Efforts in Russia

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Efforts in Russia

• V. Sinev
• Kurchatov Institute

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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

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• 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, (RovnoBugey)
• Comparison of neutrino fluxes at Rovno and Bugey

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Bugey data
Ratio of fluxes Bugey/Rovno 0.987 /- 1.4
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• 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)

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On the determination of the reactor fuel isotopic
content by antineutrino method
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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
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Positron spectra of 235U and 239Pu in natural
normalization, per fission
235U
239Pu
Evis, MeV
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The same spectra of 235U and 239Pu in
normalization per unit
239Pu
235U
Evis, MeV
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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
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Thanks to David Lhuillier
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Statistics a5 a9
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
Da0.01
Rleft/right
Da5 0.0005 per day, 0.01 per 20 days Necessary
to have statistics at least 50 000 per day to see
Da50.01
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Ratio of left/right parts of the positron
spectrum during the reactor operational run
Rleft/right
a235
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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.
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The model of nuclear reactor similar to russian
VVER (PWR)
Starting loading 238U 66 tons, 235U 2,31
tons in 163 fuel rods 8 layers with step 23.8 cm
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Neutron flux goes down from the centre to sides
of a reactor, Fuel are in 163 rods
Z
R
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Accumulation of 239Pu in fresh fuel

• R, cm kg/year
  g/60 days in one rod
• 1 11.9 2.94 807
  ? 1
• 37.5 2.90 793 ?
  6
• 59.5 2.80 753
  ? 12
• 83.3 2.62 686
  ? 18
• 107.1 2.35 595
  ? 24
• 130.9 1.99 480
  ? 30
• 154.7 1.51 346
  ? 36
• 178.5 0.90 195
  ? 36

Total 304 kg 75 kg
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Scheme of changing rods according to scenario
Totally 13.6 kg of 239Pu in 20 rods
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Changes of the 235U part of fissions during the
first run
a235
0.026
0.008
t, days
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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.
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Antineutrino detector for reactor monitoring in
Russia
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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.
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Detector construction
PMT (40-50)
Gamma catcher, LS
The target 1 m3, LSGd
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• 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

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Scintillator on base of LAB doped with Gd

• LAB Linear Alkyne benzene. It is a mixture of
  synthetic carbohydrates C6H5R, where
  RC10,C11,C13
• Fractions of R are C10 - 15, C11 55, C13
  30
• Physical properties
• 0.858 0.002 g/cm3,
• Flash point 147C
• Transparency is gt 20 m,
• LY 95 relative to PC PPO(5g/l)

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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
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High stability in small amounts, 1 liter during
1 year doesnt 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.
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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.

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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.

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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.