Characterization of Nuclear Waste from...
Transcript of Characterization of Nuclear Waste from...
Characterization of Nuclear Waste from Decommissioning
XiaolinHouTechnical University of Denmark
Center for Nuclear Technologies, Risø Campus, Roskilde, DenmarkE-mail: [email protected]
Steps of decommissioning of nuclear facility• Preparation (investigating the background radioactivity around NPP)• Cleanout
– Removal of most radioactive component such as spend fuel elements, reactor internals, reactor vessel, etc. which is transferred for storage and disposal. (high level waste). (Evaluation of radioactivity before transferring)
• Decontamination– Removal of contamination from surfaces of facilities or equipment by
chemical or mechanical methods, which can reduce the waste volume and active level in the waste. (Measurement of radioactivity to evaluation the decontamination, and estimation of radioactivity in the waste)
• Dismantling– Equipments within the facility are dismantled and classified by
estimation of the radioactivity)• Demolition and site clearance
– Buildings demolished and radioactive wastes removed to storage or disposal facilities after estimation of the radioactivity in the waste.
• Release of the site to alternative use (measure the radioactivity level in the released area)
Production of main radionuclides in nuclear reactors
•Long-lived fission products137, 135Cs,106Ru, 90Sr, 99Tc, 129I, etc.
•Neutron activation products (long-lived)58,60Co, 133Ba, 134Cs, 152,154, 155 Eu, 3H, 14C, 36Cl, 41Ca, 63, 69Ni, 94Nb, 55,59Fe, 93Zr, 93Mo,54Mn, 110mAg, 238-241Pu, 241Am, 243,244Cm, 237Np, etc.
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• Gamma radionuclides60Co, 133Ba, 137Cs, 134Cs,
106Ru, 152,154, 155 Eu, 58Co, 54Mn,59Fe, 110mAg, 94Nb, etc.
No chemcial separation is normally needed.
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Beta Emitter3H, 14C, 36Cl, 41Ca, 55Fe, 63, 59Ni, 90Sr, 99Tc, 129I,93Zr, 93Mo.
Difficult to measure, separation of individual radionuclide from matrix and all other radionuclides is needed before measurement.
3H 14C32P
Emax: 18, 156 and 1700 keV for H-3, C-14 and P-32 respectively
LSCGas flow multi-channel beta counter
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• -emitter (actinides)238-241Pu, 241Am, 243,244Cm, 237Np, etc.
High toxicity, difficult to measure, separation of individual radionuclide from matrix and all other radionuclides is needed.
238Pu
239+240Pu
242Pu
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• Graphite (reactor)– 3H, 14C, 55Fe, 63, 59Ni, 60Co, 152Eu
• Concrete (normal or heavy)– 3H, 14C, 41Ca, 60Co, 55Fe, 63, 59Ni, 133Ba, 152Eu
• Steel/stainless steel– 55Fe, 63, 59Ni, 36Cl, 93Zr, 93Mo, 94Nb, 60Co, 152Eu,
transuranics• Other metals (Aluminium, Lead)
– 60Co, 63Ni, 55Fe, 36Cl• Water
– 3H, 14C, 63Ni, 99Tc, 129I, 90Sr, 60Co, 137Cs, transuranics• Ion exchange resin
– 14C, 55Fe, 63,59Ni, 99Tc, 36Cl, 93Zr, 93Mo, 94Nb 90Sr, 129I, 137Cs,60Co, 135Cs, transuranics
Waste samples and the relevant critical radionuclides for decommissioning
Radiochemical Analysis of Radionuclides
Samples
Pre-concentration
- spectrometry measurement(137Cs, 134Cs, 60Co, 152Eu)
Radiochemcial separation of target radionuclides from matrix and interferring radionuclideds
- couting(3H, 14C, 55Fe, 63Ni, 90Sr, etc.)
