Current Status and Perspective of R&D-Element Separation-
Yasuji Morita
Nuclear Science and Engineering Center
Section of Nuclear Science Research
Japan Atomic Energy Agency
October 9-10, 2014International Symposium on
“Present Status and Future Perspective for Reducing Radioactive Wastes
~Aiming for Zero-Release~”
2
Two Types of Fuel Cycles for P and T TechnologyDouble-strata
PowerGeneration
Fuelfabrication
Dedicated Transmutation
by ADS
TransmutationCycle
Commercial Fuel Cycle
Fuel fabricationPower
Reactors(LWR and FR)
Transmutation
Homogeneous Recycle in FBR
Commercial FBR Cycle
Fuel fabrication
FR power plantwith transmutation
Reprocessing
Spent fuel
MA–bearing fuel
Pu,MA
Pu
Finaldisposal
Spent fuel
Spent fuel
・Transmutation cycle is attached to commercial cycle.
・ADS is used as dedicated transmutation system.・MA can be confined into a small cycle and transmuted efficiently.
・Transmutation cycle is attached to commercial cycle.
・ADS is used as dedicated transmutation system.・MA can be confined into a small cycle and transmuted efficiently.
・MA is transmuted by commercial FBRpower plants in a closed cycle
・MA is transmuted by commercial FBRpower plants in a closed cycle
FPFP
Reprocessing
Reprocessing
MA
MA–bearing fuel
PowerGeneration Transmutation
Finaldisposal
FP: Fission ProductMA: Minor Actinide (Np, Am, Cm)ADS: Accelerator-Driven System
Reprocessing in both system can acceptthe same separation technology.
High-level Liquid Waste -Start solution for MA separation-
3
PWR spent fuel:Initial enrichment 4.5%、Burn-up 45GWd/t、cooled for 5 yearsMA-recycle fast reactor spent fuel (FR-MA):core fuel + axis blanket (69.4%:30.6%)
Core fuel:Initial composition Pu19.6%, MA0.92%、Burn-up 147.1GWd/t、cooled for 5 yearsBlanket fuel:Depleted uranium (0.3%)、Burn-up 21GWd/t (Average burn-up 108.5GWd/t)
FP
MA
Pu
U
Fig. Example of spent fuelcomposition
FP
Pu
U
MA
※ based on data in JAEA Review 2008-037 “Handbook on Process and Chemistry of Nuclear Fuel Reprocessing”.All figures were obtained per 1 ton of spent fuel.
Reprocessing(U, Pu recovery)
U, Pu 99.5%Np 95%
Kr, Xe 100%Br, I 99%removal
Normalized by 10GWd/t
Higher ratio of residual U in PWR. Higher ratio of MA and Pu in FR-MA
Fig. Example of elementcomposition after reprocessing
Ln:La~DyAm
Ru
Pu
U
Cm
Rh
Pd
Ba
Cs
Tc
Zr MoY
Sr
Higher ratio of Am-Cm and PGM (Ru, Rh, Pd) in FR-MA
CmAm
Sr+Y
Rh
Cs+Ba
Ln
Mole ratio
Heat emission ratio
Very high ratio of heat emission by Cm in FR-MA4
High-level Liquid Waste -Start solution for MA separation-
※ based on data in JAEA Review 2008-037 “Handbook onProcess and Chemistry of Nuclear Fuel Reprocessing”
FP:2.1kW, An:0.16kW, 計2.3kW
FP:3.1kW, An:3.8kW, 計6.9kW
per 1 ton of spent fuel
Element to be separated
5
1) Minor Actinides(MA)=Np, Am, Cm- Long-lived nulides to be transmuted- Np can be separated together with U and Pu, andtherefore main MA to be separated from HLLW areAm and Cm.
- Am and Cm are stable in trivalent state (An(III)),and rare earths (RE) shows similar behavior.
Mole ratio of An(III) to RE is 0.025 in PWRand 0.136 in FR-MA
- In many cases, An(III) are separated by two steps.2) Heat emitters =Sr, Cs
- Most of the heat by FP are emitted by Sr and Cs.- Highly loaded waste form would be possible afterSr and Cs removal.
3) Platinum group metals (PGM)=Ru, Rh, Pd- Valuable elements- They shows bad effect in vitrification
4) Long-lived fission products=Tc- Tc can be separated with PGM in many cases.- to be transmuted, and also a valuable element
U
Other FP
U, Pu, Np
Sr, Cs
An(III)+RErecovery
Partial U separation
FP without RE
Sr-Cs sep.
IodineDissolution
Am Cm
Am/Cm sep.RE
Tc
PGM
Tc-PGM sep.
