IFMIF Lithium Target

D. Bernardi, P. Agostini, G. Miccichè,

F.S. Nitti, A. Tincani, M. Frisoni

ENEA

with the contribution of Prof. A. Di Maio and the staff of DIN Department (University of Palermo)

ISLA 2011 - Princeton April 28th 2011

Outline

Main aspects of TA engineering design:

TA mechanical design Thermohydraulics Neutronics Thermomechanics Lifetime assessment

• Average heat flux 1 GW/m2

• Footprint area 100 cm2 (20 x 5 cm)• Jet width/thickness 260 / 25 mm• Li velocity 10-20 m/s• Damage rate on the BP 50-60 dpa/y• Erosion/corrosion rate 1 μm/y (nozzle and BP)• BP replacement frequency 11 months

IFMIF Target Assembly (TA) requirements:

TA mechanical design

INTEGRAL Target - SS(JAEA)

TA with BAYONET Back-Plate – RAFM steel(ENEA)

• Lower activated waste• Easier replacement operations• More complex than integral concept

EVEDA Loop prototype(already installed in the loop)

TA mechanical design

Each skate consists of a chassis in which triple bearings are mounted on six parallel axes.

Each bearing axis comprises three wheels: the two outside wheels push on the fixed frame while the central wheel runs on the inclined plane and transmits the pushing force to the back-plate

The skate tightening concept has been successfully tested and qualified on experimental mock-ups realized at ENEA Brasimone for a previous BP design. However, qualification for the new IFMIF design will be performed in the future

One driving screw for each skate

Tightening bolts

Skate

Gasket groove

TA mechanical design

Qualification of the sealing gasket

HELICOFLEX® HNV200 Gasket

Static Li Ti getter @ 550 °C Li Temp = 350 °C Exp. time = 1800 h

SS316 home-made test rigs

(soft iron)

(SS304)

(Nimonic)

TA mechanical design

Thermohydraulics

The back-plate geometry reported in the CDR is made by a straight wall of 90 mm at nozzle exit + curved wall of 250 mm radius up to the beam axis

Pressure increase

Curved wall creates centrifugal force producing a pressure increase in the Li that avoids boiling

Onset of centrifugal force

Experiments and numerical simulations of the behaviour and stability of the IFMIF-like lithium jet flowing on a straight + curved wall were made by IPPE.Two main issues were observed at the straight-curve transition:

1) Detachment of the jet from the straight wall

2) Instability of the jet due to sudden appearance of centrifugal force when it moves from straight to curved wall

Experiments confirmed the numerical results

Thermohydraulics

02

2322

g

vxD

x

yCarctg

x

yBarctg

x

yAarctgyx

In order to have a gradual pressure increase, ENEA designed a new profile by imposing:

Using simplified Navier-Stokes equations:

A, B, C, D are determined from geometrical constraints

Thermohydraulics

Pressure increase

Preliminary assessment done with REGEL code (ENEA)

Updated detailed calculations are being carried out by ULB (Belgium) within ED03-EU PA in coordination with ENEA

Li Temperature and saturation point

Boiling margin

Thermohydraulics

Li depth [mm]

Li velocity [m/s]

Preliminary neutron/gamma transport calculations have been performed at ENEA for the BP via Monte Carlo MCNP5 code

The McDeLicious-05 neutron source code provided by KIT was used

This code uses the newly evaluated (d + 6,7Li) cross section data files, produced under a collaboration of IPPE (Obninsk) and KIT (Karlsruhe), containing the cross sections and the energy-angle distributions of the reaction products for deuteron energies up to 50 MeV.

The neutron-induced cross section data files used in the calculations are mainly from IPPE-50 library, developed at IPPE-KIT, for neutron energies up to 50 MeV,)and LANL-150N, developed at Los Alamos National Laboratory, for neutron energies up to 150 MeV.

Back Plate

HFTMLithium jet

Neutronics

Mapping on BP via “superimposed mesh tally”feature of MCNP5 code

zzz zz

y

Atom Displacement, dpa/fpy 4.7×10-1

He production, appm/fpy 2H production , appm/fpy 9

Total heating W/cm3 3.8×10-1

Atom Displacement, dpa/fpy 54He production, appm/fpy 598H production , appm/fpy 2742

Total heating W/cm3 23.8

x = 0 (axis of symmetry)

Neutronics

The calculations of deuteron energy deposition in lithium were firstly performed with the “standard” MCNPX 2.7d code.