- spectrometry(239,240Pu, 237Np, 226Ra)
AMS(129I, 36Cl, 59Ni,41Ca)
ICP-MS(239Pu, 240Pu, 237Np, 99Tc)
Other MS
LSC AMS ICP-MS
Radioanalytical Chemistry of important radionculides for decommissioning
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3Hand14C41Ca 36Cl 55Feand63Ni Automatedsystemforrapidanalysis
• Production of 3H in reactor• 2H (n, )3H• 6Li(n, )3H • 3He(n, p)3H
Determination of 3H and 14C in graphite, concrete, and other solid materials
• Production of 14C in reactor
– 13C(n, )14C– 14N(n, p)14C– 17O(n, )14C
Nuclides Half life Decay Emax, keV
3H 12.35 y 18.6
14C 5736 y 156
Rapid separation of 3H and 14C waste samples by combustion using Packard Oxidizer
...h7\Q010601N.001 11
...h7\Q010601N.001 12
...h7\Q010601N.001 21
...h7\Q010601N.001 22
Sample Spectrum
1,0009008007006005004003002001000
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...C0\Q014001N.001 11
...C0\Q014001N.001 12
Sample Spectrum
1,0009008007006005004003002001000
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14C
3H
3H and 14C in concrete and graphite
Nootherimpuritynuclideswere seenintheH‐3andC‐14spectrum 0
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1000
100 150 200 250 300
conc
entr
atio
n of
3H
, B
q/g
Distance to the core, cm
Core-A
Core-B
Average SD % Average SD % Average SD %C-14 TK5.5 Yi 2,12E+02 4,50 2,08E+02 5,2 2,17E+02 3,8C-14 TK7.5 Yi 2,67E+04 2,19 2,54E+04 2,93 2,64E+04 4,27H-3 TK5.5 Yi 4,70E+03 17,33 4,72E+03 3,74 4,66E+03 4,12H-3 TK7.5 Yi 1,11E+06 3,39 1,05E+06 5,79 1,05E+06 4,8
Nuclide code
15-01-2003 Room temperature 110 °C (first measurement) 4 months for 5 days
3Hand14Cingraphiteandtheirstability
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Distance to the core, cm
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14C in concrete
EC (421.4 keV, 100%)
41Ca (21.03x105y)
41K (stable)
Nuclide Target isotope Aboundance %
Reaction Cross section, bar
Half life Decay
41Ca 96.94 40Ca(n, )41Ca 0.41 1.03105 y EC45Ca 2.086 44Ca(n, )45Ca 0.84 162.7 d -47Ca 0.004 46Ca(n, )47Ca 0.7 4.54 d , 49Ca 0.187 48Ca(n, )49Ca 1.0 8.72 min. ,
41Ca in concreteActivation products of calcium isotopes
Energy of X-rays and Auger electrons : 0.3-3.6 keVDetermination: X-ray spectrometry (<0.08%)
LSC (10-20%)
Determination 41Ca in concrete
• Separationfromatrix
– Decompositionofheavyconcretebyalkalifussion
– LeachingCabyacids
• Separationfromactivemetalssuchas60Co,152Eu,55Fe,63Ni,65Zn,54Mn,51Cr,etc.
– PrecipitationwithFe(OH)3 byhydroxidesatpH9
• Separationfromotheralkalinemetals,suchas133Ba,226Raand90Sr.
– Ca(OH)2 precipitationinNaOHsolution
Element Recovery,
%
redionuclide Decontamination
factor
Ca 97.73.9 137Cs (4.50.3)105
85Sr 97.92.1 60Co (1.20.4)105
133Ba 97.32.8 152Eu (8.50.5)105
59Fe (2.50.1)105
63Ni (2.50.2)105
• Separation of Sr from Ca by Ca(OH)2 precipitation• Ca(OH)2: insoluble, Ksp = 5.2 10-6
• Sr(OH)2 and Ba(OH)2: Soluble in alkine solution
Separation of Ca from Sr and Ba using hydroxide precipitation
Precipitate Ca as Ca(OH)2 at 0.5 –0.8 mol/l NaOH, repeat 3 times, 85% Ca can be recovered, and the decontamination factor for Sr and Ba are higer than 5x104
41Ca in heavy concrete from DR-2
...A6\Q024201N.002 12
...A6\Q044401N.002 12
...A6\Q054501N.001 12
Sample Spectrum
1,000800600400200
0.2870.2660.2460.2250.2050.1840.1640.1430.1230.1020.0820.0610.0410.02
0
Spectrum of 41Ca in concrete
Features of Method for 41Ca
• Aseparationof41Cafromconcrete iseasy tooperate
• Gooddecontaminationfrominterferringradionuclides (>104)
• Thechemicalyieldsoftheseparationproceduresfor41Cais80‐90%.
• Thedetectionlimitsfor41Ca is0.020Bq.
Hou X.L., Radiochim Acta, 2005
36Cl is long-lived radionuclides (3x105 yrs) 36Cl decays mainly by pure beta emission of
Emax=708.6 keV. 36Cl measurement is normally carried out by LSC
and AMS
Determination of 36Cl
Determination of 36Cl in graphite--- Sample decomposition
• Ashingat900˚C:‐‐‐iodineandpartofClarelost.
• Decompositionat900˚CwithO2 andtrappingiodineinNaOHsolution:‐‐‐notgoodforchlorine
• Leachingwithacid(HNO3)atheating:‐‐‐ notcompleteremoveiodineandClfromgraphite,andlossoftheleachediodine.
• DigestionwithHNO3 andtrappingiodineandchlorinewithNaOH:‐‐‐‐ Notcompleteremovalofiodineandchlorine
• How to Do?
