ILIAS, Jaca, Spain 5 of December 2006 Se-82 purification: distillation and rectification procedures...

ILIAS, Jaca , Spain 5 of December 2006

Se-82 purification: distillation and rectification procedures

Kornoukhov Vasily

INR RAS (Moscow)

for IChHPS (Nizhny Novgorod) and IRE (Moscow)

LAL, Orsay , Spain 1 – 2 of June 2006

SuperNEMO: radiopurity requirements

Tl-208 (232Th chain) <= 2 Bq/kg

(<= 1.5 ppt of Th-232)

Bi-214 (238U chain) <= 10 Bq/kg

(< = 10 ppt of U-238)

232Th 1,41·1010 y

228Ra 5,75 y

228Ac

6,15 hours

228Th 1,91 y

224Ra 3,64 d

220Rn 55,3 sec

216Po 0,158 sec

212Pb 10,64 h

212Bi 60,5 min

208Tl 3,10 min

36,2 %

T1/2 ~ 1010 y

T1/2 ~ years

T1/2 ~ days

T1/2 ~< hours


SuperNEMO: dangerous isotopes from 232Th chain

Th-232, Ra-228, Th-228

We must remove Th and Ra

How to check the procedure:

Th: 232Th (MS), 228Th (HPGe: 208Tl line)

Ra: 228Ra (HPGe: 228Ac line)

238U 4,51·109 y

234Th 24 d

234mPa

1,18 min

234U 2,47·105 y

230Th 8,0 ·104 y

226Ra 1602 y

222Rn 3,824 d

218Po 3,05 min

214Pb 26,8 min

214Bi 19,7 min

T1/2 ~ 103 - 109 y

T1/2 ~ days

T1/2 ~ minutes


SuperNEMO: dangerous isotopesfrom 238U chain

Ra-226

We must remove Ra

How to check the procedure:

Ra: 226Ra (Champagne method, HPGe: 214Bi line)


SuperNEMO: dangerous isotopes and elements

• 238U chain:

Ra-226

• 232Th cain:

Th-232, Ra-228, Th-228

Conclusion: we must remove Ra and Th


Industrial scale production of 82Se

At present

the only technology for industrial scale production of 82Se is centrifugation method

and

only site for ~ 100 kg-scale production is Svetlana (the ECP, Siberia)


82Se transformation at Svetlana (the ECP)(V.Kornoukhov for ILIAS meeting, Orsay, April 2005)

Patent #… is “valid” in Russia onlynatSe natSeF6 centrifugation 82SeF6

82SeF6 (glow discharge) 82Se + …

82Se washing with H2O (to remove F-ions)

Distillation of 82Se in vacuum

“Chemical features” of impurities (chemical forms): fluorine compounds (!)


General remarks concerning the problem:(+)

• Se is material for semi-conductive industry: there are many methods for its purification;

(-)• 82Se is a result of chemical transformation through

SeF6 compound, and behavior of U-, Th-, Ra-impurities presented in such product (fluorine compounds) could be quite different of impurities in selenium produced accordingly to standard technology.


Chemical forms of U, Th, Ra impurities in isotopically enriched Se

There is no exact information on chemical forms of U, Th, Ra impurities at their low concentration in selenium.

There are no data on solubility of U, Th, Ra compounds with oxygen, selenium, fluorine in liquid Se.

No data on adsorption ability of U, Th, Ra impurities on heterogeneous particles of submicron size.


Some properties of elementary seleniumMolecular composition of Se:

Vapor (at 700 – 1300 K): Se2 – Se8

Melt (at 494.3 – 958.4 K): mixture of cyclo-Se8, katenapoly-Sen

(n = 102 – 103), and polycyclo-Sen in chemical equilibrium.

Solid: Seα, Seβ – Se8, Sehex. - Sen

Melting Point, K. Se - 443; Se - 453; Sehex – 494,3

Boiling point, K – 958.4

Density, g/cm3: Seα – 4.46; Seβ - 4.50; Se hex. – 4.717; Seliq (550 K) – 3.918

Industrial sources of Se of technical grade (99.0 – 99.7 %):

Production of sulfuric acid and non-ferrous metals


Distillation procedure & NEMO detector

Group from INR RAS (in 1997):

116Cd distillation for NEMO-3 detector

(two portions, 0.15 kg + 0.15 kg):

good result!


