european commission 7th euratom - silereuropean commission 7th euratom framework programme 2007-2013...

EUROPEAN COMMISSION 7th EURATOM FRAMEWORK PROGRAMME 2007-2013

THEME [Fission-2011-2.3.1] [R&D activities in support of the implementation

of the Strategic Research Agenda of SNE-TP]

SILER Seismic-Initiated events risk mitigation

in LEad-cooled Reactors

Grant Agreement N°: 295485

Deliverable title: Complex dynamic phenomena in ADS system (D3.2)

Work Pakage

Deliverable number

Lead contractor Date

WP3 D3.2 SRS 23-12-2013

Responsible person details name: Giuseppe Moretti e mail: [email protected]

Starting date Due date Actual date Delay* Nature

Description of the activities: Study the complex dynamic phenomena related to the accelerator/reactor coupling.

The deliverable contains the procedure and methodology used in the Task 3.1 of WP3

SIGNATURES Author:

WP Leader; Coordinator:

Giuseppe Moretti SRS Bong Yoo, SCK-CEN

Pavel Kudinov

M. Forni, ENEA

S.R.S. Servizi di Ricerche e Sviluppo S.r.l

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Cliente – SILER Doc. N: S1165SI1002 Rev. N.01del 23/12/2013

CONTENTS

1 INTRODUCTION ........................................................................................................... 8

2 REFERENCIES ........................................................................................................... 10

3 DESCRIPTION OF PLANT AND SPALLATION TARGET ASSEMBLY .................... 11

3.1 PLANT LAYOUT ..................................................................................................................... 11

3.2 REACTOR BUILDING .............................................................................................................. 11

3.3 REACTOR ASSEMBLY ............................................................................................................ 12

3.3.1 Reactor Vessel and Support ....................................................................................... 16

3.3.2 Reactor Cover ............................................................................................................. 16

3.3.3 Diaphragm ................................................................................................................... 17

3.3.4 Core Support Structure ............................................................................................... 17

3.3.5 Reactor Core and Fuel Assembly ............................................................................... 18

3.3.6 Above Core Structure .................................................................................................. 21

3.3.7 Primary Heat Exchangers ........................................................................................... 22

3.3.8 Primary Pumps ............................................................................................................ 22

3.3.9 In-Vessel Fuel Handling System (IVFHS) ................................................................... 22

3.3.10 Cooling Systems ......................................................................................................... 22

3.4 SPALLATION TARGET ASSEMBLY .......................................................................................... 23

3.4.1 Functional AND OTHER requirements ........................................................................ 24

3.4.2 Beam Window ............................................................................................................. 26

3.4.3 Beam Tube .................................................................................................................. 30

3.4.4 Spallation Assembly Hexagonal Wrapper ................................................................... 30

3.4.5 Spallation Target Assembly Plug ................................................................................ 30

3.4.6 Velocity Profile Device ................................................................................................. 31


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3.4.7 Pressure Drop Device ................................................................................................. 31

3.4.8.3 Beam trips ...................................................................................................................... 32

3.4.8.4 Beam misalignment ........................................................................................................ 32

3.4.8.5 Beam tube failure ........................................................................................................... 32

3.4.9 Mechanical design ............................................................................................................. 33

4 SEISMIC ISOLATION SOLUTIONS FOR REACTOR/TARGET COUPLING ............. 34

4.1 SEISMIC ISOLATION OF REACTOR BUILDING .......................................................................... 36

4.2 SEISMIC ISOLATION OF REACTOR VESSEL ONLY .................................................................... 37

4.3 SEISMIC ISOLATION OF REACTOR PEDESTAL ONLY................................................................ 38

5 PHASE 1: SEISMIC INPUT ....................................................................................... 44

5.1 SOIL TYPE ............................................................................................................................ 44

5.2 SEISMIC ISOLATION ............................................................................................................... 45

5.3 SEISMIC LEVEL ..................................................................................................................... 46

5.4 INPUT TIME-HISTORIES ......................................................................................................... 46

6 PHASE 2: GLOBAL MODEL TRANSIENT ANALYSIS ............................................ 53

6.1 GLOBAL FE MODEL GEOMETRY ............................................................................................ 53

6.2 DESCRIPTION OF THE GLOBAL FINITE ELEMENT MODEL ........................................................ 53

6.2.1 Geometry and components ......................................................................................... 53

6.2.2 Element types .............................................................................................................. 56

6.3 MODAL ANALYSIS ................................................................................................................. 60

6.4 BOUNDARY CONDITIONS AND LOADS .................................................................................... 65

6.5 TRANSIENT ANALYSIS RESULTS ............................................................................................ 68

6.5.1 Output Nodes .............................................................................................................. 68

6.5.2 Results ........................................................................................................................ 68


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7 PHASE 3: LOCAL MODELTRANSIENT ANALYSIS ................................................ 70

7.1 INTRODUCTION ..................................................................................................................... 70

7.2 DESCRIPTION OF FE MODEL ................................................................................................. 72

7.2.1 Geometry ..................................................................................................................... 72

7.2.2 Material properties ....................................................................................................... 75

7.2.3 Element Type .............................................................................................................. 76

7.2.4 Boundary Conditions ................................................................................................... 77

7.2.5 Loads ........................................................................................................................... 78

7.3 INITIAL CONFIGURATION ........................................................................................................ 78

7.4 FINAL CONFIGURATION ......................................................................................................... 79

7.5 RESULTS .............................................................................................................................. 81

7.5.1 Initial configuration – No fixing points .......................................................................... 81

7.5.2 Final configuration – Five fixing points ........................................................................ 82

7.6 STRESS ANALYSIS ................................................................................................................ 86

8 DESIGN SOLUTION WITH SEISMIC ISOLATION FOR PROTON BEAM TUBE AND REACTOR COUPLING ................................................................................................... 104

9 CONCLUSIONS ........................................................................................................ 105

10 APPENDIX A ............................................................................................................ 106


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FIGURES

Figure 3.1: Layout of Proton Beam Line from LINAC to Reactor............................................. 11

Figure 3.2: Vertical Section in Reactor Building (L90m x W49m x H64.8m, -26.5m

underground, 38.3m above ground) .................................................................................. 11

Figure 3.3: Section View of Reactor Assembly (Rev. 1.2) ....................................................... 13

Figure 3.4 Core Support Structure (Core barrel and Core support plate) ................................ 18

Figure 3.5 Core and Fuel Assemblies ..................................................................................... 19

Figure 3.6 Fuel Assemblies ..................................................................................................... 20

Figure 3.7 Above Core Structure ............................................................................................. 22

Figure 3.8 Section view of Spallation Target Assembly, Fuel Assemblies and Core Support

Plate .................................................................................................................................. 27

Figure 3.9 General View of Spallation Target Assembly ......................................................... 29

Figure 3.10 Details of hexagonal wrapper, .............................................................................. 29

Figure 4.1 fixed Base ADS Reactor Building ........................................................................... 40

Figure 4.2 Seismic Isolation for Whole ADS Reactor Building ................................................ 40

Figure 4.3 Seismic Isolation for Reactor Vessel Only with Fixed Base Reactor Building ........ 41

Figure 4.4 Seismic Isolation for Reactor Pedestal Only with Fixed Base Reactor Building ..... 42

Figure 4.5 Expansion Joints for Beam Line for Different SI Solutions, RB and RA Only

Isolation for ADS (BOA's design ........................................................................................ 43

Figure 5.1: Reactor Building analysis FE model...................................................................... 47

Figure 5.2: Cases analyzed .................................................................................................... 48

Figure 5.3: Nodes for calculation of results ............................................................................. 48

Figure 5.4: Nodes for calculation of results on Reactor Vessel Support ................................. 49


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Figure 5.5: Reactor Vessel Support’s nodes displacements – x direction ............................... 50

Figure 5.6: Cases to analyze in MYRRHA analysis ................................................................ 52

Figure 6.8: Reactor Vessel FE Model – 3D view ..................................................................... 54

Figure 6.9: Reactor Vessel components ................................................................................. 56

Figure 6.10: Element type – BEAM181 ................................................................................... 57

Figure 6.11: Element type – SHELL181 .................................................................................. 58

Figure 6.12: Element type – FLUID80 ..................................................................................... 59

Figure 6.13: Element type – MASS21 ..................................................................................... 61

Figure 6.14: Modal analysis CTRL Nodes ............................................................................... 63

Figure 6.15: Modal analysis CTRL Nodes ............................................................................... 65

