9th IEM Meeting Nimes 2006 September 25th to 29th
MEGAPIE Target :DESIGN IMPLEMENTATION AND PRELIMINARYTESTS OF THE FIRST PROTYPICAL SPALLATIONTARGET FOR FUTURE ADS
Ch. Latge1,(CEA) France (christian.latge@cea.fr) F. Groeschel2 (PSI)
Switzerland (friedrich.groeschel @ psi.ch)2, P. Agostini3, M. Dierckx4, C. Fazio5,
A. Guertin6, Y. Kurata7, G. Laffont1, T. Song8, K. Thomsen2, W. Wagner2, K.
Woloshun9

1 CEA Cadarache, 2 PSI Villigen;
3 ENEA Brasimone; 4 SCK-CEN Mol;
5 FZK Karlsruhe; 6 SUBATECH Nantes;
7 JAERI;; 8 KAERI; 9 DOE-LANL

Departmentof Energy

MEGAPIE-TESTIntroduction 1/2
Partitioning and Transmutation (P&T) techniques could
contributeto reduce the radioactive inventory and its
associated radiotoxicity.
Sub-critical Accelerator Driven Systems (ADS) are potential
candidates as dedicated transmutation systems, and thus
their development is a relevant R&D topic in Europe.
Following a first phase focused on the understanding of the basic
principles of ADS, the R&D has been streamlined and focused onpractical demonstration key issues. These demonstrations coverparticularly spallation targets of high power.

General consensus :- up to 1MW of beam power solid targets are feasible from a heatremoval point of view.
- for higher power levels, liquid metal targets are the option of choicebecause of their higher heat removal capability, higher spallation material
density in the volume, lower specific radioactivity,…
Fraction ofGridenergy (1-f)
Fraction of energy f
1 GeV

Accelerator

Spallation
TargetSub-critical
reactorExtraction of energy Ef

Introduction 2/2
A key experiment in the ADS roadmap,
MEGAwatt PIlot Experiment (MEGAPIE)(1 MW) initiated in 1999 in order to design and build aliquid lead-bismuth spallation target, then to operate it into
the Swiss spallation neutron facility SINQ at PSI .
It has to be equipped to provide the largest possible amountof scientific and technical information without jeopardizing
its safe operation.

SINQ @ PSI

Minimum design service life fixed at 1 year (6000 mAh).
Nota : PSI interest lies also in the potential use of a LM target as a SINQ standard
target providing a higher neutron flux than the current solid targets. Calculations of theradial distribution of the undisturbed thermal neutron flux for the LBE target incomparison to the former Zircaloy and current steel-clad solid lead target were donewith different nuclear codes ; nevertheless, variations between various codes
enlightened the necessity of flux assessment by direct measurement.

Main challenges

Three main challenges :- to design a completely different concept of target in the same
geometry of the current spallation targets used at PSI.
- to develop and integrate two main prototypical systems : a specificheat removal system and an electro magnetic pump system for the hot heavy
liquid metal in a very limited volume.
- to design a 9Cr martensitic steel (T91)reach the assigned life duration.

beam window able toChoice of Lead-Bismuth
Lead bismuth eutectic (Pb44.5%-Bi55.5%) has been selected, due to its
attractive neutronic and physical properties : heat transfer coefficient, lowmelting point (125°C); nevertheless bismuth induces to the production ofactivation products i.e. polonium,...

Choice of T91 for the beam window
Compared to austenitic steel 316L, T91 has :- higher strength.
- much better resistance to heat deposit (due to a lower thermal
expansion coefficient and a higher thermal conductivity). As a result,thermal stresses are about twice as high in 316 as in T91 for a given geometry andheat deposit.
- better corrosion resistance in Pb-Bi due to a low nickel content.
Furthermore, for applications under irradiation up to high doses attemperatures higher than about 400°C, T91 has additional advantages over 316 :- much lower swelling.
-better resistance to the “high temperature helium embrittlement”
phenomenon.
Of course, the main weakness of martensitic steels is the existence of theDuctile-to-Brittle Transition temperature (DBTT) which is shifted as a result ofirradiation. This shift is small for 9Cr martensitic steels up to high doses at irradiation
temperatures higher than 400°C. At lower irradiation temperature, a significant DBBT shift occurs.

