Introduction. CNS Prototype was made under the frame of the ANSTO CNS project.

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1 Title

2 Introduction CNS Prototype was made under the frame of the ANSTO CNS project. The Prototype was built and tested in PNPI. Comparison of calculated and experimental data for a single phase Thermosiphon with liquid deuterium was done. Results of the experiment and calculation are presented in the talk.

3 Thermosiphon dimensions # Parameter Value 1 Shell-and-tube heat exchanger Amount of tubes 133 Amount of baffle plates 12 Inner diameter of tubes 8 mm Outer diameter of tubes 10 mm Diameter of shell 198 mm Length of tubes 1 m 2 Tube in tube heat exchanger Inner diameter of the tube 36 mm Outer diameter of the tube 39 mm Inner diameter of the outer tube 54 mm Length of the tube 1.2 m 3 Moderator Chamber Inner diameter of the deuterium cell 294 mm Outer diameter of the deuterium cell mm Inner diameter of the helium jacket mm Wall thickness 1.3 mm 4 Tube in tube heat exchanger Inner diameter of the tube 36 mm Outer diameter of the tube 39 mm Inner diameter of the outer tube 54 mm Length of the tube 2.2 m

4 CNS Prototype

5 Thermosiphon diagram liquid deuterium flow cold helium flow through the Heat Exchanger cold helium flow through the Moderator Chamber helium flow to the refrigerator

6 DP 1 Facility diagram DT 1 HeT 3, HeP 3 HeT 1 to Chamber 19 K Heat load on D W 19 HeT 2 to HX 19 K Heat load on He 2130 W 19 HeF 1 to Chamber 80 HeF 2 to HX 80 g/s 80 g/s DT 2 D pressure 2 Vacuum 330 kpa ~10-2 Pa HeT 2, HeP 2, HeF 2 HeT 1, HeP 1, HeF 1 HeQ DQ

7 Heaters

8 Prototype Moderator Cell Assembly

9 Calculation model The model for the thermo-hydraulic hydraulic calculation of the Prototype consists of five elements: 1. shell-and and-tube counter flow heat exchanger; 2. tube-in in-tube parallel flow heat exchanger; 3. heat load part of the Moderator Chamber; 4. heat exchanger part of the Moderator Chamber; 5. tube-in in-tube parallel flow heat exchanger.

10 Thermal-hydraulic hydraulic calculation Natural circulation occurs due to a temperature difference between the upward and downward streams. The Thermosiphon consists of several elements. In steady states, the total driving force is equal to the total hydraulic resistance of the Thermosiphon at natural circulation: where n - thermosiphon elements (n=4). n n P mov = dp i= 1 i= 1 There is a thermal balance between a heat release and a heat removal in the Thermosiphon: Q release = Q removal The Thermosiphon elements are the heat-exchange and flow resistant elements. An iterative calculation is carried out until the simultaneous balances between driving force - hydraulic resistance and between heat release - heat removal. Some output data of an element are the input data for the following one at calculation, thus modelling the interconnected elements. These data include mass flow, temperature and pressure for deuterium and helium flows. A driving force for each Thermosiphon element is described by equation: For an element with upward stream: P P mov mov Hydraulic resistance is described with equation: n i= 1 = ( ρ ρ ) g h out in = ( ρ ρ out 2 ρυ l dp = ξ + ζ 2 d in ρυ 2 ) g h where: ξ - friction resistance coefficient; ζ- local resistance coefficient; ρ - density; υ - velocity; - length; - diameter. l d 2

11 Thermal and Hydraulic Balances Thermal balance for D flow 2 Main HX Moderator Chamber Upwards tube Total: Element Downwards tube Heat load 2170 W 2170 W Heat removal W -171 W -170 W -87 W W Hydraulic balance for D flow 2 Main HX Upwards tube Total: Element Downwards tube Moderator Chamber Driving force Pa 5.0 Pa Pa Pa Pa Resistance Pa Pa 0 Pa Pa Pa

12 Design parameters Parameter Heat Exchanger Thermosiphon s s elements Downwards tube Chamber Upwards tube Heat load on deuterium 2170 W Heat load on helium 2130 W Heat removal from D W -171 W W - 87 W D 2 flow rate 82 g/s 82 g/s 82 g/s 82 g/s D velocity m/s 0.48 m/s m/s Deuterium T in 25.8 K 22.8 K 22.5 K 25.9 K Deuterium T out 22.8 K 22.5 K 25.9 K 25.8 K Helium flow rate 80 g/s 80 g/s 80 g/s 80 g/s Helium Tin 19.0 K 19.0 K 19.4 K 24.9 K Helium Tout 23.1 K 19.4 K 24.9 K 25.1 K Inlet helium pressure 170 kpa 167 kpa 165 kpa 152 kpa Outlet helium pressure 150 kpa 165 kpa 152 kpa 150 kpa

13 Temperature calculation error Uncertainty Calculation error Heat transfer in D cell 2 ät ± 1.2% cell ± 0.4% Hydraulic resistance ± 1.6% D 2 ± 0.6% D 2 ± 0.6% D 2 ± 0.2% Total error (Tä tot ) ± 2.2%

14 Temperature of deuterium 27 Temperature,K EDT1 EDT2 CDT1 CDT Total heat load,w

15 Deuterium flow rate m=q/(cp Τ) D 2 flow rate, g/s Total heat load, W

16 Conclusion 1. Thermo-hydraulic hydraulic calculations for the CNS Thermosiphon with a single phase moderator have been verified on the CNS Prototype Facility. 2. Results of calculations are in a good agreement with experimental ental data.

17 Acknowledgements Designers Dmitry Markushin Maksim Sazhin Dmitry Tytz Programmers Alexander Firsov Natalya Grosheva Madlen Kolkhidashvilly Operators Dmitry Golomzin Anatoly Kobilyatsky Victor Parfeev Reactor staff Ivan Alekseev Sergey Bondarenko Renard Pikulik Tatyana Vasyanina Cooperators Osvaldo Lovotti Nestor Masriera