Figure 6.16: DOF nodes .......................................................................................................... 66

Figure 6.17: Input Accelerations ax, ay, az – CASES: 1, 2 – Time step: 0-20 [s] .................... 67

Figure 6.18: Input Accelerations ax, ay, az – CASES: 6, 7 – Time step: 0-20 [s] .................... 67

Figure 6.19: Control Nodes (Global Model Output) ................................................................. 68

Figure 6.20: IP 23763 (Core) – ax,ay,az [m/s2] ....................................................................... 69

Figure 6.21: IP 21376 (Steel Cover) – ax,ay,az [m/s2] ............................................................ 69

Figure 7.1: Local model – Initial and Final configurations ....................................................... 71

Figure 7.2: Local model overview ............................................................................................ 73

Figure 7.3: Local Model components ...................................................................................... 73

Figure 7.4: Local Model mesh detail / Input nodes (MASS21) and CERIG ............................. 74

Figure 7.5: Components connections (3D solid elements) ...................................................... 75

Figure 7.6: DOF Nodes ........................................................................................................... 78


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Figure 7.7: Local model – Initial Configuration ........................................................................ 79

Figure 7.8: Fixing Points ......................................................................................................... 80

Figure 7.9: 1st Local model – P.B./H.W. relative displacements (X-dir) ................................... 81

Figure 7.10: 1st Local model – P.B./H.W. relative displacements (Y-dir) ................................. 81

Figure 7.11: 2nd Local Model – Fixing Points; CTRL nodes ..................................................... 82


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1 INTRODUCTION

This document is the deliverable D3.2 corresponding to the SILER project (Seismic Risk events-Initiated Lead-cooled Reactors) belonging to the Seventh Framework Programme of the European Union. The SILER project aims to study the risk associated with events triggered by an earthquake with special attention to beyond the design envelope events on Generation IV Heavy Liquid Metal Cooled reactors, addressing the subsequent mitigation measures and focusing on seismic isolation strategies and devices.

Siler Project is divided into the following Work Packages (WP) as defined in [Ref. 1]

WP1: Consortium Management

WP2: Systems Modelling

WP3: Risk analysis for critical components

WP4: Development and characterization of isolators

WP5: Additional components design

WP6: Recommendations for standardization

WP7: Dissemination of information

WP8: Scientific Coordination

The current document describes conditions, methods and development of the numerical analysis performed on the ADR reactor and its internal components.

The scope of the work is to studies the complex dynamic phenomena related to the accelerator/reactor coupling under severe seismic condition.

More in detailthe following aspect will be analyzed:

- Relative displacement between Proton Beam and hexagonal wrapper;

- Stress and failure of the coupling proton beam/hexagonal wrapper.

Seismic condition are reported in the doc.[Ref. 2] – Appendix F.

The analysis is developed through the following steps:

PHASE 1: Definition of seismic input loads

Seismic input choice among the different seismic configurations of Reactor building studied in WP2

Definition of cases to analyze


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PHASE 2: Global FEM of ADS reactor and its internal

Linear dynamic analysis for specific case of soil, seismic level and foundation layout, defined in WP2 activities;

For each case, results in term of displacements and accelerations have been evaluated in correspondence of some interface points (IP) with Proton Beam, core and hexagonal wrapper.

PHASE 3: Local FEM of Proton Beam assembly

Linear dynamic analysis considering as input load IP result of the global model

Design the location of spacers between hexagonal wrapper and Proton Beam arising from the analysis results with different spacers configurations up to reach the design value of relative displacement equal to 2mm among the two components.

Stress analysis of the main internal components


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2 REFERENCIES

[Ref. 1] Seventh Framework Programme. Theme [Fission-2011-2.3.1] [R&D activities in support of the implementation of the Strategic Research Agenda of SNE-FP] Annex I – “Description of Work”. GA no: 295485, Version Date: 2011-07-19

[Ref. 2] ED1327061383_092_260_F_C_00102_Ed_01.pdf –WP2; Deliverable D2.1, Part II: Description of Systems: ADS

[Ref. 3] UTSISM – P10A – 001 – WP2; Deliverable D2.2 – Part I: Description of the design of seismic isolator for ELSY Reactor

[Ref. 4] prEN 1998-1 2005, Doc CEN/TC250/SC8/N335: Eurocode 8: Design of structures for earthquake resistance Part 1: General rules, seismic actions and rules for buildings

[Ref. 5] TH-uva_key.pdf

[Ref. 6]Seismic Isolation of Reactor Assembly for a Fixed Base ADS Reactor Building, Bong Yoo and Didier De Bruyn, SILER Workshop at Rome, 2013-06-19


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3 DESCRIPTION OF PLANT AND SPALLATION TARGET ASSEMBLY

11

Figure 3.1:Vertical Section in Reactor Building(L90m x W49m xH64.8m, -26.5m underground, 38.3m

above ground)


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3.1 REACTOR ASSEMBLY

The Reactor Assembly as shown in Fig 3.3 and Table 1 below consists of

- reactor vessel and support

- reactor cover

- reactor diaphragm

- core support structure (core barrel and core support plate)

- above core structure

- fuel assemblies

- control rods and shutdown rods

- spallation target assembly

- primary heat exchanger

- primary pump

- in-vessel fuel handling machine(IVFHM) and so on.


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Figure 3.2:Section View of Reactor Assembly (Rev. 1.2)


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Table 1. Summary of ADS Reactor Assembly general design characteristics

General Design Parameters MYRRHA-FASTEF rev 1.2 Reactor vessel

Outer diameter About 8140mm Length About 11200mm

Material AISI 316L Reactor cover

Cover thickness About 2m Material AISI 316L and concrete

Reactor diaphragm Function Separation of cold and hot

plenum, accommodation of the in-vessel fuel storage

Material AISI 316L In-vessel fuel storage capacity 2x152 positions

Core Support Structure Core Barrel Inner Diameter 1450mm

Core barrel material AISI 316L Core support plate material T91

Above Core Structure Number of multi-purpose channels 37

Above core structure material AISI 316L Primary heat exchanger

Type Tube-and-shell Material AISI 316L

Number of exchangers 4 Rated Power 27.5MW Primary fluid Liquid Lead-Bismuth

Maximum Primary fluid inlet temperature 350 C deg Maximum Primary fluid outlet temperature 270 C deg

Secondary coolant fluid Saturated water/steam Secondary coolant fluid pressure 16 bar

Secondary coolant fluid temperature 200 C deg Tertiary coolant fluid Air

Primary Pump Type Mixed type dynamic pump Material AISI 316L Number of pumps 2 Mass flow 4750kg/s Discharge head 2.5m – 3.5m

In-vessel fuel handling machine

Type SCARA (Selective Compliant Assembly Robot Arm)

Material AISI 316L Number of in-vessel fuel handling machines 2


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The Table 2 summarizes the weight of the Reactor Assembly and its reactor internals:

Table 2. Weights of RV and RV internals

ID Unit mass

(kg) Units (units

or m³) Mass/Weight

(kg) Reactor Vessel (RV) 320000 1 320000 Reactor Vessel Support 140000 1 140000 Diaphragm (DIA) 185000 1 185000 Reactor Cover (RC) 338000 1 338000 Above Core Structure (ACS)* 12700 1 12700 Core support structure(Core Barrel+CoreSupportPlate)* 8570 1 8570 Primary Heat Exchanger (PHX) 7075 4 28300 Primary Pump (PP)* 29000 2 58000 Fuel Assembly (FA) 57.56 190 10936.4 Reflector Assembly (RA)* 50 60 3000 Dummy Assembly (DA)* 50 50 2500 Control rod (CR) 330 6 1980 Safety rod (SR) 380 3 1140 IVFHM* 83762 2 167524 Spallation Target Assembly (STA)** 100 1 100 Fuel transfer device** 350 2 700 Wet‐sipping device** 350 2 700 Si‐doping device* 20808 2 41616 Mo‐IPS* 338 6 2028 LBE inventory* 4350000 1 4350000 TOTAL WEIGHT

NA NA 5672794.4


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3.1.1 REACTOR VESSEL AND SUPPORT

The reactor vessel is approximately cylindrical shaped, closed at the bottom and open at the top, with a support ring to be set on the concrete pedestal. It is made of AISI 316 L and weighs about 320 ton. It has total height of about 11.2m, and an outer diameter of 8.14m and a thickness of 80mm.