(T91 : (0.1C, 0.32Si, 0.43Mn, 8.73Cr, <0.01W, 0.99Mo, 0.19V, 0.031Nb, 0.029N, 0.24Ni))

Heat Exchanger (Oil)
10 i/s, 5.5 m/s
140-175°C inside

L

Heat Exchanger
4 l/s, 0.33 l/s/pin
0.46 m/s
380-230°C insideF

Main Pump
4 l/s, 1.2 m/s
380°C
F

Guide Tube
4 l/s, 0.33 m/s
380°C
Downcomer
3.75 l/s, 0.33 m/s
230-240°C

Beam Window
380°C outside
330°C inside

Bypass Pump
0.25 l/s, 0.2 m/s
230°C

Bypass Tube
0.25 l/s, 1m/s
230-240°C

Nozzle 1.2 m/s
Beam Window 1 m/s

MEGAPIE – Target main characteristics
Beam energy:

575 MeV

Deposited heat:

650 kW

Beam current:

1.74 mA

Cold temperature:

230 – 240°C

380°C(design)Length:5.35 mHot temperature:

LBE volume:~ 82 lDesign temperature: 400°C

Weight:~ 1.5 tOperating pressure: 0 – 3.2 bar

Wetted surface:~ 8m2

Design pressure:

16 barGas expansion volume: ~ 2 l

Total LBE flow rate: 4 l/s

Insulation Gas:

By-pass flow rate:

0.5 bar He

0.25 l/s

The MEGAPIE project : support to design
The preparation of the complete design of the target with ancillary systems
required first the definition of critical issues and required R&D needs
which are inherent in the design and operation of a spallation target.
- An answer to target specific critical issues was given using analytical,
numerical and experimental approaches.
- The results of these dedicated studies contributed to the validation of thedesign and operating options .
- Moreover, these studies also contributed to safety and reliability
assessment ofaspects which might endanger the integrity andoperability of the target.
Support to the MEGAPIE design has been mainly devoted to the following
fields :- Neutronics- Materials- Structure Mechanics- Thermal hydraulics- Mass and heat transfer- Liquid Metal Technology

MEGAPIE : Main Results
The Megapie target has been designed andsuccessfully manufactured in France*, under the QA of PSI,
with the Design Support activities of the MEGAPIE
partnership.
* Pumps designed and manufactured in Latvia.
A very large amount of experimental tests, calculations,projectstudies have been carried out in various fields.
It has been demonstrated that:– the target is coolable– there are no major problems linked to liquid metal technology,– corrosion is limited and window lifetime has been estimated toan acceptable value (23 weeks).
– no critical points for ancillary systems have been evidenced– irradiated target handling and waste management is welldefined,– safety demonstration is possible.

MEGAPIE – Target components
Target window: T91, 1.5 mm
Target heat exchanger
12 pin LBE – Diphyl THT
Target head
Connector interface toancillary systems
Main and by-pass tube
LBE flow guideAncillary systems
Ancillary systems were designed by PSI, ENEA and Ansaldo.

Heat removal system, HRS, with Diphyl THT® oil a cooling medium and anintermediate water loop,
Cover Gas System, CGS, to cope with the overpressure in the target and to assure theconfinement of all radioactive gases produced by the spallation process (about 8 liters)
and a regular and controlled venting. (gases collected in the target expansion tank andperiodically evacuated via filters into a decay tank).
LBE Fill and Drain System, F&D, with a double containment and an appropriate
system for disconnecting the tubes after operation.
Beamline adaptations including advanced beam monitoring : implementation of
Catcher, funnels, collimator slit, VIMOS (beam position visualization system).
Handling devices for the target decommissioning, storage, dismantling anddisposal.

Integral Tests
Integral Test: September to December 2005
–to integrate the target and the ancillary systems,– to carry out LBE filling and draining operations,– to check the operability of the main components of the target,– to check and calibrate the instrumentation (mainly flow-meters)– to determine the thermal hydraulics characteristics of the system,– to simulate heat deposition (with a heater)– to characterize the heat transfer and hydraulic behavior at thewindow,– to obtain the vital parameters for system control,– to provide enough information for licensing the target for irradiation
test,– to gather technical and scientific data for model verification, in order
to be able to extrapolate the Megapie experience for the future ADSs

Transfer to SINQ:

January to March 2006

Main characteristics of the main EMP
7.0

Flow Rate, liter/second

6.0
T < 200 °C
200 °C < T < 215 °C
215 °C < T < 230 °C

5.0

T ≥ 230 °C
Line 1
Line 2
Line 34.0

Line 4
3.0

2.0
10

15

20

25

30

Average Current (main EMP), Ampere

35Thermohydraulic tests : results for control system
Four tests Æ set of the data for the system characterization.
Requirements for the control of the target for an efficient and safe control :- Keep the target (window) at a constant temperature of 230°C :Æ not too low to have a safe margin before freezing,Æ not too high to limit thermal stress on the heat exchangers.
- Limit temperature excursions during beam transients : beam on / off
operations, beam trips and interrupts.
- Assure stable target temperature in the three reference operating cases :- isolation (target isolated from heat removal system),- hot standby (awaiting beam operation) and- full beam power.

