I ntegrated L arge I nfrastructures for A stroparticle S cience. ILIAS-JRA2. Production of enriched Selenium 2 kilos « ITEP-Kurchatov » New contacts with ECP-Krasnoyarsk New production from Tomsk What’s next ?. Second kilogram of enriched Selenium “ITEP-Kurchatov”
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Integrated Large Infrastructures for Astroparticle Science
(A. Barabash, L. Sosnin and A. Cheltsov)
22 days of statistics
First kilogram, reminder:
U238 (4.5 109 years) ……….Ra226 (1622 years) …………. Bi214
Th232 (13.9 109years) … Ra228 (6.7 years)…Th228 (1.9 years)… Tl208
1- remaining pollution of radioelements :
Ra226 gives the Bi214 contamination
3 mBq/kg in the second kilo, 100 times too high
Ra228 and Th228 gives the Tl208 contamination so
3 mBq/kg is a factor of 1000 too high for a source of SuperNEMO
Ru106 is a beta emitter of Q ~ 3 MeV so pollution is catastrophic ! (20 mBq/kg)
2- need of « new producers » : ECP-Krasnoyarsk contacts
Orsay, March 9-10, 2006
Dmitry Kononov, Yuri Kulinich, Elena Nikitina, ECP-Krasnoyarsk
Serge Jullian, Dominique Lalanne, Xavier Sarazin, LAL-Orsay
Alexander Barabash, ITEP-Moscow
Goal of the meeting
study of a possible production of enriched 82Se in the ECP-Krasnoyarsk facility in order to test the level of purity of the final product and comparison to the level needed for the next generation of Double Beta experiment.
Yuri Kulinich presented the possibilities in ECP-Krasnoyarsk.
For hundreds of kilograms it is without problems, the facility has the goal of mass production. For example it is ~ 30% of Russian enriched Uranium production and ECP is largest producer of stable isotopes in the world.
There are different units and the one devoted to enriched Selenium will be a new one, never used before, so in principle with a low level of radio-impurities.
This facility is closely connected to units for chemical purification and chemical treatment. Each new isotope needs special equipment and there is for each a special unit dedicated to.
Dmitry Kononov is an expert in the chemical treatment of Selenium. For the current Selenium production the level of chemical impurities at the output of
the facility are the following :
Bismuth : 40. 10-11 g/g ( = 5000 mBq/kg if…)
Thallium : 7. 10-11 g/g ( = 400 mBq/kg if…)
(if… = supposing chain at equilibrium)
SURPRISE : ECP-Krasnoyarsk…
…and a second answer : Chemgas (France)
Choice done for Chemgas (better price)
According the procedure, not possible to make a different choice
Need of a new order to ECP, but of lower amount of money and
a new funding, ILIAS being not enough
Purification of Selenium
Chemical purification at INL (Idaho National Laboratory)
results of sample of natural selenium
purification of the first kilo of ITEP-Kurchatov
Tests on natural Se before purification of the batch of enriched Se82
Purification for Ru : adding natural Ru to 485 ppb
then purification and redissolution of Se
level of Ru = 3ppb
purification factor = 160
Test of losses of Se : none in dissolution of nitric acid, drying down and redissolution
in HCl and barium sulfate precipitation
Reduction of Se to metal : not 100% but can be worked around by concentration the
Se in solution (similar to Mo). No problem
Purification of the batch of enriched Se82 : October 2006
To be finished beginning of 2007
Mikhail Churbanov, Institute of Chemistry of High Purity Substances/ Russian Academy of Sciences (IChHPS/RAS), Nishny Novgorod
Remind : the level to be reached for SuperNEMO is
10 mBq/kg for Bi214 and 2 mBq/kg for Tl208.
Mikhail Churbanov, Director of IChHPS, presented the studies of the purification of Selenium and the installations existing at IChHPS. This Institute has been purifying Selenium since 20 years and has a deep knowledge of the physical and chemical processes involved in chemistry and distillation.
Distillation has to deal with different compounds of Selenium as cycloSe8, katenopoly-Se and polycyclo-Se in chemical equilibrium. Melting and boiling points depend on the structure. With radium it has to be taken into account the existence of compound as RaSe. At IChHPS various techniques are used for distillation :
rectification (multistage in one run)
In the case of rectification the level that can be reached for Uranium traces is less than 9.10-14 g/g (corresponding to 1 mBq/kg if the chain is at equilibrium). This method seems to be appropriate to the requirements of the double beta source we have in project.
ILIAS-JRA2 Substances/ Russian Academy of Sciences (IChHPS/RAS), Nishny Novgorod
Measurements of residual radioactivity in selenium batch
Matthias Laubenstein at Gran Sasso (Germanium crystal)
Vassily Kornoukhov at INR (with proportionnal counters
measuring radon emanation,
but so, only for Bi214)
Warsaw group : TPC imaging, possible for Radon (Rn222)
and Thoron (Rn220)
Matthias Laubenstein Substances/ Russian Academy of Sciences (IChHPS/RAS), Nishny Novgorod
If it is possible to hope a level of 300 Substances/ Russian Academy of Sciences (IChHPS/RAS), Nishny NovgorodmBq/kg for Bi and Tl at the production level
(as mentionned before)
A factor of 50 on Ra226 will fit the specification for Bi214
A factor of 10 (but may be it’s better, here only limits) for Ra228
is much too small for Tl208, we need a factor 100
We must choose a new sample of natural Se with a greater level
of Tl208 before purification, then purify it…then measure it..
… or measure the sample purified by John Baker,
as we have only limits, by a more sensitive technique, but how ???
Only possible with BiPo !