In the interior of the vessel we can find the cylindrical shaped diaphragm that defines two surfaces, one, external, the other, internal. The external one is devoted to the cold LBE surrounding the diaphragm. The cold LBE occupies a 500mm high volume.

The external surface occupies 2500mm below the external one and is occupied by the Hot LBE. The Hot LBE flows through the diaphragm, whereas the cold LBE flows

outside, surrounding the diaphragm.

The vessel is supported at its top by means of two rings connected and stiffened by

24 gussets. The lower ring has an internal diameter of 11.15m and an outer diameter of 13.65m, and thickness of 150mm. The upper ring has an internal diameter of 10.8m and an outer diameter of 13.10m, and thickness of 150mm. The gussets have a small width of 975mm and a large one of 1150mm with a thickness of 200mm. The entire vessel support is made of AISI 316L and has a total weight of about 140 ton.

3.1.2 REACTOR COVER

The reactor cover is a short cylinder of steel filled in with reinforced concrete, with different holes

to house various components. This short cylinder is 2m high, has an outer diameter of 9.5m and

weighs a total of 338 ton. The cover is penetrated by the following components:

- IVFHMs (2 units) - PHXs (4 units) - Pumps (2 units) - Si-doping channels (2 units) - Recovery channels (2 units) - Fuel transfer channels (2 units) - LBE-conditioning inlet (2 units) - LBE-conditioning outlet (2 units) - Cover gas conditioning system inlet (2 units) - Cover gas conditioning system outlet (2 units)


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- Wet-sipping device (2 units)

3.1.3 DIAPHRAGM

The diaphragm is an open steel cylinder divided into three volumes by two steel plates perpendicularly intersecting the axis. Parallel to the axis and penetrating the plates there are a number of cylinders, each corresponding with the penetrations of the Reactor Cover. The diaphragm serves as a rack for the various in-vessel components and plays the role of a baffle for the coolant. To that end, it has some vented baffling plates hanging from the lower plate. The diaphragm has a total height of 7.35m and an outer diameter of 7.78m. The steel wall is 40mm thick, whereas the upper plate is 80mm thick and the lower one 40mm. It is made of AISI 316L and the total weight is 185 ton.

3.1.4 CORE SUPPORT STRUCTURE

The Core Support Structure is composed of two elements, the core barrel and the core support

plate as shown in Fig 3.4:

Core Barrel. The core barrel is basically an AISI 316L steel cylinder 20mm thick and about 8.85m high, with an inner diameter of about 1450mm. It is vented with multiple holes at mid height and houses the core support plate at the 1st lower quarter of its height. It is supported at three locations: on the reactor cover at the upper part and by the diaphragm at the bottom and at the 1stlower quarter of its height.

Core Support Plate. This is a circular plate of T91 material with an outer diameter of 1450mm and a thickness of 200mm, vented by hexagonal and circular holes. A total weight of 8570 kg is estimated for the whole Core Support Structure.


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Figure 3.3Core Support Structure (Core barrel and Core support plate)

3.1.5 REACTOR CORE AND FUEL ASSEMBLY

The reactor core has 151 sites for fuel assemblies, CR and SR, IPS and dummies as shown in

Figure 3.4.


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Figure 3.4Core and Fuel Assemblies

(151 positions, Diameter: 1450mm, 37 multifunctional plugs)

Plugged-in and hanging from the core support structure we find the fuel assemblies.

Each fuel assembly as shown in Fig 3.6 is a hexagonal prism. Each prism is 2m high with the fuel

bundle all along its height, anchored to the bottom and to the plug on the top.

The fuel bundle is 1.4m long and each fuel element has a 15-15Ti cladding and is wire wrapped.

The fuel assembly is a hexagon 104mm width between sides. The total weight of the Fuel

Assemblies is assumed to be 10936.4 kg, which corresponds to 190 elements of 57.56 kg each.


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Figure 3.5Fuel Assemblies

(Fuel, Cladding in 15-15 Ti and hexagonal Wire wrapper)


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3.1.6 ABOVE CORE STRUCTURE

The Above Core Structure as shown in Fig 3.7 is an AISI 316L steel cylinder on top ofthe Core

Barrel and located partially within the Reactor Cover, housing 37 Multi-Functional circular

channels, (buoyancy driven control rods, gravity driven safety rods, spallation target…). It has a

total height of 7m and an outer diameter of1500mm. The above core structure is estimated to

weight 12700 kg

Figure 3.6Above Core Structure (Height: about 7m, Outer diameter: about 1500mm)


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3.1.7 PRIMARY HEAT EXCHANGERS

Each primary heat exchanger is basically an AISI 316L double walled steel tube of about 8m long,

anchored to the Reactor Cover on top and to the lower plates of the diaphragm. On top we find

the water inlet along the axis and, a bit lower, the water outlet. The inlet is a tube along the axis

surrounded by a 700 tubes bundle, 16mm of diameter each for the hot water to return towards the

outlet.

The inlet and outlet of the LBE are located immediately above the diaphragm upper plate, and

immediately above the diaphragm lower plate. The internal pressure is 16bar and the Power

27.5MW. Each Primary Heat Exchanger is estimated to weight 7075 kg.

3.1.8 PRIMARY PUMPS

Each primary pump is designed for a mass flow of 4750 kg/s and for a pressure between 2.5 – 3.5

bar working at a rotating speed of 490 rpm. It is basically an AISI 316L steel cylinder 9m high and

1100mm diameter. It is supported on top of the Reactor Cover and in the horizontal plates of the

diaphragm. The estimated weight of each primary pump is 29000 kg.

3.1.9 IN-VESSEL FUEL HANDLING SYSTEM (IVFHS)

The IVFHS is composed of the two In-Vessel Fuel Handling Machines, which mainly consist of the

machinery to move and support the SCARA (Selective Compliant Assembly Robot Arm) to allow

blind manipulations of the fuel assemblies and their surroundings. Each machine is housed in an

8m highand 2m diameter AISI 316L steel cylinder within one of the diaphragm cylinders. Total

weight can be estimated in 83762 kg per unit.

3.1.10 COOLING SYSTEMS

There are four loops, each with three cooling systems as described below.


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- Primary System: The LBE is cooled by water in the four in-vessel PHXs (27.5 MW each) - Secondary System: The saturated water from the PHXs is converted into steam by a Steam

Separator Drum with make up water from a supply tank. - Tertiary System. The steam is cooled by 55 MW air condensers on the Reactor Building

roof so that the heat is dissipated to the atmosphere.

The reactor has passive capabilities (natural convection in primary, secondary andtertiary

systems) so that the Ultimate Decay Heat Removal (UDHR) is through thereactor vessel cooling

system. Each cooling loop is independent and redundant, with a 50% to 100% capacity.

3.2 SPALLATION TARGET ASSEMBLY

The spallation target is able to produce 1017neutrons/s at the reactor mid-plane to feed sub

critical core. As is well known, the reactor is hybrid also due to its ability to move from critical to

sub critical depending on the spallation target off/on status. The target fits into the central hole in

the core plate along the total core depth and must be able to remove heat from inside (2.1 MW

heat from the proton beam, of 600 MeV and 3.5 mA). Its working temperature is between 450-

500C deg, and it should resist at least 3 months at full power (1 cycle). Estimated weight is 100

kg.

The Beam Tube is composed of the following elements:

Protecting hexagonal wrapper: this is an external hexagonal prism with anexternal width of

101.55mm enclosing the target assembly plug and the beam window

Beam window: this is a tube within the hexagonal wrapper separated by a 2mm gap from

it. Its outer diameter is 87.05mm. The 2mm gap determines themovement tolerance

between the window tube and the wrapper, since that gapis related to the heat removal on

the target that must be granted.

Target assembly plug: located at the bottom of the hexagonal wrapper. Itconsists of a

hexagonal rack supporting on top a cylinder with the velocity profile and pressure drop

devices for beam control, and the various target wafers to be irradiated at the bottom.


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3.2.1 FUNCTIONAL AND OTHER REQUIREMENTS

The functional requirements of the spallation target assembly are:

Lead the proton beam to the centre of the core; Evacuation of the spallation heat deposit; Guarantee the barrier between the LBE and the reactor hall.

The spallation target assembly brings the proton beam via the beam tube into the central core

region and creates the optimal conditions for the spallation reactions. The assembly occupies the

central position of the subcritical core.

The target assembly is conceived as an in pile section (IPS). It is easily removable and

replaceable. Until more experience is gathered concerning the irradiation damage of the window

material, the device shall be replaced every cycle (90 FPD1).

