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Our decontamination technologies for NPSs

Our decontamination technologies for NPSs. Tadasu Yotsuyanagi Advanced Chemistry & Decontamination System Group Chemical System Design & Engineering Dept. Toshiba Corporation. Contents. Radiation exposure in BWR plants What is decontamination ? Chemical decontamination T-OZON

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Our decontamination technologies for NPSs

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  1. Our decontamination technologies for NPSs Tadasu Yotsuyanagi Advanced Chemistry & Decontamination System Group Chemical System Design & Engineering Dept. Toshiba Corporation

  2. Contents • Radiation exposure in BWR plants • What is decontamination ? • Chemical decontamination • T-OZON • Mechanical decontamination • Jet Cleaning • Zirconia Blast • Summary

  3. Materials of the primary system Corrosion Product ｎ Fuel crud Reactor internals Activation Reactor Water Insoluble activity Soluble activity RWCU Crud activity Source(CRD,LPRM etc.) Ionic activity Source (PLR & RWCU Piping) Radiation Exposure Behavior of Radioactivity in Reactor Water

  4. Crud Crud Reactor Water Reactor Water Material 54Mn 60Co Ion 60Co 58Co Material Oxide Film Ionic Activity Source Crud Activity Source Source of Radioactivity in Reactor Water Activation Reaction of Major Corrosion Product 59Co (n,γ) 60Co Half Life 5.3 y 58Ni (n,p) 58Co 70.9 d 54Fe(n,p) 54Mn 312.2 d 58Fe(n, γ) 59Fe 45.1 d 50Cr(n,γ)51Cr 27.7 d

  5. EarlyPlant NewlyPlant ABWR △ △／○ △ △ △ －／△ △ △ － ＊ ＊ △ △ － △ △ △ △ △ △ △ － ○ ○ ○ ○ ○ ○ ○ ○ △/○/－ ＊ △ △／○ △／○ － － － － ＊ △ △／○ △／○ －／○ ○ ○ ○ ○ ○ ○ ○ ○ － － ○ ○ － ○ － － － － － ○ － ○ Measures for Reducing Radiation Dose Rate in BWRs ○：Design Base △：Partial Application or Retrofit ＊：In Consideration －：No Application Crud Generation Reduction & removal Corrosion Resistant Material Oxygen Injection Shutdown Lay-up Dual Condensate polishing Sys. Impurity removal RWCU Capacity Optimization Feedwater Heaters ACP Reduction Core materials Low Cobalt Material Others/SS & Stellite RadiationDose RateLevelReduction Ni/Fe Control Zn Injection Water Control Ultra Low Fe Control Fuel Springs Surface Treatment Recirculation Piping ACPRemoval RWCU Piping Fuel Mechanical Decon. Out of Core Components Core Components Chemical Decon. System Optimal Shielding Equipments Drywell Reactor Building Improvement of components & Systems RWCU Pump

  6. Occupational Radiation Exposure in Japanese Plants

  7. Occupational Radiation Exposure Trend of Japanese BWRs

  8. 1. Distance 2. Shield 3. Time 4. Removal of Source Decontamination What is Decontamination ? • Maintenance of high dose rate piping & equipment

  9. Chemical Mechanical Dissolution of Oxide Film Removal of Deposits T-OZON, CORD Jet-Cleaning, Blast Electrochemical Electro-chemical Dissolution of material W/O Contact Categories of Decontamination Re-use Radiation Build-up Tight films Loose Deposits Strong Chemical Material Chemical Dissolution of material strongly Formic Acid For Disposal

  10. High Decontamination Factor (DF) Minimize Secondary Waste Optimum Temp., LV and Reagents Conc. Oxi. Cr Resins Fe Red. Oxidizing Reagents To be Decomposed Reducing Reagents Ferrites Chromites CrO42- Fe2+ Material To RW system Ion exchanger Principle of Chemical Decontamination Integrity of material

  11. Optimum method for various needs 2001 First T-OZON for re-use 2000 First T-OZON for disposal T-OZON 1997 First Full System Decon. (FSD) For NPSs 1990s CORDTM Minimize Waste 1980s TED-40 High DF Reduce Waste History of Chemical Decontamination in TOSHIBA

  12. Ferrites Reducing reagents：oxalic acid (COOH)2　Fe2O3+(COOH)2+ 4H+ →2Fe2++3H2O+2CO2 Chromates Oxidizing reagents：Ozone Cr2O3+3O3+2H2O→2CrO42-+4H++3O2 Reagents decomposed easily Material Principle of T-OZON Example of decontamination conditions Reducing : 95oC, 2000 ppm oxalic acid Oxidizing : 80oC, a few ppm ozone

  13. Main Features of T-OZON • High DF • Minimum Secondary waste volume • No adverse impacts on material integrity Volume of Secondary Waste Results of Lab. Tests Reagents Ozone = 1 ppm Before DF > 100 Arb. unit Mn After Fe Fe Fe CORD TED-40 T-OZON

  14. Number of Chemical Decon. T-OZON CORD TED-40 ’80～‘85 ’85～‘90 ’90～‘95 ’95～‘00 ’00～05　 Experiences of Chemical Decon. in NPSs In 13 BWRs, T-OZON applied to system decon.

  15. PLR piping Before After DF = 10 - 20 Application to System Decon. in BWR

  16. Chemical Mechanical Dissolution of Oxide Film Removal of Deposits T-OZON, CORD Jet-Cleaning, Zirconia Blast Electrochemical Electro-chemical Dissolution of material W/O Contact Categories of Decontamination Re-use Radiation Build-up Tight films Loose Deposits Strong Chemical Material Chemical Dissolution of material strongly Formic Acid For Disposal

  17. Water Jet Cleaning Spiral nozzle Guide Pump Hose reel Nozzle Filter Short period to get reasonable DF

  18. Duster Cyclone separator Blasting Chamber Exhaust Dust Nozzle Feeder Object Fraction (%) Compressor Abrasive Compressed air Diameter (um) Zirconia Blast • Main Features • High repetition • Good Separation • High DF

  19. Summary • Line-up of decontamination technologies • Chemical Decontamination • We promote T-OZON application to NPPs • Mechanical Decontamination • Zirconia blast has high performance for reducing wastes • Future scope • T-OZON application to FSD • Application to Back-End Facilities • Decommissioning • Recycle Facilities Decon. Equipment Inlet MCR Zirconia Blast Clearance Monitor

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