Thermohydraulic tests : results for control system
During the integral tests, it was seen that :- the characteristics of the oil three-way valve are highly non-linear, and- the target heat exchanger performance was better then expected (20 to 40 %according different evaluations);
Æ main consequence : only about 40% oil flow through oil/water heat exchanger
during full beam power operation

Oil three way valve characteristics

Influence of oil flow-rate on Heat transfer coefficientIntegral test : beam trip simulation
Main assumption for the system characteristics analysis : main LBE
flow rate computed from the heat balance of known power input.
Ætest simulating a beam trip (average temperatures of LBE, target
structures, and main EMP) and showing the capacity of the Heat Removal
system to react to the transient situation.

(a) during beam trip(b) during beam interrupt (c) restarting from how standby

Experimental / calculated temperatures for an unprotected trip.

RELAP model more or less verified but could be improved by a better estimation of :- the thermal masses of LBE and structures (Cp,…)- the heat transfers coefficients (using T of the main and bypass EMPs, ),Integral tests : THX design validation
Sufficient capacity of the Heat Removal Systemtocope with about 600 kW of heating in the target
andflexible to the changes, though the operating
conditions might be differed from the predictions.
But : after the integral tests, bypass flow conditions still tobe determined
Analysis of the experimental data of the LBE-oil thermal
exchanger of the target ( with analytical heat exchanger
calculations (Global
model, ε-NUT, and numerical
model
(
n
(1D), finite volumes)
volumes :ÆFor each of the 4 campaigns, computed values inagreement with the corresponding experimental
results.(maximum variance between calculations andexperiments very low, andbelow the accuracy of the model is about 20%).
ÆThus, THX heat transfer model used to its design,designvalidated, even if some uncertainties hang over flow rates
assessments.
ÆParametric study of sensitivity : large margins on the
THX thermal exchange capacity.

Full scale leak test
Main goals : to validate :- the design of the Lower Target Enclosure (LTE)under worst case leak conditions,- the leak detector system, implemented in the lower
part of the LTE.
2 different sensors implemented :- Thermocouples (9 individual andindependent sensors, 3 electricallypreheated) as main leak sensor, and,- Stripe sensors type “AC impedance” (3separate units)
Main results :- Lower target enclosure : able to contain LBE.
- Validation of the leak detector system :- detection of < 0.5 liter LBE within 1 s with a very high reliability,- 100 % detection efficiency with a very low false alarm rate,- temperature resistant.

Full scale leak test simulation

3.7 sec
IN: Fluid dynamic transient of liquid metal in the containment hull

Time=100msec

Time=300
msec

Time=1sec

Time=2sec

OUT : Principal stress in the hull as a function of time during leak

LBE-water interaction : simulation with MATTINA and SIMMER codes
Main goals : Analysis of the potential consequences of 3 simultaneous
failures of the target shells and Lbe-water contact :Independent investigations with MATTINA and SIMMER codes, able to model
the hypothetical interaction between lead bismuth alloy and D2O, inducing
water vaporisation and target pressurisation (Target can withstand P<30 bar).
Main results :Æevaluation of the accidental sequence,ÆExclusion of the vapour explosion eventÆ demonstration of the structure integrity (Pmax << 30 bars ).

600000

0

2

4

6

8

Pressure in the proton tube

10
600000No shutdown
Shutdown

600000

Fall 'schwer'
500000500000500000400000Gasdruck im Zentralrohr
Druck unten im Innenspalt
Gasdruck im Innenspalt

300000300000200000200000100000100000

0

0

2

4

6

Zeit [sec]

8

0
10

p re s s u re (P a )Druck [Pa]4000004000003000002000001000000
0

2

4

6
time (s)810Large Eddy Scale Simulations
Main goals : For the future Post Test analysis phase after irradiation:ÆLarge Eddy Scale simulations (LES) by CEA to analyse the instability,
close to the window. ( CEA TRIO-U-VEF parallelized code)ÆAssessment of the level of temperature and velocity fluctuations near
the window, to give realistic data for thermo-mechanical studies aiming todemonstrate the integrity of the T91 window.

MEGAPIE target in SINQ hallTarget installation in TKE
After the end of the integral tests :-central rod of the target cleaned theninsertion of the neutron flux detectors.
- electrical cabling and other connections- implementation of the LBE leak detector-Lower target enclosure final welding,-Checking of the LTE tightness by X-ray
and pressure and leak test.
Æthen target installed in SINQ, andconnected to ancillary systems :- Fill and Drain,- Heat Removal System,- Cover Gas System,- Isolation Gas System,..