The 600 MeV protons pass through the beam window into the LBE, where they interact with the

heavy atoms creating spallation neutrons. This interaction deposits an important quantity of heat

into the window and the LBE. The assembly is designed to remove the spallation energy by

means of the core coolant and to withstand the irradiation doses by protons and neutrons.

The main parts of the spallation target assembly are the beam tube, the beam window, the

protecting hexagonal wrapper, the target assembly plug, the velocity profile device and the

pressure drop device.

Design requirements

For the design of the spallation target assembly, different operational states for the

subcritical working conditions have been considered. The most limiting part of the target

assembly is the beam window. The window has to resist to the harsh conditions. But also

1FPD = Full Power Days


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the positioning of the beam onto the axis of the window imposes stringent structural

requirements to the target assembly.

Thermal requirements

Based on the current knowledge on the material properties of T91, the preferable

temperature range of the beam window is between 450 °C and 550 °C (compromise

between corrosion and hydrogen- and liquid metal embrittlement). By the limitation of the

temperature ranges for the 15-15 Ti and 316L induced by the oxygen concentration control

(200 °C to 470 °C) however, the normal operation design working range of the window is

shifted somewhat and set to 410-470 °C.

As both the beam tube and the target assembly wrapper are fixed to the reactor cover plug,

they penetrate the LBE free surface. This means that these structures are subject to the

thermal loadings induced by the free surface fluctuations during normal and off normal

situations.

Material requirements

The material damage induced by the protons and the neutrons, the corrosion by the LBE

and the temperature gradients are taken into account. By limiting the residence time of the

target assembly into the reactor to 1 cycle, the material damage and corrosion issues are

controlled.

Hydraulic requirements

The design flow rate of the spallation zone is determined by the maximum heat deposition

(1.29 MW) of the spallation reaction and the allowed temperature difference over the

assembly. The required mass flow rate is 49 kg/s.

The general requirement for the design of all components in contact with LBE to avoid

erosion by limiting the maximum bulk velocities to 2 m/s is somewhat released in the design


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of the target zone. Very local higher velocities are tolerated (up to 2.4 m/s). This is justified

by the limited residence time of the target assembly.

The spallation target assembly forms a parallel channel to the standard fuel assemblies.

This determines the pressure difference over the target assembly (2.5 bar). As the mass

flow rate is already defined, this means the flow resistance of the target assembly has to be

designed accordingly. The pressure drop device into the lower part of the target assembly

accounts for this.

Structural requirements

The spallation target assembly is a very long and slender structure. A good alignment of the

assembly axis with the proton beam axis is required. The mechanical loads on the spallation

target are mainly due to the buoyancy and the hydraulic forces. The upward forces due to

the buoyancy are large because of the vacuum inside the beam tube. The hydraulic forces

(external LBE static pressure) effect the thin walled tube. Thermal loadings are important at

the window, but also on the beam tube and the wrapper. With a perfect alignment of the

beam tube with the beam axis, the thermal loads are axisymmetric, but a small shift in the

alignment causes non symmetric thermal loads, inducing bending of the beam tube. The

accuracy of the

horizontal beam positioning is in the order of 2 mm at the level of the window. The final

accuracy of the alignment should be in the same order. Therefore, several support levels to

the target assembly wrapper and the beam tube are foreseen.

3.2.2 BEAM WINDOW

The beam window is a hemispherical shell, which forms the separation between the vacuum for

the proton beam and the coolant of the reactor. The coolant acts below the window also as

spallation target. The position of the window is determined to centre the spallation zone close to

the active core mid plane. The penetration depth of the 600 MeV protons is about 300 mm. Most


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of the spallation neutrons however are formed just below the window. According to neutronic

calculations, the optimal position of the window is situated at about 50 mm above the active core

midplane.

The outer diameter of the shell is 87.05 mm and the inner diameter is 84.30 mm, which results in

a shell thickness of 1.375 mm. The material for the window is T91.

Figure 3.7Section view of Spallation Target Assembly, Fuel Assemblies and Core Support Plate


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Figure 3.8 General View of Spallation Target Assembly (beam tube, beam window, protecting

hexagonal wrapper, target assembly plug, velocity profile device, pressure drop device)


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Figure 3.9Details of hexagonal wrapper,velocity profile device, and pressure drop device


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3.2.3 BEAM TUBE

The beam tube extends the beam line from the level of the reactor cover plug to the beam

window. It guarantees the vacuum for the proton beam. The cylindrical tube has the same

thickness as the window for the lower part. Above the core support plate the thickness is

increased to withstand the buoyancy forces to avoid buckling.

3.2.4 SPALLATION ASSEMBLY HEXAGONAL WRAPPER

The spallation assembly wrapper is a hexagonal tube placed around the beam tube. It is made of

T91. The function of the wrapper is to protect the beam tube during manipulation, to stiffen the

beam tube structure and to guide the flow in the spallation target zone. The wrapper is fixed to the

target assembly plug at the level of the reactor cover and ends at the core inlet plane. Into the

core it has the same dimensions as the standard wrapper of the fuel assemblies. The wrapper

passes through the special central hexagonal hole in the core support plate. At the height of the

core inlet a pressure drop device is placed into the wrapper to limit the flow rate in the target

assembly. Between the pressure drop device and the spallation zone, the velocity profile device is

placed.

Above the core support plate, the wrapper is foreseen of holes to allow the target cooling flow to

mix up with the core cooling flow in the upper plenum of the reactor vessel. The spallation

assembly wrapper is at multiple levels guided by the above core structures to the core support

plate. At the same levels it also supports the beam tube by means of guiding pads to limit the

bending of the beam tube.

3.2.5 SPALLATION TARGET ASSEMBLY PLUG

The spallation target assembly plug mounts the spallation target assembly to the reactor cover

plug at the central position. The target assembly plug is similar to the standard IPS plug, but with

a larger diameter to allow the passage of the spallation target assembly wrapper through the

reactor cover plug.


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3.2.6 VELOCITY PROFILE DEVICE

The velocity profile device forms the optimal velocity profile to cool the spallation zone, the beam

window, the beam tube and the wrapper. It consists of 2 concentric tubes placed just below the

spallation zone and fixed to the spallation assembly wrapper. These concentric tubes create 3

parallel flow paths. The ratio of the flow rates into the parallel paths are governed by the plate with

calibrated holes which fixes the concentric tubes to the wrapper.

3.2.7 PRESSURE DROP DEVICE

During normal operation, the spallation target assembly experiences the same pressure drop as

the fuel assemblies in the core. As the pressure drop of the beam tube into the wrapper is limited

an additional device must be placed to limit the flow through the target assembly, to avoid high

velocities around the beam tube and overcooling of the window. The pressure drop device sets

the mass flow rate through the spallation target assembly without causing too high local velocities.

3.4.8 OPERATIONAL CONDITIONS

3.4.8.1 Normal operation: at constant reactor power level

During normal operation the spallation reaction provides the neutrons to maintain the fission into

the core. The burn up of the fuel increases during the cycle, which has to be compensated. This

compensation can be made in two ways. The first way subsists in adding more neutrons by

increasing the current of the proton beam, the second reducing the anti-reactivity by means of

extraction of the control rods.

At the moment preference is given to the second option: compensation via the available control

rod system but both options are still studied. The control rod compensation allows to keep the

beam current constant during the cycle. The compensation by means of the control rods has no

direct impact on the cooling of the window which results in a constant window temperature

situation.


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However, as the core power is determined for each cycle depending on the loading conditions

(IPS, etc.) the beam current levels can vary between different cycles.

For the thermal analyses beam current values considered are 2.8 mA and 3.5 mA.

3.4.8.2 Off normal operation

The two off normal operation states that have been considered are the unattended beam trip and

the misalignment of the beam axis compared to the window axis.

3.4.8.3 BEAM TRIPS

Unattended beam trips are very likely to occur. Operational experience of high power, high

energetic linear accelerators show that beam trips are unavoidable. The effect of a beam trip is

the drop of power of the full core from nominal power to decay heat power. Within the spallation

zone the heat deposition drops from 1.3 MW to near zero almost instantaneously.

3.4.8.4 BEAM MISALIGNMENT

The positioning of the beam on the window is very important. The distance from the last bending

magnet to the beam window is in the order of 20 m. Due to the large distance the smallest

positioning error results in a large deviation at the window. The important buoyancy forces on the

beam tube also result in bending of the tube and by this in horizontal displacements. A

misalignment of the beam with respect to the window axis of 2 mm has been studied. The relative

position will be monitored by a wire sensor near the beam window.

