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)