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Decontamination Efficiency of Metal Mesh Polonium Filter for Lead Alloy Cooled Reactors
Toru Obara, Yu YamazawaTokyo Institute of TechnologyToshinobu SasaJapan Atomic Energy Agency
The Third International Symposium on Innovative Nuclear Energy Systems (INES-3), 31 October – 3 November 2010, Tokyo, Japan
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Toru Obara, INES-3, Tokyo, Japan (2010).
Background• Lead-Bismuth Eutectic (LBE)
– Coolant of innovative nuclear reactor– Coolant and target of ADS
• Advantage– Low MP(125℃), High BP(1670℃)– Chemically inert with air and water
• Issues to be solved– Erosion/corrosion– Production of polonium
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Background (continued)
• Polonium issue– 210Po emits alpha particle of 5.3 MeV– Half life 138.4 days– Possibility of radiation by inhalation in maintenance and coolant
leakage accident
Toru Obara, INES-3, Tokyo, Japan (2010)
)2064.138210013.5210209 StablePbPoBiBi ddcaptureneutron( → → →
− αβ
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J-PARC Transmutation Experimental FacilityNuclear Physics
FacilityMaterial& Life Science Facility
50GeV Synchrotron
Neutrino Facility
LINAC(350m)
3GeV Synchrotron
Transmutation Experimental Facility
TEF-T Facility
Critical Assembly
Pb-Bi Spallation Target
TEF-P Facility
Proton Beam
Po Isotope
Maximum Yield(Bq)
Release Radioactivity
(Bq/cc)
Limit at non-controlled area
(Bq/cc)Half Life
Total 1.22×1014 3.55×10-8 − −
Po-208 1.97×1012 4.98×10-9 Not specified 2.90 years
Po-209 3.70×1010 9.35×10-11 Not specified 102 years
Po-210 1.20×1013 3.06×10-8 5.0×10-8 138.4 days
• 600MeV-200kW Pb-Bi spallationtarget is located at TEF-T facility
• Several kinds of Po isotopes will be generated by nuclear reaction analyzed by DCHAIN-SP code system
• Most of Po stayed in Pb-Bi as a chemical form of lead polonide(PbPo) and about 0.2% exists as a monadelphous form. In this table, 100% of monoadelphous Po is assumed to be released through cover gas.
• About 1000 of decontamination factor (DF) for Po removal is required in the radioactive gaseous waste removal circuit
Reference: T.Sasa, et. al, JAERI-Tech2005-021
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Polonium filter
Toru Obara, INES-3, Tokyo, Japan (2010)
基板ヒーター
銅箔
フィルター
カバー
メインヒーター 基板ヒーター
るつぼヒーター
冷却水経路
LBE試料
石英ガラス管
30mm
フィルター試料設置位置
Heater
Copper foil
Stainless mesh filter
Stainless plate
Heater
CoolantThermocouple
Heater
Thermocouple
Quartz glass tube
Filter
Heater
LBE
SS316 wire mesh
Number of meshesSample 1: 200×1400 meshes/inchSample 2: 270×2000 meshes/inch
Wire diameterSample 1: (a) 0.04mm (b) 0.028mmSample 2: (a) 0.035mm (b) 0.024mm
Number of filters:one (single filter), two (double filter)
Toru Obara, et. al,”Progress in Nuclear Energy, 50, 556 (2008).
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Purpose of study
• To estimate decontamination efficiencies of the polonium filter by experiments in penetration condition.
• To confirm that it can be useful device for the removal of polonium in gas phase
Toru Obara, INES-3, Tokyo, Japan (2010)
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Stainless steel wire mesh
Toru Obara, INES-3, Tokyo, Japan (2010)
Fine mesh Loosemesh
Number of meshes (1/inch)
270x2000 200x1400
Wire diameter (a) (mm)
0.04 0.07
Wire diameter (b) (mm)
0.028 0.04
(a) (b)
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Experimental apparatus
Toru Obara, INES-3, Tokyo, Japan (2010)
Heater
Crucible
Filter
Vacuum pump
Window
Vessel
Thermocouple
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Estimation of Decontamination Factor (1)
Toru Obara, INES-3, Tokyo, Japan (2010)
DF(C/R) = (AC/AR) [with filter]/ (AC’/AR’) [without filter]
Ac : activity of cross shaped plate surface
AR: activity of ring shaped plate surface
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Estimation of Decontamination Factor (2)
Toru Obara, INES-3, Tokyo, Japan (2010)
DF(filter) = (Afilter, out) / (Afilter, in)
PoAfilter, in
Afilter, out
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Experimental condition
High temperaturecondition
Low temperature condition
Heater temperature more than 690 ℃ 560℃Estimated filter temperature more than 328℃ about 271℃Vacuum pressure less than 2Pa less than 2PaHeating time 15minutes 8hours
Toru Obara, INES-3, Tokyo, Japan (2010)
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Experimental results - DF(C/R) -
Toru Obara, INES-3, Tokyo, Japan (2010)
High Temp. Fine mesh
High Temp. Loose mesh
Low Temp. Fine mesh
Number of mesh layers in the experiment
DF(
C/R
)
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Experimental results - DF(filter) -
Toru Obara, INES-3, Tokyo, Japan (2010)
FINE MESH
0
100
200
300
400
500
600
0 1 2 3 4 5 6
メッシュ枚数
DF DF(FILTER)
DF(C/R)
Number of mesh layers in the experiment
Fine mesh
DF
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Experimental results - DF(filter) -
Toru Obara, INES-3, Tokyo, Japan (2010)
LOOSE MESH
0
100
200
300
400
500
600
0 1 2 3 4 5 6
メッシュ枚数
DF DF(FILTER)
DF(C/R)
Loose mesh
Number of mesh layers in the experiment
DF
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Conclusions
• Experiments to estimate the effect of polonium filter in gas phase using stainless steel wire mesh were performed in penetration condition.
• If the filter temperature is about 328 ℃, DF value is expected to more than 173, which means 99.4% of polonium in the gas phase is removed by the filter.
• It is also expected that DF value can be more than 160, which means 99.4% of polonium in the gas phase is removed by the filter when the temperature is about 271℃.
Toru Obara, INES-3, Tokyo, Japan (2010)
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Conclusions (continued)
• The expected DF is independent from the number of mesh layers.
• There is no difference in the estimated DF’s between the fine wire mesh and loose wire mesh used in the experiments.
• It is confirmed that polonium filter made of stainless steel wire mesh can be very useful device for the removal of polonium in gas phase.
Toru Obara, INES-3, Tokyo, Japan (2010)