3.4.8.5 BEAM TUBE FAILURE

For a beam tube failure inside the reactor vessel 2 positions can be distinguished, below the free

liquid surface and above. A failure into the LBE would cause the fill up of the beam tube with LBE.

The maximum LBE level reached in the beam tube depends on the size of the hole, but after the


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transient the LBE level will be comparable to the LBE level in the upper plenum. As the vapour

pressure of LBE is low the vacuum will only be affected in a limited way. Fast closure valves at

the containment boundary protect the beam line to be contaminated outside the containment

building. A failure of the beam tube into the cover gas would cause cover gas to enter the beam

line. The same fast closure valves can avoid contamination of the beam line outside of the

containment.

3.4.9 MECHANICAL DESIGN

Similar to the thermal design, the verification of the mechanical design has been focussed on the

window integrity. The following evaluations to be performed are the dimensioning of the beam

tube and the target assembly wrapper above the core support plate and their supports within the

above core structures. Specific attention points are the buckling of the column as a whole,

buckling of the tube due to external pressure forces and the accuracy of the positioning of the

window.

Produces about 1017 neutrons/s at the reactor mid-plane to feed subcritical core @ keff=0.95

Fits into a central hole in core o Compact target o Remove produced heat

Accepts megawatt proton beam o 600 MeV, 3.5 mA ~2.1 MW heat o Cooling of window is feasible

Material challenges o Preferential working temperature: 450 – 500°C o Service life of at least 3 full power months (1 cycle) is achievable


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4 SEISMIC ISOLATION SOLUTIONS FOR REACTOR/TARGET COUPLING

There has been several concepts of application of seismic base isolation for nuclear

facilities listed in the Table 3:

Table 3 Seismic Isolation Methods of Nuclear Facilities

Note; Under construction(*), under design (in red)

The application of seismic base isolation(SI) have been constructed and developed for nuclear

facilities since 1980s, for example, for the standard design of LWR at larger seismicity sites, and

for the design of Sodium Fast Reactors at high temperature with low operation pressure, and for

reduction of seismic loads to enhance seismic safety margin for research reactor and ITER at

higher seismicity zone, and for heavy liquid metal Fast Reactors.

The characteristics of SI applications can be summarized as follows.


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The advantages for the SI application are

- Reduction of acceleration load on RB and components inside RB Constant horizontal FRS of whole RB and internal SSC Less inertial force and stress Larger seismic safety margin

- No horizontal relative displacements among components inside RB Simple design of pipings CR/SR safe shutdown during/after DBE Less core compaction during/after DBE

- Standardization of SSC for NPP Independent of site conditions(except very long period motion) Only dependent on design of isolation systems

- Easier restart of isolated NPP even exceeding DBE

However there are also some disadvantages to overcome;

- Accommodate the interconnection systems between isolated RB and nonisolated Buildings; Main Steam Lines and connecting pipings Electrical cables Beam line in ADS MYRRHA

- Need additional foundation slab and fail safe system LRB support pedestal and upper mat for SI maintenance Defender(shock absorber) for impact due to excessive displacement

- Need free seismic gap around RB Joint cover of seismic gap Retaining wall

In the SILER project we consider only horizontal seismic isolation for the LFR and ADS reactors.

Different SI strategies from conventional fixed base seismic design have been considered for

seismically isolating the most sensitive parts of the ADS plant. Seismic design approaches for

ADS Reactor Building can be schemetically designed as shown in the Figs 4.1- 4.4. The locations

of interface components to accommodate relative displacements due to SI application such as

flexible joints, seismic gap, joint cover, fail safe system should be varied depending upon the SI

strategies. The Fig 4.5 typically depicts different installation locations of expansion joints for two

SI strategies. The SI approaches are described below.


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4.1 SEISMIC ISOLATION OF REACTOR BUILDING

This is probably the most expensive solution as far as the pit size and numbers of isolation

devices are concerned. However, it would allow the anchor points of the beam line to move jointly

with the building. One reason supporting this solution is the difficulty of dividing the building into

structurally recognizable and constant along the height building parts if we keep the current layout

of the reactor building, so the easiest way would be to isolate it as a whole.

Another advantage of this solution is that it permits access to the isolation devices in order to

maintain and replace them if needed. Moreover, this solution is the safest in terms of radiation

shielding, as the isolation devices are out of the range of radiation.

This solution is proposed as the main one understanding that some interfaces will still have to be

solved, like the joints between the reactor building and the annex buildings, or the beam line

tunnel.


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4.2 SEISMIC ISOLATION OF REACTOR VESSEL ONLY

Based on preliminary results of WP5.1 (Study of ADS Interface Components)[Ref. 6] the seismic

responses at Reactor Vessel Support between RV only SI and whole RB SI are in good

agreement in relative displacement between non-isolated and isolated structures and ZPA.

The main advantage of isolating only the reactor vessel is that it minimizes the number of

bearings and eliminates the need for the reactor building pit.

However, it raises serious problems regarding space allocation in the most sensitive and

congested area of the plant which is the surroundings of the Reactor Vessel and connecting

pipings. The most sensitive pipe lines of the plant would have seismic expansion joints and the

isolation bearing devices would have a tested and acceptable rheological behaviour against

temperature and radiation.

Another disadvantage of this strategy is that the devices are placed inside the reactor

containment hall, where the levels of radiation are significant, thus making it problematic to

inspect and maintain the isolators. In any case, what prevents the Reactor Vessel being isolated

alone from the rest of the plant is the interface with the beam line, which is embedded in the

reactor and would have to be highly flexible, which is not the case. It is important to note that the

last stretch of the beam line has at least two main anchor points, the first on top of the reactor

containment hall and the second inside the reactor at the Reactor Cover.

Moreover the large seismic gap around the Reactor Vessel in RVonly SI strategy would not meet

the safety requirements of the emergency reactor cooling. It means that in case of the Reactor

Vessel failure the reactor core cannot be coveredwith the LBE coolant to cool the Reactor Vessel

with LBE coolant natural convection.

For the reasons set out above, this solution is not advisable.


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4.3 SEISMIC ISOLATION OF REACTOR PEDESTAL ONLY

Similar to SI of RV only, the seismic responses at Reactor Vessel Support between SI of Reactor

pedestal only and SI of whole RB would be in the similar order of magnitude in ZPA and relative

displacement between non-isolated and isolated structures due to rigid body motion of seismically

isolated structures.

Seismic Isolation of the reactor pedestal solves the issues related to safety in cooling core without

increasing seismic gap at Reactor pit since seismic gap moves not in Reactor pit but in between

isolated contaiment boundary and nonisolated wall boundary, and the rheological behaviour of the

rubber bearings under high temperature and radiation. And the number of bearings would still be

much less than that of whole RB SI.

However the fundamental problems would remain regarding on differential movement of the beam

line and other safety related interconnection pipings cross over the seismically isolated reactor

hall containment boundary on reactor pedestal. The layout of the seismically isolated reactor hall

containment with remaining non isolated structures of the Reactor Building would be designed

very complex and enlarged. In addition the secondary and the tirtiary cooling systems and their

components classified as safety classes to be installed on nonisolated reactor building should be

seismically qualified by amplified seismic loads.

For the reasons set out above, this solution is not recommended.


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Figure 4.1 fixed Base ADS Reactor Building


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Figure 4.2Seismic Isolation for Whole ADS Reactor Building


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Figure 4.3Seismic Isolation for Reactor Vessel Only with Fixed Base Reactor Building


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Figure 4.4Seismic Isolation for Reactor Pedestal Only with Fixed Base Reactor Building


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Figure 4.5Expansion Joints for Beam Line for Different SI Solutions, RB and RA Only Isolation for

ADS (BOA's design


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5 PHASE 1: SEISMIC INPUT

Seismic loads to apply in the Global Model transient analysis (PHASE 2 of the work) have been chosen following the analysis of the activities developed by the WP2 partners.

In these activities the seismic behavior of MYRRHA Reactor building, under different seismic configurations, was studied. In particular the environmental variables taken into account concern:

- Soil type

- Seismic isolation device

- Seismic level

As a result of these studies, different load cases and different reactor’s interface points to analyze were chosen, as reported here in the following.