New calculations were performed with the MCUNED code that allows to describe better the deuteron nuclear interactions with matter.

209 KW/cm3

161 kW/cm3

Power deposition profile in the Lithium

Neutronics

Effect of beam gaussian energy dispersion

(FWHM=1.177)

The energy dispersion slightly increases the beam penetration range in the target

Neutronics

Thermal loads and boundary conditions

• Forced convection with Lithium

• Internal irradiation

• External irradiation

Mechanical loads and boundary conditions

• Thermal deformations

• Internal and external pressures

• Tightening screws loads

• Skate-based clamping system loads

• Target Assembly system constraints

ABAQUS code~ 280 000 nodes ~ 1.2x106 tetrahedral elements

EVEDA Target Assembly

Materials• EUROFER : back-plate• INCONEL X-750 : gasket• F82H: remaining TA components

Thermomechanics

Back plate

T field

Nominal scenario

Thermomechanics

Li Temp. = 275°C Internal pressure = 0.18 MPa

Von Mises stress

NO Yielding !

Thermomechanics

Li Temp = 275°C Internal pressure = 0.18 MPa

Nominal scenario

Displacements

Thermomechanics

Nominal scenario

Li Temp = 275°C Internal pressure = 0.18 MPa

Thermomechanical calculations for IFMIF TA are underway

Miwa Y. et al. , J. Nucl. Mater., 283 (2000)

13 He appm/dpa

SS 316 RAFM steel

RAFM steel is considered as reference material due to its lower activation, better swelling resistance and higher mechanical properties compared to SS

In the BP footprint region : ~ 11 He appm/dpa (similar to F82H-3) → ~ 0.015 x 60 dpa = 0.9 % ΔV/V max. = 0.3 % Δl/l max. @ 400 °C

Tirr = 400°C

0.015 % / dpa

SDC-IC ITER code

Linear swelling ~ 0.3 % > 0.017 % (negligible swelling test from B 3022 SDC-IC rule) swelling analysis is requested considering also the mitigating effect of irradiation-creep stress relaxation

Lifetime assessmentSwelling/creep effect

A more detailed analysis is needed to assess the stresses due to constrained swelling caused by irradiation and temperature gradients at the footprint

A numerical assessment considering the competitive effects of irradiation swelling and creep can be performed using the approach of ITER SDC-IC code (rule B3024.1.1.1)

Visco-elastic analysis

Numerical calculations with evaluated dpa and T maps are ongoing at ENEA

Simplified elastic analysis

Lifetime assessmentSwelling/creep effect

Gaganidze, et al., J. Nucl. Mater. , 355 (2006)Schaaf B. et al., J. Nucl. Mater., 386 (2009)

ΔDBTT up to 240 °C ( corresponding to DBTT max 150 °C @ 60 dpa)Apparent “saturation” might be due to T sensitivity

High T sensitivity in [300 – 350 °C] range

16 dpa (4 month)

“Optimistic” approach:BP Temp. > DBTT max ( 150 °C) always → > 1 year

Very conservative approach:~20 ΔDBTT /dpa → ~16 dpa to reach -80 °C → 250 °C → ~ 4 months

T unirr. = -80 °C

Lifetime assessmentNeutron-induced embrittlement effect

T = 300-350 °C

SDC-IC rule IC-3214.1

a = max (4au, t/4) ; au largest undetectable crack by applied NDE technique

Very few data for KC !!KC min ~ 30-40 Mpa√m

Lifetime assessmentNeutron-induced embrittlement effect

Other important factors can limit the lifetime of the BP:

Erosion/corrosion of the channel and the nozzle

Thermal fatigue due to Li surface oscillations

More detailed assessment of these effects will be possible once that experimental results will be available from LIFUS 3 facility at ENEA Brasimone and EVEDA Li Loop at Oarai (Japan)

Lifetime assessment

Thank you !Thank you !