REPROCESSING OF FAST REACTOR FUELS AT
INDIRA GANDHI CENTRE FOR ATOMIC RESEARCH KALPAKKAM

We, the Reprocessing Group People@IGCAR, are
pursuing R&D on equipments and process, running a
pilot plant for FBTR Fuel processing, constructing
demo plant for FBTR and PFBR fuel reprocessing
and designing PFBR reprocessing plant

Introduction

   Fast Breeder Reactors (FBRs) create a large energy resource by converting the U238 present in natural Uranium to Plutonium.

   The Indian nuclear power programme can expand from 10 GWe to 350 GWe capacity using the modest indigenous uranium resources with breeder technology.

   This technology requires closing of the nuclear fuel cycle. The Plutonium produced in FBRs is recycled by reprocessing the irradiated fuel discharged from the reactors.  Thus, the requirement of fresh uranium for FBR is substantially reduced.


Fast Reactor Fuel Cycle

In Fast Breeder Reactors, there is an increase in plutonium content while uranium is consumed.  The irradiated fuel is reprocessed for recovering Uranium and Plutonium for reuse in the reactor. In the Fuel Reprocessing Plant, the fuel pins are dismantled from the subassembly. These pins are then chopped and dissolved in nitric acid. Solvent extraction process with tributyl phosphate as solvent, is used to separate Uranium, Plutonium and fission products. A very large fraction of the radioactive fission products and long-lived radioactive elements are fixed in suitable solid matrices such as glass and disposed and monitored in deep geological repositories. A tiny fraction gets released along with the gaseous and liquid effluents from the reprocessing plants, which is controlled and maintained as per the stringent regulatory requirements.

The Plutonium and the Uranium recovered from the reprocessing plant along with fresh uranium are fabricated as fuel elements in fabrication plant. The refabricated fuel is used in the reactor. The fuel cycle is thus closed.

Process Development


Schematic of PUREX process

Process Equipment Development


Prototype Rotary Dissolver


Indigenously Developed Centrifugal Extractor Bank


Indigenously Developed High efficiency Mixer-Settler Bank

     In-situ electrolytic partitioning mixer settler

     Constant volume feeders for accurate metering of active liquids

    Maintenance-free Fluidic pumps for active liquid transfer


 

Instrumentation and Control

    Development of drives and speed sensing systems for centrifugal extractors and constant Volume Feeders

    Hull characterization/Assay of leached hulls

    On-line assaying of Pu in high active streams

Materials

     Development of Ti-5%Ta-1.8%Nb Alloy for dissolver and raffinate evaporators

     Dissimilar Metal Joints

     Development of electrode coatings

Remote Handling Systems

     Development of remote sampling and analytical systems

     Development of remote visual systems for highly radioactive areas

     Development of remote inspections and repair techniques

 Waste Management

    Removal of radioactive Iodine, krypton, xenon and tritium from the gaseous effluents

    Technologies for near zero activity discharges of low and intermediate level wastes

    Minor actinide separation for Encapsulation in ceramic waste forms

    Separation of fission products such as Cs and Sr for encapsulation in ceramic waste forms
 

Four-Stage Programme of FBR Fuel Reprocessing

Stage I:    Development of process, equipment and hot cell systems

Stage II:  Reprocessing of FBTR fuels in the CORAL pilot plant (earlier known as lead mini cell)

Stage III: Reprocessing of FBTR fuel & demonstration of PFBR fuel reprocessing in DFRP

Stage IV: Reprocessing of PFBR fuel in PFRP

R&D Facility for Reprocessing

Process and equipment development: Highlights

    The process & equipment development work is carried out in the Reprocessing R&D Laboratory at IGCAR. The equipment are tested in the engineering laboratory before deploying them in radioactive environment.

    Some of these equipment have been used for reprocessing of irradiated thorium fuel for U233 recovery.

    With this U233, PFBR MOX fuel for irradiation experiments in FBTR has been fabricated.

    Part of this fuel is also used for KAMINI reactor (30 KWt), the only reactor operating with U233  as the driver fuel in the world.

    A few examples of equipment developed for Fast Reactor Fuel Reprocessing are, Single pin chopper, Electrolytic dissolver, Centrifuge clarifier and Centrifugal extractors.

Prototype Single pin Chopper

 Bundle chopping is used in thermal reactor reprocessing plant. Since, the cladding of fast reactor fuels is harder and pins are smaller in diameter, single pin chopping process is developed. This reduces crimping of the ends while chopping.

 The fuel subassembly is dismantled into individual pins. These pins are chopped in single pin chopper. It is modular in construction. All parts are remotely maintainable with master slave manipulators.

 The prototype is installed in the hot cell facility and is undergoing performance trials for reprocessing in FBTR fuel pins.