5.1 SOIL TYPE

Three soil types were considered for the analyses as described in the description of ADS System [Ref. 2]. Soil parameters are reported in Table 5.1 for the three considered soil types:

- Hard

- Soft

- Site (specific soil for MYRRHA’s analysis)


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Table 5.1 – Soil types – Parameters

5.2 SEISMIC ISOLATION

Seismic isolation of the whole reactor building was studied taking into account three different configurations:

- SOI

- HDRB

- LRB

the first solutiondoes not provide the presence ofisolatorsandconsidersthe building basefixed on the soil. It corresponds to a “non isolated” condition.

The other twosolutionsrequire the presence of two different types of isolators: a “High Damping Rubber Bearing” (HDRB), well-known and largely used for civil applications in buildings or a “Lead Rubber Bearing” (LRB), an elastomeric isolator with a lead core [Ref. 3].


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5.3 SEISMIC LEVEL

Time-histories are spectrum compatible ([Ref. 2]; cap.5) with two types of response spectrum depending on the soil type.

The first tern of accelerograms was selected to be spectrum compatible with the RG (Regularity Guide) 1.60 extended to the east coast. This type of spectra was used for hard soils.

The second one was selected to be compatible with the Eurocode 8 [Ref. 4] EC8 – type 1 – soil type E – elastic spectrum (type 1). This type of spectra was used for soft soils.

The maximum PGA considered was 0.3g in DBE conditions.

The considered seismic level are de following:

DBE (design base earthquake);

OBE (Operative base Earthquake) = 1/3 DBE;

BDBE (Beyond Design Base Earthquake)=3 x DBE.

The calculated artificial time history represents the DBE seismic level.

5.4 INPUT TIME-HISTORIES

Nonlinear time-history analyses were carried out on all the reactor building [Ref. 5] shown in the Figure 5.1.

The cases have been carried out from WP2 partner EMPRESARIOS AGRUPADOS INTERNACIONA L SA (EA).

Sixteen load cases resulting from the combinations of the three described variables (soil type, seismic isolation and seismic level) were analyzed, as shown in Figure 5.2.

In particular, taken into account the type of isolation bearings, we can see that:

- from CASE1 to CASE6 the structure is in non-isolated conditions;

- from CASE6 to CASE10 the base of the structure results isolated with HDRB bearings;

- from CASE11 to CASE 16 the base of the structure results isolated with LRB bearings;


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Figure 5.1: Reactor Building analysis FE model


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Figure 5.2: Cases analyzed

Results in terms of displacements and accelerations were calculated for several nodes in different zones of the model (see Figure 5.3).

Figure 5.3: Nodes for calculation of results


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For the analysis of the complex dynamic phenomena of the reactor vessel, the nodes illustrate in the Figure 5.4 have been chosen among all nodal calculated time histories.

Figure 5.4: Nodes for calculation of results on Reactor Vessel Support

Comparing the results of the selected nodes in term of displacement (see Figure 5.5) , all nodal response displacements are similar because the reactor cover can be considered as a rigid body.

For that reason only one representative node has been chosen for representing the seismic response of the vessel and the node n.913 has been selected as representative one.


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Figure 5.5: Reactor Vessel Support’s nodes displacements – x direction

Four time-histories were chosen to apply the results of analyses described above as input for the Reactor Vessel model.

With SI application, the seismic responses in FRS at the Reactor Vessel Support

are remarkbly reduced by 1/3 or even 1/7. It is forseen that the seismic

responses of the reactor assembly, reactor internals and spallation target

assembly with SI be much less than those with the fixed base Reactor Building

since natural frequencies of the these safety related components inside the

Reactor Asssembly could be in higher than 2 Hz, consequently the imposed

horizontal seismic loads on these components be as low as ZPA; for instance

for HDRB SI, ZPA = 0.3 g, but for the fixed base the imposed seismic load be

amplified as 2.0 g.

The CASE 1 and 2 are typical fixed base Reactor Buiding on site specific soil

condition subjected to DBE and BDBE, and CASE 6 and 7 are chosen as typical

HDRB SI of the Reactor Building on the site specific soil condition subjected to


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the same DBE and BDBE, respectively. The SI responses of soft soil condition

are similar to those of the site specific soil condition due to similar shear wave

velocity, and the SI responses of the hard soil are more reduced than those of

soft or site specific soil conditions. It is noted that the SI responses in vertical

direction in hard soil condition are much more amplified than those in soft soil

conditions. The SI responses of LRB cases show similar to those of HDRB

cases.

Among the sixteen cases analyzed, it was decided to consider the following time-histories belonging to the most representative cases:

- CASE 1:

bearings type: non isolated structure,

soil type: Myrrha site SSP,

seismic level: Myrrha site EDRS

- CASE 2:

bearings type: non isolated structure,


seismic level: Myrrha site BEDRS

- CASE 6:

bearings type: HDRB,


seismic level: Myrrha site EDRS

- CASE 7:

bearings type: HDRB,


seismic level: Myrrha site BEDRS


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Figure 5.6: Cases to analyze in MYRRHA analysis


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6 PHASE 2: GLOBAL MODEL TRANSIENT ANALYSIS

6.1 GLOBAL FE MODEL GEOMETRY

Reactor’s geometries, materials and other parameters for FEM development were taken from [Ref. 2] – Appendix E.

6.2 DESCRIPTION OF THE GLOBAL FINITE ELEMENT MODEL

6.2.1 GEOMETRY AND COMPONENTS

FE model was created using software Hypermesh v10.0. It represents the reactor vessel and its internal components (see reference drawings).

Next figure shows a 3D view of the entire model.


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Figure 6.1: Reactor Vessel FE Model – 3D view

The model contains 642627 nodes and 597553 elements.

In the following different components of the model are described.


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Figure 6.2: Reactor Vessel components

For Proton Beam and hexagonal wrapper a dedicated model was built (see cap. 7).

6.2.2 ELEMENT TYPES

Following element types were used in the FE model:

o 1D bar elements: BEAM181

1D bar elements were used to model fuel bars in the fuel rooms of reactor, as shown in next figure

Pumps


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Figure 6.3: Element type – BEAM181

o 2D shell elements: SHELL181

DESCRIPTION: SHELL181 is suitable for analyzing thin to moderately-thick shell structures. It is a four-node element with six degrees of freedom at each node: translations in the x, y, and z directions, and rotations about the x, y, and z-axes.

Shell elements were used to represent all the stainless steel components of the model, as shown here below.


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Figure 6.4: Element type – SHELL181

o 3D solid elements: FLUID80

ELEMENT CONFIG: hex8

DESCRIPTION: is used to model fluids contained within vessels. It is particulary well suited for calculating hydrostatic pressure and fluid/solid interactions. Acceleration effects, such as in sloshing problems.


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Fluid 3D elements were used to model LBE fluid contained in the reactor, as represented in Figure 6.5.

Figure 6.5: Element type – FLUID80


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Lead bismuth coolant has been modelled by two different approaches to evaluate

whether the sloshing effect of the fluid be negligible for the dynamic response of

the reactor internals including Spallation Target Assembly.

- GLOBAL MODEL 1 – LBE fluid modelled with 3D SOLID ELEMENTS (FLUID80) (sloshing effect) - high computation time for calculation

- GLOBAL MODEL 2 – LBE fluid modelled through nodal masses applied on the nodes of the 2D interface components between solid (without sloshing effect) – low computation time for calculation

6.3 MODAL ANALYSIS

A particular study was developed to estimatethe value of thedamping coefficientto be applied tothe global modelin the seismic analysis. Thedamping coefficientto be appliedto the structure,in fact, it is difficult to evaluateprecisely because of thepresence offluid elements, which givetheir contributionto the damping.

An inverse processhas been adopted, according to which thedamping coefficientwas obtained froma quadratic function, setting, as boundary conditions,specificmodalfrequencies calculated from the analysisof another model

Therefore a second model was considered, in which LBE fluid was represented by nodal masses (ET MASS21) obtained evaluating the masses of FLUID 3D solid elements. The model was divided in 5 different zones. Total mass of each zone was distributed by the number of interfaces nodes to obtain the mass to apply on the single node (see Figure 6.6).

This alternative model was used to adjust damping coefficient to assign to solid elements in the global model.


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Figure 6.6: Element type – MASS21

Principal modes of the structure were observed for mass model deducing frequencies of vibration with the major participating mass ratio of the whole structure.

