UNIVERSITÀ DI PISA DIPARTIMENTO DI INGEGNERIA MECCANICA, NUCLEARE E DELLA PRODUZIONE VIA DIOTISALVI 2, PISA

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1 UNIVERSITÀ DI PISA DIPARTIMENTO DI INGEGNERIA MECCANICA, NUCLEARE E DELLA PRODUZIONE VIA DIOTISALVI 2, PISA Gruppo di Ricerca Nucleare San Piero a Grado (GRNSPG) IAEA CRP No. I31018 Vienna, Austria, April 26-28, 2011 Experimental results from L2 Natural Circulation loop D. Araneo F. D Auria

2 Content Introduction L2 Natural circulation loop facility description Proposed tests Matrix (after RCM2) Experimental results Preliminary numerical simulations

3 Introduction Collaboration between UNIPI and UNIGE DIPTEM-TEC laboratories belong to the Italian High Quality Laboratory System In particular at DIPTEM-TEC laboratories an experimental deep study on Single-Phase Natural Circulation is already consolidate ( ; 35 papers: 8 Int. Journals, 15 Int. Conferences, 9 Nat. Conferences, 1 Edited book, 2 invited lectures. A lot of papers were published under a collaboration with prof. F. D Auria ) Available experimental apparatus are: 2 large-scale loops 2 mini-scale loops large-scale loops are equipped with al least 30 thermocouples mini-scale loops are equipped with al least 10 thermocouples high velocity data acquisitions pressure transducer Cryostat (-30;+20 C) programmable power supplier High speed camera 500fps)

4 L2 natural circulation loop facility Available Natural circulation loops (Large and Mini-scale) L1 L2 ML1 ML2 Tab.1 Natural circulation loop facilities

5 L2 loop facility description Thermocouples locations The number identifies each thermocouple Each location on the vertical tube has 5 thermocouples The P across the heated zone is measured P Fig. 1 Measurements locations

6 L2 loop facility description Capabilities of L2 loop Loop inclination (reduced gravity) Working with different fluids Tab.2 Working fluid properties

7 TEST MATRIX Proposed test matrix Based on an available experimental data set (see Tab. 3); A transition stable/unstable region has been identified in the range 10-20; The matrix has been designed for identifying the transition temperature. Tab. 3 Stability map This test is unstable (US) because steam bubbles are generated No. Power [kw] (Heater) Temperature [ C] (Heat sink) Number of runs Tab. 4 Preliminary text matrix

8 The procedure followed during the experiments execution EXPERIMENTAL PROCEDURE Fluid in stagnant condition; Before starting each test, the temperature of the internal bath of the cryostat is set to the test value. Both the power input and the temperature of the coolant were maintained constant during the entire test.

9 Final test matrix TEST MATRIX The experimental evidence is that the transition S/US is not a single temperature but there is a range of temperatures in which the loop shows a S/US behavior; For higher temperature at Heat Sink the behavior is more stable. The experimental data for the tests summarized in Tab. 4 are available to IAEA and all the CRP partecipants. No. Power [kw] (Heater) Temperature [ C] (Heat sink) Number of runs Tab. 4 Final test matrix

10 EXPERIMENTAL RESULTS The results are represented by mean: The average temperature difference at the heater T, defined as: 5 5 T T h i 1 5 i i 1 T 10 i P across the heater; Temperature at Heat Sink (HS). Heat Sink (HS) P heater

11 EXPERIMENTAL RESULTS H.S. Temp=4.6 C H.S. Temp=5.3 C H.S. Temp=7.6 C H.S. Temp=8.5 C

12 EXPERIMENTAL RESULTS H.S. Temp=10.0 C H.S. Temp=11.4 C H.S. Temp=18.9 C

13 Relap5/mod3.3 L2 Loop Nodalization Expansion tank Coil Expansion tank connection point

14 PRELIMINARY RESULTS

15 PRELIMINARY RESULTS

16 Conclusions The L2 Natural circulation loop experimental facility has been described; The results of the experimental data coming from the test matrix proposed during the RCM2 have been shortly analyzed. The results show that in the range of the HS temperature analyzed the L2 natural circulation facility has a transition region from a fully unstable to a stable behavior. Few preliminary results of the calculation performed with relap5/mod3.3 have been shown.