• Aciddigestion(graphite,steel,Al,Pb,) Graphite(H2SO4:HNO3:HClO4=15:4:1) Steel,aluminum(8mol/lH2SO4) Lead(8mol/lHNO3)
Decomposition of sample to release chlorine and iodine
Flask9:3H,129I,99Tc,36ClFlask10,11:14C,129I,Sampleflask:non‐voltile elements,Ca,Ni,Fe,Cs,Co,Ba,tritium,Cl,Tc,transuranics,etc.
Determination of 36Cl in concrete--- Sample decomposition
Digestion with HNO3 and trapping iodine and chlorine with NaOH: ---- Not complete removal of iodine and chlorine
Alklinal fussion using NaOH and Na2CO3, dissolution of fused cake in water, the supernatant is used for 129I and 36Cl: ---- sample is completely decomposed and iodine and Cl are released. Iodine and Cl are not lost in alkaline medium.
Determination of 36Cl in stainless steel--- Sample decomposition
Stainless steel is normally dissolved with HCl or HCl+HNO3: --- could not be used for 36Cl because of too much Cl in HCl is introduced.
Single acid, HNO3, could not dissolve stainless steel.
10M H2SO4 with H3PO4 is sucessfully used for dissolve stainless steel 36Cl: ---- sample is completely decomposed and iodine and Cl are released.
Separation of Chlorine and iodine from
matrices and other radionuclides
Specific precipitation of Cl- with Ag+ (AgCl) can be used to selectively separation of Cl from matrix and other radionuclides (except iodine and bromine).
The separated AgCl can be dissolved in NH4OH and mixed with scintillation cocktail for LSC: But less AgCl can be used and high quench effect. How to improve?
0 .0
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0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0
v o lu m e , m l
Cl-3
6, B
q or
Ag,
x10
0 m
g
100m g C l, 0 .2 M N H 4N O 3-0 .6 M N H 4O H e lu t ing200m g C l 0 .2 M N H 4N O 3-0 .6 M N H 4O H e lu t ing50 m g C l, 0 .1 M N H 4N O 3-0 .6 M N H 4O H e lu t ing100 m g C l, 0 .1 M N H 4N O 3-0 .6 M N H 4O H e lu t ing
b )
c )
d )
a)
A g +
C l-
Separation of Ag+ and Cl– in anion exchange chromatography
Performance of the chemical separation procedure
Element AgClprecip.
Anion exch.
Whole proced.
Cl (recovery, %)
96.5 98.3 94.73.2
I (125I) 1.4 103 1.4 103 8.9 105
S 1.5 103 5.6 105
tritium 2.1 103 4.8 106
14C (CO32-) 1.5 103 2.8 106
Co (60Co) 1.9 103 2.5 103 1.5 106
Eu (152Eu) 4.7 103 6.5 103 8.9 106
Cs (137Cs) 3.8 103 5.1 103 7.9 106
Ba (133Ba) 6.7 103 4.9 103 5.6 106
Sr (85Sr) 4.7 103 3.3 103 6.7 106
Ni (63Ni) 5.9 103 3.8 103 4.8 106
Fe (55Fe) 1.9 103 2.8 103 2.1 106
Before separation
After separation
LSC measurement of 36Cl in waste samples
...L1\Q015101N.001 11
...18\Q010101N.001 11
...18\Q020201N.002 11
...19\Q010101N.001 11
...19\Q020201N.001 11
...19\Q030301N.001 11
Sample Spectrum
1,0009008007006005004003002001000
0.737
0.655
0.573
0.492
0.41
0.328
0.246
0.164
0.082
0
36Cl in Steel and graphite from DR-2
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ntin
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NaCl
NH4Cl
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Effic
ienc
y, %
SQP(E)
100 mg Cl (NaCl)200 mg Cl (NaCl)
Recovery of Cl: >70%
Detection limit using LSC : 14 mBq
Hou et al., Anal. Chem., 2007
63Ni and 55Fe
Fe-55 decays by electron capture emitting X-rays, conversion electrons and Auger electrons (5 - 6 keV)
X ray (5.89 keV, 25.4%)
55Fe (2.73 y)
55Mn (stable)
EC (232 keV, 100%)
No gamma ray
(66.95 keV, 100%)
No gamma ray
63Ni (100.1y)
63Cu (stable)
• 63Ni: – 62Ni(n, Ni =14.5 b; Ni=3.63%)– 63Cu(n, p)63Ni, ( Cu=69.17%)
• 55Fe:– 54Fe(n, Fe =2.3 b; Fe=5.85%)– 56Fe(n, 2n)55Fe, (Fe=91.75%)
Atomic ratio: 59Ni/63Ni=6.5:1
Activity ratio: 59Ni/63Ni=1:133
Separation of Ni and Fe by anion exchange chromatography
• Ni can be completely separated from Fe, Co, Cu, Zn, U, Pu, etc.