TOTAL MASS: 5.29E+06 [kg]

MODE F [Hz] m (x) [kg] m (y) [kg] % m (x) % m (y)

1 1.35061 4.77E-02 5.82E+03 0% 0%

2 1.35162 5.82E+03 4.23E-02 0% 0%

3 5.00422 5.42E+03 3.40E+06 0% 64%

4 5.01119 3.58E+06 5.48E+03 68% 65%

37 10.9095 7.06E-08 2.84E-07 70% 70%

38 11.4474 1.66E+03 3.29E+05 70% 76%

39 11.4616 3.42E+05 7.31E+02 77% 76%


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50 12.2496 1.94E+05 7.00E+02 81% 79%

Table 6.1 – LBE properties

Principal frequencies were used to extract damping coefficient functions for both models. Following aniterative process value for principal frequencies was fixed at 5% for 2nd model (masses) and 2% for the 1st one (solid) considering the adding damping due to the fluid.

Damping curves were built using the following equation:

Damping values to use in the transient analysis were calculated.

Transient analyzes were run on both models deducing displacements of some control nodes (see Figure 6.7).


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Figure 6.7: Modal analysis CTRL Nodes

Resulting relative displacements are shown in next graphs.

Central_Up

Central_Middle

Central_Down

Vessel_Inf


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‐10

‐8

‐6

‐4

‐2

0

2

4

6

8

10

0 5 10 15 20Ux [m

m]

t [s]

CENTRAL UP‐DOWN

NODAL MASSES

SOLID MODEL

‐6

‐4

‐2

0

2

4

6

0 5 10 15 20Ux [m

m]

t [s]

CENTRAL UP‐MIDDLE

NODAL MASSES

SOLID MODEL

‐15

‐10

‐5

0

5

10

15

0 5 10 15 20Ux [m

m]

t [s]

CENTRAL UP‐VESSEL_INF

NODAL MASSES

SOLID MODEL


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Figure 6.8: Modal analysis CTRL Nodes

The parallel study of the two models has shown that the analysis carried out on the 1st model with solid elements representing LBE fluid with a 2% of critical damping, provides reliable results and will be used to derive the accelerations, input of the local model.

6.4 BOUNDARY CONDITIONS AND LOADS

Time histories for input accelerations were provided as input data by the WP2 partners [Ref. 5] for different cases deriving from the studyof SILER structure responseto differentseismic loading conditions, divided by isolators types, soil type and seismic level (see cap.5).

Accelerations corresponding to meaningful cases (see Figure 6.10, Figure 6.11), were applied in the transient analysis of the global model, to obtain displacements in specific nodes.

Input accelerations were applied on DOF constrained nodes of the upper part of the model (superior plane of Support ASM component), as shown in next figure.


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Figure 6.9: DOF nodes

DOF NODES


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Figure 6.10: Input Accelerations ax, ay, az – CASES: 1, 2 – Time step: 0-20 [s]

Figure 6.11: Input Accelerations ax, ay, az – CASES: 6, 7 – Time step: 0-20 [s]


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6.5 TRANSIENT ANALYSIS RESULTS

6.5.1 OUTPUT NODES

A linear time history analysis has been carried out by the software ANSYS.

Six nodes were chosen on specific points of the model (see Figure 6.12) on whichdisplacements andaccelerationswere calculated, as results of the transient analysis. Three nodes are located on the upper plane of Steel Cover component, the other three on Core level.

6.5.2 RESULTS

Results for the four chosen load cases are reported in “appendix a” for all output nodes.

Figure 6.12: Control Nodes (Global Model Output)

DOF Steel Cover (SC) nodes

DOF Core nodes


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As typical example,in the following charts,plotsof the accelerationsoftwocontrol nodesfor theworstcaseload(CASE 2) are reported.

Figure 6.13: IP 23763 (Core) – ax,ay,az [m/s2]

Figure 6.14: IP 21376 (Steel Cover) – ax,ay,az [m/s2]

Output accelerations on the IP nodes of the global model will be applied as input on the correspondent nodes in local model (see next chapter).


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7 PHASE 3: LOCAL MODELTRANSIENT ANALYSIS

7.1 INTRODUCTION

The scope of the local modelis toobtain,by a linear dynamic analysis, a preciseestimationof the stressesand relative displacementsof the two components Proton Beam and the Hexagonal Wrapper,due to applicationofseismic accelerations. The aim of the analysis is to reachthe maximumcalculated relative displacementsto be within 2 [mm]; design gap betweenthe two components.

To reach the goal, different local models were analyzed, starting from the first configuration in which Proton Beam and Hexagonal Wrapper are completelyfree to move through them,unlessthe points ofthe top, correspondingto the heightof thesteelcover(see Figure 7.1).

Following an iterative process, different numbers and layouts of internal constraints were added between the two components, up to ensure the requested relative displacement. A final configuration was reached as a result of the iteration process in which a relative displacement less than 2 [mm] was ensured by laying out five fixing points between the components, as reported in Figure 7.1.


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Figure 7.1: Local model – Initial and Final configurations

In addition to the twocomponents, objectof the study,Core Plate component was modeled to have a more realistic estimation of displacements and stresses.

Points of application for input seismic accelerations match with the output nodes of global model, in terms of load entities and geometrical position (see following paragraphs).

In the following paragraphsthe description of thelocal model,on whichlineardynamic analyseswere carriedout,is given for the twodifferentboundary conditions:

- Initial configuration (no fixing points)

- Final configuration with (five fixing points)

Proton Beam - Hexagonal Wrapper

connection

iterative process


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7.2 DESCRIPTION OF FE MODEL

7.2.1 GEOMETRY

The local model represent the internal part of the reactor, in which the protonsare acceleratedto cause thefission reaction.

The model contains the following components:

Proton Beam Tube, in which the protons are carried to fission.

Dimensions: H= 8.40 [m]; Dext= 88.3 [mm]; th= 2 [mm]

Hexagonal Wrapper, structurallyconnectedto both theprotonbeamtube tothe core.

Dimensions: H= 9.25 [m]; Lmin/Lmax= 97.5/115 [mm]; th= 2 [mm]

Core Support Plate, made of T91 alloy having special mechanical properties .

Dimensions: Dext= 1450 [mm]; th= 200 [mm]

The model is entirely built with 3D solid elements and loads are applied on 6 mass elements rigidly connected with the structure through CERIG elements (rigid links).

Also the upper connection between Proton Beam Tube and Hexagonal Wrapper was modeled with 3D solid elements and, in the same manner, the connection between Hexagonal Wrapper and Core Support Plate (see Figure 7.5).

Following figures show a 3D model’s view, its components, mesh details and connections.


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Figure 7.2: Local model overview

Figure 7.3: Local Model components

Proton Beam

Hexagonal Wrapper

Core


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Figure 7.4: Local Model mesh detail / Input nodes (MASS21) and CERIG

CERIG (rigid links)

MASS21 (nodes)


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Figure 7.5: Components connections (3D solid elements)

7.2.2 MATERIAL PROPERTIES

Materials used for local model analysis are the same employed for the global one.

In particular, materials used for each component are the following:

Proton Beam Tube Y AISI 316 L

Proton Beam – Hexagonal Wrapper connection

Hexagonal Wrapper – Core Plate connection


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Hexagonal Wrapper Y AISI 316 L

Core Support Plate Y T91

7.2.3 ELEMENT TYPE

o 1D mass elements: MASS21

DESCRIPTION: MASS21 is a point element having up to six degrees of freedom: translations in the nodal x, y, and z directions and rotations about the nodal x, y, and z axes. A different mass and rotary inertia may be assigned to each coordinate direction.

o 1D rigid link relation: CERIG

DESCRIPTION: The MPC184 rigid link/beam element can be used to model a rigid constraint between two deformable bodies or as a rigid component used to transmit forces and moments in engineering applications.

o Contact elements: CONTA173

DESCRIPTION: CONTA173 is used to represent contact and sliding between 3-D " target" surfaces (TARGE170) and a deformable surface, defined by this element. The element is applicable to 3-D structural and coupled field contact analyses. This element is located on the surfaces of 3-D solid or shell elements without midside nodes

o Target elements: TARGE170

DESCRIPTION: TARGE170 is used to represent various 3-D "target" surfaces for the associated contact elements

o 3D solid elements: SOLID45

DESCRIPTION: SOLID45 is used for the 3-D modeling of solid structures. The element is defined by eight nodes having three degrees of freedom at each node: translations in the nodal x, y, and z directions.


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7.2.4 BOUNDARY CONDITIONS

Output accelerations calculatedfrom global model analysis were applied on DOF nodes shown in Figure 7.6. MASS21 elements having a mass equal to zero were employed as nodes of applications of loads and they were rigidly connected with the structure through CERIG elements (rigid links).

In the following table DOF nodes are listed.