High-level liquid solution (HLLW)
U-Np-Pu separation
Example of separation process flow
An(III)/REseparation
MA Separation (An(III) Separation)
Separation Process for MA with an extractant, DIDPA or CMPO was tested withreal HLLW and the separation performance was confirmed in JAEA.
Both processes have, however, drawbacks to be overcome.DIDPA extraction : Nitric acid concentration of HLLW should be reduced, which results
in formation of precipitation. Waste generation by P atom.CMPO extraction : Huge volume of solution. Waste generation by P atom.
OP
HO
O
O
iso-C10H21
iso-C10H21
P
O
H2C C
O
N
i-C4H9
i-C4H9
C8H17
CMPO
DIDPA
Experimental apparatus in NUCEFfor tests of DIDPA extraction process
with real HLLW from LWR SF
New research and development① Application of some new extractants② Application of extraction chromatography 6
Experimental apparatus in CPF for testswith real HLLW from FR SF
Solvent extraction and Extraction chromatography
7
1) Solvent extraction : separation method using difference in distribution equilibriumbetween aqueous phase such as nitric acid solution and organic phase containingextractant(s) by each element
Advantage : Easy continuous operation giving high recovery with high purity. Muchexperience in nuclear industry.
Problem : Treatment of spent solvent. Scale of extractors. The third phase formation.2) Extraction chromatography : extraction between solution and adsorbent which is
impregnated with extractant(s).Advantage : No diluent. High separation factor. Compact apparatus.Problem : Less experience in nuclear industry. Difficulty in remote operation.
※ Problem of adsorbent swelling was solved by using porous silica particles.
Solvent Extraction Extraction chromatography
Porous silica particlescoated with organic
polymerSize : several tens m
Development of new extractants for An(III)+RE recovery
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CC
O
O
OC
CH2
NN C12H25
H25C12
H2
C12H25
H25C12 CC
O
O
OC
CH2
NN C12H25
H25C12
H2
C12H25
H25C12
TDdDGA(dodecyl-DGA)
Requirements for An(III)+RE extractants・Extraction from the solution of high nitric acid
concentration to avoid precipitation・Effective extraction and back-extraction・Compound without P to avoid secondary waste
Tridentate DGA extractants are developed.・An(III) can be extracted from 1~3M nitric acid solution and
back-extracted with 0.1M nitric acid・Amide compound without P (CHON principle)・Soluble in n-dodecane・TDdDGA has high extraction capacity without formation of
the third ・ Acceptable durability against radiation
Status of TDdDGA extraction process development・Continuous extraction tests using simulated HLLW with Am
tracer gave the Am recovery of more than 99.99%.・Process simulation code was developed.・Optimization of process condition is underway.・Tests with real HLLW will be carried out as a next step.
DGA extractant is also applied to extraction chromatography.
Nitric acids (M)
Dis
tribu
tion
ratio
ofA
m(-
)
Easy back-extraction
Effectiveextraction
Malonamide
Present workTODGA
CMPO
An(III)/RE separation by solvent extraction
・Study on soft-donor extractants※soft-donor : nitrogen(N), sulfur(S)
hard-donor : oxygen(O)Soft-donor extractant gives higher distributionratio with An(III) than with RE.
→ Selective extraction of An(III)・Hybrid extractants which have both soft and hard
donor in the molecule are also studied.
In both DIDPA extraction and CMPO extraction, a complexing agent, DTPA, isused for An(III)/RE separation, which makes more stable complex with An(III).Problem ・Treatment of organic phase and aqueous solution including
complexing agent・Control of pH ・secondary waste
Separation by the combination of TDdDGA andDTPA is also examined and separation factor of9.4 between Am and RE was confirmed (figure)
Still in the stage of extractant selectionand basic data acquisition 9
TDdDGA-DTPA
pH after back-extractionD
istri
butio
nra
tio(-
)
Separationfactor of 9.4
An(III)/RE separation by solvent extraction
10
Status of separation process development and the near future・Continue to obtain extraction data (extraction rate, extraction capacity, stability, etc.)・Process integration with An(III)+RE recovery.・After optimization of process condition and continuous extraction test with simulated
HLLW, tests with real HLLW will be performed.
pH
Dis
tribu
tion
ratio
TPDN■ Am● Eu
Organic phase:[TPDN] = 10 mM in nitrobenzeneAqueous phase: pH = 1.0 〜 4.8
TPDN
ADAAM(EH)
Multi-dentate N donorextractant, TPDN, provideAm/Eu separation(center figure)
Hybrid type extractants,ADAAM(EH) is being examinedand separation factor of morethan 20 was obtained betweenAm and Eu
Application of TPDN to extractionchromatography is also examined.
