Karlsruhe , November 20/2012 luciano.cinotti@gmail

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KarlsruheKarlsruhe,, November 20/2012 November 20/2012

[email protected]@gmail.com

LEADER Project LEADER Project Working Package Working Package 33 – Task – Task 33..77

““Feasibility study of the flat-spiral-tube Feasibility study of the flat-spiral-tube bundle steam generator with integrated bundle steam generator with integrated

primary pumpprimary pump„„

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Task 3.7 Feasibility study of the flat-spiral-tube bundle steam generator with integrated primary pump

The ELSY project, developed in the 6th FP of Euratom, features an innovative configuration with the primary pump installed inside the inner shell of a spiral-tube steam generator.Both components need a careful study to confirm the feasibility and shop manufacturability of the assembly especially challenging due to the specific request of no intermediate tube-welding.Objective of the activity about the variable-speed electrical motor driven pump is the feasibility and installation with support bearings located in the cover gas above the free level of the coolant. The study will include the mechanical inertia necessary to maintain adequate coolant flow rate during pump coast down.Considering the novelty of the steam generator bundle, the Steam Generator main fabrication sequence along with the equipment needed for construction will be identified in order to confirm the feasibility and to provide feedback to the design.The study will indicate also the main on site assembly sequence and a preliminary cost estimate.

LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012

D39 - Feasibility study of the flat-spiral-tube bundle steam generator with integrated primary pump.

The activity is in progress

Extended-stem Fuel Assemblies

Spiral-tube SG

Primary Pump

Core

The Pump- Spiral-Tube Steam Generator Assembly

The Pump- Spiral-Tube Steam Generator Assembly is one of the main innovations of ELSY/ELFRThe Pump- Spiral-Tube Steam Generator Assembly is one of the main innovations of ELSY/ELFR


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Advantages

Feasibility / mechanical issues

Advantages

Feasibility / mechanical issues

The Spiral-Tube Steam Generator

- Del Fungo Giera Energia -

Titolo del documento

Rev. Data Descrizione Elaborazione Verifica Approvazione

Progetto Cl.ris. Identificativo documento Foglio Scala Formato

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For a given volume the cross section of the STSG perpendicular to the lead flow path is at least 3 time that of a generic SG,

½*Π*(D+d)*h ≥ ¾*Π**D^2( d~1/2*D and in general h>D)

¼*Π*(D^2)

STSG GSG

½*(D-d) ~ ¼*Dh ≥ 1*D

and the length of the lead flow path inside the bundle of the STSG is about 4 times shorter than

that of a generic SG.

1) A STSG can feature a small tube-pitch resulting in a tube bundle with half the volume of a helical-tube SG,

Smaller diameter and shorter reactor vessel 2) while limiting the primary pressure loss to half of that of a helical tube SG. Shorter reactor vessel

Advantages:Remind of the ELSY study on impact of the STSG on primary systemcompactness 1/2

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3) The free space inside the inner shell of the STSG can be used to locate the primary pump.

Smaller diameter of the reactor vessel

4) The outlet of the cold lead all along the outer shell of the STSG keeps the reactor vessel at uniform cold temperature without need of insulation, “deversoir”, heat exchangers…

Smaller diameter of the reactor vessel

ELSY/ELFR

SPX1

5) A short STSG can be positioned high in the reactor vessel because: - fed from the bottom, does not present risks of gas entrainment. - the radial flow path is not interrupted by a lowered lead free level resulting from a reactor vessel leakage.

Shorter reactor vessel

Advantages:Remind of the ELSY study on impact of the STSG on primary systemcompactness 2/2


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Feasibility/mechanical issues

From the web:Spiral Tube Heat Exchangers utilize one continuous Spiral-Wound Tube or several Parallel Tubes in a Circular Pattern connected to Headers on both ends. This Spiral Coil is then installed in a Shell where another fluid is circulated around the outside of the tube.The spaces or gaps between the coils of the spiral tube bundle become the shell side flow path. The profile of a spiral is very compact and fits in asmaller footprint than a shell and tube design. The shell side is usually smaller than a comparable shell and tubedesign and there are no requirements for tube supports or pass dividers.

