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”
(A. Barabash, L. Sosnin and A. Cheltsov)
22 days of statistics
First kilogram, reminder:
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.
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.
the facility are the following :
Bismuth : 40. 10-11 g/g ( = 5000 mBq/kg if supposing chain at equilibrium)
Thallium : 7. 10-11 g/g ( = 400 mBq/kg if supposing chain at equilibrium)
So both at a level 100 times too high
SURPRISE : ECP-Krasnoyarsk…
…and a second answer : Chemgas -Tomsk
Choice done for Chemgas-Tomst (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
For Se82, the choice of Chemgas is Tomsk
Actually Alexander Barabash thinks that the 2 kilos tagged « ITEP-Kurchatov »
were produced in Tomsk (September 2006 announcement !). At my last questioning
in June 2006 at Santa Fe, Alexander confirmed me that the 2 physicists of Kurchatov
were doing the job (but I have still no report on this from Kurchatov).
In 2003, what we thought :
1- Selenium was not possible to buy, but as in NEMO 3 we have to rent it
(possible for years…)
2- Kurchatov (via ITEP) was the only producer in our case
So, we did a Convention with ITEP for a rent of 2 kilos
In 2006 what we know :
1- after a meeting in Munich with the Gerda team : it is possible to buy
Selenium as they do for Germanium
2- There is 3 possible plants in Russia, Krasnoyarsk (able to produce hundreds of kg),
Tomsk (almost able of hundred), Kurchatov (for kilograms).
3- there is a French importer (Chemgas) in touch with these 3 centers,
ready to organize meetings with the real producers.
After the first kilogram production, the pollution of Ru should have been
discussed for understanding the origin.
We never had any information on this discussion, and the second kilo
had the same pollution.
Actually, what we discovered in november 2006 :
1- the 2 kilos were not produced in Kurchatov but in Tomsk
2- the information of Ru pollution was never sent to Tomsk
Purification of Selenium
Chemical purification at INL
results of sample of natural selenium
purification of the first kilo of ITEP-Kurchatov
Next talk from John Baker
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
Next talk from Vasily Kornoukhov
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.
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)
Measurements of residual radioactivity in selenium batch
Matthias Laubenstein at Gran Sasso (Germanium crystal)
Vasily 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)
(as mentionned before)
A factor of 50 on Ra226 fits 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 ???
or…. wait for BiPo !
of 1 mBq/kg when measuring 1 kg (with a greater statistics, that could be as
low as 500 mBq/kg
To reach the level of mBq/kg, we all know that the BiPo detector is needed but
new developments are possible
(Vasily Kornoukhov, INR)
Development scheduled in 2007
Next talk from Vasily Kornoukhov
Possibility of Radon 220 measurement in SuperNEMO gas
Next talk from