IGS:
STEAM CONDENSER

View of TKE

FILL & DRAIN
SYSTEMHEAT REMOVALSYSTEM

COVER GASSYSTEM

SMALL BOXTARGET HEAD

Safety optimization tasks
Measures for reduction of the source term incase of an incidental release of activity toreach the 1 mSv criterion for the public:- better sealing of the TKE & STK- O2-Reduction system for the TKE & STK toprevent fire due to oil- connecting the TKE with the Cooling Plant inorder to reduce the possible activity concentration- upgrade of the ventilation system (earthquake
resistant stand-alone exhaust equipment) and of
the filter systems (both with activated carbon andparticle filters).

Collimator slit: mounting in QHJ30 and view inside

MEGAPIE: proposed start-up procedure (1)Phase 1Retrieve dosimetersfrom TKE (first set)Proton beam current (mA)

1.0
Beam on target?
First neutrons @beamlines

0.5
beam interrupt system:
end-to-end test

20μA / ∼4h0
day 1
Review

MEGAPIE: proposed start-up procedure (2)Phase 1Retrieve dosimetersfrom TKE (first set)

Phase 2

Proton beam current (mA)

1.0
Beam on target?

Fresh gas sampling in TKE
after ca. 2 mAh

Retrieve dosimetersfrom TKE (second set)

HRS/WCL reactions:comparison with MITS,
poss. adjustments

First neutrons @beamlines

0.5
LBE leak detector:
first signals

beam interrupt system:
end-to-end test

50-250 μA / 8 h
20μA / ∼4h

0
day 1

day 2
Review

12 h

Review

Beam control systems : VIMOSVIMOS: optical visualisation of the beamfootprint in front of the SINQ beam window

VIMOS hat in insertion
tool with LED on

MEGAPIE: proposed start-up procedure (3)1.2 mA

Proton beam current (mA)

1.0

SU: Radiation mappingin SINQ- and guide hallPhase 3800μA/∼4h

beam ramp-up
to full power

see VIMOS
comming up
500μA/∼4h

HRS/WCL reactions:poss. adjustments

0.5

LBE leak detector:
watch signals

200μA/∼4h

Follow neutron flux
at beamlines

0days 3 and 4 and + +Interrupts or extended intermediate steps and additional reviews on demand:
SU-mapping, HRS parameter adjustments, LBE leak detector etc.

Review

Reviews after start-up phases
Questions to be addressed:
Systems behavior as expected?
All tests done and o.k.?
Preliminary test reports available (minimum: note inlogbook), are the results stored?
Parameter-/SW-adjustments necessary?
BAG requirements fullfilled?
Safe continuation possible?

Target « experimental » monitoring
During irradiation phase of MEGAPIE, numerous operating parameters aremonitored :- pressure, fluid flow-rates and temperatures.
- neutron fluxes at various positions of the facility,- gas production; ( for Monte Carlo calculations of the measured quantities)
Æ goal : codes validation MCNPX and FLUKA fitted with appropriate models

Various neutron measurements :a- Measurements at beam lines :- with activation foils (Measurement of the thermal neutron flux
and of the epithermal flux (at a single resonance point at 4.9 eV by wrapping thefoil with a Cd layer).
- with Bonner spheres (Measurements performed with poly spheres of different
radius surrounding 3He detectors, for sensitivity to different neutron energy range.
(By Lausanne university)- time-of-flight measurements performed at the SINQ ICON facility using a chopperb- Other neutron measurements :- neutron flux inside the target using 8 micro-fission chambers. ( from thermal to
10 MeV)- neutron flux with activation Au foils inside D2O tank (NAA/PNA stations)- delayed neutrons in the upper part of the target (It is calculated that with aprompt neutron flux in the TKE of about 105 n/cm2/s, the DN flux should be oneorder of magnitude higher)Target irradiation
Irradiation :2006 August 14th to end of 2006

Main goals :– confirm the main operating parameters,– obtain neutronic performances, in order to validate
the neutronic codes and spallation models– to confirm material performances evaluated during
design support phase,– more generally demonstrate the ability to operate
a liquid metal target in ADS relevant conditions

On Monday, August 14 at 15:30, the target received the first protons !!!.

ca. 2:30 pm first protons hit the target
and produce first neutrons
Protonenbeam current 40µA
∼ 25 kW
Test duration ca. 3.5 h
Stable beam for ca. 90 min
ca. 60 µAh total charge received(sufficient for TKE dosimetry)End-to-end Test @ 40 μA: response time < 40 ms