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Adsorption/Elution assessmentMA can be adsorbed by adsorbents with CMPO and
TODGA from HLLW, and eluted with some FPs (Ln)MA can be adsorbed by adsorbents with R-BTP
(iHex-BTP) from HLLW, and eluted selectivelyMA can be adsorbed by adsorbents with HDEHP
and TOPEN from diluted HNO3 solution, and eluted selectively
0 2 4 6 8 10 12 14 16 18 20 22 24 26 280
0.5
1 Sr Pd Ru-106 Sb-125 Cs-137 Ce-144 Eu-155 Am-241 Cm-242 pH
C/C
0
Through Bed Volume
DV Feed 3M HNO3 H2O 50mM DTPA (pH=3)
3
1.5
pH
Chromatographic separation of real HLLW by the column with iHex-BTP/SiO2-P adsorbents
(FUGEN spent fuel test at TRP)
Chromatographic separation of real HLLW by the column with CMPO/SiO2-P adsorbents
(JOYO spent fuel test at CPF)
An(III)+Ln recovery
An(III) Separation by Extraction Chromatography
0.0
0.2
0.4
0.6
0.8
1.0
0 1 2 3 4 5 6 7 8 9 10 11 12
C/C
0
Sr YZr MoBa LaCe NdSm EuGd AmCm
DeadVol.
Feed 1 M HNO3 H2O
Through bed volume
Selective An(III)recovery
Y. Sano, et al., IOP Conf. Ser.: Mater. Sci. Eng. 9 012064 (2010)S. Watanabe, et al., Proc. of GLOBAL2011 (2011)
iHex-BTP
TOPEN
12
Durability of Adsorbents against Gamma Irradiation
Durability assessment Adsorbents with CMPO and TODGA have a similar durability Adsorbent with R-BTP is unstable in high HNO3 condition Adsorbents with R-BTP, HDEHP and TOPEN have a similar durability
in diluted HNO3 condition
Contact time : 180 min, Temp. : 25ºCAdsorption solution : [HNO3]=4.8M, [Eu(III)]=10mM
Contact time : 180 min, Temp. : 25ºCAdsorption solution : [HNO3]=2M, [U(IV)]=10mM
Distribution coefficient of Eu from 4.8M HNO3 by TODGA/SiO2-P adsorbents
Distribution coefficient of U from 2M HNO3 by iHex-BTP/SiO2-P adsorbents
10-1
100
101
102
103
0 1 2 3 4 5D
istri
butio
n co
effic
ient
(cm
3 /cm
3 )
ray dose (MGy)
0.01 M *
2 M
* [HNO3] at exposure
10-1
100
101
102
103
0 1 2 3 4 5
Dis
tribu
tion
coef
ficie
nt (c
m3 /c
m3 )
ray dose (MGy)
0.1 M *
4.8 M
* [HNO3] at exposure
Y. Koma, et al., Proc. of GLOBAL2009 (2009)
Separation of Fission Products
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◎ Separation of Sr-Cs(1)Adsorption with inorganic ion exchangers
- Titanic acid for Sr and Zeolite (mordenite) for Cs.The adsorbents can be converted to a stable formby calcination.
- Experiments with real HLLW showed a good performancefor Sr-Cs recovery.
- Drawback : Reduction of acid concentration is required.
(2)Extraction chromatography- Crown-ether for Sr and Calix-crown for Cs.- Very small scale test with real HLLW was performed.- Drawback : High cost for extractants.
◎ Separation of Tc-PGM(Ru, Rh, Pd)- Adsorption method with active carbon was developed.- Precipitation method by denitration was tested with
real HLLW, and the recovery of Tc-PGM was confirmed.- Extraction with oxime for Pd separation and volatilization with electrochemical
oxidation for Ru separation were investigated.◎ Other elements
- Zr and Mo are separated by precipitation in DIDPA extraction.- Separation process for Zr-Mo by extraction with HDEHP was developed.
Very small scale test with realHLLW for Sr-Cs separation byextraction chromatography
Performance of eachseparation process wasconfirmed. Integration oftotal process is important.
Summary
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In An(III) separation and FP separation, several methodshave been already confirmed to give good performance.
Methods to give better separation performance should beinvestigated.
High-level liquid solution from spent fuel of LWR and thesolution after U-Pu recovery from spent fuel of fast reactor,as a starting solution of An(III) separation, can be treated ina similar manner considering the difference in actinidecontent.
Integration of separation processes for An(III) and FP isimportant.
Together with the real HLLW tests, cold mock-up tests in anindustrial scale should be performed, and then it becomepossible to proceed to active tests in the industrial scale.