdown dose rate in the region of maintenance is higher that 100 μSv/h. The main contribution is due to the cross-talk with the other experimental ports, which must be better described in the MCNP model and further investigated.

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ThankYou!

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