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Karlsruhe , November 20/2012 luciano.cinotti@gmail

LEADER Project Working Package 3 – Task 3 . 7 “ Feasibility study of the flat-spiral-tube bundle steam generator with integrated primary pump „. Karlsruhe , November 20/2012 luciano.cinotti@gmail.com. 1.

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Karlsruhe , November 20/2012 luciano.cinotti@gmail

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  1. LEADER Project Working Package 3 – Task 3.7 “Feasibility study of the flat-spiral-tube bundle steam generator with integrated primary pump„ Karlsruhe, November 20/2012 luciano.cinotti@gmail.com 1

  2. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 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. D39 - Feasibility study of the flat-spiral-tube bundle steam generator with integrated primary pump. The activity is in progress 2

  3. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 The Pump- Spiral-Tube Steam Generator Assembly Extended-stem Fuel Assemblies Spiral-tube SG Primary Pump Core The Pump- Spiral-Tube Steam Generator Assembly is one of the main innovations of ELSY/ELFR 3

  4. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 The Spiral-Tube Steam Generator Advantages Feasibility / mechanical issues 4

  5. Advantages: Remind of the ELSY study on impact of the STSG on primary system compactness 1/2 LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 STSG GSG 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) 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. ½*(D-d) ~¼*D h≥ 1*D 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)whilelimiting the primary pressure loss to half of that of a helical tube SG. Shorter reactor vessel 5

  6. Advantages: Remind of the ELSY study on impact of the STSG on primary system compactness 2/2 LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 SPX1 ELSY/ ELFR 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 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

  7. Feasibility/mechanical issues LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 ELSY SG vs usual Spiral-tube SG The 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. 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 a smaller footprint than a shell and tube design. The shell side is usually smaller than a comparable shell and tube design and there are no requirements for tube supports or pass dividers.

  8. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 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 dices Wavy strips 8

  9. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 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. 9

  10. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 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. 10

  11. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 Mock up geometry Water collector with tubeplate accessible for testing of different ferrules Small diameter tubes make the manufacturing more difficult than in case of a SG for a LFR Window Tube support with interlinked perforated dices under evaluation 11

  12. ……..The study will include the mechanical inertia necessary to maintain adequate coolant flow rate during pump coast down……. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 Core Temperatures Lead Flowrate at Core Inlet PLOF+PLOH: Station Blackout (ELSY) • 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 12

  13. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 Motor-shaft-impeller assembly • 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. Tubes for lead inlet 13

  14. LEADER Project “Feasibility study of the STSG with integrated primary pump” Karlsruhe, November 20 /2012 Deliverable issue Issue of the deliverable D39 - Feasibility study of the flat-spiral-tube bundle steam generator with integrated primary pump. will respect the schedule M36 14

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