1. 20 F POWER MEASUREMENT FOR GENERATION IV SODIUM FAST REACTORS R. Coulon, S. Normand, M. Michel, L. Barbot, T. Domenech, K. Boudergui, J-M Bourbotte, V. Kondrasovs, A-M. Frelin-Labalme, H. Hamrita, G. Ban, E. Barat, T. Dautremer, T. Montagu, F. Carrel, H-P Brau, V. Dumarcher, J-L Portier, P. Jousset, N. Saurel CEA, LIST, Laboratoire Capteurs et Architectures Electroniques, F-91191 Gif-sur-Yvette, France. European Nuclear Conference Tuesday, June 2 nd 2010

2. 1. Introduction Delayed γ spectrometry measurement  Alternative for real time estimation of the power magnitude  Activation products have a high fission rate representativeness  ADONIS system : high metrological grade in high count rate and in fluctuating situations Sodium Fast Reactor power measurement  Neutron measurement (real time estimation but no accuracy)  Heat balance measurement (accurate measurement ; periodically used to set the nominal operating point) The Ph é nix reactor The ADONIS electronics

3. Neutron activation products 2. Activation products Delayed gamma T 1/2 =15h E=1.37&2.75MeV T 1/2 =23s E=440keV T 1/2 =11s E=1.63MeV T 1/2 =2y E=1.28MeV T 1/2 =1.8h E=1.29MeV Sodium coolant activation

4. 3. Model for delayed gamma spectrometry on SFR 1. In-core activation based on nuclei balance:  Nuclear data  Neutron spectrum  Velocity, flow rate, temperature and neutron flux profile 2. Build-up and transit model:  Coolant cycle time  Dilution function  Transit time 3. Gamma transport and pulse high tally simulation using MCNP code: Germanium diode RX radiography Simulated γ spectrum

5. 4. How to obtain a real time power measurement? The response time is composed of 2 integration times: 1.A physical integration time due to the build-up transient stage 2.A statistical integration time due to the 24 Na Compton background noise and Poisson process of the counting measurement

6. 4.1 Physical integration time Concentration (cm -3 ) Time (s)  2 candidates:  The fluorine 20  T 1/2 =11 s  Build-up rate =0.01%  Transient time=70 s  The neon 23  T 1/2 =23 s  Build-up rate =5.2%  Transient time=4 min Requirement : Use of a short decay period tagging agent

7.  Use of a high gamma energy emitter  Fluorine 20: 1.634 MeV  Neon 23: 440 keV  Use a short transit time to measurement sample  Use of a high count rate and high energy resolution spectrometry system  Hyper-Pure Germanium diode  Adaptive ADONIS γ pulse analyser 4.2 Statistical integration time 20 F Direct measurement on sodium 23 Ne Measurement after a degassing stage E. Barat & Al. Nucl. Instr. A 567 (206) 350-352

8. 6. Power dynamic range vs. response time Pseudo-optimal configuration : 5 s of transit time and using the High count rate abilities ADONIS system

9. 6. Statistical accuracy vs. response time Pseudo-optimal configuration : 5 s of transit time and using the High count rate abilities ADONIS system Transit time

10. 5. 20 F measurement at the Phénix reactor May, 21 st Pb & Cu RX peaks Annihilation peak 20 F peak at 1.634 MeV 24 Na peak at 1.369 MeV 24 Na peak at 2.754 MeV Escape peaks

11. 6. Phénix power measurement

12. P=302 MWth P=308 MWth P=335 MWth P=337 MWth Reactor shutdown to 14 MWth Power increase 7. Experimental results for 20 F Linearity with power --- Non-optimal accuracy due to the configuration of the test Comparison of 20 F signal vs. accurate thermal balance measurement

13. P=302 MWth P=308 MWth P=335 MWth P=337 MWth Cumulative effect Power increase = Na Temperature & flow rate effects Reactor shutdown = High cumulative effect impact P=14 MWth S 24Na /P=9± 1 8. Experimental results for 24 Na Comparison of 24 Na signal vs. accurate thermal balance measurement

14. 9. Accuracy limitation of the method During power increasing  Flow rate and temperature changes induce distortion (shown in Phenix test) In nominal operating  Flow rate and temperature are stable  Breeding and burn-up could potentially induce distortion by neutron spectrum hardening? (other data analysis are in process)

15. 10. Perspectives 23 Ne and 20 F dual analysis could be a solution to correct theses distortions as well for temperature and flow rate distortion and as well for burn- up and breeding potential distortion

16. 11. Conclusion Tagging agents  20 F measurement on sodium coolant sample  23 Ne measurement after a degassing stage System  Sampling at the reactor core outlet  Short transit time  High count rate gamma spectrometry analyzer (ADONIS) Other simulations and experimental studies have to be done :  Build-up phenomenon  Burn-up and breeding impact  Multi-gamma analysis Delayed gamma power measurement for SFR could be an alternative to neutron measurement for real time power monitoring To be continued.

17. Thanks for your attention