Physical methods of Se purification

Distillation methods: 1. One – Stage (Simple) distillation

2. Multi-Stage distillation methods:

a. Repeated simple distillation of purified product from previous stages.

b. Rectification – multi-stage counter – current method, realized in one apparatus and in one process.

Purification of selenium by distillation method

Essence of method: impurity content in equilibrium vapor and liquid is different. х ≠ y

Elementary separation process:

Influence on the system with initially uniform impurity distribution leading to appearance of spatially divided parts of system with different impurity content. The physical action leading to separation in distillation methods:

- evaporation part of liquid

- condensation part of vapor.

Condition of separation:

у

α = ≠ 1

х

Conditions of effective separation at distillation:

у

α = >> 1 for highly volatile impurities

х

у

α = << 1 for non-volatile impurities

х

Separation coefficient at the equilibrium

“ liquid-vapour” for some impurities in Se at 684oC

Impurity Content, mas.%

S

Te

As

Sb

Hg

Metals

0,1-1,0

0,01-1,0

0,014-0,3

0,3-2,0

0,04-0,006

0,01-0,001

2,12

2,6

66,6

625

4,7

102-107*

* ideal separation coefficient

60 80 100 120 140 160

105

106

107

108

Se commercial

Se after special purification

ni, cm-3

d, nm

Distribution on size of heterogeneous particles in selenium.Determination method – laser ultramicroscopy

0,1 1 10 100

0

20

40

60

80

100

2

1

ef

Veval

*106, cm3cm-2s-1

Particles diameter, 1 - 130-140;2 - 80-90.

Effective separation coefficient ofheterogeneous particles in Se as function of evaporation rate


Distillation method: One – Stage (Simple) distillation

Multi-Stage methods

1. Repeated simple distillation of purified product from previous stages.

2. Rectification – multi-stage counter – current method, realized in one apparatus and in one process.

Impurity Content Impurity Content

Na 3.00E-08 Al <6.00E-04

Fe <4.00E-04 Mg <3.00E-04

Mn <1.00E-04 P <1.00E-04

Sn <7.00E-05 Ni <7.00E-05

Te <6.00E-05 Bi <4.00E-05

Pb <4.00E-05 As <2.00E-05

Rb <6.00E-06 Sb <2.00E-06

W <3.00E-07 Ta <2.00E-07

Ir <2.00E-07 Au <4.00E-08

K <1.00E-08 Zn <5.00E-09

Cr <4.00E-09 Ag <2.00E-09

Co <8.00E-10 Cs <2.00E-10

Cd <2.00E-10 Hf <1.00E-10

Cu <1.00E-10 Sc <6.00E-11

Ga <4.00E-11 La <1.00E-11

U <9.00E-12

Impurity content, (at %), in Se, purified by rectification

Determination method of impurity content – activation analysis

10-4 at% - 1 at. ppm

10-7 at% - 1 at. ppb

10-10 at% - 1 at. ppt


Organizations/institutes could be involved in purification of 82Se

Russia (distillation method):Svetlana (the ECP, Siberia)Kurchatov Institute (Moscow)The IChHPS (Nizhny Novgorod)The Institute of Rare Earths (Moscow)Mendeleev Institute (Moscow)

USA (“wet” chemistry):

INEEL (Idaho Falls)

Coordinator (ILIAS/SuperNEMO): Dominique Lalanne


The IChHPS & the IRE: goal and content of workGoal: Foundation and selection of technique for production of

high-purity 82Se according to the requirements of SuperNEMO project; its technological realization for production of ~100 kg.

Parameters of the productElementary selenium enriched with 82Se isotope with the

content of impurities of Th, Ra (U) 10-10 at.% ( 1 ppt).Requirements to technology

- The yield of the product is 90-95% (to be specified during investigations)

- Output of technological scheme and equipment is 5-10 kg/cycle

- The process instrumentation should preclude the unrecovered losses of 82Se even in force majeur (destruction of equipment)

- To exclude the isotopic dilution during purification procedures


The IChHPS& the IRE: content of work

1. Thermodynamic and experimental evaluation of chemical and aggregate forms of the limiting impurities and of their relative volatility in selenium produced from SeF6.

