The Status of Developments in Nuclear Fuel Processing

1
The Status of Developments in Nuclear Fuel
Processing

• Gregory R. Choppin
• Dept. of Chemistry Biochemistry
• Florida State University
• Tallahassee, Florida, USA

2
Important Factors in Design of Separation ligands
for Actinides Use

• An-N bonds are longer-lived than An-O bonds
• An-O bonds promote and may be necessary to the
  formation of An-N bonds
• Five-membered chelate rings are the most stable
• Prearranged structures more stable but may be too
  slow to react
• Bulky steric groups can slow dissociation
  kinetics
• Redox, steric effects, high CN, and weak bond
  covalency (in extractant ligands) can be
  exploited to improve specificity in separations

3
Feed 0.7-5 M HNO3 0.0.3 M Oxalic
acid Actinides Lanthanides
Scrub 0.25-1.8 M HNO3 0-0.3 M Oxalic acid
Strip 1 0.04 M HNO3
Am, Cm 100 Am 1-2 Pu 80-100 Ln lt2 Fission
Prod. 10-100 Tc
Extraction
Strip 1
Scrub
0.1-0.3 M CMPO 1.4 M TBP
Aqueous Raffinate 0.7 5 M HNO3 0 -80 Tc 100
Oxalic acid
Strip 2
Np, Pu Product 98-99 Np, Pu
Strip 2 0.05 M HNO3 0.05 M HF
Solvent Wash 0.25 M Na2CO3
Flowsheet for TRUEX Process
4
Advanced Fuel Cycle (Generation (IV))

• Quantitative recycling of U and Pu into LWR
  mixed oxide (MOX) fuel
• Reprocessing of the spent LWR-MOX fuel
• Separations of minor actinides (e.g., Np, Am, Cm)
  from the HLLW
• Fabrication of Fast Reactor Fuel (FR) (MOX,
  metallic or nitride)
• Reprocessing of spent fuel
• Quantitative separations of all TRU elements from
  the spent fuel
• Separation of certain fission products for
  disposal
• Separation of other fission products for use in
  Industry, medicine, etc.

5
Spent Fuel from Commercial Plants
Advanced, Proliferation- Resistant Recycling
Conventional Reprocessing
Spent Fuel
Advanced Separations
PUREX
Pu
U MOX
Spent Fuel Recycle
Recycle
Pu Actinide
U
LWRs/ ALWRs
Gen IV LWRs/ALWRs
Repository
U and Pu Actinides Fission Products
Some U and Pu Actinides, Fission
Some U and Pu Actinides, Fission
Proliferation Resistant Fuel Cycle
Once-Thro Mode
Normal Fuel Cycle
Advanced Fuel Cycle Technologies
6
Kr, Xe Atmospheric discharge
Fuel Chopping
Acetohydroxamic Acid (AHA)
Nitric Acid Dissolution
Off-gas Treatment
I2
First Extraction Cycle
(org)
U Strip Dil. HNO3
(org)
(org)
TBP Extraction
Scrub HNO3/AHA
Tc Strip Conc. HNO3
U, Tc
U
U, Tc
Pu
Pu
Tc
U
Most Fp, Most Np, Pu, Am, Cm
U Purification
TRU 99.9
Remaining Np
HLW
Denitrification Calcination
Tc gt95
Further Processing
Storage
UO2 gt99.9
Vitrification
Flow Diagram for the UREX Process
7
EFFICIENT SNF SEPARATIONS

• Efficient separations would remove longest lived
  nuclides for destruction by transmutation to
  short-lived nuclides
• Also, nuclides of use in medical, industrial,
  space research applications would be separated
• Such efficient separations would result in much
  fewer radionuclides to be disposed in permanent
  repositories
• Such an efficient system requires much further
  research

8
NON-AQUEOUS SEPARATION PROCESS

• Volatility some ?-diketones complexes of
  lanthanides and actinides provide good separation
  of U and Pu from Am
• Molten Salt (a) mixed fluoride salts can be used
  as coolant and fuel in reactors
• (b) chloride eutectic salts used as ionic
  solvent in pyrochemical processing of spent
  metallic fuels at T 500-800oC
• Electrochemical used in purifying U and Pu metal
  alloys in molten ionic salt media

9
Needs in Chemistry for AFC

• Development of novel, non-aqueous processes
• Use differences in volatility of halides (e.g.,
  Fluorides)
• Liquid-liquid extraction scheme for molten salt
  and liquid metals
• Electrorefining to remove metal from molten salt
  by deposition on a cathode
• Advantages
• Higher radiation resistance, shorter cooling time
• Recycling of reagents, generation of less waste
• Lower capital plant costs
• Disadvantages
• Smaller separation factors require multiple
  stages
• Controlled atmospheres to avoid hydrolysis and
  precipitation
• Batch process, limited throughput

10
SNF Cutting Oxide Reduction
Electrorefiner
Anodic Dissolution
Steel Cathode
LiCl/KCl 500oC
Salt, Pu, TRU U, FPs
Hulls, Noble metal FPs
Zeolite columns
Pure U
U fraction
Hulls, Noble Metals Fission Products
Pu, TRU, U Fission Products
Product Stream
Waste Streams
Cast Metal Ingot
Fe/Zr metal Waste Form
Waste Form
Interim Storage
Geologic Storage
ANL Electrometallurgical Process for treatment of
SNF
11
Volatile Fluorides including U, Pu, Np and Tc
separation by distillation
Oxide or Carbide Fuel
separation by molten salt electrolysis
Fluorinator
Non-volatile Fluorides including Rare Earths, Am
and Cm
separation by laser photochemistry
F2
separation by aqueous reprocessing
Conceptual flowsheet of a general fluoride
volatility process
12
Reasonable Policy for Future Energy Reprocessing

• Reprocessing spent nuclear fuel by non- aqueous
  reprocessing
• Removal of unburnt Uranium/Plutonium for recycle
  and further burning
• Removal of long-lived nuclides (e.g.,Tc-99,
  I-129,
• Np-237) for transmutation
• Permanent disposal of remaining wastes in deep
  repository