From the web:Spiral Tube Heat Exchangers utilize one continuous Spiral-Wound Tube or several Parallel Tubes in a Circular Pattern connected to Headers on both ends. This Spiral Coil is then installed in a Shell where another fluid is circulated around the outside of the tube.The spaces or gaps between the coils of the spiral tube bundle become the shell side flow path. The profile of a spiral is very compact and fits in asmaller footprint than a shell and tube design. The shell side is usually smaller than a comparable shell and tubedesign and there are no requirements for tube supports or pass dividers.

ELSY SG vs usual Spiral-tube SGThe shell side radial flow path distinguishes the ELSY-SG from classical Spiral–tube SG with tube side and shell side spiral flow path. Differences in flow path Established technology and feasibility as regard to the Spiral-wound Tube. Need for the SG of ELSY of an adapted tube support system.


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The tube support system

Several solutions are under investigations ranging from the simplest wavy strips to perforeted interlinked dices

Wavy strips represent a rigid support system and the differential radial displacents must be compensated by the flexibility of the tubes.

Interlinked perforated dices :- Allow relative radial displacement among tubes (particularly important in case of plugged tubes)- Allow relative axial displacements among spires placed at different radial positions)- Provide circumferential porosity to mitigate SGTRA

Interlinked perforated dicesWavy strips


Important information on the feasibility of the steam generator is expected from the upcoming manufacturing of a mock up. (out of scope of the LEADER task)..

Besides the use in lead, the STSG can be used for heat recovery from the exhaust gases of the motors of biomass plants.

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Objectives of the mock up manufacturing and testing

For use in biomass plant:- Performance verification

For use in LFR:- Manufacturing confirmation- Parallel flow stability at low power- Verification of resilience towards differential thermal expansion

The spiral tube SG mock up will be manufactured in Taranto by Tecnomec (a shareholder of M.E.Rivus) and tested in high temperature exhaust gas ( from an oil burner) in the ENEA labs of Saluggia.

Tests in gas does not allow to reproduce the power density of the SG for LFR, but:- severe thermal gradients can be reproduced (gas inlet/outlet T= 600°C/200°C, water/steam inlet outlet T= 80°C/450°C;- through a window it will be possible to observe the tube thermal expansions.

The spiral tube SG mock up will be manufactured in Taranto by Tecnomec (a shareholder of M.E.Rivus) and tested in high temperature exhaust gas ( from an oil burner) in the ENEA labs of Saluggia.

Tests in gas does not allow to reproduce the power density of the SG for LFR, but:- severe thermal gradients can be reproduced (gas inlet/outlet T= 600°C/200°C, water/steam inlet outlet T= 80°C/450°C;- through a window it will be possible to observe the tube thermal expansions.

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Minimum diameter of the inner spiral (mm) 350Maximum diameter of the outer spiral (mm) 672Number of tubes 18Lenght of tubes (m) 27Outer diameter of tubes (mm) 8Thickness of tubes (mm) 1Radial pitch (mm) 9,5Axial pitch (mm) 9,5

Mock up geometryMock up geometry

Window

Water collector with tubeplate accessible for testing of different ferrules

Tube support with interlinked perforated dices under evaluation

Small diameter tubes make the manufacturing more difficult than in case of a SG for a LFR

PLOF+PLOH: Station Blackout (ELSY)

0

20000

40000

60000

80000

100000

120000

140000

950 1000 1050 1100 1150 1200

Time (s)

Flo

wra

te (

kg/s

)

Core flow

350

400

450

500

550

600

650

950 1000 1050 1100 1150 1200

Time (s)

Te

mp

erat

ure

(°C

)

Core inlet

Core outlet

Max clad

Lead Flowrate at Core Inlet Core Temperatures

Natural circulation in the primary circuit stabilizes at 6% of nominal value after primary pumps trip – Pump inertia (864 kg-m2)

Clad peak temperature of 637 °C at t = 1007 s

……..The study will include the mechanical inertia necessary to maintain adequate coolant flow rate during pump coast down…….


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Tubes for lead inlet

A pump shaft diameter progressively increasing towards the free level (tapered shaft with lead inside) is the solution found:- to make uniform the flow rate of lead- to increase the pump inertia without adding steel and without increasing the footprint above the reactor roof.

Motor-shaft-impeller assembly


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Issue of the deliverable

D39 - Feasibility study of the flat-spiral-tube bundle steam generator with integrated primary pump.

will respect the schedule M36

Deliverable issue

Documents

Karlsruhe , November 20/2012 luciano.cinotti@gmail