2. Experimental verification of purity of Se with natural isotopic composition with respect to the limiting impurities purified by multi-stage vacuum distillation and rectification. Verification of abilities of these methods during production of kilograms amounts of Se extracted from SeF6.

3. Selection of technological process scheme with optimization by numerical methods of the degree of purity, output capacity and reliability.

4. Fabrication of equipment for the process with output capacity of 5-10 kg/cycle.

5. Production of pilot lots, characterization of the product, modifications of the selected scheme and technological modes.


Basic stages at development of ultrapurification process

1. Characterization of initial substance (determination of content and nature of impurities).

2. Development of analytical method(s) to control limited impurities with necessary detection limit.

3. Choice of purification method; a priori calculation of apparatus and mode of operation. Fabrication of apparatus.

4. Preliminary experiments on purification.

5. Correction of apparatus construction and mode their operation.

6. Final experiments on ultrapurification. Characterization of high-purity products.


Last stage of Se purification and Rn extraction


Conclusion• At present the only technology for 82Se production is

centrifugation method and only site for 100 kg- scale production is Svetlana (the ECP, Siberia)

• “Chemical features” of impurities in such a product (chemical forms): fluorine compounds.

• Multi-stages distillation and rectification methods of purification: the IChHPS and the IRE are ready to start purification of Se in the framework of ILIAS.

• Quality control with “champagne” method could be easy organize at very last stage of the purification procedure

C, мкг/гЭлемент Метод ПО, мкг/г Se-82

Li MS, AES 0,001 < ПОBe MS 0,001 < ПОB MS 0,04 < ПО

Na AES 0,7 < ПОMg AES 0,02 < ПОAl MS, AES 0,1 < ПОK AES 2 < ПОCa AES 0,5 < ПОSc MS 0,1 < ПОTi MS, AES 0,2 < ПОV MS, AES 0,1 < ПОCr MS 0,1 < ПО

Mn MS, AES 0,02 < ПОFe AES 0,6 28,2Co MS, AES 0,05 < ПОNi MS, AES 0,3 < ПОCu MS, AES 0,07 < ПОZn MS, AES 0,1 0,30Ga MS 0,01 < ПОSe AES ОсноваRb MS 0,001 < ПОSr MS, AES 0,003 < ПОY MS 0,001 < ПОZr MS 0,002 < ПОNb MS 0,02 < ПОMo MS 0,05 < ПОRh MS 0,0001 < ПОPd MS 0,0005 < ПОAg MS 0,01 0,030Cd MS 0,003 < ПОSn MS 0,05 < ПОSb MS 0,008 < ПОTe MS 0,02 161Cs MS 0,003 < ПОBa MS, AES 0,005 < ПО

La MS 0,001 < ПОCe MS 0,001 < ПОPr MS 0,0008 < ПОNd MS 0,0005 < ПОSm MS 0,001 < ПОEu MS 0,0001 < ПОGd MS 0,00008 < ПОTb MS 0,00001 < ПОDy MS 0,0002 < ПОHo MS 0,0001 < ПОEr MS 0,00002 < ПОTm MS 0,00006 < ПОYb MS 0,00005 < ПОLu MS 0,00007 < ПОHf MS 0,00009 < ПОTa MS 0,003 0,056W MS 0,5 11,1Re MS 0,001 < ПОIr MS 0,00002 < ПОPt MS 0,0001 < ПОAu MS 0,001 < ПОHg MS 0,009 < ПОTl MS 0,00007 < ПОPb MS 0,02 < ПОBi MS 0,0004 < ПОTh MS 0,00006 < ПОU MS 0,00003 < ПО

ILIAS, Jaca, Spain 5 of December 2006 Se-82 purification: distillation and rectification procedures...

Documents

Transcript of ILIAS, Jaca, Spain 5 of December 2006 Se-82 purification: distillation and rectification procedures...