• Fe can be separated from Ni, Cr, Mn, Th, etc.
• Ni cannot be efficiently separated from Cr, Eu, Sm, Mn, V, Sc, Ti, Zr, Ba, Th, Am.
Element
Content, %
Ni fraction Fe fractionFe3+ <0.001 >98.5Ni2+ >99.5 <0.001Co2+ <0.01 <0.001Ba2+ <7.5 <0.001Eu3+ >99.8 <0.001Cs+ >99.5 <0.001Sr2+ >99.5 <0.001
Element Recovery or decontamination factor
Ni2+ > 98.5%
Fe3+ 104
Co2+ 103
Ba2+ 104
Eu3+ 104
Cs+ 104
Sr2+ 104
Purification of Ni by specific Ni-extraction chromatography
Ni specific extraction chromatography has a higher decontamination to most of elements, such as Fe, Co, Cu, Cr. Mn, Ba, Eu, transuranics, etc.
•A higher recovery of Ni can be obtained in the procedure.
• Yellow colour Fe3+ is a very effective quenching agent
• Reduction of Fe3+ to Fe2+ using suitable reductant, such as ascorbic acid can reduce the quench, but Fe2+ is not stable and can be oxidize to Fe3+ again, and Fe2+ also has some colour quench.
• Solvent extraction of Fe3+ using some organic compounds such as di-2-ethylhexyl phosporic acid can reduce the Fe3+ colour quench, but not effective for large Fe content sample.
• In H3PO3 solution, a stable and colourless Fe-H3PO3 complex can be formed, therefore can significantly reduce the Fe3+ colour quench.
• As high as 40% counting efficiency of 63Ni in 1.5 ml of 2 mol/l H3PO3 solution.
Preparation of separated 55Fe for LSC
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ienc
y, %
Content of Fe (mg)
FeCl3 solutionFe3+ +H3PO3(2M)
Combined analytical procedure for 36Cl, 129I, 41Ca, 63Ni, and 55Fe
29 8 October 2013
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
100 150 200 250 300
Distance to core, cm
Activ
ity c
once
ntra
tion,
Bq/
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55Fe63Ni36Cl
Sample 36Cl measured, Bq
Value Uncertainty
SWIPE-111-2 2.14 0.18
SWIPE-111-1 2.04 0.19
36Clin2swipsamplesfromIgnalinaNPP
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41Ca in concrete core
Sample Code 36Cl, Bq/g
meanSD
63Ni,
Bq/g
36Cl/63Ni
Activity ratioGraphite 5.5 Yi 0.180.03 5.76 0.030Graphite 5.5 Yy 3.580.13 102 0.035Graphite 5.5 Ii 22.61.5 499 0.045Graphite 5.5 Iy 6.610.52 74.9 0.088Graphite 7.5 Yi 6.370.48 134 0.048Graphite 7.5 Yy 5.570.54 88.3 0.063Graphite 7.5 Ii 39.93.4 758 0.053Graphite G 3.330.28 61.2 0.054
Aluminum B1 0.0270.003 15.6 0.0017Aluminum B2 0.0230.03 15.5 0.0015
lead B4 0.00320.0012 2.58 0.0012
36Cland63Niingraphite,AluminumandleadfromDR2
Automatation of of radioanalysis
ICP-MS/ AMS
HC
SV
SP
Carrier
S WE
R2R1
Flow/Sequential injection
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Eluates
Extraction or anion exchange chromatography
Sample solution, with Pu (IV) and Np(IV) in 8M HNO3 medium
Sequence 2: Wash with 100mL of 9M HCl, 1.2mL/min
Matrix (Ca, Mg, Fe, Pb…) Am, U
Sequence 3: Elute with 40mL of 0.5M HCl, 1.2 mL/min
Th
ICP-MS
Sequence 1: Wash with 100 mLof 8M HNO3, 1.2 mL/min
2 mL AGMP-1M
Pu and Np
Sequence 1 Sequence 2 Sequence 3
Load, 1.2 mL/min
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An automated method for determination of 99Tc, Pu and Np
ICP-MS for 99Tc
Shi, Hou et al. Anal. Chem. 2012
One column is not enough
Two TEVA columns
1) High chemical yield of Tc
2) Sufficient removal of Mo and Ru
Separation of 99Tc from Mo and Ru
Developed methods Reported methods
Decontamination factor for Mo 4×104 ~ 1×106 < 5×103
Decontamination factor for Ru 1×105 ~ 7×106 < 1×104
Analytical time (h) < 24 > 30
Recovery (%) 60-95 60-90