Efforts in Russia

1. Efforts in Russia V. Sinev Kurchatov Institute

2. Plan of talk • Rovno experiments at 80-90-th • On the determination of the reactor fuel isotopic content by antineutrino method • Antineutrino detector for reactor monitoring in Russia • Conclusion and Outlook

3. Firstly the idea of using antineutrinos for nuclear reactor control was proposed by Lev Mikaelyan (Neutrino 77) • Later, in former USSR there was organized Neutrino Laboratory at Rovno NPP, where we did first in the USSR experiments with reactor antineutrinos. • In these experiments: • Reactor antineutrino spectrum at statistics 174000 events, • Fuel burn up, • Measurement with high precision of inverse beta decay cross section, 6.75 ± 1.4%, (Rovno+Bugey) • Comparison of neutrino fluxes at Rovno and Bugey

4. Bugey data Ratio of fluxes Bugey/Rovno = 0.987 +/- 1.4%

5. In Kurchatov Institute the nonproliferation activity is developing in a number of directions. Antineutrino method is one among them. • We regard to use antineutrinos for: • Nuclear reactor monitoring, • Monitoring of the spent fuel storages, • Nuclear explosions control, • Geophysics (geoneutrinos)

6. On the determination of the reactor fuel isotopic content by antineutrino method

7. What uncertainty could be achieved in obtaining the content of nuclear rector fuel composition by using the antineutrinos? Let us suppose we know exactly the spectra of fissile isotopes (235U, 239Pu, 238U, 241Pu). One can mix them in proportion corresponding parts of fissions and simulate their detection by neutrino spectrometer. Than, fitting the M-C spectrum, one can find the coefficients used when initial spectrum was calculated. For 10 thousand events we find Da5 = 0.082, 100 thousand events we find Da5 = 0.026 and for 1 million Da5 = 0.008

8. Positron spectra of 235U and 239Pu in natural normalization, per fission 235U 239Pu Evis, MeV

9. The same spectra of 235U and 239Pu in normalization per unit 239Pu 235U Evis, MeV

10. Positron spectrum changes during reactor run so, that normalizing on unit it rises in left part and diminishes in right part being the same in one point – 3.25 MeV End of run Beginning of run 3.25 MeV Evis, MeV

11. Thanks to David Lhuillier

12. Statistics a5a9 right 1000183. 0.7200 0.1500 528561.419 0.001 471621.305 0.001 1.121 0.002 1000183. 0.7100 0.1600 529057.729 0.001 471125.755 0.001 1.123 0.002 1000184. 0.7000 0.1700 529557.591 0.001 470626.634 0.001 1.125 0.002 1000185. 0.6900 0.1800 530061.079 0.001 470123.911 0.001 1.127 0.002 1000186. 0.6800 0.1900 530568.205 0.001 469617.543 0.001 1.130 0.002 left Da=0.01 R=left/right Da5 = 0.0005 per day, 0.01 per 20 days Necessary to have statistics at least 50 000 per day to see Da5=0.01

13. Ratio of left/right parts of the positron spectrum during the reactor operational run Rleft/right a235

14. Scenario: After 60 days of irradiating they extract 20 rods containing 13-14 kg of weapons-grade plutonium. On the place of extracting rods they place fresh fuel rods. We try to calculate what will be the change in parts of 235U fission. If it is possible to detect this by super exact powerful detector without background.

15. The model of nuclear reactor similar to russian VVER (PWR) Starting loading: 238U 66 tons, 235U2,31 tons in 163 fuel rods 8 layerswith step 23.8 cm

16. Neutron flux goes downfrom the centre to sides of a reactor, Fuel are in 163rods Z R

17. Accumulation of 239Pu in fresh fuel • R, cm kg/year g/60 days in one rod • 1 11.92.94 807 х 1 • 37.5 2.90 793 х 6 • 59.5 2.80 753х 12 • 83.3 2.62 686х 18 • 107.1 2.35 595х 24 • 130.9 1.99 480х 30 • 154.7 1.51 346 х 36 • 178.5 0.90 195х 36 Total: 304 kg75kg

18. Scheme of changing rods according to scenario Totally 13.6 kg of 239Pu in 20 rods

19. Changes of the 235U part of fissions during the first run a235 ± 0.026 ± 0.008 t, days

20. Uncertainty 0.026 for 100 thousand events is established only on statistics of Monte Carlo. There is also uncertainty in spectra ILL ~4-5% (90% CL) For cross section of 235U uncertainty is 1.9% (68% CL) Also when measuring we have systematical error coming from detector, reactor and backgrounds. But it is seen that if neglect the most of appointed uncertainties, in any case, it is impossible to see the jump in part of fission of uranium or plutonium. A small antineutrino detector, so, could be used only as a tool to control the authorized regime of nuclear reactor operational run.

21. Antineutrino detector for reactor monitoring in Russia

22. We suppose to use antineutrino monitoring detector as a tool for controlling the planned regime of nuclear reactor operational run. The detector may be installed in the same plant where the fuel would be sold as close as possible to the reactor core. The most important to control first 60 days of fuel irradiation. The construction of a detector will be chosen after testing experiments. We think about doing liquid scintillation detector of about one cubic meter in volume. May be it would be separated in some sections.

23. Detector construction PMT (40-50) Gamma catcher, LS The target 1 m3, LS+Gd

24. Collaboration in Russia: • Kurchatov Institute – construction, assembling, testing • VNIIA (All-Russian Research Institute for Automatics) - mechanical construction • Institute for Physical Chemistry RAS – liquid scintillator • Corporation “Marathon” - electronics

25. Scintillator on base of LAB doped with Gd • LAB – Linear Alkyne benzene. It is a mixture of synthetic carbohydrates C6H5R, where R=C10,C11,C13 • Fractions of R are: C10 - 15%, C11 – 55%, C13 – 30% • Physical properties: • = 0.858 ± 0.002 g/cm3, Flash point +147°C Transparency is > 20 m, LY ~95% relative to PC+ PPO(5g/l)

26. Light yield as a function of Gd and PPO concentrations relatively to pure LAB scintillator PPO concentration, g/l LY,% LY,% Gd concentration, g/l

27. High stability in small amounts, 1 liter during 1 year doesn’t change its properties. We are preparing the mock-up containing 100 l of scintillator on base of LAB with Gd. We plan to construct the detector with a target 1 m3 and 1 m3 surrounding volume, that should be installed at Power Plant.

28. Conclusion • Using of antineutrino spectrum for obtaining the fuel composition of a core is difficult for the moment. One could not see the disappearing of 10-15 kg of plutonium. • A small detector placed in vicinity of the core (under the core) can control the non declination from the standard regime of reactor run. • In Russia we try to design a prototype of small detector placed close to the reactor core. The tests of scintillator stability are on run now. The mock-up is under construction. PMTs are bought. Electronics is under developing.

29. Outlook • We regard a possibility to do an International experiment under the patronage of IAEA in some country. For example it may be Ukraine (Rovno) where we did the first experiments. • France (Chooz, Bugey)? or Brazil (Angra)? or somewhere else ??? • This experiment could demonstrate not only the possibility of the method (was done at Rovno and San-Onofre), but the opportunity of doing it for safeguard purposes.

31. S.N. Ketov et al. Talk at Safeguards International Symposium, Vienna, IAEA-M-293/62, v. 2, 1986. V.I. Kopeikin, L.A. Mikaelyan, V.V. Sinev, Physics of Atomic Nuclei, v. 60, No. 2, p. 172, 1997. M.D. Skorokhvatov, Talk at Safeguards International Symposium, Vienna, 2003.