 Dissolution of Pu rich fuels is generally difficult. Mixed carbide fuels used in FBTR, pose additional problem because of the formation of complex organic compounds, during the dissolution. These compounds interfere in solvent extraction process. Advanced dissolution processes, such as Ag(II) catalysed electrolysis and ozone based processes have been developed. 


Separated solids in centrifuge bowl

The dissolver solution is filtered to remove very fine particles of cladding and undissolved fuel. These particles accumulate in the organic-aqueous interface during solvent extraction and degrade the solvent. The performance of the extraction process is reduced by these fine particles. A high speed air operated centrifuge has been developed for filtering dissolved solution. This equipment is designed for remote operation and maintenance in hot cells.


Hulls after dissolution of mixed-carbide fuels


A view of CORAL Hot cells

Centrifugal extractors for low solvent damage

The success of the Indian fast reactor programme lies in reprocessing the fuel from the reactor within a short time of discharge. This calls for processing feed solutions, which are highly radioactive.  Since the solvent undergoes radiolytic degradation, short residence time contactors are developed. In centrifugal extractors, developed in IGCAR, the residence times are of the order of seconds compared to minutes in pulse columns (used in thermal reactor fuel reprocessing).

This improves the solvent extraction performance for FBR fuel reprocessing.

 

CORAL HOT CELLS: A Pilot Plant for FBTR Irradiated Fuel Reprocessing

    The CORAL facility provides a testing bed for the prototype equipment for FBR fuel reprocessing in realistic environment. This facility is a pilot plant for reprocessing the FBTR fuel. The process flowsheet and the equipment designs will be fine tuned for deployment in DFRP, the plant being built for reprocessing the FBTR fuel.

    CORAL comprises of an a-tight stainless steel containment box with adequate lead shielding. The cell is based on a compact layout, constructed on an area of 11 m * 2 m.

    All the equipment such as singe pin chopper, dissolver, centrifuge, centrifugal extractors and sampling systems are housed in the containment box.

    All the equipment and systems are designed on the basis of remote maintenance concept.

    The cell is provided with radiation-shielding windows, in-cell crane and articulated arm type master slave manipulators to facilitate remote operation and maintenance of these equipment and systems in the containment box.

    Specially designed tanks (annular and slab type) have been installed to store solutions containing plutonium to avoid criticality.

    The facility has about 2 km of intricate stainless steel piping with approximately 3000 bends and 2000 X-radiography joints.

Demonstration FBR Fuel Reprocessing Plant (DFRP)

    The design of DFRP, under construction, is based on the process flowsheet evolved in the pilot plant, Lead Mini Cell.

    This plant will reprocess the FBTR mixed carbide fuel and also will demonstrate the reprocessing of PFBR mixed oxide fuel.

FBTR Reprocessing Milestones

    The FBTR fuels (mixed carbide, 70%PuC+30%UC) of 25, 50 and 100 GWd/t have been successfully reprocessed.

    A FBTR assembly is to be fabricated from the Pu reprocessed in CORAL cells shortly.

    The FBTR fuel (mixed carbide, 70%PuC+30%UC) of 150 GWd/t is to be reprocessed shortly.

ORGANIZATION

REPROCESSING GROUP

              DIRECTOR  
Shri. R. NATARAJAN
 

Process Design & Commissioning Group         AD   Shri. V. Sundararaman  
 

Fuel Reprocessing Process Division

  HEAD   Shri. V. Sundararaman    
    Process Design Section   HEAD   Shri. N. Ramnath    
    Utilities-DFRP   HEAD   Shri. B. Krishnamurthy    
 

Commissioning Incharge DFRP

      Shri. V. Vijayakumar    
    Commissioning Engineer, Process & Piping Systems   HEAD   Shri. K. Rajan    
    Commissioning Engineer, Control Laboratory & Reconversion HEAD   Dr. R. V. Subbarao    

Reprocessing Projects & Operation Group   AD   Shri. A. Ravishankar    
 

Reprocessing Plant Operations Division

  HEAD   Shri. V. Vijayakumar    
    Plant Operation Section   HEAD   Shri. V. Vijayakumar    
 

Piping Engineering Section

  HEAD   Shri. K. Rajan    
 

Hot Cells Equipment Engineering Section

  HEAD   Shri. E. Balu    
 

Reprocessing Plant Design Division

  HEAD   Shri. B.M. Anandarao    
    PFRP Design Section   HEAD   Shri. T. Selvaraj    

Reprocessing Research & Development Division   HEAD   Dr. U. Kamachi Mudali    
    Process Development & Equipment Section   HEAD   Shri. Shekar Kumar    
    Process Engineering & Modelling Section   HEAD   Shri. N.K. Pandey    
    Process Chemistry & Materials Section   HEAD   Dr. C. Mallika    

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