Proof of
Functionality
and Sensitivity
at very low
signal level

30 ms

MEGAPIE: proposed start-up procedure (phase 2)

Proton beam current (mA)

1.0

Fresh gas sampling in TKE
after ca. 2 mAh

Phase 1

Phase 2Retrieve dosimetersfrom TKE (second set)

HRS/WCL reactions:comparison with MITS,
poss. adjustments

0.5
LBE leak detector:
first signals
50-250 μA / 8 h
20μA / ∼4h

0
day 1

day 2
Review

12 h

Review

MEGAPIE start-up : phase 2

On Tuesday, the beam current was ramped up in steps to 250 mA and the target wason-beam for almost 8 hours.
During a scheduled shutdown of the accelerator on Wednesday :- cover gas samples extracted- dosimeters were retrieved.
Æsecond review : OK to go on
On Thursday operation continued by ramping up to “full power” (about 1200 mA) (700kW). The target continued to work as expected.
Measurement of neutron flux in the target and delayed neutrons in TKE : successful.
ÆCalibration of the LBE flow measurements carried out : OK.
ÆCalibration of the LBE leak detectors carried out : OKTu, Aug 15, 2006

Phase 2

12:00

14:00

16:00

18:00

200 μA
100 μA

250 mA ∼150 kW

MEGAPIE start-up : phase 3

On Thursday operation continued byramping up to “full power” (about 1200
mA). The target continued to work as
expected.
Measurement of neutron flux in the targetand delayed neutrons in TKE : successful.
ÆCalibration of the LBE flow
measurements carried out : OK.
ÆCalibration of the LBE leak detectors
carried out : OK

VIMOS triggered correctly @ 900 μA

Proof of Functionality
and Sensitivity at
Very Low Signal Level(frames enhanced)

Steady state operation Mo, Aug 21 2006

31. Aug. 2006

Strahlstrom: 1200 μA

MEGAPIE: calculated neutron flux gain
Performance comparison for different target materials under SINQ conditions(calculations with the code LAHET)

2.5

Zr rods
Pb + steel cladding (0.5 mm)
Pb + Zr cladding (0.7 mm)
Pb-Bi

1

0.5

cold
source1.5

beam tubes

target region

thermal flux [rel. units]

2

0
0

10

20

30

40

50

60

70

80

90

100

radial position [cm]

LAHET calculations A. Dementjev, E. Lehmann

Expected: >40% higher neutron flux as with solid lead target

Protons

MEGAPIE : neutronic flux

Thermischer Fluss (HRPT): 41%

Kalter Neutronenfluss (SANS I): ca. 70%

NEXt STEPSPost Test Analysis: 2006 & 2007
Target transfer and cutting : 2008
PIE:

2009 & 2010

Several steps :-cooling circuits and gas volumes emptied rinsed and dried,Band saw ( Behringer),- target disconnected and sealed up with blind flanges,- target stored for several months.
- transfer to SWILAG hot laboratories, using a steel container.
- target cut with band saw (provided by Behringer), in 19 slices.
- pieces of target transported to the Hotlab at PSI (8 (weight) %)- extraction of samples material for Post Irradiation examinations.
- Remaining target pieces (92%) conditioned in steel cylinder ina KC-T12 concrete container.

Container for transportation

Conclusions
The Scientific Design Support of this international project was an
example of collaboration between design and researchteams .
The target and ancillaries systems have been designed, manufactured,and integrated very efficiently.
Integral tests was a very useful step for the definition of the operationg
conditions, control system parameters, and training of the PSI operating
team.
PSI team has shown an impressive efficiency in order to reach thisstatus.
The Megapie –test European project is a very important support and toolwith regards to the integration of the results for the design of ADS
demonstrator.
.

Departmentof Energy

MEGAPIE-TESTThank You for your attention

TARGET OPERATION : 3 operational modes
The target can be operated following three main operational modes :1. Isolation case :The target is “disconnected” from the Heat Removal System by closed
isolation valves in oil loop; the two electromagnetic pumps are
running(possibly at reduced power)
and the target temperature iscontrolled by thecentral rod heater
2. Hot standby case :The target is “connected” to the Heat Removal System; all pumps (lead-bismuth, oiland water) are running in nominal conditions and the target temperature is controlled by
the three way valve in oil loop. Then the system is ready to accept beam operation.
3. Beam operation case :The target is operated as in the hot standby case but with beam operation. If during
the beam operation status, an anomaly in the signals is detected, the beam is switched
off and the target will go into “hot standby case” or into “isolation case” if a criticalproblem is detected. If during the “hot standby”case, it is not possible to maintain theselected operational conditions, the target will go into “isolation case”