Node name Node ID

DOF_Core_1 236962

DOF_Core_2 236963

DOF_Core_3 236961

DOF_SC_1 236954

DOF_SC_2 236960

DOF_SC_3 236953

Table 7.1 – DOF Nodes


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Figure 7.6: DOF Nodes

7.2.5 LOADS

Input accelerations were applied on DOF nodes (Table 7.1) for load cases: 1, 2, 6, 7.

Transient analysis was run considering a total time step of 20 [s].

Applied loads are reported in Figure 6.13, Figure 6.14 for two sample points in worst load case (CASE 2) .

Loads for the four chosen load cases are listed in “appendix a” for all DOF nodes.

7.3 INITIAL CONFIGURATION

In the initial configuration, the only connection between Proton Beam Tube and Hexagonal Wrapper is the connection between the components in their upper part (see Figure 7.5).

Control nodes were placed at the top and at the bottom of Proton Beam Tube and Hexagonal Wrapper (see Figure 7.7), to obtain output relative displacements of the two components (see 7.5).


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Figure 7.7: Local model – Initial Configuration

7.4 FINAL CONFIGURATION

In the final configuration model five fixing points were introduced to reduce relative displacements between hexagonal wrapper and proton beam tube in x and y horizontal directions. In particular fixing points 4 and 5 (see Figure 7.8) are placed near the core to have the same deformed shape for hexagonal wrapper and proton beam tube.

MPC184 contact elements were introduced at the fixings interface between hexagonal wrapper and proton beam tube to allow displacements in vertical direction.

CTRL nodes


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The position of the lower fixing point was chosen at a distance of 20 cm from the end of the proton beam tube (cylindrical part) to allow a correct behavior due to the different thermal expansion of components.

Figure 7.8: Fixing Points


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7.5 RESULTS

7.5.1 INITIAL CONFIGURATION – NO FIXING POINTS


Displacements in x and y directions were calculated using ANSYS v.14.0.

Results are shown,for the considered direction, in next graphs for the worst case (CASE 2).

Figure 7.9: 1st Local model – P.B./H.W. relative displacements (X-dir)

Figure 7.10: 1st Local model – P.B./H.W. relative displacements (Y-dir)

‐800

‐600

‐400

‐200

0

200

400

600

800

0 2 4 6 8 10 12 14 16 18 20

DELTA_UX [mm]

‐200

‐100

0

100

200

300

0 2 4 6 8 10 12 14 16 18 20

DELTA_UY [mm]

UxMAX: 670 [mm]


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Maximum relative displacement in x direction results to be 670 [mm] at the bottom of Proton Beam. Fixing points are needed to maintain the components at the requested minimum distance of 2 [mm]

7.5.2 FINAL CONFIGURATION – FIVE FIXING POINTS


Several preliminary analysishave been carried outon thelocal model, placing agrowing number offixing pointsat different heights.An iterative processhas led todeterminetheidealnumber of fixingsin five. The two lower fixings,were placedaboveandbelow thecoresupport plate, because of the large deformationof the componentsat the heightof loads application points.

The position of the lower fixing point was chosen at a distance of 20 [cm] from the end of the Proton Beam Tube (cylindrical part) to allow the different thermal expansion of components.

The other fixing points were regularly spaced, as shown in next figure.

Figure 7.11: 2nd Local Model – Fixing Points; CTRL nodes


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Control nodes for output displacements were considered between all the fixings.

Control nodes relative displacements (DELTA_U) between Proton Beam Tube and Hexagonal Wrapper were calculated in x and y directions for each load case.

Results are shown here below.

The maximum relative displacements between hexagonal wrapper and spallation

target is 0.8 [mm] for CASE 2, Fixed base_BDBE_MYRRHA Site BEDRS.

CASE 1


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CASE 2

UxMAX: 0,8 [mm]


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CASE 6

CASE 7


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7.6 STRESS ANALYSIS

In the following, results in terms of Von Mises stress are reported for the final configuration (five fixing points) in which the respect of design parameters is guaranteed.

Maps of Von Mises stress are reported for the time instant more onerous, from the transient analysis.

CASE 1 – PROTON BEAM


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CASE 1 – HEXAGONAL WRAPPER


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The maximum Von Mises stresses calculated for 4 selected CASES are tabulized at Hexagonal

wrapper and beam tube as shown in Table

Table 7.2Stress Analysis results for hexagonal wrapper and cylidrical beam tubefor 4

selected CASES

Hexagonal Wrapper

CASES Rel Displ (mm) at gap Stress(Mpa)

UX UY top mid bottom

1 275 50

2 0.8 275 153 30

6 30 5

7 100 20

Circular Beam Tube

CASES Stress(Mpa)

top mid bottom

1 275 30

2 500

6 50 5

7 275 10


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Both for Proton Beam Tube and Hexagonal Wrapper stresses result to be within the yield stress in all the zones of the components for CASE1, CASE6 and CASE7.

For CASE2 instead, there is a critical stress scenario in the upper zone of the structure, in correspondence of the connection of the components to the Steel Cover.


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8 DESIGN SOLUTION WITH SEISMIC ISOLATION FOR PROTON BEAM TUBE AND REACTOR COUPLING

Based on this study and partial results from WP5.1, three different SI applications (whole RB SI,

RV SI only, and reactor pedestal SI only) can provide large seismic margin by reducing the

accelerations against a fixed base RB, while SI solutions induce large differential movements

between non-isolated and isolated structure, as a result, need to design interface components

such as flexible joints, seismic gap, joint cover and fail-safe system. The installation locations of

the interface components should be varied depending on which SI solutions be applied as

discussed in the section 3.

Especially with the whole RB SI solution, the structural integrity of target (Hexagonal Wrapper)

and beam tube under DBE and BDBE could be met when 5 guide thimbles in between the

hexagonal wrapper and the beam tube are implemented.


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9 CONCLUSIONS

The analyses described in this document were developed with the aim of the study of dynamic behavior of target and reactor coupling to calculate and evaluate the maximum relative displacement between Proton Beam Tube and Hexagonal Wrapper to be within 2[mm] and the maximum stress under DBE and BDBE conditions to be within allowable.

To do this, the most representative load cases have been identified in the PHASE 1,to be applied in the PHASE 2 of the work on certain DOF nodes of a global model.

- The global models of the Reactor Assembly, reactor internals and LBE coolant are modelled and analyzed using linear transient analysis to produce input motions for dynamic behaviors of target and reactor coupling; Hexagonal Wrapper and circular Beam Tube, here relative displacements and stress under 4 different cases(non-isolated DBE and BDBE, HDRB seismic isolation DBE and BDBE).

In the phase 3 the five intrim guides between Proton Beam Tube and HexagonalWrapperare to be designed o achieve the objective of having a maximum relative displacement of less than 2[mm].

Lastly stress on the structure were calculated for all load cases. Both for Proton Beam Tube and Hexagonal Wrapper stresses result to be within the yield stress in all the zones of the components for CASE1, CASE6 and CASE7. With SI application the stresses at the both Hexagonal Wrapper and Beam Tube are reduced by about a half.

For CASE2 instead, there is a critical stress scenario in the upper zone of the structure, in correspondence of the connection of the components to the Steel Cover.

- The SI solutions for ADS MYRRHA are evaluated in 3 different cases such as SI of whole Reactor Building, SI of Reactor Vessel only, and SI of Reactor pedestal only, and the Seismic Isolation of the whole Reactor Building is recommended.


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10 APPENDIX A

GLOBAL MODEL OUTPUT / LOCAL MODEL INPUT ACCELERATIONS

CASE 1

DOF_CORE_1

DOF_CORE_2

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az


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DOF_CORE_3

DOF_SC_1

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az


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DOF_SC_2

DOF_SC_3

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az


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CASE 2

DOF_CORE_1

DOF_CORE_2

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az


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DOF_CORE_3

DOF_SC_1

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az


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DOF_SC_2

DOF_SC_3

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az


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CASE 6

DOF_CORE_1

DOF_CORE_2

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

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DOF_CORE_3

DOF_SC_1

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

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DOF_SC_2

DOF_SC_3

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

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CASE 7

DOF_CORE_1

DOF_CORE_2

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

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DOF_CORE_3

DOF_SC_1

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

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DOF_SC_2

DOF_SC_3

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

‐20

‐15

‐10

‐5

0

5

10

15

20

0 2 4 6 8 10 12 14 16 18 20

ax [m/s^2]

T [s]

ax

ay

az

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